Search

Syntheses and structural characterization of supraicosahedral rhodaborane clusters are reported. Reaction of [(Cp*RhCl2)2], (Cp* = η(5)-C5Me5) with [LiBH4·thf] followed by thermolysis with excess of [BH3·thf] afforded 16-vertex closo-[(Cp*Rh)3B12H12Rh{Cp*RhB4H9}], 1, 15-vertex [(Cp*Rh)2B13H13], 2, 12-vertex [(Cp*Rh)2B10Hn(OH)m], (3a: n = 12, m = 0; 3b: n = 9, m = 1; 3c: n = 8, m = 2) and 10-vertex [(Cp*Rh)3B7H7], 4, and [(Cp*Rh)4B6H6], 5. Cluster 1 is the unprecedented 16-vertex cluster, consists of a sixteen-vertex {Rh4B12} with an exo-polyhedral {RhB4} moiety. Cluster 2 is the first example of a carbon free 15-vertex supraicosahedral metallaborane, exhibits icosihexahedron geometry (26 triangular faces) with three degree-six vertices. Clusters 3a-c have 12-vertex isocloso geometry, different from that of icosahedral one. Clusters 4 and 5 are attributed to the 10-vertex isocloso geometry based on 10-vertex bicapped square antiprism structure. In addition, quantum-chemical calculations with DFT methods at the BP86 level of theory have been used to provide further insight into the electronic structure and stability of the optimized structures which are in satisfactory agreement with the structure determinations. 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 compounds 1-5.

The reaction of [Cp*MoCl(4)] with an excess of LiBH(4), followed by thermolysis with tellurium powder in toluene, afforded a tricapped cubane cluster, [(Cp*Mo)(4)B(4)H(4)(μ(4)-BH)(3)] (1), which represents an unprecedented metal-rich metallaborane cluster with a cubane core containing 58 cluster valence electrons (cve) and three metal-metal bonds.

Vanadaborane, [(CpV)(2)(B(2)H(6))(2)] (Cp = eta(5)-C(5)H(5)), 1 reacts with elemental sulfur to afford the hexasulfide cluster [(CpV)(2)S(4)(mu-eta(1)-S(2))], 2 in high yield. Compound 2 is a notable example of an organovanadium sulfide cluster in which the [V(2)S(4)] atoms define a bicapped tetrahedron framework, with one mu-eta(1)-S(2) ligand bridged the two (CpV) moieties. The sulfur atom in [V(2)S(4)] core in 2 is a four-skeletal-electron donor isoelectronic with the BH(3) unit; therefore, the replacement of boron hydride in 1 by four sulfur atoms necessitates the formation of a bicapped tetrahedron [V(2)S(4)] framework. Furthermore, this is the only reported example of a bimetallic hexasulfide cluster containing vanadium. Pyrolysis of 1 with bis-chalcogenide ligands such as Ph(2)S(2) and Bz(2)Se(2) (Bz = PhCH(2)), results in the formation of substituted vanadahexaboranes [(CpV)(2)B(4)H(12-x)L(x)], 3-5 (3: L = SPh: x = 3; 4: L = SPh, x = 2; 5: L = SeBz: x = 1) in modest yield. All these new compounds have been characterized by mass, (1)H, (11)B, (13)C NMR spectroscopy, and elemental analysis, and the structural types were unequivocally established by crystallographic analysis of compounds 2-5.

This work reports the results of a thermally driven cluster expansion of arachno-1-{eta5-C5Me5IrH2}B3H7, 1, with BH3.THF. In addition to the previously reported product, arachno-1-{eta5-C5Me5IrH}B4H9, 2, formed at lower temperatures, reaction at 100 degrees C permits the isolation of four new iridaboranes. Two products, nido-1-(eta5-C5Me5Ir)B5H9, 3, and nido-3-(eta5-C5Me5Ir)B9H13, 4, contain a single Ir atom and five and nine framework boron atoms, respectively. One, nido-3,4-(eta5-C5Me5Ir)2B8H12, 5, contains two Ir atoms and eight framework boron atoms. Their structures are predicted by the electron counting rules to be a nido-iridahexaborane, 3, nido-iridadecaborane, 4, and nido-diiridadecaborane, 5. The accuracy of these predictions in each case is established experimentally by spectroscopic characterization in solution and structure determinations in the solid state. A less stable metallaborane has been identified and the available spectroscopic and crystallographic information are consistent with the formulation nido-3,4-(eta5-C5Me5Ir)2B8H13(eta-BH2), 6, i.e., a species containing an exopolyhedral bridging BH group. These new observations, along with earlier ones on ruthenaborane cluster systems, are used to fully define a general mechanism for a cluster expansion reaction, i.e., addition of borane to form an exopolyhedral adduct followed by cage insertion.

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]

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]

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]

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]

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]

Building upon our earlier studies of cobaltaheteroboranes, we explore the chemistry with heavier group 9 metals. Reaction of [Cp*M(µ‐Cl)Clx]2 (Cp* = η5‐C5Me5; M = Co, x = 0; M = Rh or Ir, x = 1) with [LiBH4·THF], followed by thermolysis with an excess of chalcogen powders (S or Se), affords dimetallaheteroboranes nido‐[(Cp*M)2B2H2E2], 1–4 (1: E = S; 2: E = Se, M = Co; 3 and 4: E = Se, M = Rh and Ir, respectively) in moderate‐to‐good yields. The solid‐state structures of these compounds show open‐cage triple‐decker clusters. Attempts to isolate the Te analogue have failed; however, in the case of cobalt, we have isolated an 11 skeletal‐electron‐pair nido‐[(Cp*Co)2B5H5Te2], 5. The X‐ray diffraction structure of 5 shows monocapped square antiprismatic geometry, with two Te atoms in the core. To close the central four‐membered B2E2 open ring of nido‐1 and nido‐2, we have performed a reaction with [Ru3(CO)12], which leads to the formation of closo‐[(Cp*Co){µ‐η5:η5‐B2H2E2M}M{µ‐Ru(CO)4}], 6 and 7 [6: E = S; 7: E = Se; M = Ru(CO)2]. In contrast, the reactions of nido‐2 and nido‐3 with [Fe2(CO)9] result in heterometallic clusters nido‐[(Cp*M)Fe(CO)3B2H2Se2], 8 and 9 (8: M = Co; 9: M = Rh), [(Cp*Co)Fe3(CO)8Se2], 10, and [(Cp*Co)Fe2(CO)7Se], 11. As nido‐8 also contains a four‐membered open ring B2Se2, we have treated this with [Ru3(CO)12], which yields closo‐[(Cp*Co){µ‐η5:η5‐B2H2Se2M}M{µ‐Fe(CO)4}], 12 [M = Ru(CO)2], which is analogous to that of 7. In addition, we have analyzed the divergence in the reactivity of nido‐[(Cp*M)2B2H2E2], 2–4, with the help of density functional theory calculations. [ABSTRACT FROM AUTHOR]

The quadruply bridged bimetallic dithiolato complex [(Cp*W)2(µ-S)2(µ,η2-S2CH2)] (3) and the open-cage triple-decker complex [(Cp*W)2(µ-S)(µ-η4:η4-B2H2S2)] (2) have been prepared by treatment of CS2 with in situ generated [(Cp*W)2(B2H6)2] (1) obtained by the reaction of [Cp*WCl4] with [LiBH4·thf]. The solid-state X-ray diffraction structures of these complexes show the presence of doubly bridging η2-S2B2H2 and η2-S2CH2 ligands with a short W–W bond. While many dimolybdenum–sulfur compounds are known, examples of the tungsten–dithilato complexes are relatively few, and in this respect, the isolation of [(Cp*W)2(µ-S)2(µ,η2-S2CH2)] represents a rare example of this type. Electronic-structure analysis, on the grounds of density functional theory (DFT), together with X-ray diffraction studies, has rationalized the presence of short W–W and B–B bonds. Large HOMO–LUMO gaps have been observed for both compounds, which is consistent with their thermodynamic stability. All of the compounds have been characterized by mass spectrometry, IR spectroscopy, and 1H NMR, 11B NMR, and 13C NMR spectroscopy in solution, and the structural architectures have been unambiguously established by X-ray diffraction crystallographic analysis. [ABSTRACT FROM AUTHOR]

Several early-late heterodimetallaborane clusters have been isolated and structurally characterized through spectroscopic and crystallographic analysis. The thermolysis of [Cp2Zr(BH4)2] (Cp = η5-C5H5) with [Cp*IrB3H9] (Cp* = η5-C5Me5) and [(Cp*Rh)2B2H6] yielded arachno-[(Cp2Zr)(Cp*Ir)B3H9] ( 2) and arachno-[(Cp2Zr)(Cp*Rh)B4H10] ( 4), respectively. In a similar fashion, the reaction of [Cp2Hf(BH4)2] was performed with the same set of group 9 metallaboranes that led to the formation of arachno-[(Cp2Hf)(Cp*M′)B4H10] ( 5: M′ = Ir; 6: M′ = Rh). To the best of our knowledge, 2 is the first structurally characterized pentaborane(11) analogue containing zirconium, while the clusters 5 and 6 are the first examples with Hf in a hexaborane(12) core. The bonding between the Zr atoms and the boron ring was studied computationally by DFT methods, and 2 can be defined as a dimetallic analogue of arachno-B5H11 on the basis of the combined experimental and computational results. [ABSTRACT FROM AUTHOR]

Phenothiazines with a dimesityl boron moiety, a new class of aminoboranes with B−N linkage, were synthesized. These aminoboranes exhibited interesting photophysical behavior including aggregation-induced emission (AIE), mechanochromism (MC), mechanoluminescence (ML), and a mega Stokes shift (up to 312 nm in hexane). The solid-state emission of the aminoboranes could be switched reversibly by grinding-fuming processes. Furthermore, the phenothiazine derivative with a bromo and an arylborane group at 3- and 7-positions exhibited bright mechanoluminescence. [ABSTRACT FROM AUTHOR]

Thermolysis of [Cp*Ru(PPh2(CH2)PPh2)BH2 (L2)] 1 (Cp*=η5-C5Me5; L=C7H4NS2), with terminal alkynes led to the formation of η4-σ,π-borataallyl complexes [Cp*Ru(μ-H)B{R-C=CH2}(L)2] (2 a-c) and η²-vinylborane complexes [Cp*Ru(R-C=CH2)BH(L)2] (3 a-c) (2 a, 3 a: R=Ph; 2 b, 3 b: R=COOCH3; 2 c, 3 c: R=p-CH3-C6H4; L=C7H4NS2) through hydroboration reaction. Ruthenium and the HBCC unit of the vinylborane moiety in 2 a-c are linked by a unique η4-interaction. Conversions of 1 into 3 a-c proceed through the formation of intermediates 2 a-c. Furthermore, in an attempt to expand the library of these novel complexes, chemistry of σ-borane complex [Cp*RuCO(μ-H)BH2L] 4 (L=C7H4NS2) was investigated with both internal and terminal alkynes. Interestingly, under photolytic conditions, 4 reacts with methyl propiolate to generate the η4-σ,π-borataallyl complexes [Cp*Ru(μ-H)BH{R-C=CH2}(L)] 5 and [Cp*Ru(μ-H)BH{HC=CH-R}(L)] 6 (R=COOCH3; L=C7H4NS2) by Markovnikov and anti-Markovnikov hydroboration. In an extension, photolysis of 4 in the presence of dimethyl acetylenedicarboxylate yielded η4-σ,π-borataallyl complex [Cp*Ru(μ-H)BH{R-C=CH-R}(L)] 7 (R=COOCH3; L=C7H4NS2). An agostic interaction was also found to be present in 2 a-c and 5-7, which is rare among the borataallyl complexes. All the new compounds have been characterized in solution by IR, ¹H, 11B, 13C NMR spectroscopy, mass spectrometry and the structural types were unequivocally established by crystallographic analysis of 2 b, 3 a-c and 5-7. DFT calculations were performed to evaluate possible bonding and electronic structures of the new compounds. [ABSTRACT FROM AUTHOR]

In an effort to synthesize supraicosahedral iridaboranes, pyrolysis of [Cp*IrCl2]2 with excess [BH3·THF] was carried out, and this synthesis afforded the isomeric iridaborane [(Cp*Ir)2B6H6] clusters 1 and 2. The geometry of 1 was determined to be dodecahedral, i.e., similar to that of [B8H8]2−, whereas 2 was found to exhibit a cluster shape that can be derived from a nine-vertex tricapped trigonal prism by removing one of the capped vertices. The calculation of a large HOMO–LUMO gap further rationalized the isocloso structures for these isomers. [ABSTRACT FROM AUTHOR]

A series of agostic σ-borane/borate complexes have been synthesized and structurally characterized from simple borane adducts. A room-temperature reaction of [Cp*Mo(CO)3Me], 1 with Li[BH3(EPh)] (Cp*=pentamethylcyclopentadienyl, E=S, Se, Te) yielded hydroborate complexes [Cp*Mo(CO)2(μ-H)BH2EPh] in good yields. With 2-mercapto-benzothiazole, an N,S-carbene-anchored σ-borate complex [Cp*Mo(CO)2BH3(1-benzothiazol-2-ylidene)] ( 5) was isolated. Further, a transmetalation of the B-agostic ruthenium complex [Cp*Ru(μ-H)BHL2] ( 6, L=C7H4NS2) with [Mn2(CO)10] affords a new B-agostic complex, [Mn(CO)3(μ-H)BHL2] ( 7) with the same structural motif in which the central metal is replaced by an isolobal and isoelectronic [Mn(CO)3] unit. Natural-bond-orbital analyses of 5-7 indicate significant delocalization of the electron density from the filled σBH orbital to the vacant metal orbital. [ABSTRACT FROM AUTHOR]

Building upon previous studies on the synthesis of bis(sigma)borate and agostic complexes of ruthenium, the chemistry of nido-[(Cp*Ru)2B3H9] ( 1) with other ligand systems was explored. In this regard, mild thermolysis of nido- 1 with 2-mercaptobenzothiazole (2-mbzt), 2-mercaptobenzoxazole (2-mbzo) and 2-mercaptobenzimidazole (2-mbzi) ligands were performed which led to the isolation of bis(sigma)borate complexes [Cp*RuBH3L] ( 2 a- c) and β-agostic complexes [Cp*RuBH2L2] ( 3 a- c; 2 a, 3 a: L=C7H4NS2; 2 b, 3 b: L=C7H4NSO; 2 c, 3 c: L=C7H5N2S). Further, the chemistry of these novel complexes towards various diphosphine ligands was investigated. Room temperature treatment of 3 a with [PPh2(CH2) nPPh2] ( n=1-3) yielded [Cp*Ru(PPh2(CH2) nPPh2)-BH2(L2)] ( 4 a- c; 4 a: n=1; 4 b: n=2; 4 c: n=3; L=C7H4NS2). Mild thermolysis of 2 a with [PPh2(CH2) nPPh2] ( n=1-3) led to the isolation of [Cp*Ru(PPh2(CH2) nPPh2)(L)] (L=C7H4NS2 5 a- c; 5 a: n=1; 5 b: n=2; 5 c: n=3). Treatment of 4 a with terminal alkynes causes a hydroboration reaction to generate vinylborane complexes [Cp*Ru(RCCH2)BH(L2)] ( 6 and 7; 6: R=Ph; 7: R=COOCH3; L=C7H4NS2). Complexes 6 and 7 can also be viewed as η-alkene complexes of ruthenium that feature a dative bond to the ruthenium centre from the vinylinic double bond. In addition, DFT computations were performed to shed light on the bonding and electronic structures of the new compounds. [ABSTRACT FROM AUTHOR]

A combined experimental and quantum chemical study of Group 7 borane, trimetallic triply bridged borylene and boride complexes has been undertaken. Treatment of [{Cp*CoCl}2] (Cp*=1,2,3,4,5-pentamethylcyclopentadienyl) with LiBH4 ⋅thf at −78 °C, followed by room-temperature reaction with three equivalents of [Mn2(CO)10] yielded a manganese hexahydridodiborate compound [{(OC)4Mn}(η6-B2H6){Mn(CO)3}2(μ-H)] ( 1) and a triply bridged borylene complex [(μ3-BH)(Cp*Co)2(μ-CO)(μ-H)2MnH(CO)3] ( 2). In a similar fashion, [Re2(CO)10] generated [(μ3-BH)(Cp*Co)2(μ-CO)(μ-H)2ReH(CO)3] ( 3) and [(μ3-BH)(Cp*Co)2(μ-CO)2(μ-H)Co(CO)3] ( 4) in modest yields. In contrast, [Ru3(CO)12] under similar reaction conditions yielded a heterometallic semi-interstitial boride cluster [(Cp*Co)(μ-H)3Ru3(CO)9B] ( 5). The solid-state X-ray structure of compound 1 shows a significantly shorter boron-boron bond length. The detailed spectroscopic data of 1 and the unusual structural and bonding features have been described. All the complexes have been characterized by using 1H, 11B, 13C NMR spectroscopy, mass spectrometry, and X-ray diffraction analysis. The DFT computations were used to shed light on the bonding and electronic structures of these new compounds. The study reveals a dominant BHMn, a weak BBMn interaction, and an enhanced BB bonding in 1. [ABSTRACT FROM AUTHOR]

Recently we described the synthesis and structural characterization of various dimetallaherteroborane clusters, namely nido-[(CpMo)BEClH], 1- 3; ( 1: E = S, x = 0; 2: E = Se, x = 0; 3: E = Te, x = 1). A combined theoretical and experimental study was also performed, which demonstrated that the clusters 1- 3 with their open face are excellent precursors for cluster growth reaction. In this investigation process on the reactivity of dimetallaheteroboranes with metal carbonyls, in addition to [(CpMo)BHEFe(CO)] ( 4: E = S, 6: E = Te) reported earlier, reaction of 2 with [ Fe(CO)] yielded mixed-metallaselenaborane [(CpMo)BHSeFe(CO)], 5 in good yield. The quantum chemical calculation using DFT method has been carried out to probe the bonding, NMR chemical shifts and electronic properties of dimolybdaheteroborane clusters 4- 6. [Figure not available: see fulltext.] [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]

A series of novel Cp*-based (Cp*=η5-C5Me5) agostic, bis(σ-borate), and boratrane complexes have been synthesized from diruthenium and dirhodium analogues of pentaborane(9). The synthesis and structural characterization of the first neutral ruthenadiborane(6) analogue are also reported. This new route offers a very efficient method for the isolation of bis(σ-borate) and agostic complexes from diruthenapentaborane(9). [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]

The reaction of [Cp nMCl4− x] (M=V: n=2, x=2; M=Nb: n=1, x=0; Cp=η5-C5H5) with LiBH4 ⋅THF followed by thermolysis in the presence of dichalcogenide ligands E2R2 (E=S, Te; R=2,6-( tBu)2-C6H2OH, Ph) and 2-mercaptobenzothiazole (C7H5NS2) yielded dimetallaheteroboranes [{CpV(μ-TePh)}2(μ3-Te)BH ⋅thf] ( 1), [(CpV)2(BH3S)2] ( 2), [(CpNb)2B4H10S] ( 3), [(CpNb)2B4H11S( tBu)2C6H2OH] ( 4), and [(CpNb)2B4H11TePh] ( 5). In cluster 1, the V2BTe atoms define a tetrahedral framework in which the boron atom is linked to a THF molecule. Compound 2 can be described as a dimetallathiaborane that is built from two edge-fused V2BS tetrahedron clusters. Cluster 3 can be considered as an edge-fused cluster in which a trigonal-bipyramidal unit (Nb2B2S) has been fused with a tetrahedral core (Nb2B2) by means of a common Nb2 edge. In addition, thermolysis of an in-situ-generated intermediate that was produced from the reaction of [Cp2VCl2] and LiBH4 ⋅THF with excess BH3 ⋅THF yielded oxavanadaborane [(CpV)2B3H8(μ3-OEt)] ( 6) and divanadaborane cluster [(CpV)2B5H11] ( 7). Cluster 7 exhibits a nido geometry with C2 v symmetry and it is isostructural with [(Cp*M)2B5H9+ n] (M=Cr, Mo, and W, n=0; M=Ta, n=2; Cp*=η5-C5Me5). All of these new compounds have been characterized by 1H NMR, 11B NMR, and 13C NMR spectroscopy and elemental analysis and the structural types were established unequivocally by crystallographic analysis of compounds 1- 4, 6, and 7. [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]

Treatment of [Cp*TaCl SB 4 sb ] with chalcogen-ligated monoborate nucleophiles, [BH SB 3 sb (EPh)] SP - sp (E = S or Se) yielded various smaller borane analogues. Cover Feature: Metal Coordinated Tri- and Tetraborane Analogues (Eur. J. Inorg. Keywords: Boranes; Chalcogens; Metallaheteroboranes; Tantalum; Structure elucidation EN Boranes Chalcogens Metallaheteroboranes Tantalum Structure elucidation 4407 4407 1 11/24/21 20211122 NES 211122 B The Cover Feature b shows triborane and tetraborane analogues which are stabilized in the coordination sphere of tantalum atom(s). [Extracted from the article]

Correction for ‘Chemistry of group 9 dimetallaborane analogues of octaborane(12)’ by Subrat Kumar Barik, et al., Dalton Trans., 2015, 44, 669–676. [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]

• 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]

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]

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]

Abstract: Chalcogen-stabilized dimolybdaboranes 3–5 (3: [(Cp∗Mo)2B4H5Se(Ph)], 4: [(Cp∗Mo)2B4H3Se2(SeCH2Ph)] and 5: [(Cp∗Mo)2B3H6(BSR)(μ-η1-SR)] (R=2,6-( t Bu)2-C6H2OH)) have been isolated from the mild pyrolysis of dichalcogenide ligands, RE-E‘R (R=Ph: E=S, E‘=Se; R=CH2Ph, [2,6-( t Bu)2-C6H2OH]: E=E‘=Se, S) and [(Cp∗Mo)2B4H8], 2, an intermediate generated from the reaction of [Cp∗MoCl4] (1) (Cp∗ =η5-C5Me5), with [LiBH4.thf]. The geometry of [(Cp∗Mo)2B4H5Se(Ph)] is similar to that of [(Cp∗Mo)2B5H9], in which one BH3 unit on the open face is replaced by a triple bridged selenium atom. All the compounds have been characterized in solution by 1H, 11B, 13C NMR and IR spectroscopy and elemental analysis. The structural types were unequivocally established by X-ray crystallographic analysis of compounds 3–5. [Copyright &y& Elsevier]

Abstract: Reaction of [(η5-C5Me5)MCl4], 1–2 (1: M=Mo and 2: W) with six fold excess of [LiBH4·thf] followed by thermolysis with excess chalcogen powders (S, Se and Te) yielded dichalcomolybda- and tungstaboranes, [(η5-C5Me5M)2B4H4E2], 5–8 (5: M=Mo, E=S; 6: M=Mo, E=Se; 7: M=Mo, E=Te; 8: M=W, E=Se) in modest yields. The geometry of 5–8 resembles a hexagonal bipyramid with a missing connectivity of two chalcogen vertices and a very short cross cage metal–metal bonding. All these new dichalcometallaboranes have been characterized by mass, 1H, 11B, 13C NMR spectroscopy, and the structural types were unequivocally established by crystallographic analysis of compound 6. [Copyright &y& Elsevier]

A new structural analogue of nido -homobimetallahexaborane(10), nido -[3,6-{(OC) 3 Mn} 2 (B 4 H 8 ·THF)], 1 is synthesized (see picture). • Bimtellahexaborane(10) analogue, nido -[3,6-{(OC) 3 Mn} 2 (B 4 H 8 ·thf)], 1 is synthesised. • 1 is a novel homometallic M 2 B 4 cluster known without a M−M bond. • Theoretical calculation indicated the higher relative thermodynamic stability for 1. • Reaction of nido -[1,2-(Cp*Ru) 2 (µ -H)B 4 H 9 ] with borane led to cluster build-up. Cluster nido -[3,6-{(OC) 3 Mn} 2 (B 4 H 8 ·THF)], 1 , (THF = tetrahydrofuran), has been synthesized from the irradiation of [Mn 2 (CO) 10 ] with [BH 3 ·THF] at 255 nm along with [{(OC) 4 Mn}(η 6-B 2 H 6){Mn(CO) 3 } 2 (µ -H)], 2. Cluster 1 represents the new structural analogue of nido -homobimetallahexaborane(10) where the metal centers are arranged symmetrically in the non-adjacent basal positions of a pentagonal pyramid core. Theoretical calculation suggests that nido- 1 is thermodynamically more stable as compared to the other hypothetical possible isomer nido -[4,5-{(OC) 3 Mn} 2 (B 4 H 8 ·THF)], II. Further, the reactivity of another homobimetallahexborane(10), nido -[1,2-(Cp*Ru) 2 (µ -H)B 4 H 9 ], 3 has been explored with borane that led to cluster build-up reaction to yield bimetallaoctaborane(12) analogues, nido -[(Cp*Ru) 2 B 6 H 10 (OH) 2 ], 4 and nido -[(Cp*Ru) 2 B 6 H 11 (OH)], 5. All the clusters have been characterized by multinuclear NMR and IR spectroscopies as well as by mass spectrometric analysis. The structural types of 1 and 4 were unequivocally established by crystallographic analysis. [ABSTRACT FROM AUTHOR]

Abstract Thermolysis of diphenyl dichalcogenides, Ph 2 E 2 (E = S, Se and Te) with an insitu generated intermediate, obtained from the reaction of [Cp*WCl 4 ] (Cp* = η 5-C 5 Me 5) with [LiBH 4 ·THF], yielded new tungstaheteroboranes, [(Cp*W) 2 (μ -EPh)(μ 3 -E)(μ -H)(B 3 H 2 EPh)], 1 and 2 (1 : E = S; 2 : E = Se), and [(Cp*W) 2 (μ -TePh)B 5 H 5 (μ -H) 3 ], 4. Formation of compounds 1 and 2 substantiate the evidence of [(Cp*W) 2 B 4 H 10 ], which supports our previous studies. Compound 4 has a capped octahedral geometry that is unique due to the presence of three W-H-B bridging hydrogens in a closo cluster. Alternatively, the shape of cluster 4 can be defined as oblatoarachno that can be derived from a heptagonal bipyramid. All the compounds have been characterized by mass spectrometry, 1H, 11B{1H}, IR and 13C{1H} NMR spectroscopy in solution and the structural architectures of 1 and 4 were unequivocally established by X-ray crystallographic analysis. The density functional theory calculations also yielded geometries in close agreement with the observed structures. Graphical abstract New tugstaheteroboranes, [(Cp*W) 2 (μ -EPh)(μ 3 -E)(μ -H)(B 3 H 2 EPh)], an analogue of [(Cp*W) 2 B 4 H 10 ] (right) and [(Cp*W) 2 (μ -TePh)B 5 H 5 (μ -H) 3 ], a capped octahedron having three W-H-B bridging hydrogens (left). Image 1 Highlights • Explored the synthesis of tungstaheteroboranes employing diphenyl dichalcogenides. • [(Cp*W) 2 (μ -EPh)(μ 3 -E)(μ -H)(B 3 H 2 EPh)] (E = S and Se) supports the existence of [(Cp*W) 2 B 4 H 10 ] as the intermediate. • [(Cp*W) 2 (μ -TePh)B 5 H 5 (μ -H) 3 ], is exceptional due to the presence of three W-H-B bridging hydrogens. [ABSTRACT FROM AUTHOR]

In an attempt to synthesize expanded-cage metallaheteroboranes containing heavier chalcogen atoms, the reaction of diruthenaborane analogue of pentaborane(9), nido -[1,2-(Cp*RuH) 2 B 3 H 7 ] ( 1 ) with phenyl-chalcogenoborates Li[BH 3 (EPh)] (E = S, Se or Te) was carried out. Thermolysis of nido - 1 with Li[BH 3 (SPh)] led to the formation of the dimetalla-pentaborane(11) analogue arachno -[(Cp*Ru) 2 B 3 H 8 (SPh)] ( 2 ). In parallel to the formation of 2 , the reaction also yielded three B-H functionalized compounds, namely [(Cp*Ru) 2 B 4 H 7 (Ph)] ( 3 ), [(Cp*Ru) 2 B 4 H 7 (Cl)] ( 4 ) and [(Cp*Ru) 2 B 4 H 6 (SPh)(Cl)] ( 5 ). On the other hand, reaction of 1 with Li[BH 3 (SePh)] led to the formation of the diruthenium analogue of hexaborane(10) nido -[(Cp*Ru) 2 B 4 H 9 (SePh)] ( 6 ), whereas Li[BH 3 (TePh)] yielded the capped nido -pentagonal-pyramidal [(Cp*Ru) 2 B 4 H 6 Te] ( 7 ). Compound 7 is a rare ruthenaborane cluster containing a heavier chalcogen element (Te). All the compounds were characterized by mass spectrometry and 1 H, 1 H{ 11 B}, 11 B{ 1 H} and 13 C{ 1 H}NMR spectroscopy. The solid state X-ray structures of all the compounds were unequivocally established by crystallographic analysis. Additionally, the electronic properties of compound 2 were analyzed. [ABSTRACT FROM AUTHOR]

The chemistry of ruthenium–borane complex, [Cp ∗ RuCO(μ-H)BH 2 L] (Cp ∗ = η 5 -C 5 Me 5 ; L = C 7 H 4 NS 2 ), 1 with various alkynes has been explored. Photolysis of 1 with alkynyl-Grignard, [HC CMgBr] in toluene led to the isolation of vinyl hydroborate complex [Cp ∗ Ru(μ-H)BH{HC CH 2 }L], 2a as a sole product. Compound 2a can be viewed as a ruthenium–borate complex with an ethylene moiety. Further, the chemistry of 1 with various internal and terminal alkynes has been performed in photolytic conditions. Photolysis of 1 with [RC CR] (R = CO 2 Me) yielded vinyl hydroborate complex [Cp ∗ Ru(μ-H)BCl{RC CR}L], 2b . Terminal alkynes [HC CR] (R = Ph or CO 2 Me) under the same reaction conditions led to the isolation of metal vinyl complexes [Cp ∗ Ru(CO)(C 2 HR)(L)], 3a and 3b ( 3a : R = Ph; 3b : R = CO 2 Me). In addition, DFT calculations were carried out to analyze the bonding and electronic structures of these new compounds. [ABSTRACT FROM AUTHOR]

A series of novel isocloso-diiridaboranes [(Cp*Ir)2B6H6], 1, 2; [1,7-(Cp*Ir)2B8H8], 4; [1,4-(Cp*Ir)2B8H8], 5; [(Cp*Ir)2B9H9], 8; isonido-[(Cp*Ir)2B7H7], 3; and 10-vertex cluster [5,7-(Cp*Ir)2B8H12], 6 (Cp* = η5-C5Me5) have been isolated and structurally characterized from the pyrolysis of [Cp*IrCl2]2 and BH3·thf. On the other hand, the corresponding rhodium system afforded 10- and 11-vertices clusters [5-(Cp*Rh)B9H13)], 7, and [(Cp*Rh)2B9H9], 9, respectively. Clusters 1 and 2 are topological isomers. The geometry of 1 is dodecahedral, similar to that of its parent borane [B8H8]2-, in which two of the [BH] vertices are replaced by two [Cp*Ir] fragments. The geometry of 2 can be derived from a nine-vertex tricapped trigonal prism by removing one of the capped vertices. Compounds 4 and 5 are 10-vertex isocloso clusters based on a 10-vertex bicapped square antiprism structure. The only difference between them is the presence of a metal-metal bond in 5. The solid-state structures of 8 and 9 attain an 11-vertex geometry in which a unique six-membered B6H6 moiety is bonded to the metal center. In addition, quantum-chemical calculations have been used to provide further insight into the electronic structure and stability of the clusters. All the compounds have been characterized by IR and ¹H, 11B, and 13C NMR spectroscopy in solution, and the solid-state structures were established by X-ray crystallographic analysis. [ABSTRACT FROM AUTHOR]

In an effort to synthesize supraicosahedral iridaboranes, pyrolysis of [Cp*IrCl2]2 with excess [BH3·THF] was carried out, and this synthesis afforded the isomeric iridaborane [(Cp*Ir)2B6H6] clusters 1 and 2. The geometry of 1 was determined to be dodecahedral, i.e., similar to that of [B8H8]2−, whereas 2 was found to exhibit a cluster shape that can be derived from a nine-vertex tricapped trigonal prism by removing one of the capped vertices. The calculation of a large HOMO–LUMO gap further rationalized the isocloso structures for these isomers. [ABSTRACT FROM AUTHOR]

This work describes the synthesis, structural characterizations, and electronic structures of a series of novel homometallic cubane clusters [(Cp*Ru)2{Ru(CO)2}2BH(μ3-E)(μ-H)B(μ-H)3M], (2, M = Cp*Ru, E = CO; 3, M = Ru(Cp*Ru)2(μ-CO)3(μ-H)BH), E = BH), [(Cp*Ru)3(μ3-CO)(BH)3(μ3-H)3], 4, and [(Cp*Ru)2(μ3-CO){Ru(CO)3}2(BH)2(μ-H)B], 5 (Cp* = η5-C5Me5). These cubane clusters have been isolated from a thermally driven reaction of diruthenium analogue of pentaborane(9) [(Cp*RuH)2B3H7], 1, and [Ru3(CO)12]. Structural and spectroscopic studies revealed the existence of triply bridged hydrogen (μ3-H) atoms that participate as a vertex in the cubane core formation for compounds 2, 3, and 4. In addition, the crystal structure of these clusters clearly confirms the presence of an electron precise borane ligand (borylene fragment) which is triply bridged to the trimetallic units. Bonding of these novel complexes has been studied computationally by DFT methods, and the studies demonstrate that the cubane clusters 2 and 3 possess 60 cluster valence electrons (cves) with six metal-metal bonds. All the new compounds have been characterized in solution by mass spectrometry; IR; and ¹H, 11B, and 13C NMR studies, and the structural types were unequivocally established by crystallographic analysis of compounds 2-5. [ABSTRACT FROM AUTHOR]

Reactions of the CS2 and CO2 heterocumulene ligands with nido-ruthenaborane cluster [1,2-(Cp*Ru)2(μ-H)2B3H7], 1, were explored (Cp* = pentamethylcyclopentadienyl). Compound 1 when treated with CS2 underwent metal-assisted hydroboration to yield arachno-ruthenaborane [(Cp*Ru)2(B3H8)(CS2H)], 2, with a dithioformato ligand attached to it. The chemistry of 2 was then explored with various transition metal carbonyl compounds under photolytic and thermolytic conditions. Thermolysis of 2 with [Mn2(CO)10] resulted in the formation of an unprecedented cubane-type cluster [(Cp*Ru)2Mn(CO)3(CS2H2)B3H4], 3, with a rare [M3E5] formulation (E = B, S). On the other hand, when compound 2 was photolyzed in the presence of [Mn2(CO)10], it yielded an incomplete cubane-type cluster [(Cp*Ru)2Mn(CO)3BH2(CS2H2)], 4. The room-temperature reaction of 2 with [Fe2(CO)9] yielded heterometallic arachno clusters [(Cp*Ru)(CO)2{Fe(CO)3}2S2CH3], 6 and [(Cp*Ru)2(B3H8)(CO){Fe(CO)3}2(CS2H)], 7. In contrast, photolysis of 2 with [Fe2(CO)9] yielded a tetrahedral cluster [(Cp*Ru)(CO)2S(μ-H){Fe(CO)3}3], 8, tethered to an exo-polyhedral moiety [(Cp*Ru)(CO)2]. Compound 6 provides an unusual bonding pattern by means of fusing the wing-tip vertex (S) of the [Fe2S2] butterfly core by an exo-polyhedral [(Cp*Ru)(CO)2] unit. Density functional theory calculations were carried out to provide insight into the mechanistic pathway, electronic structure, and bonding properties. [ABSTRACT FROM AUTHOR]

Abstract: Reaction of [Cp∗MoCl4] (Cp∗ = η5-C5Me5) with excess of [LiBH4·thf] followed by pyrolysis with NaI yielded B–I inserted [(Cp∗Mo)2B5H9−n I n ], 1–3 (1: n = 1; 2: n = 2; 3: n = 3). In parallel to the formation of 1–3, the reaction also produced known [(Cp∗Mo)2B5H9] and [(Cp∗Mo)2(μ-I)4] in good yields. Under the similar reaction conditions, dimolybdathiaborane [(Cp∗Mo)2B4H4S2] yielded iodine substituted dimolybdathiaboranes, [(Cp∗Mo)2B4S2H4−n I n ], 4 and 5 (4: n = 2; 5: n = 3) in good yields. All the new compounds have been characterized in solution by IR, 1H and 11B NMR as simple substituted derivatives of [(Cp∗Mo)2B5H9] and [(Cp∗Mo)2B4H4S2]. The solid state structures were established unambiguously by crystallographic analysis of compounds 1–5. [Copyright &y& Elsevier]

Reaction of [Cp∗CoCl]2 (Cp∗ = η5-C5Me5) with [LiBH4·THF] in toluene at −70 °C, followed by thermolysis with 2-mercaptobenzothiazole (C7H5NS2) in boiling toluene led to the isolation of a range of cobaltaborane clusters, [(Cp∗Co)2B7H6OMe], 1; [(Cp∗Co)3B8H7R], 2a, b (2a: R = H; 2b: R = Me); [(Cp∗Co)3B8H8S], 3 and [(Cp∗Co)2B4H4RR′], 4a–d (4a: R, R′ = H; 4b: R = Me, R′ = H; 4c: R = H, R′ = Me and 4d: R, R′ = Me). In parallel to the formation of compounds 1–4, the reaction also yielded known [(Cp∗Co)3B4H4] in good yield. Compound 1 may be considered as 9-vertex hypoelectronic cluster with C1 symmetry, where cobalt atoms occupy the degree 5 vertices. All the dicobaltaboranes 4a–d contains two μ3-H protons and found to be very reactive. As a result, one of them (4a) when reacted with Fe2(CO)9 and sulfur powder yielded, almost immediately, [(Cp∗Co)2B4H5SFe3(CO)9], 5 and [(Cp∗Co)2B3H3(μ-CO)Fe(CO)3], 6. All the new compounds have been characterized in solution by mass, 1H, 11B, 13C NMR spectroscopy and elemental analysis. The structural types were unequivocally established by X-ray crystallographic analysis of compounds 1–6. Density functional theory (DFT) calculations on the model compounds 1′ and 2′ (1′, and 2′ are the Cp analog of 1, and 2a respectively, Cp = C5H5) yield geometries in agreement with the structure determinations. The existence of large HOMO–LUMO gap of these molecules rationalizes the isocloso description for 2a. Bonding patterns in the structure have been analyzed on the grounds of DFT calculations. [ABSTRACT FROM AUTHOR]

Metal assisted borane condensationmethod has been employed forthe preparation of novel metallaborane cluster containing group 4metal. Pyrolysis of [Cp*IrB3H9], 1, with in situ generated zirconium bisborohydrate [Cp2Zr(BH4)2], produced from the fast metathesisreaction of [Cp2ZrCl2] and LiBH4,and excess of BH3·THF yielded arachno-[(Cp2Zr)(Cp*Ir)B4H10], 2, in 56% yield. Compound 2constitutes the first crystallographicstructure determination of hexaborane(12) metal analogue containingzirconium. The observed geometry of 2can be generatedfrom a dodecahedron by removing two vertices and an edge. Anticipatinga straight metal fragment substitution/addition reaction, mild thermolysisof 2with [Fe2(CO)9] was carriedout. However, the reaction led to the formation of known trimetallic[Cp*IrFe2(CO)9] cluster via cluster degradation.In addition, density functional theory (DFT) calculations have beencarried out for 2and other hypothetical early–latecombinations of hexaborane(12) metal analogues to reveal the electronicstructures. [ABSTRACT FROM AUTHOR]

We have synthesized and structurally characterized several dimetallaheteroborane clusters, namely, nido-[(Cp*Mo)2B4SH6], 1; nido-[(Cp*Mo)2B4SeH6], 2; nido-[(Cp*Mo)2B4TeClH5], 3; [(Cp*Mo)2B5SeH7], 4; [(Cp*Mo)2B6SeH8], 5; and [(CpW)2B5Te2H5], 6 (Cp* = η5-C5Me5, Cp = η5-C5H5). In parallel to the formation of 1-6, known [(CpM)2B5H9], [(Cp*M)2B5H9], (M = Mo, W) and nido-[(Cp*M)2B4E2H4] compounds (when M = Mo; E = S, Se, Te; M = W, E = S) were isolated as major products. Cluster 6 is the first example of tungstaborane containing a heavier chalcogen (Te) atom. A combined theoretical and experimental study shows that clusters 1-3 with their open face are excellent precursors for cluster growth reactions. As a result, the reaction of 1 and 2 with [Co2(CO)8] yielded clusters [(Cp*Mo)2B4H4E(μ3-CO)Co2(CO)4], 7-8 (7: E = S, 8: E = Se) and [(Cp*Mo)2B3H3E(μ-CO)3Co2(CO)3], 9-10 (9: E = S, 10: E = Se). In contrast, compound 3 under the similar reaction conditions yielded a novel 24-valence electron triple-decker sandwich complex, [(Cp*Mo)2{μ-η6:η6-B3H3TeCo2(CO)5}], 11. Cluster 11 represents an unprecedented metal sandwich cluster in which the middle deck is composed of B, Co, and Te. All the new compounds have been characterized by elemental analysis, IR, 1H, 11B, 13C NMR spectroscopy, and the geometric structures were unequivocally established by X-ray diffraction analysis of 1, 2, 4--7, and 9--11. Furthermore, geometries obtained from the electronic structure calculations employing density functional theory (DFT) are in close agreement with the solid state structure determinations. We have analyzed the discrepancy in reactivity of the chalcogenato metallaborane clusters in comparison to their parent metallaboranes with the help of a density functional theory (DFT) study. [ABSTRACT FROM AUTHOR]

Thermolysisof [(Cp*RuCO)2B2H6] (1; Cp* = η5-C5Me5) with [Ru3(CO)12] yielded the trimetallaborane[(Cp*RuCO)3(μ3-H)BH] (2)and a number of homometallic boride clusters: [Cp*RuCO{Ru(CO)3}4B] (3), [(Cp*Ru)2{Ru2(CO)8}BH] (4), and [(Cp*Ru)2{Ru4(CO)12}BH] (5). Compound 2is isoelectronic and isostructural with the triply bridgedborylene compounds [(μ3-BH)(Cp*RuCO)2(μ-CO){Fe(CO)3}] (6) and [(μ3-BH)(Cp*RuCO)2(μ-H)(μ-CO){Mn(CO)3}] (7), where the [μ3-BH] moiety occupies the apicalposition. To test if compound 2undergoes hydroborationreactions with alkynes, as observed with 6, we performedthe reaction of 2with the same set of alkynes underphotolytic conditions. However, neither 2nor 7undergoes hydroboration to yield a vinyl–borylene complex.On the other hand, thermolysis of 6with trimethylsilylethyleneyielded the novel diruthenacarborane [1,1,7,7,7-(CO)5-2,3-(Cp*)2-μ-2,3-(CO)-μ3-1,2,3-(CO)-5-(SiMe3)-pileo-1,7,2,3,4,5-Fe2Ru2C2BH] (8). The solid-state X-ray diffractionresults suggest that 8exhibits a pentagonal -bipyramidalgeometry with one additional CO capping one of its faces. Cluster 3is a boride cluster where boron is in the interstitial positionof a square-pyramidal geometry, whereas compound 4canbe described as a tetraruthenium boride in which the Ru4butterfly skeleton has an interstitial boron atom. Electronic structurecalculations of compound 2employing density functionaltheory (DFT) generate geometries in agreement with the structure determinations.The existence of a large HOMO–LUMO gap in 2isin agreement with its high stability. Bonding patterns in the structurehave been analyzed on the grounds of DFT calculations. Furthermore,the B3LYP-computed 11B and 1H chemical shiftsfor compound 2precisely follow the experimentally measuredvalues. All the compounds have been characterized by IR and 1H, 11B, and 13C NMR spectroscopy, and the geometriesof the structures were unambiguously established by crystallographicanalyses of 2–4and 8. [ABSTRACT FROM AUTHOR]