Synthesis of heterometallic nitridoruthenium(VI) complexes with nickel, palladium, or platinum: New catalysts for the aerobic oxidation of alcohols

Palladium, nickel and ruthenium-based organometallic complexes are increasingly used as aerobic alcohol oxidation catalysts. Heterometallic complexes may offer an advantage over their monometallic counterparts, if the metals act cooperatively. This thesis discusses the synthesis, characterization and reactivity of two heterometallic complexes based on ruthenium, palladium, nickel and platinum.;The reaction between Ni(dppe)(SSiMe₃)₂ and two equivalents of [N(nBu)₄][Ru(N)Cl₂Me₂] produces ClSiMe₃ and the heterometallic complex (dppe)Ni(μ₃-S) ₂{Ru(N)Me₂}₂. The molecular structure of this complex shows the three metals and the two nitrido ligands in a plane with the bridging sulfur atoms above and below that plane. There is an interaction between one of the ruthenium centers and the nickel. The structure differs from that of the closely related complex (dppe)Pt(μ₃-S) ₂{Ru(N)Me₂}₂ which has equivalent Pt-Ru distances and no strong metal-metal interactions. The complexes (dppe)M(μ₃-S) ₂{Ru(N)Me₂}₂ (M=Pt, Pd, Ni) catalyze the oxidation of benzyl alcohol to benzaldehyde in toluene and in supercritical carbon dioxide.;The reaction between [Y][Ru(N)(OH)₂Me₂] (Y = PPh _4, N(n-Bu₄)) and M(OSiMe₃)₂((-)-sparteine) (M = Ni, Pd), produces ((CH₃)₃Si)₂O, H ₂O and the heterobimetallic complex [Y][Ru(N)Me₂(μ ₂-O)₂M(-sparteine)]. Preparations of the new precursors [Y][Ru(N)(OH) ₂Me₂], NiCl₂((-)-sparteine, Ni(OSiMe₃) ₂((-)-sparteine) and Pd(OSiMe₃)₂((-)-sparteine) are described. The complex [PPh₄][Ru(N)Me₂(μ ₂-O)₂Pd((-)-sparteine)] is identified and characterized by NMR spectroscopy and elemental composition as determined by ESI-mass spectrometry.;The scope and limitations of [PPh₄][Ru(N)Me₂(μ-O) ₂Pd((-)-sparteine)] as a catalytic aerobic oxidant of organic alcohols is explored. The complex [PPh₄][Ru(N)Me₂(μ₂ -O)₂Pd((-)-sparteine)] oxidizes aryl and allyl alcohols to their corresponding aldehydes. The complex also catalytically rearranges allylic alcohols to their corresponding unsaturated aldehydes. The mechanism of oxidation for [PPh₄][Ru(N)Me(μ₂-O)₂Pd((-)-sparteine)] closely mirrors that of the previously described heterobimetallic complex [N(n-Bu4)][Os(N)(CH₂SiCH₃)2(μ ₂-O)₂CrO₂]. It is first order in complex and first order in benzyl alcohol.