RUTHENIUM PYRIDYL-CARBOXYLATE METALLOLIGANDS AND HETEROMETALLIC ASSEMBLIES

Abstract

Two types of ruthenium(II) pyridyl-carboxylate metalloligands with different pendants were synthesized: [Ru(dppm)2(eta2-O2C¿R¿C5H4N)](OTf) type with pyridine pendants & [RuCl2(dppb)(NC5H4¿R¿COOH)2] type with carboxylic acid pendants. Complementary hydrogen bonding formed between neighboring nicotinic acids in [RuCl2(dppb)(NC5H4¿m-COOH)2] helps to link the molecules into a one-dimensional zigzag chain. Polar and apolar channels are formed by stacking the adjacent chains and they selectively wrap up THF and hexane, respectively. The metalloligand potentials of [Ru(dppm)2(eta2-O2C¿R¿C5H4N)](OTf) were evidenced by reacting them with Lewis acidic MCl2(CH3CN)2 (M = Pd, Pt) or AgOTf to afford heterotrimetallic complexes {[Ru(dppm)2(eta2-O2C¿R¿C5H4N)]2[MCl2]}(OTf)2 (M = Pd, R = -, CH2, C2H2, C6H4; M = Pt, R = -), {[Ru(dppm)2(eta2-O2C¿m-C5H4N)]2[PdCl2]}(OTf)2 and {[Ru(dppm)2(eta2-O2CC5H4N)]2Ag}(OTf)3. The electrochemical properties of both the metalloligands and heterometallic complexes were investigated by Cyclic Voltammetry. Coordination of the metalloligands has greatly improved the reversibility of the redox process and the oxidation potentials of RuII/III.