Stereoselective coordination of prochiral olefins to asymmetric platinum(II) complexes and a diplatinum(II) complex with a single unsupported halide bridge

The chiral complexes [PtMe{cis-1-(N=CHC6H4)-2-(N=CHPh)C6H10}] 1, and [PtMe{trans-1-(N=CHC6H4)-2-(N=CHPh)C6H10}], 2, react with protic acids HBF4 or [H(OEt2)(2)][BAr4] (Ar = 3,5-(CF3)(2)C6H3) in the presence of olefin, with loss of methane, to give complexes of the type [Pt(eta (2)-CH2=CHR){cis/trans-1-(N=CHC6H4)-2-(N=CHPh)C6H10}][BX4] (R = H, Me, Ph, 4-Me-C6H4; X = F, Ar). For prochiral olefins, R = Me, Ph, and 4-Me-C6H4, highly stereoselective (90-95%) olefin coordination was demonstrated by using H-1 and C-13 NMR spectroscopy, and for the complex [Pt(eta (2)-CH2=CHPh){cis-1-(N=CHC6H4)-2-(N=CHPh)C6H10}][BF4] by an X-ray structure determination. Olefin dissociation from [Pt(eta (2)-CH2=CHPh){trans-1-(N=CHC6H4)-2-(N=CHPh)C6H10}[BAr4] occurred in CD2Cl2 to give the dinuclear complex [Pt-2(mu -Cl){trans-1-(N=CHC6H4)-2-(N=CHPh)C6H10}(2)][BAr4], and hydrolysis of [Pt(h(2)-CH2=CH-C6H4-4-Me){trans-1-(N=CHC6H4)-2-(N=CHPh)C6H10}][BF4] gave PhCH=O and [Pt(eta (2)-CH2=CH-C6H4-4-Me){trans-1-(N=CHC6H4)-2-(NH2)C6H10}][BF4]. These are useful model compounds for intermediates in stereoselective alkene polymerization since they contain mutually cis alkenes and M-C sigma -bonds.