Selective Formation of cis(X)- and trans(X)-Ru(dmbpy)(CO)2X2 Complexes (X = Cl, Br, I, SCN) from Monomeric and Dimeric Ru-mono(dmbpy) Carbonyl Complexes (Dmbpy = 4,4-Dimethyl-2,2-bipyridine)

Aqueous hydrogen halides HX (X = Cl, Br, I) are shown to be excellent halogen sources for the synthesis of a series of halogen-containing ruthenium mono(2,2ʹ-bipyridine) carbonyl complexes Ru(dmbpy)(CO)2X2 (dmbpy = 4,4ʹ-dimethyl-2,2ʹbipyridine), as well as effective reagents for the attack of the Ru-Ru bond in the dimer [Ru(dmbpy)(CO)2Cl]2. Selective syntheses were established for both cis- and trans-halogen complexes in the case of Cl- and of Br-containing derivatives, but the only stable isomer containing iodine was trans(I)-Ru(dmbpy)(CO)2I2. The failure to obtain the cis isomer was probably due to sterical effects. Furthermore, a novel S-bound trans(SCN) analogue was synthesized and structurally characterized. In all experiments, the reaction conditions selected led to complete halogen exchange; no mixed halogen or pseudohalogen complexes were detected.