Isomerisation following the platination of [7,8-Ph2-9,11-I2-7,8-nido-C2B9H7]2−

The synthesis, by electrophilic substitution, and characterisation of two new B-substituted nido diphenylcarboranes is described. [HNMe3][7,8-Ph2-9-I-7,8-nido-C2B9H9] (1) and [HNMe3][7,8-Ph2-9,11-I2-7,8-nido-C2B9H8] (2) were characterised spectroscopically with the structure of the latter additionally confirmed by a crystallographic study. [7,8-Ph2-9,11-I2-7,8-nido-C2B9H8]2− was treated with a source of {Pt(PMe2Ph)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-Ph2-2,2-(PMe2Ph)2-6,7-I2-2,1,8-closo-PtC2B9H7 with both (iodide) substituted boron vertices in the upper part of the icosahedron. The minor products 4 and 5 are, respectively, 1,8-Ph2-2,2-(PMe2Ph)2-6,12-I2-2,1,8-closo-PtC2B9H7 and 1,8-Ph2-2,2-(PMe2Ph)2-10,12-I2-2,1,8-closo-PtC2B9H7, 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.

9-substituted- and 9,11-disubstituted-7,8-nido-diphenylcarboranes have been prepared and the latter platinated to afford three C atom isomerised species.Figure optionsDownload as PowerPoint slide