Isomerisation following the platination of [7,8-Ph 2-9,11-I 2-7,8- nido-C 2B 9H 7] 2−

Abstract

The synthesis, by electrophilic substitution, and characterisation of two new B-substituted nido diphenylcarboranes is described. [HNMe 3][7,8-Ph 2-9-I-7,8- nido-C 2B 9H 9] ( 1) and [HNMe 3][7,8-Ph 2-9,11-I 2-7,8- nido-C 2B 9H 8] ( 2) were characterised spectroscopically with the structure of the latter additionally confirmed by a crystallographic study. [7,8-Ph 2-9,11-I 2-7,8- nido-C 2B 9H 8] 2− was treated with a source of {Pt(PMe 2Ph) 2} 2+ and three new platinacarboranes isolated. All were characterised by a combination of 1H, 11B and 31P NMR spectroscopies and by single crystal X-ray diffraction, and all were found to have undergone a 1,2 → 1,7 cage C atom isomerisation, relative to the presumed first product of the metallation. The major product 3 is 1,8-Ph 2-2,2-(PMe 2Ph) 2-6,7-I 2-2,1,8- closo-PtC 2B 9H 7 with both (iodide) substituted boron vertices in the upper part of the icosahedron. The minor products 4 and 5 are, respectively, 1,8-Ph 2-2,2-(PMe 2Ph) 2-6,12-I 2-2,1,8- closo-PtC 2B 9H 7 and 1,8-Ph 2-2,2-(PMe 2Ph) 2-10,12-I 2-2,1,8- closo-PtC 2B 9H 7, having one and two substituted boron vertices in the lower pentagonal belt. These structural results allow speculation on the mechanism of isomerisation of crowded platinacarboranes.