Synthesis and electrochemistry of ruthenium complexes with an oxygen tripod ligand

Abstract

Reaction of [Ru(COD)Cl2]x (COD = 1,5-cyclooctadiene) with NaLOEt afforded LOEt(COD)RuCl (1). The average Ru-O, average Ru-C and Ru-Cl distances in 1 are 2.129, 2.164, and 2.398(3) ̊, respectively. Treatment of 1 with AgBF4 in acetone/H2O afforded [LOEt(COD)Ru(OH2)]BF4 (2), which reacts with L to give the respective adducts [LOEt(COD)RuL]BF4 (L = t-BuNH2 (3), p-MeC6H4NH2 (4), NH3 (5), N2H4, (6), pyridine (7), 4,4′-bipyridine (8), MeCN (9), Et2S (10), and Me2SO (11)). The structures of 3 and 4 have been characterized by X-ray crystallography. The average Ru-O, Ru-C, and Ru-N distances in 3 are 2.115, 2.162, and 2.197(6) ̊, respectively. The corresponding bond distances for 4 are 2.113, 2.160 and 2.174(5) A. Reaction of 8 with 2 afforded the 4,4′-bipyridine-bridged binuclear complex [{LOEt(COD)Ru}2(μ-4,4′-bipy)](PF6)2 (12). Deprotonation of complexes 2 and 4 gave the hydroxide LOEt(COD)RuOH (13) and the amide LOEt(COD)Ru(NHC6H4Me-p) (14), respectively. The structure of [LOEt(CO)(PPh3)Ru(OH2)]BF4 (15) has been characterized by X-ray crystallography. The average Ru-O(LOEt), Ru-C, Ru-P, and Ru-O(aquo) distances in 15 are 2.118, 1.83(1), 2.285(3), and 2.091(7) A, respectively. Interaction of 15 with p-MeC6H4NH2 PPh3, and NaN3 gave [LOEt(CO)(PPh3)Ru(p-MeC6H4NH 2)]BF4 (16), [LOEt(PPh3)2Ru(CO)]PF6 (17), and LOEt(CO)(PPh3)RuN3 (18), respectively. Deprotonation of 15 and 16 afforded the hydroxide LOEt(CO)(PPh3)Ru(OH) (19) and amide LOEt(CO)(PPh3)Ru(NHC6H4Me-p) (20), respectively. Treatment of Ru(CO)Cl(H)(PPh3)3 with NaLOEt afforded the hydride LOEt(CO)(PPh3)RuH (21), which reacts with tosyl azide to give the Ru(II) tosylamide LOEt(CO)(PPh3)Ru(NHSO2C6H 4Me-p) (22). Reaction of [LOEt(PPh3)2Ru(MeOH)]+ with t-BuNC, CNpy (4-cyanopyridine), Me2SO, and SO2 afforded the respective adducts [LOEt(PPh3)2RuL]+ (L = t-BuNC (23), CNpy (24), Me2SO (25), SO2 (26)), isolated as their PF6 salts. The cyclic voltammograms for the Ru-LOEt complexes show reversible oxidation couples assignable to Ru(III/II) couples. The availability of electrons in the LOEtRu complexes for back-bonding can be accessed by their v(C≡O) and Ru(III/II) potentials. © 1999 American Chemical Society.