Synthesis and Reactivity of Platinum(II) cis-Dialkyl, cis-Alkyl Chloro, and cis-Alkyl Hydrido Bis-N-heterocyclic Carbene Chelate Complexes

Platinum(II) cis-dimethyl and cis-dineopentyl complexes bearing the alkyl-substituted bis-NHC ligands L-t-Bu, L-Me, and Li-Pr (Lt-Bu = 1,1'-di-tert-butyl-3,3'-methylenediimidazolin-2,2'-diylidene, LMe = 1,1'-dimethyl-3,3'-methylenediimidazolin-2,2'-diylidene, Li-Pr = 1,1'-diisopropyl-3,3'-methylenediimidazolin-2,2'-diylidene) as well as novel cis-alkyl chloro and cis-alkyl hydrido compounds were synthesized. The reactivity of the dimethyl complexes toward dichloromethane and methanol was investigated. Reductive elimination of alkanes from cis-alkyl hydrido complexes requires much higher temperatures than in related bisphosphine systems, which limits their applicability for the generation of reactive, bent platinum(0) d(10)-ML2 fragments for bond-activation chemistry. The platinum(II) complexes were characterized by NMR and IR spectroscopy, mass spectrometry, elemental analysis, and X-ray diffraction in most cases.