The use of (NHC)AgX salts as transmetallating agents for platinum can be tuned to introduce either one or two NHC ligands per platinum in high yield. Complexes with a single NHC ligand are prepared with an additional DMSO ligand, which can conVeniently be replaced by other ligands such as phosphines to giVe mixed cis NHC/phosphine complexes. Variable-temperature NMR and DFT haVe been used to probe the nature of the restricted rotation of the NHC ligand about the square planar platinum center: experimentally, the barrier has been established as at least 85 kJ mol -1 , and the computational Value has been determined to be 92 kJ mol -1 .

Synthesis of bis(carboxamide) proligands derived from (R,S)-2,2‘-diamino-6,6‘dimethylbiphenyl was readily achieved by treatment of the amine with acid chlorides. Direct reaction with homoleptic alkyls of the group 4 metals cleanly yielded amidate complexes. These complexes were shown by single-crystal X-ray diffraction to be monomeric in the case of titanium and dimeric in the case of zirconium. The complexes formed do not yield well-defined cations upon reaction with standard borate/borane activators, and although some hydroamination catalysis was observed, it was not at a rate that is useful. In-situ treatment of Zr(NMe2)4 with the proligands H2L1-4 yielded complexes of varying nuclearity depending on the steric bulk of the amide substituents, but in contrast to the metal alkyl series, mononuclear species are accessible; the mesityl derivative [(S)-L4Zr(NMe2)2] was found to be a highly enantioselective catalyst for the hydroamination/cyclization of 1-amino-2,2-dimethylpent-4-ene, with an enantiomeric excess of 91%.