Long-Lived Five-Coordinate Platinum(IV) Intermediates: Regiospecific C–C Coupling
journal contributionposted on 25.10.2016, 16:34 by Paul A. Shaw, Guy J. Clarkson, Jonathan P. Rourke
Three different phosphine derivatives of doubly cyclometalated diphenypyridine complexes of Pt(II), 1, were reacted with methyl iodide to give octahedral Pt(IV) complexes, 2, as two isomers. Treatment of either isomer of complexes 2 with AgBF4, to abstract iodide, gave long-lived five-coordinate complexes 3, which could be trapped as pyridine adducts. Complexes 3 underwent a C–C coupling reaction, at a rate that depended on phosphine size, to give a methyl group attached to the original diphenylpyridine. Recylometalation was then performed, and the cycle of reactions was repeated to give a diphenylpyridine doubly methylated on only one phenyl, with complete regiospecificity. NMR was used to demonstrate the geometry of all complexes in solution, with multiple X-ray crystal structures confirming these assignments.