The relationship between the molecular structure of and the mechanism of the fluxional behaviour of M(PR3)2-units in closo-twelve-atom metallaheteroboranes

Article abstract of DOI:10.1016/0022-328X(95)05718-5

The upper limit of the free energy of the barrier to rotation of the platinum bis-phosphine unit in <3,3-(PMe2Ph)2-closo-3,1,2-PtC2B9H11> 1 is < 30 kJ mol^-1 in dichloromethane solution.This relatively low value is similar in magnitude to crystal-packing forces, and compound 1 crystallises from CH2Cl2-hexane solution as a 1:1 mixture of two different conformers with significantly different, platinum-to-C2B3 bonding.These observations lead to the proposal of a general mechanism for the mutual rotation of units above C2B9H11.Keywords: Platinum; Carborane; Metallacarborane; Fluxionality; Crystal structure; Mechanism.