Asymmetrically Substituted Tetrahedral Cobalt NHC Complexes and Their Use as ALD as well as Low-Temperature CVD Precursors

The synthesis of novel asymmetrically substituted cobalt complexes of the type [Co(CO)(NO)(NHC)(PR3)] (NHC = iPr2Im, PR3 = PMe3 (1), PEt3(2), PHiPr2 (3); PR3 = PMe3;, NHC = Me2ImMe (4), MeiPrIm (5), MetBuIm (6), iPr2ImMe (7); R2Im = 1,3-dialkylimidazolin-2-ylidene) is reported. These complexes are stabilized by N-heterocyclic carbene (NHC), phosphine, carbonyl, and nitrosyl ligands and have been synthesized from the reaction of a NHC-substituted precursor of the type [Co(CO)2(NO)(NHC)] and the corresponding phosphine. The synthesis of [Co(CO)(NO)(MetBuIm)(PMe3)] (6) and [Co(CO)(NO)(iPr2ImMe)(PMe3)] (7) proceeds in a thermal reaction even at room temperature by quantitative replacement of one carbonyl with a phosphine ligand. All of the other complexes were synthesized using photochemical conditions. Complexes 1–6 have been characterized by elemental analysis, IR spectroscopy, and multinuclear NMR spectroscopy and in some cases by X-ray crystallography. All complexes are volatile, are stable upon sublimati...