Electron Precise Group 5 Dimetallaheteroboranes [{CpV(μ-EPh)}{μ-η:η-BHE}] and [{CpNb(μ-EPh)}{μ-η:η-BHE}] (E = S or Se).

Synthesis and structural elucidation of various electron precise group 5 dimetallaheteroboranes have been described. Room temperature reaction of [CpVCl] with Li[BH(EPh)], generated from the treatment of LiBH·THF and PhE (E = S or Se), for 1 h in toluene, followed by thermolysis, led to the formation of bimetallic complexes [{CpV(μ-EPh)}{μ-η:η-BHE}], 1 and 2 (1: E = S and 2: E = Se), and [{CpV(μ-SePh)}{μ-η:η-BH(OCH)Se}], 3. One of the striking features of these compounds is that they represent a rare class of distorted tetrahedral clusters having bridging hydrogens. Evaluating the skeletal electron pairs and bonding types, compounds 1, 2, and 3 may be considered as isoelectronic with our earlier reported [(CpV)(BH)]. In an attempt to synthesize the Nb analogues of 1-3, room temperature reactions of [CpNbCl] and Li[BH(EPh)] (E = S or Se) were carried out that afforded compounds [{CpNb(μ-EPh)}{μ-η:η-BHE}], 4 and 5 (4: E = S and 5: E = Se). The solid-state X-ray structures of both 4 and 5 exemplify electronically saturated [MB] systems, and their geometries are analogous to that of [(CpMoCl)BH]. For the extension of this work, reaction of [CpTaCl] (Cp* = η-CMe) with Li[BH(SePh)] was carried out that yielded a tantalaselenaborane cluster [(Cp*Ta)(μ-Se)BHSe(CH)] (6). All the new compounds have been characterized using H, B{H}, C{H} NMR, UV-vis absorption, and IR spectroscopy, mass spectrometry, and X-ray diffraction studies.