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The preparation, characterization, and electronic structure of the first heterometallic μ9-boride cluster [(Cp*Rh)2{Co6(CO)I2}(μ-H)(BH)B)] has been reported. The interstitial boron atom in the title cluster is within the bonding contact of eight metal and one boron atom in a unique tricapped trigonal prism geometry. [ABSTRACT FROM AUTHOR]

Synthesis and structural elucidation of various electron precise group 5 dimetallaheteroboranes have been described. Room temperature reaction of [Cp 2 VCl 2 ] with Li[BH 3 (EPh)], generated from the treatment of LiBH 4 ·THF and Ph 2 E 2 (E = S or Se), for 1 h in toluene, followed by thermolysis, led to the formation of bimetallic complexes [{CpV(μ-EPh)} 2 {μ-η 2 :η 2 -BH 3 E}], 1 and 2 (1: E = S and 2: E = Se), and [{CpV(μ-SePh)} 2 {μ-η 2 :η 2 -BH(OC 4 H 8 )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) 2 (B 2 H 6 ) 2 ]. In an attempt to synthesize the Nb analogues of 1-3, room temperature reactions of [CpNbCl 4 ] and Li[BH 3 (EPh)] (E = S or Se) were carried out that afforded compounds [{CpNb(μ-EPh)} 2 {μ-η 2 :η 2 -B 2 H 4 E}], 4 and 5 (4: E = S and 5: E = Se). The solid-state X-ray structures of both 4 and 5 exemplify electronically saturated [M 2 B 3 ] systems, and their geometries are analogous to that of [(Cp*MoCl) 2 B 3 H 7 ]. For the extension of this work, reaction of [Cp*TaCl 4 ] (Cp* = η 5 -C 5 Me 5 ) with Li[BH 3 (SePh)] was carried out that yielded a tantalaselenaborane cluster [(Cp*Ta) 2 (μ-Se)B 3 H 6 Se(C 6 H 5 )] (6). All the new compounds have been characterized using 1 H, 11 B{ 1 H}, 13 C{ 1 H} NMR, UV-vis absorption, and IR spectroscopy, mass spectrometry, and X-ray diffraction studies.