RUTHENIUM PI-COMPLEXES OF O-BENZOQUINONE

The oxidative addition of catechol to triruthenium dodecacarbonyl results in either tetranuclear ([Ru2(eta2:eta6-mu2-O2C6H4)(CO)4]2, 1a) or hexanuclear ([Ru3(eta2:eta4-mu2-O2C6H4)(CO)8]2, 2) complexes which contain pi-bound o-benzoquinone ligands. Lewis bases readily add to these complexes to give either the mononuclear complexes Ru(eta2-O2C6H3R)(CO)2{EPh3}2 (3a-d: R = H, Me; E = P, As) and Ru(O2C6H4)(CO)n(py)3-n (8 (n = 2), 9 (n = 1)), or eta4-pi-complexes such as [Ru2(eta2:eta4-mu2-O2C6H4) (CO)4{EPh3}]2 (4a,b: E = As, Sb). Mild oxidants such as iodine also oxidatively add to the Ru-Ru bond in 1a to give the dinuclear complex Ru2(mu2-I)(eta2:eta4-mu2-O2C6H4)(CO)4I (5), where the ruthenium atoms are bridged by both iodide and quinone ligands. New complexes have been characterized by elemental analyses, IR, Raman, and H-1 and C-13 NMR spectroscopy, and electrochemistry. X-ray crystallographic results for four of these compounds are presented, with important unit cell data being as follows: 1a, Ru4C20H8O12, crystallizes in the triclinic space group P1BAR, Z = 1, a = 6.585(2) angstrom, b = 8.813(2) angstrom, c = 10.416(2) angstrom, alpha = 99.31(3)degrees, beta = 105.65(3)degrees, gamma = 108.92(3)degrees; 3a, RuC44H34O4P2, crystallizes in the orthorhombic space group Pbcn, Z = 4, a = 19.694(3) angstrom, b = 10.770(2) angstrom, c = 17.348(2) angstrom; 4a, Ru4C56H38As2O12, also crystallizes in the orthorhombic space group Pbcn, Z = 4, a = 16.412(3) angstrom, b = 20.624(3) angstrom, c = 15.483(3) angstrom; 5, Ru2C10H4I2O6.1/2CH2Cl2, crystallizes with two independent molecules per unit cell in the triclinic space group P1BAR, Z = 4, a = 10.222(2) angstrom, b = 12.418(2) angstrom, c = 14.621(2) angstrom, alpha = 107.97(1)degrees, beta = 102.59(1)degrees, and gamma = 93.87(1)degrees.