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-(tBu)2-C6H 2OH)) have been isolated from the mild pyrolysis of dichalcogenide ligands, RE-E'R (R = Ph: E = S, E' = Se; R = CH2Ph, [2,6-(tBu) 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. © 2011 Elsevier Ltd.

Sundargopal Ghosh

Department Of Chemistry

Venkatachalam Ramkumar

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Polyhedron

Recently we described the synthesis and structural characterization of various dimetallaherteroborane clusters, namely nido-[(Cp∗Mo)2B4ECl x H6-x ], 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 [(Cp∗Mo)2B4H6EFe(CO)3] (4: E = S, 6: E = Te) reported earlier, reaction of 2 with [ Fe2(CO)9] yielded mixed-metallaselenaborane [(Cp∗Mo)2B4H6SeFe(CO)3], 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.] © 2014 Indian Academy of Sciences.

Fulltext

Journal of Chemical Sciences

Dimetallaheteroborane clusters containing group 16 elements: A combined experimental and theoretical study

The reaction of [CpnMCl4-x] (M=V: n=2, x=2; M=Nb: n=1, x=0; Cp=Î·5-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)2B 4H10S] (3), [(CpNb)2B4H 11S(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 LiBH 4·THF with excess BH3·THF yielded oxavanadaborane [(CpV)2B3H8(μ3- OEt)] (6) and divanadaborane cluster [(CpV)2B5H 11] (7). Cluster 7 exhibits a nido geometry with C2v symmetry and it is isostructural with [(Cp*M)2B 5H9+n] (M=Cr, Mo, and W, n=0; M=Ta, n=2; Cp*=Î·5-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. Group 5 alive: Divanadatellura- and divanadathiaboranes were obtained from the treatment of Group 5 metal polychlorides with dichalcogenides and monoboranes. The treatment of [Cp2VCl2] with monoboranes yielded an oxavanadaborane and a divanadaborane (see structures). Copyright © 2012 WILEY-VCH Verlag GmbH &amp; Co. KGaA, Weinheim.

Chemistry - A European Journal

Synthesis and structural characterization of new divanada- and diniobaboranes containing chalcogen atoms

Chemistry and reactivity of dimolybdathiaborane, [(Cp*Mo) 2B2SH2], 1, obtained from the reaction of 2-mercaptobenzothiazole, [Cp*MoCl2] and [LiBH2.thf], has been explored with dinuclear metal carbonyl [Fe2(CO) 2]. As a result, reaction of 1 with [Fe2(CO)2] yielded heterometallathiaborane, [(Cp*Mo)2B2H 2SFe(CO)2], 2 in good yield. Both the new compounds have been characterized in solution by 1H, 11B and 13C 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)3} 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)3} fragment to 1. © Indian Academy of Sciences.

Synthesis and reactivity of dimolybdathiaborane cluster [(Cp*Mo) 2B2SH2] (Cp* = η5-C 2Me2)

Vanadaborane, [(CpV)2(B2H6)2] (Cp = η5-C5H5), 1 reacts with elemental sulfur to afford the hexasulflde cluster [(CpV)2S4(μ- η1-S2)], 2 In high yield. Compound 2 is a notable example of an organovanadium sulfide cluster In which the [V2S 4] atoms define a bicapped tetrahedron framework, with μ-η1-S2 ligand bridged the two (CpV) moieties. The sulfur atom In [V2S4] core in 2 Is a four-skeletal- electron donor isoelectronlc with the BH3 unit; therefore, the replacement of boron hydride in 1 by four sulfur atoms necessitates the formation of a bicapped tetrahedron [V2S4] framework. Furthermore, this Is the only reported example of a bimetallic hexasulflde cluster containing vanadium. Pyrolysls of 1 with bis-chalcogenide ligands such as Ph2S2 and Bz2Se2 (Bz = PhCH 2), results In the formation of substituted vanadahexaboranes [(CpV)2B4H12-xLx], 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, 1H, 11B, 13C NMR spectroscopy, and elemental analysis, and the structural types were unequivocally established by crystallographic analysis of compounds 2-5. © 2010 American Chemical Society.

Inorganic Chemistry

Chemistry of vanadaboranes: Synthesis, structures, and characterization of organovanadium sulfide clusters with disulfido linkage

Reaction of {η5 -C5Me5)MoCl 4 with a 10-fold excess of LiBH4 followed by thermolysis with excess BH3·THF in toluene led to the formation of two oxamolybdaborane clusters, (η5-C5Me 5Mo)2B5(μ3OEt)H6R (2, R = H; 3, R = n-BuO). Clusters 2 and 3 have been characterized by 1H, 11B, and 13C NMR spectra and X-ray crystal structure determinations. 2 and 3 are notable examples of oxametallaborane compounds where oxygen is contiguously bound to both the cluster metal (molybdenum) and the boron atom. © 2009 American Chemical Society..

Organometallics

Unusual open eight-vertex oxamolybdaboranes: Structural characterizations of (η5-C5Me5Mo)2B 5(μ-OEt)H6R (R = H and n-BuO)

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. © 2009 Elsevier B.V. All rights reserved.

Journal of Organometallic Chemistry

Direct insertion of sulfur, selenium and tellurium atoms into metallaborane cages using chalcogen powders

Reaction of [CpMoCl4], 1 (Cp* = η5-C 5Me5), with [LiBH4 thf] in toluene at -70 °C, followed by pyrolysis with excess dichalcogenides RE-ER (R = Ph, CH 2Ph, 2,6-(tBu)2-C6H2OH, (CH3)3C = tBu); E = S, Se) yielded a new class of hybrid clusters, 3-8: (3, [(CpMo)2(μ-η1-SPh) 2(μ3-S)(H2BSPh)]; 4, [(CpMo) 2B5H8(SPh)]; 5, [(CpMo)2B 5H8(SePh)]; 6, [(CpMo)2B2S 2H2(μ-η1-S)]; 7, [(CpMo) 2B2H5(BSR)2(μ-η1- SR)], (R = 2,6-(tBu)2-C6H2OH); and 8, [(CpMo)2B2H5(BSePh)2(μ- η1-SePh)]. Compounds 3-8 have been isolated in modest yields as green or brown crystalline solids. In parallel with 3-8, [(CpMo) 2B5H9] was isolated as a major product in all cases. The isolation and structural characterization of compounds 3 and 6-8 provided the first direct evidence of the existence of [(CpMo)2B 4H8], 2, an intermediate in the formation of [(CpMo) 2B5H9]. These new compounds have been characterized in solution by mass spectrometry, 1H, 11B, 13C NMR, and IR spectroscopy, and elemental analysis. The structural types were unequivocally established by X-ray crystallographic analysis of compounds 3-8. © 2010 American Chemical Society.

Chemistry of molybdaboranes: Synthesis, structures, and characterization of a new class of open-cage dimolybdaheteroborane clusters

Reaction of [Cp*TaCl4] (Cp* = η5- C5Me5) with a sixfold excess of LiBH4· thf followed by BH3·thf in toluene at 100°C led to the isolation of hydrogen-rich metallaboranes [(Cp*Ta)2B 4H10] (1), [(Cp*Ta)2B5H 11] (2), [(Cp*Ta)2B5H10) (C6H4CH3)] (3), and [(Cp*TaCl) 2B5H11] (4) in modest yield. Compounds 1-3 are air- and moisture-sensitive but 4 is reasonably stable in air. Their structures are predicted by the electron-counting rules to be a bicapped tetrahedron (1), bicapped trigonal bipyramids (2, 3), and a nido structure based on a closo dodecahedron (4). Yellow tantalaborane 1 has a nido geometry with C2v symmetry and is isostructural with [(Cp*M)2B4H 8] (M = Cr and Re); whereas 2 and 3 are C3v-symmetric and isostructural with [(Cp*M)2B5H9] (M = Cr, Mo, W) and [(Cp*ReH)2B5Cl5]. The most remarkable feature of 4 is the presence of a hydride ligand bridging the ditantalum center to form a symmetrical tantalaborane cluster with a long Ta-Ta bond (3.22 Å). Cluster 4 is a rare example of electronically unsaturated metallaborane containing four TaHB bonds. All these new metallaboranes have been characterized by mass spectrometry, 1H, 11B, and 13C NMR spectroscopy, and elemental analysis, and the structural types were unequivocally established by crystallographic analysis of 1-4. © 2008 Wiley-VCH Verlag GmbH &amp; Co. KGaA.

Metallaboranes of the early transition metals: Direct synthesis and characterization of [{(η5-C5Me5)Ta} 2BnHm] (n=4, m = 10; n = 5, m = 11), [{(η5-C5Me5)Ta}2B 5H10(C6H4CH3)]

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ISSN	02775387
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