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

Abstract

The benzyne–platinum(>0>) complex [Pt(PPh3)2(η2-C6H4)] has been generated by treatment of a mixture of [Pt(PPh3)2(η2-C2H4)] and chlorobenzene with 2,2,6,6-tetramethylpiperid-1-yllithium at 0 °C and identified by comparison of its 31P NMR parameters with those of the cyclohexyne analogue, [Pt(PPh3)2(η2-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(η1∶η1-C6H4C6H4)(PPh3)2], formed by reaction of [Pt(PPh3)2(η2-C6H4)] with free benzyne, and the orthometallated (η1-phenyl)platinum(II) complex [Pt{C6H4(PPh2)-2}(C6H5)(PPh3)], formed by internal hydrogen-atom migration in [Pt(PPh3)2(η2-C6H4)]. The complex [Pt(PPh3)2(η2-C6H8)] undergoes a similar isomerization on heating in benzene to give the (η1-cyclohexen-1-yl)platinum(II) complex [Pt{C6H4(PPh2)-2}(C6H9)(PPh3)], whose structure has also been determined by X-ray crystallography.