Generation of (η2-benzyne)bis(triphenylphosphine)platinum(0):: orthometallation of the Pt(PPh3)2 complexes of benzyne (C6H4) and cyclohexyne (C6H8)

The benzyne-platinum(0) complex [Pt(PPh3)(2)(eta(2)-C6H4)] has been generated by treatment of a mixture of [Pt(PPh3)(2)(eta(2)-C2H4)] and chlorobenzene with 2,2,6,6-tetramethylpiperid-1-yllithium at 0 degrees C and identified by comparison of its P-31 NMR parameters with those of the cyclohexyne analogue, [Pt(PPh3)(2)(eta(2)-C6H8)]. The compounds isolated from the reaction and identified by NMR spectroscopy and X-ray crystallography are the (2,2'-biphenyldiyl)platinum(II) complex [Pt(eta(1):eta(1)-C6H4C6H4)(PPh3)(2)], formed by reaction of [Pt(PPh3)(2) (eta(2)-C6H4)] with free benzyne, and the orthometallated (eta(1)-phenyl)platinum(II) complex [Pt{C6H4(Ph-2)-2}(C6H5)-(PPh3)], formed by internal hydrogen-atom migration in [Pt(PPh3)(2)(eta(2)-C6H4)]. The complex [Pt(PPh3)(2)(eta(2)-C6H8)] undergoes a similar isomerization on heating in benzene to give the (eta(1)-cyclohexen-1-yl)platinum(II) complex[Pt{C6H4(PPh2)-2)(C6H9)(PPh3)], whose structure has also been determined by X-ray crystallography.