ETA-5-PENTAMETHYLCYCLOPENTADIENYLRUTHENIUM(II) COMPLEXES CONTAINING ETA-6-COORDINATED ALPHA-AMINO-ACIDS

Reaction of [Cp*RuCl2]2 with L-alanine (L-alaH) in methanol at room temperature in the presence of NaOMe yields the complex Na[Cp*RuCl(L-ala)] (1), which contains a five-membered N,O-coordinated chelate ring. The analogous complex Na[Cp*RuCl(L-phe)] (2) is obtained under similar conditions but at 0-degrees-C in 90% yield. At temperatures above 20-degrees-C both 2 and the eta6-coordinated complex [Cp*Ru(L-pheH)]Cl (4) are obtained, with the proportion of the latter increasing with temperature. Compound 4 is obtained in 88% yield by refluxing [Cp*RuCl2]2 and L-phenylalanine (L-pheH) in CH3OH/CH3ONa followed by separation from 2. The analogous ruthenium(II) sandwich complexes 5-10 were obtained from L-tyrosine and L-tryptophane and various derivatives. [Cp*Ru(L-met)] (3), prepared by the reaction of [Cp*RuCl2]2 with L-methionine (L-metH) in CH3OH/CH3ONa, displays N,O,S-coordination.