Synthesis, Characterization, and Rearrangements of Methoxymethyl Ruthenium(II) Complexes with Polypyridine Ligands
摘要:
Three stereoisomeric methoxymethyl complexes, [Ru(bpy)(eta(2)-tpy)(CO)CH2OMe]PF6 (2a-c), have been synthesized and structurally characterized. Also, the precursor complexes cis-[Ru(eta(3)-tpy)(CO)(S)CH2OMe]PF6 (3, 4; S = MeCN, MeOH) have been synthesized and structurally characterized. Packing diagrams indicate extensive pi-pi stacking interactions for 2a-2c. Compounds 2b and 2c are linkage isomers, while 2a has distinct stereochemistry; 2b and 2c establish equilibrium in solution and slowly convert to 2a. Independent studies beginning with pure 2b or 2c did not establish whether one, or both, can isomerize to 2a. Nondissociative trigonal twist mechanisms, in some cases followed by linkage isomerization, can rationalize the isomerizations. Alternatively, isomerization of 2b to 2a may occur by a "conrotatory twist" pathway followed by linkage isomerization. The compounds are models for putative intermediates in electrocatalytic reductions of CO2.