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In recent years, the chemistry of transition metal borane and borate complexes has advanced fast with reasonable growth. Frequent utilisation of these complexes in hydrofunctionalisation reactions is one of the key driving forces for their development. As a result, the important role of borate complexes in the hydroboration/hydrosilylation/hydroamination of unsaturated organic species has been successfully demonstrated together with the isolation of many different boron-containing transition metal complexes such as borataallyl, vinylborane, silyl complexes featuring the known bonding modes of boron. Both the uncatalysed and catalysed hydroboration reactions using the transition metal borane/borate complexes are known, which show these complexes' huge potential. Careful investigation and fine-tuning of the electronic and steric properties of the borane/borate ligands has facilitated the synthesis of these transition metal complexes which are convenient for use in the hydroboration reactions. Furthermore, the systematic development of this field has established the connection between the structure and reactivity of these complexes and their utilisation in hydroboration reactions. This Frontier sheds light on the recent developments that have been made with hydroboration reactions using transition metal borane/borate complexes. Also, in this Frontier we have provided meaningful synthetic methods to make new boron-containing transition metal complexes together with mechanistic insights for some of these reactions. [ABSTRACT FROM AUTHOR]

Transition metal triple‐decker complexes are an interesting class of sandwich complexes that engrossed great attention due to their structures and properties. Over the decades, synthesis of triple‐decker complexes featuring homocyclic, heterocyclic or π‐conjugated rings as middle decks have been abundantly reported. In this regard, the chemistry of such complexes bearing boron in the middle deck are well explored due to the ability of boron‐containing cycles to readily coordinate bifacially with metal atoms thereby forming triple‐decker complexes. On the other hand, electron counting rules and theoretical calculations have strengthened our knowledge of the structure and bonding in these complexes. Further, these complexes can be used as synthons to generate organometallic polymers having interesting electronic, optical and magnetic properties that can be appropriately tuned to cater to a wide range of applications. In our quest for novel metallaboranes and metallaheteroboranes, we have been successful in isolating various triple‐decker complexes that feature boron in the middle deck. This review explained elaborately the synthesis, structures, and bonding in such complexes reported by us and others. [ABSTRACT FROM AUTHOR]

Building upon our earlier results on the chemistry of nido‐1,2‐[(Cp*RuH)2B3H7] (Cp*=ɳ5‐C5Me5) (nido‐1) with different transition metal carbonyls, we continued to investigate the reactivity with group 7 metal carbonyls under photolytic condition. Photolysis of nido‐1 with [Mn2(CO)10] led to the isolation of a trimetallic [(Cp*Ru)2{Mn(CO)3}(μ‐H)(μ‐CO)3(μ3‐BH)] (2) cluster with a triply bridging borylene moiety. Cluster 2 is a rare example of a tetrahedral cluster having hydrido(hydroborylene) moiety. In an attempt to synthesize the Re analogue of 2, a similar reaction was carried out with [Re2(CO)10] that yielded the trimetallic [(Cp*Ru)2{Re(CO)3}(μ‐H)(μ‐CO)3(μ3‐BH)] (3) cluster having a triply bridging borylene unit. Along with 3, a trimetallic square pyramid cluster [(Cp*Ru)2{Re(CO)3}(μ‐H)2(μ‐CO)(μ3,ɳ2‐B2H5)] (4), and heterotrimetallic hydride clusters [{Cp*Ru(CO)2}‐{Re(CO)4}2(μ‐H)] (5) and [{Cp*Ru(CO)}{Re(CO)4}2(μ‐H)3] (6) were isolated. Cluster 4 is a unique example of a M2M′B2 cluster having diboron capped Ru2Re‐triangle. The hydride clusters 5 and 6 have triangular RuRe2 frameworks with one and three μ‐Hs respectively. All the clusters have been characterized by using mass spectrometry, 1H, 11B{1H}, 13C{1H} NMR and IR spectroscopies analyses and the structures of clusters 2–6 have been unambiguously established by XRD analyses. Furthermore, to understand the electronic, structural, and bonding features of the synthesized metal‐rich clusters, DFT calculations have been performed. [ABSTRACT FROM AUTHOR]

Building upon our ongoing studies on the highyield synthetic route to 2,3,4,5-tetracarba-1,6-nido hexaborane derivative 5, we continue to explore the chemistry of this system to isolate a range of perphenylated C4B2-type carborane isomers. As a result, the photolysis of 5 for an elongated period yielded 6, which exhibits an intense luminescence upon excitation with a UV lamp (λex=366 nm). In contrast, the conversion of 5 under thermal conditions (microwave heating) generated the isomer 7, which does not show any luminescence. The structural disparity among the three isomers 5-7 is the position of the butadiene moiety with respect to the C4B2-carborane cage as deduced from single-crystal X-ray diffraction analyses. In an attempt to generate the classical structural motif of 5, an equimolar amount of KOtBu was added to a THF solution of 5, which immediately provided the boratacyclopentadiene derivative 8 in good yield. The observed rearrangement reactions were further investigated by quantum chemical calculations to suggest a plausible reaction pathway. According to the DFT calculations, the energetically favored reaction mechanism most likely involves tricyclic transition states and classical intermediate structures. In addition, the fluorescence emission properties of 6 were investigated in solution as well as in the solid state. [ABSTRACT FROM AUTHOR]

Abstract: Ruthenaborane clusters have been modelled by performing density functional theory calculations using the B3LYP functional. The calculations gain insights into hydrogen storage and the H–H bond activation by ruthenaboranes. To study the nature of the chemical bond of H2 molecules attached to ruthenaboranes, we carried out structural optimizations for different ruthenaborane clusters and determined transition state structures for their hydrogenation addition/elimination reactions. Calculations of the reaction pathways yielded different transition-state structures involving molecular hydrogen bonded to the cluster or formation of metal hydrides. The H–H bond of H2 seems to be activated by the ruthenaborane clusters as activation energies of 24–42 kcal/mol were calculated for the H2 addition reaction. The calculated Gibbs free energy for the H2 addition reaction is 14–27 kcal/mol. The calculated activation energies and the molecular structures of the [(C5Me5)Ru2B10H16], [(C5Me5)Ru2B8H14] and [(C5Me5)Ru2B8H12] clusters with different degree of hydrogenation are compared. The mechanisms of the H2 addition and elimination reactions of the studied clusters suggest that they might be useful as hydrogen storage materials due to their ability to activate the H–H bond. They also serve as an example of the ability of hypoelectronic metallaboranes to reversibly or irreversibly bind hydrogen. [Copyright &y& Elsevier]

The recent developments in the field of transition metal (TM) borate complexes have been a landmark in modern coordination chemistry. The structural diversities of these complexes play an important role in several catalytic processes. Generally, polypyrazolyl borate ligands, [BHn(pz)4‐n]− (n=1, 2; pz=pyrazolyl), popularly known as scorpionates have been used extensively for the preparation of TM borate complexes. The presence of multiple donor atoms in the flexible borate proligands led to several coordination modes. Based on the electronic and steric properties of these ligands and the metals, the denticity of borate ligands in TM complexes varied from κ0 to κ6. The presence of different bonding modes of these borate ligands made them very interesting in main group organometallic chemistry. In addition, cooperative activation of boranes by TM complexes containing metal‐nitrogen or metal‐sulfur bonds has become an alternative to the utilization of borate proligands for the synthesis of TM borate complexes. This review summarizes the advancements of the chemistry of TM borate complexes focusing exclusively on the synthetic methods and various bonding scenarios. [ABSTRACT FROM AUTHOR]

The recent achievements and progress in the field of high-nuclearity supraicosahedral metallaborane chemistry are reviewed and compared to those made in borane, carborane and metallacarborane chemistry. In contrast to metallacarboranes, characterized large supraicosahedral metallaboranes only adopt isocloso deltahedral structural arrangements with n vertices and a non-Wadean n skeletal-electron-pair count. This anomaly can be rationalized by the preference of metal atoms for 6-connect vertices present in the cluster cages. [ABSTRACT FROM AUTHOR]

Abstract: DFT calculations were carried out on compound Cp*2Ru2(B8H14) that suggests a strong link with the pentalene complex Cp*2Fe2(C8H6). Both compounds exhibit similar bonding modes and qualitatively related electronic structures. There are however, differences which are related to the weaker B–B bond in the B8H14 ligand as compared to the C–C bond in the pentalene ligand. [Copyright &y& Elsevier]

The synthesis, electrochemical, optical, and cation-sensingpropertiesof two triazole-tethered ferrocenyl benzylacetate derivatives, C36H36O6N6Fe (2) and C23H23O3N3Fe (3), are presented. The binding event of both the receptorscan be inferred either from a redox shift (2, ΔE1/2= 106 mV for Hg2+and ΔE1/2= 187 mV for Ni2+; 3, ΔE1/2= 167 mV for Hg2+and ΔE1/2= 136 mV for Ni2+) or a highly visual output response (colorimetric) for Hg2+, Ni2+, and Cu2+cations. Remarkably,the redox and colorimetric responses toward Hg2+are preservedin the presence of water (CH3CN/H2O, 2/8), whichcan be used for the selective colorimetric detection of Hg2+in an aqueous environment over Ni2+and Cu2+cations. The changes in the absorption spectra are accompanied bythe appearance of a new low-energy (LE) peak at 625 nm for both compounds 2and 3(2, ε = 2500 M–1cm–1; 3, ε =1370 M–1cm–1), due to a changein color from yellow to purple for Hg2+cations in CH3CN/H2O (2/8). [ABSTRACT FROM AUTHOR]

The recently discovered ditantalaboranes CpTaBH ( n = 4, 5) are isoelectronic with the previously discovered dimetallaboranes CpMBH of the group 6 metals Cr, Mo, and W where Cp = η-cyclopentadienyl or substituted cyclopentadienyl. Their oblatonido polyhedral structures can be derived from the oblate (flattened) deltahedra of the oblatocloso dirhenaboranes CpReBH by removal of an equatorial BH vertex with adjustment of the skeletal electron count by changing the metal atoms and adding hydrogen atoms. In these oblatocloso dirhenaborane deltahedra, the approximately antipodal rhenium atoms are close enough together to form a formal Re=Re double bond with lengths in the range 2.69-2.82 Å. Similarly, short M=M distances are maintained in the related oblatonido derivatives CpTaBH ( n = 4, 5) and CpMBH (M=Cr, Mo, W). However, the synthesis of CpTaBH ( n = 4, 5) from CpTaCl + LiBH/BH also gives a less-reduced product CpTaClBH with a longer Ta-Ta distance of ~3.2 Å. This may be regarded as a formal single bond bridged by one of the hydrogen atoms. Vertices of degree 5 (excluding terminal atoms/groups but not edge-bridging hydrogens) are sites of highest stability/lowest chemical reactivity not only in metal-free boranes but also in the dimetallaboranes discussed in this paper. For example, all four boron vertices in CpTaBH have the favorable degree or 5. Graphical Abstract: The recently discovered ditantalaboranes CpTaBH ( n = 4, 5) are isoelectronic with the previously discovered dimetallaboranes CpMBH (M=Cr, Mo, W). They have oblatonido structures derived by removal of one BH vertex from the flattened oblatocloso polyhedra of the dirhenaboranes CpReBH. All of these structures have internal M=M formal double bonds inside the deltahedron. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Chemistry and reactivity of dimolybdathiaborane, [(CpMo)BSH], 1, obtained from the reaction of 2-mercaptobenzothiazole, [CpMoCl] and [LiBH.thf], has been explored with dinuclear metal carbonyl [Fe(CO)]. As a result, reaction of 1 with [Fe(CO)] yielded heterometallathiaborane, [(CpMo)BHSFe(CO)], 2 in good yield. Both the new compounds have been characterized in solution by H, B and C NMR spectroscopy and the structural types were unequivocally established by X-ray crystallographic analysis of compound 2. Cluster 2 has a bicapped octahedral geometry with the {Fe(CO)} fragment occupying one of the high-connectivity cluster vertexes rather than a capping position. Interestingly, cluster 1 undergoes geometric changes (bicapped trigonal bipyramid → bicapped octahedron) on the addition of two-electron {Fe(CO)} fragment to 1. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Examines how a transition metal can be used to vary the chemistry of a metalloborane. Systematic reaction chemistry; X-ray structure determinations; Comparison of spectroscopic data; Endo-hydrogen atoms of the metalloborane cluster; Connection of metalloborane chemistry to organometallic chemistry; Counterpoint to the chemistry of hydrocarbyls with metals.

The syntheses and structural elucidation of bimetallic thiolate complexes of early and late transition metals are described. Thermolysis of the bimetallic hydridoborate species [{Cp*CoPh}{µ-TePh}{µ-TeBH3-ĸ2Te,H}{Cp*Co}] (Cp* = ɳ5-C5Me5) (1) in the presence of CS2 afforded the bimetallic perthiocarbonate complex [(Cp*Co)2(μ-CS4-κ1S:κ2S′)(μ-S2-κ2S″:κ1S‴)] (2) and the dithiolene complex [(Cp*Co)(μ-C3S5-κ1S,S′] (3). Complex 2 contains a four-membered metallaheterocycle (Co2S2) comprising a perthiocarbonate [CS4]2− unit and a disulfide [S2]2− unit, attached opposite to each other. Complex 2 was characterized by employing different multinuclear NMR, infrared spectroscopy, mass spectrometry, and single-crystal X-ray diffraction studies. Preliminary studies show that [Cp*VCl2]3 (4) with an intermediate generated from CS2 and [LiBH4·THF] yielded thiolate species, albeit different from the cobalt system. Furthermore, a computational analysis was performed to provide insight into the bonding of this bimetallic perthiocarbonate complex. [ABSTRACT FROM AUTHOR]

In an effort to explore the coordination chemistry of the coordinative sulfur centers in arachno-ruthenaborane [(Cp*Ru)2(B3H8)(CS2H)] (arachno-1), we have thermolyzed arachno-1 with group-6 metal carbonyls [M(CO)5·THF] (M = Cr, Mo and W). The reaction of arachno-1 with [Cr(CO)5·THF] resulted in the formation of hetero-trimetallic triply bridging borylene [(Cp*Ru)2(μ-CO)(μ3-CH2S2-κ2S′:κ2S′′){Cr(CO)3}(μ3-BH)] (2), bridging boryl–borylene [(Cp*Ru)2(μ-CO){(μ3-BH(CH2S2)-κ2B:κ2S′:κ1S′′)}{Cr(CO)3}(μ3-BH)] (3), and sulfido bridged hetero-trimetallic complex [(Cp*Ru)2(μ-CO)3{Cr(CO)3}(μ3-S)] (4). In 2, one side of Ru2Cr-triangle features a μ3-BH ligand while the other side is quadruply bridged by a methanedithiolato ligand in an unsymmetrical fashion. Unlike 2, in complex 3, one side of the Ru2Cr-triangle has a μ3-BH ligand while the opposite side is bridged by a boryl ligand BH(CH2S2) in an unsymmetrical way (μ3–κ2:κ2:κ1) to the metal centers. Interestingly, when the similar reactions of arachno-1 were performed with heavier group-6 metal carbonyls [M(CO)5·THF] (M = Mo and W), it led to the formation of methanedithiolato bridged hetero-trimetallic chain complexes, [{Cp*Ru(CO)}2(μ-CO)2(μ3-CH2S2-κ2S′:κ2S′′){M(CO)2}] (5, M = Mo; 6, M = W) and sulfido-bridged hetero-trimetallic complexes [(Cp*Ru)2(μ-CO)3{M(CO)3}(μ3-S)] (7, M = Mo; 8, M = W), analogous to 4. In complexes 5 and 6, a Ru2M-chain is symmetrically bridged by a methanedithiolato ligand. On the other hand, in complexes 4, 7, and 8, a sulfido ligand coordinates to two ruthenium and one group-6 metal atoms in μ3-fashion. All the complexes have been characterized by 1H NMR, 13C NMR, UV-vis, IR spectroscopy, and mass spectrometry and their structural architectures have been unambiguously established by single crystal X-ray diffraction studies. In addition, theoretical investigations provided valuable insights into their electronic structures and bonding properties. [ABSTRACT FROM AUTHOR]

In an effort to establish B‐P coupling reactions without the use of phosphine‐borane dehydrocoupling agent, we have developed a new synthetic methodology employing group 8 metal σ‐borate complex [{κ3‐H,S,S′‐BH2L2}Ru{κ3‐H,H,S‐BH3L}] (L=NC5H4S), 1. Treatment of 1 with chlorodiphenyl phosphine (PPh2Cl) yielded 1,5‐P,S chelated Ru‐dihydridoborate species [PPh2H{κ3‐H,H,S‐BH(OH)L}Ru{κ2‐P,S‐(Ph2P)BH2L}], 2. The insertion of phosphine moiety (PPh2) by the cleavage of 3c–2e σ(Ru...H‐B) bonding interaction led to the formation of B‐P bond. The κ2‐P,S chelated six‐membered ring adopted a boat conformation in complex 2. The heterocycle is made of all different atoms, which is one of the rarest examples of heteroatomic ring systems. Theoretical outcomes demonstrated the electronic insight of B‐P coupling and stabilization through transition metal. In order to explore an alternate route of B‐P bond formation, we have further explored the reaction of 1 and Ru‐bis(dihydridoborate) complex, 5 with secondary phosphine oxide (SPO). Although, thermolysis of 1 with diphenylphosphine oxide yielded analogous σ‐borate complex 3, the similar reaction of 5 at room temperature led to the formation of novel phosphinous(III) acid incorporated Ru(σ‐borate)(dihydridoborate) complex, 6. In a similar fashion, the reaction of 5 with phosphite ligand generated Ru(σ‐borate)(dihydridoborate) complex, 7, which is analogous to 6. [ABSTRACT FROM AUTHOR]

The synthesis and structural characterization of a series of heterotrimetallic ruthenaborane clusters are reported. The photolytic reaction of nido-[(Cp*Ru)2(µ-H)2B3H7] (nido-1) (Cp* = 1,2,3,4,5-pentamethylcyclopentadienyl) with [M(CO)5·THF] (THF = tetrahydrofuran, M = Mo and W) yielded the heterotrimetallic clusters pileo-[(Cp*Ru)2{M(CO)3}(µ-CO)(µ-H)(µ3-BH)B2H5], M = Mo (2), W (3) and the known arachno ruthenaboranes [1,2-(Cp*Ru)(Cp*RuCO)(µ-H)B3H8] (I) and [{Cp*Ru(CO)}2B2H6] (II). In an attempt to synthesize the Mn-analog of 2 and 3, we performed a similar reaction of nido-1 with [Mn2(CO)10], which afforded the heterotrimetallic pileo-[(Cp*Ru){Mn(CO)3}(µ-H)2(µ3-BH)B2H5] (4) cluster along with the reported trimetallic hydrido(hydroborylene) species [(Cp*Ru)2{Mn(CO)3}(µ-H)(µ-CO)3(µ-BH)] (III). Ruthenaboranes 2, 3 and 4 are isoelectronic and isostructural. The geometry of 2–4 can be viewed as a triangle face-fused square pyramidal and tetrahedral geometry, in which the apical vertex of the tetrahedron is occupied by a µ3–BH moiety. All of these pileo ruthenaborane clusters obey Mingos' fusion formalism. Clusters 2–4 were characterized using multinuclear NMR, IR spectroscopies and electrospray ionization mass spectrometry. The single-crystal X-ray diffraction studies of clusters 2 and 4 confirmed their structures. Further, density functional theory (DFT) studies of these pileo ruthenaboranes have been carried out to investigate the nature of bonding, fusion and electronic structures. [ABSTRACT FROM AUTHOR]

Although Lipscomb predicted in 1977 that supra-icosahedral boron clusters would be viable, their synthesis has been impeded by the unavailability of appropriate synthetic methodologies. Herein, we report the first examples of the open 16-vertex oblato–hypho-titanaborane clusters [(Cp*Ti)2B14H17R] (1: R = H; 2: R = Me) having a non-Wadean 19-skeletal-electron-pair count. Interestingly, these clusters show a six-membered [Ti2B4] open face, which could lead to closo-19-vertex clusters. [ABSTRACT FROM AUTHOR]

Azametallacyclopropane‐containing base stabilized borane complexes of group 5 transition metals have been synthesized and their structural aspects have been described. Treatment of Cp* based Ta and Nb chlorides, Cp*TaCl4 and Cp*NbCl4 with [LiBH4 ⋅ THF] followed by addition of ligands, such as 2‐mercaptobenzothiazole, MBT, (C7H5NS2) and 2‐mercaptobenzoxazole, MBO (C7H5NSO) led to the formation of complexes [Cp*M‐[BHS(CH2ENC6H4)(C7H4NSE)] (1: M=Ta, E=S; 2; M=Nb, E=S; 3: M=Ta, E=O; 4; M=Nb, E=O, Cp*=pentamethyl‐η5‐cyclopentadienyl). By means of UV‐vis absorption spectra, the electronic properties of these complexes associated with central metal atoms and heteroatoms (S or O) have been evaluated. In contrast, treatment of Cp*TaCl4 with 2‐mercaptopyridine, MP, (C5H5NS) under the same reaction conditions yielded the agostic σ‐borane Ta complex, [Cp*Ta(H3BNC5H4) (C5H4NS)(η2‐S2)], 5. Unlike 1–4, where the metals interact with boron through bridging sulphur, 5 shows a notable σ‐B−H bond interaction with Ta. All spectroscopic data of 1–5 along with the X‐ray diffraction studies suggest complexes 2, 4, and 5 are base (amine) stabilized borane species. Computational studies based on Density Functional Theory (DFT) also supported this conclusion. [ABSTRACT FROM AUTHOR]

The reactivity of κ2‐N,S‐chelated ruthenium borate complexes, [Ru(PPh3)(κ2‐N,S‐(NC7H4S2)Ru{κ3‐H,S,S′‐H2B (NC7H4S2)2}] (1 a) and [Ru(PPh3)(κ2‐N,S‐(NC5H4S){κ3‐H,S,S′‐H2B(NC5H4S)2}] (1 b) with monoboranes have been explored. The prolonged room temperature reaction of [Ru(PPh3){κ2‐N,S‐(NC7H4S2)}{κ3‐H,S,S′‐H2B(NC7H4S2)2}], 1 a with an excess of [BH3 ⋅ THF] led to the formation of hydrogen‐rich complex, arachno‐[PPh3(κ2‐B3H8)Ru{κ3‐H,S,S′‐H2B(NC7H4S2)2] (2). In a similar fashion, the isomeric ruthenatetraborane complexes of [Ru(PPh3)(κ2‐N,S‐(B3H8){κ3‐H,S,S′‐H2B(NC5H4S)2}], 4 and 5 were isolated from the room temperature reaction of 1 b with [BH3 ⋅ THF]. In complex 2, the borate ligand, [H2B(NC5H4S)2] and the PPh3 occupy the endo and exo sites of the butterfly‐shaped RuB3 core, respectively. In contrast, the borate unit [H2B(NC5H4S)2] in 4 sits on the exo position of the butterfly core, while the phosphine ligand occupies the endo site. Multinuclear spectroscopic analyses were done to characterize all new complexes and the structures were further confirmed by single‐crystal X‐ray diffraction analysis. Density functional theory (DFT) calculations were performed to probe into the bonding modes of these complexes. [ABSTRACT FROM AUTHOR]

Reports on the synthesis and molecular structural analysis of bipyramidal 2,3-Cl[sub 2]-1,8-{Cp*Re}[sub 2]B[sub 6]H[sub 4][{Cp*Re}[sub 2]{mu-eta[sub 6]:eta[sub 6]-1,2-B[sub 6]H[sub 4]Cl[sub 2]}, Cp* = eta[sup 5]-C[sub 5]Me[sub 5]]. Difference between metal and bridging-ring orbital energies; Effect of methyl groups of Cp* ligand on antipodal BH hydrogens.

The structure and bonding of two novel tungstaboranes which were synthesized using diverse synthetic methods are described. (i) The room-temperature photolysis of [Cp*W(CO)3Me] with [BH3·SMe2] led to the isolation of the hydrogen-rich tungstaborane [Cp*W(CO)2B3H8] (1). Its geometry consists of an arachno butterfly core similar to tetraborane(10) and obeys the Wade-Mingos electron counting rules (n vertices, n + 3 skeletal electron pairs (seps)). (ii) Further, the tungstaborane [(Cp*W)3(μ-H)2(μ3-H)(μ-CO)2B4H4] (4) was isolated by thermolysis reaction of a tungsten intermediate, obtained by low temperature reaction of [Cp*WCl4] and [LiBH4·THF] with [Cr(CO)5·THF]. Compound 4 which seems to have formed by replacement of a BH unit in [(Cp*W)2B5H9] by the isoelectronic fragment {Cp*W(CO)2}, adopts an oblato-nido hexagonal-bipyramidal core (n vertices, n–1 seps). Both compounds were characterized using multinuclear NMR, IR spectroscopy, mass spectrometry as well as single crystal X-ray diffraction analysis. In addition, density functional theory (DFT) calculations were performed in order to elucidate their bonding and electronic structures. [ABSTRACT FROM AUTHOR]

Synthesis, bonding and chemistry of mono‐ and bimetallic complexes supported by chelating thiolato ligands have been established. Treatment of [Cp*VCl2]3 (1) with [LiBH4 ⋅ THF] followed by the addition of ethane‐1,2‐dithiol led to the formation of an EPR active bimetallic vanadium thiolato complex [(Cp*V){μ‐(SCH2CH2S)‐κ2S,S′)2{V(SCH2CH2S‐SH)}] (2). In complex 2, two ethane‐1,2‐dithiolato ligands are symmetrically coordinated to two vanadium atoms through μ‐S atoms. Interestingly, when similar reactions were carried out with heavier group 5 metal precursors, such as [Cp*NbCl4] (3 a), it afforded monometallic thiolato complex [Cp*Nb(SCH2CH2S)(SCH2CH2S−CH2S)] (4 a). On the other hand, the Ta‐analogue [Cp*TaCl4] (3 b) yielded thiolato species [Cp*Ta(SCH2CH2S)(SCH2CH2S−CH2S)] (4 b) and [Cp*Ta(SCH2CH2S) (SCH2CH2S−S)] (5). In complexes 4 a and 4 b, one ethane‐1,2‐dithiolato and one trithiolato ligand are coordinated to Nb and Ta centers, respectively. Whereas, in complex 5, one ethane‐1,2‐dithiolato and one 2‐disulfanylethanethiolato is coordinated to the Ta center. Moreover, the photolytic reaction of 5 with [Mo(CO)5 ⋅ THF] yielded heterobimetallic thiolato complex [(Cp*Ta){μ‐(SCH2CH2S)‐κ2S,S′}{μ‐(SCH2CH2S−CH2(CH3)S)κ2S′′ : κ1S‐′′′′ : κ1S′′′′′}{Mo(CO)3}] (6). All the complexes have been characterized by multinuclear NMR spectroscopy and single crystal X‐ray diffraction studies. Further, computational analyses were performed to provide an insight into the bonding of these complexes. [ABSTRACT FROM AUTHOR]

The trans‐mer‐[(κ2‐N,S‐NS2C7H4)PR3Ru{κ3‐H,S,S′‐H2B (NS2C7H4)2}], (trans‐mer‐1 a: R=Cy; trans‐mer‐1 b: R=Ph) complexes are kinetically controlled products that upon thermolysis led to the formation of cis‐mer‐[(κ2‐N,S‐NS2C7H4)PR3Ru{κ3‐H,S,S′‐H2B(NS2C7H4)2}], (cis‐mer‐2 a: R=Cy; cis‐mer‐2 b: R=Ph) and cis‐fac‐[(κ2‐N,S‐NS2C7H4)PR3Ru{κ3‐H,S,S′‐H2B(NS2C7H4)2}], (cis‐fac‐3 a: R=Cy; cis‐fac‐3 b: R=Ph) along with complex cis‐[(κ2‐N,S‐NS2C7H4)2Ru(PPh3)2], (cis‐4). One of the main intentions of this study was to examine the flexibility of the borate and hemilabile N,S‐chelating mercapto‐benzothiazole ligands in adapting different spatial arrangements around metal center. Multinuclear spectroscopic analyses have been done to characterize all new complexes and the structures were further confirmed by single‐crystal X‐ray diffraction analysis. Further, Density Functional Theory (DFT) calculations were performed to provide an insight into the bonding of the complexes. [ABSTRACT FROM AUTHOR]

In an effort to synthesize metallaheteroborane clusters of higher nuclearity, the reactivity of metallaheteroboranes, nido-[(Cp*M)2B6S2H4(CS3)] (Cp* = C5Me5) (1: M = Co; 2: M = Rh) with various metal carbonyls have been investigated. Photolysis of nido-1 and nido-2 with group 6 metal carbonyls, M'(CO)5.THF (M' = Mo or W) were performed that led to the formation of a series of adducts [(Cp*M)2B6S2H4(CS3){M'(CO)5}] (3: M = Co, M' = Mo; 4: M = Co, M' = W; 5: M = Rh, M' = Mo; 6: M = Rh, M' = W) instead of cluster expansion reactions. In these adducts, the S atom of C=S group of di(thioboralane)thione {B2CS3} moiety is coordinated to M'(CO)5 (M = Mo or W) in η1-fashion. On the other hand, thermolysis of nido-1 with Ru3(CO)12 yielded one fused metallaheteroborane cluster [{Ru(CO)3}3S{Ru(CO)}{Ru(CO)2}Co2B6SH4(CH2S2){Ru(CO)3}2S], 7. This 20-vertex-fused cluster is composed of two tetrahedral {Ru3S} and {Ru2B2}, a flat butterfly {Ru3S} and one octadecahedron {Co2RuB7S} core with one missing vertex, coordinated to {Ru2SCH2S2} through two boron and one ruthenium atom. On the other hand, the room temperature reaction of nido-2 with Co2(CO)8 produced one 19-vertex fused metallaheteroborane cluster [(Cp*Rh)2B6H4S4{Co(CO)}2{Co(CO)2}2(μ-CO)S{Co(CO)3}2], 8. Cluster 8 contains one nido-decaborane {Rh2B6S2}, one butterfly {Co2S2} and one bicapped square pyramidal {Co6S} unit that exhibits an intercluster fusion with two sulfur atoms in common. Clusters 3–6 have been characterized by multinuclear NMR and IR spectroscopy, mass spectrometry and structurally determined by XRD analyses. Furthermore, the DFT calculations have been carried out to gain insight into electronic, structural and bonding patterns of the synthesized clusters. [ABSTRACT FROM AUTHOR]

Thermolysis of [Ru 3 (CO) 12 ] with an in-situ generated intermediate, obtained from the reaction of [Cp*MoCl 4 ] and [LiBH 4 .THF], led to the formation of [{Cp*Mo(CO) 2 }(μ 4 -B){Ru(CO) 3 } 3 (μ-H) 2 ], 2 and [{Cp*Mo(CO) 2 } 2 (μ 4 -B){Ru(CO) 3 } 2 (μ-H)], 3 (Cp* = η 5 -C 5 Me 5 ). In a similar fashion, when [Ru 3 (CO) 12 ] was thermalized with [(Cp*Rh) 2 B 2 H 6 ], obtained from a fast metathesis reaction of [Cp*RhCl 2 ] 2 , 4 and [LiBH 4 .THF], yielded a novel heterometallic boride cluster [(Cp*Rh)(μ 6 -B){Ru(CO) 3 } 4 {RuH(CO) 2 }], 5 . Both compounds 2 and 3 can be described as 50-cluster valence electron (cve) hetero-metallic boride clusters, in which the boron atom is in semi-interstitial position of a M 4 -butterfly geometry. Compound 5 contains 86 cluster valence-electrons, in which the boron atom is inside of an octahedral hole composed of one rhodium and five ruthenium atoms. Computational studies on the ground of density functional theory has been undertaken to analyze the bonding of 2 , 3 and 5 . The structural optimization yields geometries in agreement with the structure determinations and computed 11 B chemical shifts accurately reflect the observed shifts. The molecular orbital analysis of them shows that all the valence orbitals of boron have been participated in bonding and therefore provides the “encapsulation” picture of the boron atom. All the compounds have been characterized by IR and 1 H, 11 B, and 13 C NMR spectroscopy, and the geometries of the structures were unequivocally established by crystallographic analyses of compounds 2 , 3 and 5 . [ABSTRACT FROM AUTHOR]

In an attempt to isolate boron-containing tri-niobium polychalcogenide species, we have carried out prolonged thermolysis reactions of [Cp*NbCl4] (Cp* = ɳ5-C5Me5) with four equivalents of Li[BH2E3] (E = Se or S). In the case of the heavier chalcogen (Se), the reaction led to the isolation of the tri-niobium cubane-like cluster [(NbCp*)3(μ3-Se)3(BH)(μ-Se)3] (1) and the homocubane-like cluster [(NbCp*)3(μ3-Se)3(μ-Se)3(BH)(μ-Se)] (2). Interestingly, the tri-niobium framework of 1 stabilizes a selenaborate {Se3BH}− ligand. A selenium atom is further introduced between boron and one of the selenium atoms of 1 to yield cluster 2. On the other hand, the reaction with the sulfur-containing borate adduct [LiBH2S3] afforded the trimetallic clusters [(NbCp*)3(μ-S)4{μ-S2(BH)}] (3) and [(NbCp*)3(μ-S)4{μ-S2(S)}] (4). Both clusters 3 and 4 have an Nb3S6 core, which further stabilizes {BH} and mono-sulfur units, respectively, through bi-chalcogen coordination. All of these species were characterized by 11B{1H}, 1H, and 13C{1H} NMR spectroscopy, mass spectrometry, infrared (IR) spectroscopy, and single-crystal X-ray crystallography. Moreover, theoretical investigations revealed that the triangular Nb3 framework is aromatic in nature and plays a vital role in the stabilization of the borate, borane, and chalcogen units. [ABSTRACT FROM AUTHOR]

Isolation of planar [B6H6] is a long‐awaited goal in boron chemistry. Several attempts in the past to stabilize [B6H6] were unsuccessful due to the domination of polyhedral geometries. Herein, we report the synthesis of a triple‐decker sandwich complex of titanium [(Cp*Ti)2(μ‐η6 : η6‐B6H6)(μ‐H)6] (1), which features the first‐ever experimentally achieved nearly planar six‐membered [B6H6] ring, albeit within a [B6H12] borate. The small deviation from planarity is a direct consequence of the predicted structural pattern of the middle ring in 24 Valence Electron Count (VEC) triple‐decker complexes. The large ring size of [B6H6] in 1 brings the metal–metal distance into the bonding range. However, significant electron delocalization from the M−M bonding orbital to the bridging hydrogen and B−B skeleton in the middle decreases its bond strength. [ABSTRACT FROM AUTHOR]

Isolation of planar [B6H6] is a long‐awaited goal in boron chemistry. Several attempts in the past to stabilize [B6H6] were unsuccessful due to the domination of polyhedral geometries. Herein, we report the synthesis of a triple‐decker sandwich complex of titanium [(Cp*Ti)2(μ‐η6 : η6‐B6H6)(μ‐H)6] (1), which features the first‐ever experimentally achieved nearly planar six‐membered [B6H6] ring, albeit within a [B6H12] borate. The small deviation from planarity is a direct consequence of the predicted structural pattern of the middle ring in 24 Valence Electron Count (VEC) triple‐decker complexes. The large ring size of [B6H6] in 1 brings the metal–metal distance into the bonding range. However, significant electron delocalization from the M−M bonding orbital to the bridging hydrogen and B−B skeleton in the middle decreases its bond strength. [ABSTRACT FROM AUTHOR]

• Synthesis and structural characterization of tri-niobium cluster with a trithiaborate ligand. • Synthesis and structural characterization of three nido -ruthenium clusters. • Theoretical investigations have been performed to understand the electronic structure and bonding scenario in these clusters. In an effort to synthesize niobaheteroboranes and ruthenaheteroboranes, two different synthetic methods are developed. The reactions of [Cp*NbCl 4 ] (1) with chalcogenaborate ligands [LiBH 2 E 3 ] (E = S , Se) were carried out under reflux conditions. The reaction with sulfur yielded a triniobium polysulfide cluster [(Cp*Nb) 3 (μ 3 -S) 3 {B(OCH 3)}(μ -S) 3 ] (2) in which a trithiaborate ligand [S 3 B(OCH 3)]− is coordinated to Nb 3 framework in a cubane-type geometry. While the reaction with selenium generated a diniobium polyselenide cluster [(Cp*NbCl) 2 (μ -Se 2 -κ 1Se: κ 2Se') 2 (μ -O)] (3) in which two diselenide ligands {[Se 2 ]2−} are coordinated with both the metal centres in an unsymmetrical κ 1: κ 2 fashion. On the other hand, efforts were directed towards expliciting the coordinative sulfur centres of a preformed arachno ‑ruthenaborane [(Cp*Ru) 2 (B 3 H 8)(CS 2 H)] (arachno ‑ 4) , by carrying out the pyrolysis of arachno ‑ 4 with excess [BH 3 ⋅THF]. The reaction led to the formation of sulfido stabilized pileo cluster nido ‑ruthenathiaborane [2,3-(Cp*Ru) 2 (μ -H)(B 3 H 6)S] (5) , nido ‑ruthenaborane [2,3-(Cp*Ru) 2 (μ -H)(B 4 H 5 Me)] (6) and thiomethyl bridged nido ‑ruthenaborane [2,3-(Cp*Ru) 2 (μ -SMe)(B 3 H 6)] (7). One of the key features of complex 5 is the presence of an unusual pentacoordinated sulfido ligand(μ 5 -S). All the complexes have been characterized by multinuclear NMR, mass spectrometry and their structural architectures have been unambiguously established by single-crystal X-ray diffraction studies. In addition, theoretical investigations provided valuable insights into the electronic structures and bonding of these clusters. [ABSTRACT FROM AUTHOR]

In an objective to synthesize metallaheteroboranes containing heavier chalcogen atoms, we performed the reaction of dimetallaborane analogues of pentaborane(9) with various chalcogen sources. As a result, the thermolysis of nido -[1,2-(Cp*RuH) 2 B 3 H 7 ], 1 (Cp* = η 5 -C 5 Me 5 ) with mixture of S and Se powder was carried out, that led to the isolation of half sandwich dimetallaheteroborane arachno -[(1,2-Cp*Ru) 2 B 2 H 6 S 2 ], 2 . On the other hand, the reaction of nido - 1 with diorganyldichalcogenide ligands, [Ph 2 E 2 ] afforded chalcogen bridged half sandwich complexes [(2,3-Cp*Ru) 2 B 3 H 6 (μ-η 1 -EPh)], 4a-c ( 4a : E = S; 4b : E = Se and 4c : E = Te). Compound 2 can be derived from a closo- snub disphenoid by removing a 5-connect vertex followed by the removal of a 3-connect vertex. Compound 4a – c can be described as nido -square pyramidal structures, isoelectronic and isostructural with nido - 1 . All the compounds have been characterized by mass spectrometry, 1 H, 11 B and 13 C spectroscopy. Further, the geometry of compounds 2 , 3 , 4b and 4c were unequivocally established by crystallographic analysis. [ABSTRACT FROM AUTHOR]

Building on our earlier results, the condensation of rhodium polychlorides with borane reagents (LiBH 4 ·thf, BH 3 ·thf, BHCl 2 ·SMe 2 etc.), we continue to explore the chemistry of the same system with metal carbonyl compounds. As a result, the reaction of [(Cp*Rh) 2 B 2 H 6 ], generated from fast metathesis of [Cp*RhCl 2 ] 2 and LiBH 4 , with heavier group 8 metal carbonyl compounds, yielded [(Cp*Rh) 2 B 4 H 4 Rh{Cp*RhB 3 H 8 }], 1 , [(Cp*Rh)B 3 H 7 {Ru(CO) 2 }(Cp*RhCO) 2 ], 2 [(Cp*Rh) 2 B 3 H 3 {Ru(CO) 3 } 2 ], 3 and [(Cp*Rh) 2 {Os 4 (CO) 12 }(B)H], 4 . Further, these reaction also generated two mixed-metal tetrahedral hydrido clusters [(Cp*Rh){Os(CO) 3 } 3 (μ-H) 4 ], 5 and [(Cp*Rh) 2 {Os(CO) 3 } 2 (μ-CO) (μ-H) 2 ], 6 as minor products. Compound 1 is an octahedra and a square pyramid fused cluster, whereas for 2 a square pyramid and a triangle are fused through a vertex. Both 1 and 2 follow Mingos's formalism for fused clusters. Cluster 4 is an interstitial boride composed of one boron, two rhodium and four osmium atoms. Based on its compositions, compound 4 is a rare example of heteronuclear borides. All the compounds have been characterized by IR, 1 H, 11 B, 13 C NMR spectroscopy in solution and the solid state structures were established by crystallographic analysis of 1 – 5 . [ABSTRACT FROM AUTHOR]

We describe the design, synthesis, and 'stimuli-responsive' study of ferrocene-linked Fréchet-type [poly(aryl ether)]-dendron-based organometallic gels, in which the ferrocene moiety is attached to the dendron framework through an acyl hydrazone linkage. The low-molecular-weight gelators (LMWGs) form robust gels in both polar and non-polar solvent/solvent mixtures. The organometallic gels undergo stimuli-responsive behavior through 1) thermal, 2) chemical, and 3) electrochemical methods. Among them, conditions 1 and 3 lead to seamlessly reversible with repeated cycles of identical efficiency. Results indicate that the flexible nature of the poly(aryl ether) dendron framework plays a key role in retaining the reversible electrochemical behavior of ferrocene moiety in the LMWGs. Further, the organometallic gelators have exhibited unique selectivity towards Pb2+ ions (detection limit ≈10−8 M). The metal ion-sensing results in a gel-sol phase transition associated with a color change visible to the naked eye. Most importantly, decomplexing the metal ion from the system leads to the regeneration of the initial gel morphology, indicating the restoring ability of the organometallic gel. The metal-ligand binding nature has been analyzed by using 1H NMR spectroscopy, mass spectrometry, and DFT calculations. [ABSTRACT FROM AUTHOR]

• A novel dioxadivanadaborane cluster consisting two μ 3 O units and two terminal persubstituted divanadaborane clusters have been synthesised. • The electronic properties of these complexes has been described. • The experimental results were complemented and rationalized by means of DFT studies. Thermolysis of an in situ generated intermediate which was formed by the reaction of [Cp*VCl 2 ] 3 (Cp* = η5-C 5 Me 5) and LiBH 4. THF with excess of BH 3. THF (THF = tetrahydrofuran) led to the formation of a novel dioxadivandaborane, [(Cp*V) 2 (OBH 3) 2 ], 2 along with divanadaborane [(Cp*V) 2 (B 2 H 6) 2 ], 1. In an attempt to functionalize the terminal B-H vertices by different aryl chalcogenides, 1 was thermolyzed with dinaphthyl diselenide, [Nap 2 Se 2 ] and dimesityl diselenide, [Mes 2 Se 2 ], leading to the formation of persubstituted divanadaboranes, [(Cp*V) 2 {B 2 H 4 (SeNap 2)} 2 ], 3 and [(Cp*V) 2 {B 2 H 4 (SeMes 2)} 2 ], 7. All these compounds were fully characterized with the help of mass spectrometry and 1H, 11B{1H} and 13C{1H} NMR spectroscopy and the dioxadivandaborane species 2 was additionally characterized by X-ray diffraction analysis. Density Functional Theory (DFT) calculations show geometries in agreement with the structural determinations. The reduction in the HOMO-LUMO gap due to the introduction of chalcogenide ligands in 2, 3 and 7 is in respectable agreement with their UV–Vis absorption spectra. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Metallaheteroborane clusters with group 16 elements are reviewed elaborately. • Syntheses, structures and bonding of metallaheteroborane clusters are discussed. • Various reactions of these clusters reported by others and us are summarized. Metallaheteroborane clusters containing group-16 elements as cluster constituents were initially of interest solely for the synthesis of high-nuclearity clusters. However, owing to recent developments in their chemistry towards hydrogenation and isomerization of olefins, nido to closo dehydrogenation of clusters, the development of new and improved routes for the synthesis of novel metallaheteroborane clusters have become of interest. In recent years, the chemistry of metallaheteroboranes, with chalcogen(s) as the heteroatom(s), has noted significant growth both in terms of synthetic methodology as well as the advent of unique frameworks ranging from polyhedral cages and macropolyhedral clusters to triple-decker sandwich complexes and hydrocarbon-mimics like cubanes and homocubanes. This review provides a brief account of the syntheses of diverse structural motifs adopted by the metallachalcogenaborane clusters; their electron counts along with latest advances in their chemistry. [ABSTRACT FROM AUTHOR]

The chemistry of the Cp* based κ2-N,S-chelated ruthenium complex, [Cp*RuPPh3(κ2-N,S-(NC7H4S2)], 1 with different boranes has been explored. The room temperature reaction of 1 with BH3·THF and bulky boranes, such as MesBH2 and H2BArF, led to the formation of different dihydridoborate complexes, [{κ3-S,H,H-(NBH2R)(S2H4C7)}RuCp*], 2–4 (2: R = H, 3: R = Mes, and 4: R = ArF; Mes = 2,4,6-trimethylphenyl, and ArF = 3,5-bistrifluoromethyl-benzene). In contrast, the Cp* based κ2-N,S-chelated molybdenum complex, [Cp*Mo(CO)2{κ2-N,S-(NC7H4S2)}], 5, yielded the agostic borate species, [Cp*Mo(CO)2{κ2-S,H-(NBH2R) (NC7H4S2)}], 6 and 7 (6: R = Mes and 7: R = ArF) at elevated temperatures. [ABSTRACT FROM AUTHOR]

Treatment of [Cp*RuCl2]2, 1, [(COD)IrCl]2, 2 or [(p‐cymene)RuCl2]2,3 (Cp*=η5‐C5Me5, COD= 1,5‐cyclooctadiene and p‐cymene=η6‐iPrC6H4Me) with heterocyclic borate ligands [Na[(H3B)L], L1 and L2 (L1: L=amt, L2: L=mp; amt=2‐amino‐5‐mercapto‐1,3,4‐thiadiazole, mp=2‐mercaptopyridine) led to the formation of borate complexes having uncommon coordination. For example, complexes 1 and 2 on reaction with L1 and L2 afforded dihydridoborate species [LAM(μ‐H)2BHL] 4–6 (4: LA=Cp*, M=Ru, L=amt; 5: LA=Cp*, M=Ru, L=mp; 6: LA=COD, M=Ir, L=mp). On the other hand, treatment of 3 with L2 yielded cis‐ and trans‐bis(dihydridoborate) species, [Ru{(μ‐H)2BH(mp)}2], cis‐7 and trans‐7. The isolation and structural characterization of fac‐ and mer‐[Ru{(μ‐H)2BH(mp)}{(μ‐H)BH(mp)2}], 8 from the same reaction offered an insight into the behaviour of these dihydridoborate species in solution. Fascinatingly, despite having reduced natural charges on Ru centres both at cis‐and trans‐7, they underwent hydroboration reaction with alkynes that yielded both Markovnikov and anti‐Markovnikov addition products, 10 a–d. [ABSTRACT FROM AUTHOR]

Reactivity of borate ligand derived from CS 2 with κ2- N,S -chelated ruthenium borate complexes, [Ph 3 P(κ2- N,S -L)Ru{κ3- H,S,S ′-H 2 B(L) 2 }], (L = C 7 H 4 NS 2 , C 5 H 4 NS) has been demonstrated that led to the formation of ruthenium dithioformate and trithia-borinane complexes. [Display omitted] The reactivity of κ2 - N,S -chelated ruthenium borate complexes, [Ph 3 P(κ2 - N,S -L)Ru{ κ3 - H,S,S ′-H 2 B(L) 2 }], (L = C 5 H 4 NS, C 7 H 4 NS 2) 1 and 3 with borate ligand derived from CS 2 has been investigated. The thermolysis of [Ph 3 P(κ2 - N,S -C 5 H 4 NS)Ru{ κ3 - H,S,S ′-H 2 B(C 5 H 4 NS) 2 }], 1 with Na[BH 3 (SCHS)] led to the formation of ruthenium dithioformate complexes, [PPh 3 (κ3 - H,S,S ′-H 2 B(C 5 H 4 NS)}Ru{(η 2-SCHS)}], trans- 2 and [PPh 3 (κ3 - H,S,S ′-H 2 B(C 5 H 4 NS)}Ru{(η 2-SCHS)}], cis- 2. Further, to study the reactivity of the same borate ligand derived from CS 2 , we have performed the reaction of [Ph 3 P(κ2 - N,S -C 7 H 4 NS 2)Ru{ κ3 - H,S,S ′-H 2 B(C 7 H 4 NS 2) 2 }], 3 with Na[BH 3 (SCHS)] that yielded ruthenium dithioformate, [Ph 3 P(κ2 - N,S -C 5 H 4 NS)Ru{(η 2-SCHS)}], cis- 4 and 1,3,5-trithia-2-borinane, [PPh 3 Ru{ κ3 - H,S,S′ -H 2 B(NC 7 H 4 S 2) 2 }]{(SCH 2) 2 SBH}], 5 complexes. All these studies show that cis- 4 is analogous to trans- 2 and cis- 2. The solid-state X-ray structure of 5 shows that the ruthenium center is stabilized by diborate, phosphine and six-membered ruthenacycle [RuSBNCS] ring that is fused with a {C 2 S 3 B} ring. The synthesized complexes have been thoroughly characterized by various spectroscopic techniques and single-crystal X-ray diffraction analysis of trans- 2 , cis- 2 and 5. Density functional theory (DFT) calculations further provided an insight into the electronic structures of the complexes. [ABSTRACT FROM AUTHOR]

A series of triborane and tetraborane analogues have been isolated and structurally characterized utilizing chalcogenatoborate ligands Li[BH3(EPh)] (E=S or Se). Thermolysis of [Cp*TaCl4] in the presence of Li[BH3(SPh)] afforded bimetallic tantallaheteroborane [(Cp*Ta)2(μ‐η3:η3‐B2H4S)(μ‐η2:η2‐SBH3)] (1) and hexasulfido trimetallic complex [(Cp*Ta)3(μ‐S)4(μ‐SPh)2] (2). Compound 1 is a fused ditantallaheteroborane, in which both di‐ and triborane analogues are stabilized by two tantalum atoms. In an attempt to synthesize the selenium analogues of 1 and 2, room‐temperature reaction of [Cp*TaCl4] with Li[BH3(SePh)] was carried out, which afforded bimetallic tantallaheteroborane [(Cp*Ta)2{μ‐η3:η3‐B3H6(SePh)}{μ‐SePh}2] (3), monometallic tantallaheteroboranes [Cp*Ta(SePh)2{B4H8‐n(SePh)n}] (4: n=0, 5: n=1), and trimetallic species [(Cp*Ta)3(μ‐Se)4{μ‐Se2(Se)}] (6). Compound 3 is the rarest example of triborane analogue {B3H6(SePh)} in the coordination sphere of two tantalum atoms. Whereas compounds 4 and 5 are examples of unsaturated metallaheteroboranes, in which the tetraborane analogues are stabilized in the coordination sphere of tantalum. One of the unique features of 3 and 5 is the presence of terminal B‐SePh. Compound 6 has similar Ta3Se6 trisbutterfly core as that of 2 with additional bridging selenide unit. All the compounds have been characterized by NMR spectroscopy, mass spectrometry, IR spectroscopy and single‐crystal X‐ray diffraction studies. [ABSTRACT FROM AUTHOR]

Despite the synthesis and structural characterization of closo‐hydroborate dianions, [BnHn]2− (n=6–12) more than 50 years ago, some ambiguity remains about the structure of [B8H8]2−. Although the solid‐state structure of [B8H8]2− was established by single‐crystal X‐ray studies in 1969, fast rearrangements in solution at accessible temperatures prevented its detailed characterization. We therefore stabilized a derivative of [B8H8]2− by using Cp2MBH3 and structurally characterized two new octaborane analogues, [(Cp2MBH3)2B8H6] (Cp=η5‐C5H5; M=Zr (1‐Zr) and Hf (1‐Hf)), so that the dynamics of the B8 skeleton were arrested. The solid‐state structures of both 1‐Zr and 1‐Hf comprise a dodecahedron core protected by {Cp2MBH3} moieties on both sides of the cluster. Spectroscopic characterization (11B NMR) validates the intactness of the B8 dodecahedron core in solution as well. Theoretical calculations establish that the two exo‐{Cp2MBH3} fragments provide structural and electronic structural stability to the B8 core and its intact dodecahedral dianionic nature. Furthermore, we propose isodesmic equations for the formation of higher analogues of the Bn core (n>8) guarded by different group 4 transition metals. Our analysis suggests that, as we move to higher polyhedra (n>10), the formation becomes unfavourable irrespective of metal. [ABSTRACT FROM AUTHOR]

The synthesis, structure and electronic properties of tetraruthenium dichalcogenide complexes displaying the exclusive coordination mode of dichalcogenide ligands have been discussed. The reactions of Li[BH2E3] (E = S or Se) with [ClRu(μ-Cl)(p-cymene)]2 (p-cymene = η6-{p-C6H4(iPr)Me}) at room temperature yielded tetrametallic dichalcogenide complexes [{Ru2Cl2(p-cymene)2}2(μ4,η2-E2)], 1–2 (E = S (1) and Se (2)). The solid-state X-ray structure of 1 shows that two {(p-cymene)RuCl}2 moieties are bridged by a S–S bond. In addition to 2, the reaction of Li[BH2Se3] with [ClRu(μ-Cl)(p-cymene)]2 also yielded a mononuclear tris-homocubane analogue [Ru(p-cymene){Se7(BH)3}] (3) which is an analogue of 1,3,3-tris-homocubane and possesses D3 symmetry. In order to isolate the Cp* analogue of 1, the reaction of [Cp*Ru(μ-Cl)Cl]2 with Li[BH2S3] was carried out, which led to the formation of bis/tris-homocubane derivatives [(Cp*Ru)2{μ-Sn(BH)2}] (n = 7 (4) and 6 (5)) along with the formation of ruthenium disulfide complexes [(RuCp*)2(μ,η2:η2-S2)(μ,η1:η1-S2)] and [(RuCp*)2(μ-SBHS-κ1B:κ2S:κ2S)(μ,η1:η1-S2)]. Complexes 1–5 have been characterized by multi-nuclear NMR, IR, UV-vis spectroscopy, and mass spectrometry and their molecular formulations (except 2) have been determined by single crystal X-ray crystallography. Furthermore, DFT calculations were performed that rationalize the stabilization of the dichalcogenide units (E22−) by the tetrametallic systems in 1–2. [ABSTRACT FROM AUTHOR]

Density functional theory (DFT) calculations were used to probe the reaction of the diruthenaborane nido-[1,2-(Cp*RuH)BH] (Cp* = η-CMe), ( 1) with MeC ≡ CMe to form the major product nido-[1,2-(Cp*Ru)( μ-H)( μ-BH)-4,5-Me-4,5-CBH] ( 2) along with minor product nido-(Cp*Ru)-4,5-Me-4,5-CBH ( 3). The structural features of the other related diruthenacarboranes, nido-(Cp*Ru)-4,5-Me-4,5-CBH ( 4) and closo-1,2-(Cp*RuH)-4,5-Me-4,5-CBH ( 5), were also studied. Since metallaheteroboranes with p-block group-14 elements are rare, we extend our DFT studies to explore the reaction of 1 with heavier group-14 alkyne analogs, RE ≡ ER (E = Si, Ge, and Sn; R = alkyl or aryl groups). The geometrical and electronic structures of the products nido-[1,2-(Cp*Ru)( μ-H)( μ-BH)-4,5-Me-4,5-EBH] (E = Si ( 6), Ge ( 7), Sn ( 8)) are described and compared with the ruthenacarborane analog, nido-[1,2-(Cp*Ru)( μ-H)( μ-BH)-4,5-Me-4,5-CBH] species, 2. The computed energetics and the geometries support the feasibility of the reaction and the stability of the products. NBO analysis was performed to delve further into the nature of the bonding in this kind of clusters. [ABSTRACT FROM AUTHOR]

Abstract: The synthesis, electrochemical, optical and cation-sensing properties of two triazole tethered ferrocene derivatives, C25H25ON3Fe2, 2 and C40H40O2N6Fe3, 3 are presented. The solid state structure of compound 2 has been established by X-ray diffraction analysis which reveals that the unit cell of molecule 2 consists of 3-D helical chain formed via CH⋯N interaction and π⋯π stacking. The complexation properties of the receptors can be inferred either from redox shift or visual output response (colorimetric) for Hg2+ and Cu2+ cations. The common structural feature of these ligands is the presence of other ferrocene moiety as redox unit. Interestingly, the redox and colorimetric responses, towards Hg2+ are preserved in the presence of water (CH3CN/H2O, 2/8), which can be used for the selective colorimetric detection of Hg2+ in aqueous environment over other competitor cations. The changes in the absorption spectra are accompanied by the appearance of a new low energy (LE) peak at ca. 626nm for 2 and 632nm for 3 (2: ε =669M−1 cm−1 and 3: ε =1150M−1 cm−1), due to the change in color from yellow to purple for Hg2+ cations in CH3CN/H2O (2:8). [Copyright &y& Elsevier]

Abstract: A triazole tethered triferrocene receptor, C40H40O2N6Fe3 3, has been synthesized from the reaction of mono-alkynyl substituted ferrocene, 1 and 1,1′-bis-(azidomethyl)ferrocene, 2. Consequently the cation and anion sensing properties of 3 have been examined. The receptor 3 was found to be highly selective electrochemical , optical and chromogenic chemosensor for Hg2+ ion in aqueous environment. The substantial changes in its absorption spectra are accompanied by the appearance of a new low-energy peak at 631 nm (ɛ = 3400 M−1 cm−1). This is also accompanied by a strong color change from yellow to purple, that allows a prospective for the “naked eye” detection of Hg2+ ion over other competitor cations such as Pb2+, Cd2+, Zn2+, etc. In addition, among various anions, 3 shows a distinct electrochemical recognition of dihydrogen phosphate anion by its multiple H-bonding (C–H⋯O), which is supported by electrochemical (large cathodic shift ΔE 1/2 = −175 mV) and 1H NMR titration results. [Copyright &y& Elsevier]

The electrochemical, optical, and metal cation sensing properties of the triazole-tethered ferrocene-anthracene conjugates, C48H40FeO2N6 (3) and C52H40FeO2N6 (4), and the ferrocene-pyrene conjugates, C29H25FeON3 (5) and C31H25FeON3 (6), have been documented. All the compounds 3-6 behave as very selective redox, chromogenic, and "turn-on" fluorescent probes for Pb2+ ion in an aqueous environment (CH3CN/H2O, 2/8). The significant changes in their absorption spectra are accompanied by a strong color change from yellow to greenish blue, which allows a prospective use for the "naked eye" detection of Pb2+ ion over other competitor cations such as Hg2+ and Cd2+. These chemosensors present immense brightness and fluorescence enhancement (chelation-enhanced fluorescence = 85 for 3 and 92 for 4) following Pb2+ coordination within the limit of detection at 2 ppb. Interestingly, their fluorescence, redox, and colorimetric responses are preserved in presence of water, which can be used for the selective colorimetric detection of Pb2+ ion in aqueous environment over Hg2+ and Cd2+ cations. All the compounds have been characterized by ¹H, 13C NMR spectroscopy and electrospray ionization mass spectrometry (ESI-MS) spectrometric analysis, and the solid-state structures of 5 and 6 have been unequivocally established by X-ray diffraction analysis. [ABSTRACT FROM AUTHOR]

Heterometallic cubane-type clusters were synthesized from the reaction of group 6 and 8 metallaboranes using transition-metal carbonyl compounds. Structural and spectroscopic study revealed the existence of novel "capped-cubane" geometry. In addition, the crystal structure of these clusters distinctly confirms the presence of boride unit as one of the vertices. These clusters possess 60 cluster valence electrons (cve) and six metal--metal bonds. A plausible pathway for the formation of ruthenium-capped cubane has been described. [ABSTRACT FROM AUTHOR]

Two Cu-specific colorimetric sensors, based on ferrocene-carbohydrate bioconjugates, 2, CHONFe and 3, CHONFe were designed and synthesized in good yields. Both the compounds, 2 and 3, behave as very selective and sensitive chromogenic and electrochemical chemosensor for Cu ion in aqueous environment (CHCN/HO (2:8, v/ v). The analytical detection limit (ADL) for receptor 2 was 7.5 × 10 M. The considerable changes in their absorption spectra of 2 and 3 are accompanied by the appearance of a new low energy (LE) peak at 630 nm ( 2: ε = 1600 M cm and 3: 822 M cm). This is further accompanied by a strong colour change from yellow to dark green that allows the prospective for 'naked eye' detection of Cu ion. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Photolysis of [{(μ3-BH)(Cp*Ru)Fe(CO)3}2(μ-CO)] (1; Cp* = η5-C5Me5) in the presence of various alkynessuch as 1,2-diphenylethyne, 1-phenyl-1-propyne, 2-butyne, and 1-(diphenylphosphino)-2-phenylacetyleneled to the formation of four types of novel heterometallic metallacarboranes,[1,1,1-(CO)3-μ-2,3-(CO)-2,3-(Cp*)2-4,6-Ph2-closo-1,2,3,4,6-FeRu2C2BH] (2), [1,8-(Cp*)2-2,2,7,7-(CO)4-μ-2,8-(CO)-μ-7,8-(CO)-4-Me-5-Ph-pileo-1,2,7,4,5-RuFe2C2(BH)2] (3), [1,8-(Cp*)2-2,2,7,7-(CO)4-μ-2,8-(CO)-μ-7,8-(CO)-4,5-Me2-pileo-1,2,7,4,5-RuFe2C2(BH)2] (4), and [1,2-(Cp*)2-6,6,7,7-(CO)4-μ-2,7-(CO)-exo-μ-5,6-(PPh2)-μ3-1,2,6-(BH)-4-Ph-pileo-1,2,6,7,4,5-Ru2Fe2C2BH] (5). Cluster compound 2exhibits an octahedralstructure with adjacent carbon atoms consistent with its skeletalelectron pair (sep) count of 7. The cage geometry of 3and 4is based on a pentagonal bipyramid with one additional{Cp*Ru} vertex capping one of its faces. The solid-state X-ray diffractionresults of 5suggest that the core geometry is a cappedpentagonal bipyramid, with an Fe–C bridging PPh2group. All the cluster compounds 2–5have been characterized by IR and 1H, 11B,and 13C NMR spectroscopy, and the geometries of the structureswere unequivocally established by crystallographic analysis. [ABSTRACT FROM AUTHOR]

A number of γ, δ unsaturated alkynyl substituted carbene complexes [(CO)5M=C(OCH3)CHR(CH2C≡CH)], 4-7 (4: M = Cr, R = CH2C≡CH; 5: M = Mo, R = CH2C≡CH; 6: M = W, R = CH2C≡CH and 7: M = W, R = CH(CH2)2CH3) have been synthesized from group 6 metal-carbene complexes [(CO)5M=C(OCH3)CH3], 1-3 (1: M = Cr, 2: M = Mo, 3: M = W) under biphasic reaction conditions. The alkoxy group has been readily replaced by amino groups in 6 as rotamers 8a-b and 9a-b (syn and anti isomers), (CO)5WC(NHR')- CH(CH2CCH)2, [8a-b: R' = CH3; 9a-b: R' = CH2Ph]. Further, when a CH2Cl2 solution of 4-6 was stirred at room temperature in the presence of trimethylamine- N-oxide for 30 min, the ester derivative CO(OCH3)CH- (CH2CCH)2 was formed. UV-Vis spectra have been recorded for both alkoxy and amino carbene complexes, 4-8, which showed the gradual hypsochromic shift of metal-to-ligand charge transfer bands from Cr to W. Compounds 4-9 have been isolated as yellow oils in moderate to good yields and they have been characterized by IR, 1H, 13C NMR spectroscopic analysis. [ABSTRACT FROM AUTHOR]

Abstract: Treatment of group 5 metal polychlorides such as, [CpnMCl4-x] (M = V: n, x = 2; M = Nb: n = 1, x = 0), or [Cp∗TaCl4] (Cp = η5–C5H5, Cp∗ = η5-C5Me5), with [LiBH4·THF] followed by thermolysis in the presence of diphenyl diselenide yielded metallaheteroborane clusters [{CpV(μ-SePh)}2(μ-Se)], 1 [(CpNb)2B4H9(μ-SePh)], 2 and [(Cp∗Ta)2B4H11(SePh)], 3 in modest yields. Compound 1 is an organovanadium selenolato cluster in which two (CpV) moieties bridged by (μ-Se) and two (μ-SePh) ligands. Compound 2 exhibits a bicapped tetrahedral core with one (μ-SePh) ligand. 3 is a tantalahexaborane cluster in which one of the terminal BH protons is substituted by SePh. Compounds 1–3 have been characterized by mass spectrometry, 1H, 11B, 13C NMR spectroscopy, and the geometric structures were unequivocally established by crystallographic analysis of 1–3. [Copyright &y& Elsevier]