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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]

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]

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]

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]

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]