Synthesis and Structural Characterization of New Divanada‐ and Diniobaboranes Containing Chalcogen Atoms

Abstract

The reaction of [Cp(n)MCl(4-x)] (M=V: n=2, x=2; M=Nb: n=1, x=0; Cp=η(5)-C(5) H(5)) with LiBH(4)⋅THF followed by thermolysis in the presence of dichalcogenide ligands E(2)R(2) (E=S, Te; R=2,6-(tBu)(2)-C(6)H(2)OH, Ph) and 2-mercaptobenzothiazole (C(7)H(5)NS(2)) yielded dimetallaheteroboranes [{CpV(μ-TePh)}(2)(μ(3) -Te)BH⋅thf] (1), [(CpV)(2)(BH(3)S)(2)] (2), [(CpNb)(2)B(4)H(10)S] (3), [(CpNb)(2)B(4)H(11)S(tBu)(2)C(6)H(2)OH] (4), and [(CpNb)(2)B(4)H(11)TePh] (5). In cluster 1, the V(2)BTe 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 V(2)BS tetrahedron clusters. Cluster 3 can be considered as an edge-fused cluster in which a trigonal-bipyramidal unit (Nb(2)B(2)S) has been fused with a tetrahedral core (Nb(2)B(2)) by means of a common Nb(2) edge. In addition, thermolysis of an in-situ-generated intermediate that was produced from the reaction of [Cp(2)VCl(2)] and LiBH(4)⋅THF with excess BH(3)⋅THF yielded oxavanadaborane [(CpV)(2)B(3)H(8)(μ(3)-OEt)] (6) and divanadaborane cluster [(CpV)(2)B(5)H(11)] (7). Cluster 7 exhibits a nido geometry with C(2v) symmetry and it is isostructural with [(Cp*M)(2)B(5)H(9+n)] (M=Cr, Mo, and W, n=0; M=Ta, n=2; Cp*=η(5)-C(5)Me(5)). All of these new compounds have been characterized by (1)H NMR, (11)B NMR, and (13)C NMR spectroscopy and elemental analysis and the structural types were established unequivocally by crystallographic analysis of compounds 1-4, 6, and 7.

The Wade–Mingos rules in seven-vertex dimetallaborane chemistry: Hydrogen-rich Cp2M2B5H9 systems of the second and third row transition metals

“…These two experimentally unknown Cp 2 Ta 2 B 5 H 9 systems, which differ in energy by~4 kcal/mol, have TaeTa distances differing by~0.16 Å. However, a hydrogen-richer Cp* 2 Ta 2 B 5 H 11 structure with a similar central bicapped trigonal pyramidal Ta 2 B 5 unit is known experimentally [22]. Such a hydrogen-richer Cp 2 Ta 2 B 5 H 11 is isoelectronic with the Cp 2 M 2 B 5 H 9 (M ¼ Mo, W) systems discussed above.…”

“…Stable dimetallaboranes of nido-like stoichiometry resembling the original B n H nþ4 binary boranes that have been synthesized include the five-vertex derivatives Cp* 2 M 2 B 3 H 7 (M ¼ Co [12,13], Rh [14]), the six-vertex derivatives Cp* 2 M 2 B 4 H 8 (M ¼ Ir [15,16], Ru [17], and Re [18]), and the seven-vertex derivatives Cp* 2 M 2 B 5 H 9 (M ¼ Cr [19], Mo [19,20], W [21]), where Cp* ¼ h 5 -Me 5 C 5 . Hydrogen-richer seven-vertex systems Cp* 2 M 2 B 5 H 11 (M ¼ V [22], Ta [23,24] of arachno-like stoichiometry have also been synthesized. The tantalum derivative has been shown to be capable of activating the CeH bonds in arenes and heteroarenes, possibly involving a Cp* 2 Ta 2 B 5 H 9 intermediate [25].…”

Synthesis, Structures and Chemistry of the Metallaboranes of Group 4–9 with M2B5 Core Having a Cross Cluster M–M Bond

“…Thus, they provide a platform for the evaluation of electronic compatibility or incompatibility of metal and borane fragments. One of the most studied and explored cluster systems in metallaborane chemistry is the M 2 B 5 system reported by us [23][24][25][26][27][28][29][30][31][32][33] and others [34][35][36][37][38][39][40][41]. Earlier, Fehlner and co-workers showed an attractive route for the synthesis of electronically unsaturated metallaboranes, i.e., those, which are formally electron deficient with respect to the number of skeletal electron pairs (sep), required to maintain the observed molecular geometry [34][35][36]42,43].…”

Cross-cluster transition-metal bonding in oblato-nido dimetallaboranes unveiled by topological analysis

“…Their structural peculiarities are the oblate (i. e., flattened) shape (these compounds are termed as oblato-nido species) [8] and the fact that the metal atoms occupy opposite vertexes in such a way that the T-T distance is consistent with possible existence of a cross-cluster bonding interaction. Indeed, short T-T distances have been measured experimentally [3][4][5][6][7]. Such structures are apparently highly hypoelectronic and do not obey the Wade-Mingos rules [9][10][11] as generally do boranes, carboranes and late-transition metallaboranes.…”

“…They constitute a class of compounds which has revealed numerous possibilities for the way metal and borane fragments interact to generate novel structures, demonstrating the important role for the transition metal in the structural arrangements which are observed. Among these compounds the molecules (CpV) 2 B 5 H 11 [4], (Cp ⁄ Cr) 2 B 5 H 9 [5], (Cp ⁄ Mo) 2 B 5 H 9 [6], (Cp ⁄ Ta) 2 B 5 H 11 [6], (Cp ⁄ W) 2 B 5 H 9 [3], and (Cp ⁄ Re) 2 B 5 H 2 Cl 5 [7], whereby Cp ⁄ = C 5 Me 5 , constitute examples of early transitionmetal dimetallaboranes which all adopt the same open and flattened hexagonal bipyramidal nido geometry and possess the electron count of 12 cluster valence electrons. Their structural peculiarities are the oblate (i. e., flattened) shape (these compounds are termed as oblato-nido species) [8] and the fact that the metal atoms occupy opposite vertexes in such a way that the T-T distance is consistent with possible existence of a cross-cluster bonding interaction.…”