Small heteroborane cluster systems. 3. Characterization, deprotonation, and transition-metal chemistry of the small phosphorus-bridged pentaborane(9) system (.mu.-diphenylphosphino)pentaborane

The complete spectroscopic characterization of the small phosphorus-bridged pentaborane (9) cluster (μ-diphenylphosphino)-pentaborane, [μ-(C 6 H 5 ) 2 PB 5 H 8 ] (1), is reported. The MNDO calculated structure for 1 shows that the B−P−B interaction can be best described as consisting of two two-center-two-electron B−P bonding interactions. Indirect support for the involvement of the lone pair of electrons on the phosphorus in cage bonding is obtained from the failure of 1 to react with [(CH 3 CN) 3 Mo(CO) 3 ] under forcing conditions