Platination of [3-X-7,8-Ph₂-7,8-nido-C₂ B₉H₈]^2- (X=Et, F)Synthesis and characterisation of slipped and 1,2→1,7 isomerised products

The reaction of the labelled carborane ligand [3-Et-7, 8-Ph₂-7,8- nido -C₂B₉H₈] ^2- with a source of {Pt(PMe₂Ph)₂} ²⁺ affords non-isomerised 1,2-Ph₂-3, 3-(PMe₂Ph) ₂-6-Et-3,1,2-closo-PtC₂ B₉H₈ (1). The analogous reaction between [3-F-7, 8-Ph₂-7,8- nido -C₂B₉H₈] ^2- and {Pt(PMe₂Ph)₂}²⁺ yields 1,8-Ph₂-2,2-(PMe₂Ph)₂-4-F-2,1, 8- closo -PtC₂B₉H₈ (3). Compound 1 has a heavily slipped structure (? 0.72 Å), which to some degree obviates the need for C atom isomerisation. However, that it is a kinetic product of the reaction is evident from the fact that it reverts to isomerised 1,8-Ph₂-2,2-(PMe₂Ph) ₂-4-Et-2,1,8-closo-PtC₂B₉H₈ (2) slowly at room temperature but more rapidly with gentle warming. The heteroatom and labelled-B atom positions in the isomerised compounds 2 and 3 may be explained most simply by the rotation of a CB₂ face of an intermediate based on the structure of 1. Compounds 1-3 were characterised by a combination of spectroscopic and crystallographic techniques. © 2003 Elsevier Science B.V. All rights reserved.