Synthesis and characterisation of the exo-nido molybdacarborane complex Mo(η-C3H5)(CO)2(7,8-μ-SCH2CH2S-7,8-nido-C2B9H10). Strong BHMo 3-centre bonding

Reaction of [7,8-μ-SCH2CH2S-7,8-nido-C2B9H10]− and MoBr(η-C3H5)(CO)2(MeCN)2 in THF affords the zwitterionic exo-nido molybdacarborane complex Mo(η-C3H5)(CO)2(7,8-μ-SCH2CH2S-7,8-nido-C2B9H10), characterised by 1H- and 11B-NMR spectroscopy and by a crystallographic study. The complex is fluxional (having mirror symmetry on the NMR timescale) in solution at room temperature although asymmetric in the solid state. Data are presented which suggest a significant 3c2e B3H3Mo bond. Deprotonation of [7,8-μ-SCH2CH2S-7,8-nido-C2B9H10]− with LiNiPr2 followed by reaction with MoBr(η-C3H5)(CO)2(MeCN)2 affords Li[1,2-μ-SCH2CH2S-3-(η-C3H5)-3,3-(CO)2-3,1,2-closo-MoC2B9H9] for which 1H- and 11B-NMR data are reported.