| Abstract
| - Thermolysis of hydrogen-rich {η5-C5Me5W}H3B4H8 with BH3·THF results in the formation of a bicapped closo-{η5-C5Me5W}2B6H10 (a) cluster and a B−B linked bis-{(η5-C5Me5W)2B5H8}2 (b) cluster. Closo-{η5-C5Me5W}2B6H10 (a) represents an example of a closo cluster exhibiting four bridging hydrogens.
- In addition to (η5-C5Me5W)2B5H9, (η5-C5Me5W)3(μ-H)B8H8, and (η5-C5Me5W)2B7H9 reported earlier,thermolysis of {η5-C5Me5W}H3B4H8 (1) with BH3·THF leads to the formation of bicapped closo-{η5-C5Me5W}2B6H10 (2) in parallel with a B−B linked dimer of {η5-C5Me5W}2B5H9 (4) and bis-{(η5-C5Me5W)2B5H8}2 (3). Reaction of 4 with a 3-fold excess of Fe2(CO)9 in hexane generates an iron analogueof 2, (η5-C5Me5W)2B5H9Fe(CO)3 (5) in 46% yield. All the metallaboranes, 2, 3, and 5, have beencharacterized by 1H, 11B NMR spectra and crystal structure determinations. The structures of 2 and 5appear to follow the regular electron counting rules as they possess seven skeletal electron pairs (sep)appropriate for bicapped octahedral structures. However, their electronic structures revealed by a molecularorbital analysis is more closely related to that of [{η5-C5Me5Re}2B7H7], a cluster that does not obey theclassical electron counting rules. Clusters 2 and 5 are notable examples of closo clusters containing fourbridging hydrogens. 3 is a coupled-cage structure in which two bicapped trigonal bipyramidal frameworks,W2B5, are joined by an exopolyhedral boron−boron bond.
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