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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]

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]

Synthesis, isolation, and structural characterization of unique metal rich diamagnetic cobaltaborane clusters are reported. They were obtained from reactions of monoborane as well as modified borohydride reagents with cobalt sources. For example, the reaction of [Cp*CoCl]2 with [LiBH4·THF] and subsequent photolysis with excess [BH3·THF] (THF = tetrahydrofuran) at room temperature afforded the 11-vertex tricobaltaborane nido-[(Cp*Co)3B8H10] (1, Cp* = η5-C5Me5). The reaction of Li[BH2S3] with the dicobaltaoctaborane(12) [(Cp*Co)2B6H10] yielded the 10-vertex nido-2,4-[(Cp*Co)2B8H12] cluster (2), extending the library of dicobaltadecaborane(14) analogues. Although cluster 1 adopts a classical 11-vertex-nido-geometry with one cobalt center and four boron atoms forming the open pentagonal face, it disobeys the Polyhedral Skeletal Electron Pair Theory (PSEPT). Compound 2 adopts a perfectly symmetrical 10-vertex-nido framework with a plane of symmetry bisecting the basal boron plane resulting in two {CoB3} units bridged at the base by two boron atoms and possesses the expected electron count. Both compounds were characterized in solution by multinuclear NMR and IR spectroscopies and by mass spectrometry. Single-crystal X-ray diffraction analyses confirmed the structures of the compounds. Additionally, density functional theory (DFT) calculations were performed in order to study and interpret the nature of bonding and electronic structures of these complexes. [ABSTRACT FROM AUTHOR]

A metal rich cluster made of Groups 8 and 9 metals was synthesized featuring a µ 5 -boride moiety. [Display omitted] • A new type of μ 5 -boride cluster [(IrCp*){Ru(CO) 2 }{Ru(CO) 3 } 3 (µ -H) 5 B 2 H 2 (μ 5 -B)] (1) is synthesised. • Cluster 1 is a unique boride derived from an eight-vertex closo -dodecadeltahedron by removal of one five-connected vertex followed by capping of a Ru(CO) 3 moiety. • Trimetallic and tetrametallic metallaboranes with a µ 3 -coordinated triply-bridged borylene moiety is also isolated. A series of metal-rich clusters of group 9 containing boride or borylene units have been isolated and structurally characterized. The thermolysis reaction of arachno- [IrCp*H 2 (B 3 H 7)] ( I ) with [Ru 3 (CO) 12 ] allowed to isolate the µ 5 -boride nido -[(IrCp*){Ru(CO) 2 }{Ru(CO) 3 } 3 (µ -H) 5 B 2 H 2 (μ 5 -B)] (1) and the tetrametallic cluster [(IrCp*) 2 {Ru(CO) 2 }{Ru(CO) 3 }(μ -CO) 2 (μ 3 -BH)] (2) with a µ 3 -coordinated triply-bridged borylene moiety. The geometry of cluster 1 can be derived from an eight-vertex closo -dodecadeltahedron by removal of one five-connected vertex followed by capping of a Ru(CO) 3 moiety. The borylene moiety (BH) of cluster 2 is connected in a μ 3 -fashion to the deltahedral face of a tetrametallic tetrahedron (Ir 2 Ru 2). To synthesize the Mn analogue of 2 , thermolysis reaction with [Mn 2 (CO) 10 ] was carried out, that afforded the trimetallic tetrahedral borylene [(IrCp*) 2 {MnH (CO) 3 }(μ -CO) 2 (μ 3 -BH)] (3) along with the known face-fused boride [{Ir(CO) 2 } 3 (IrCp*) 3 (μ 3 -CO)(μ -CO)(μ 5 -BH)] (4). Clusters 2 and 3 are the first triply-bridged borylenes having an Ir metal atom in the core. All these clusters were characterized by NMR (1H, 11B and 13C), infrared (IR) spectroscopies and mass spectrometry. The structure of cluster 1 was confirmed by X-ray diffraction analysis. In addition, density functional theory (DFT) calculations were conducted to interpret and study the nature of bonding and electronic structure of cluster 1. [ABSTRACT FROM AUTHOR]