363595-17-9Relevant academic research and scientific papers
Chemistry of metal-bound anion radicals. A family of mono- and bis(azopyridine) chelates of bivalent ruthenium
Shivakumar, Maya,Pramanik, Kausikisankar,Bhattacharyya, Indranil,Chakravorty, Animesh
, p. 4332 - 4338 (2008/10/08)
The reaction of the dihydride [Ru(II)(H)2(CO)(PPh3)3], 3, with excess azo-2,2'-bipyridine (abp) in boiling dry benzene has afforded the diradical bischelate [Ru(II)(abp.-)2(CO)(PPh3)], 4, and the hydridic monochelate monoradical [Ru(II)(abp.-)(H)(CO)(PPh3)2], 5. A similar reaction between 3 and 2-(p-chlorophenylazo)pyridine (Clpap) did not yield a bischelate, but the hydridic monoradical [Ru(II)(Clpap.-)(H)(CO)(Pph3)2], 6, has been isolated. Upon treatment of 4-6 with NH4PF6 in a wet dichloromethane-acetonitrile medium, the one-electron-oxidized salts 4+PF6-, 5+PF6-, and 6+PF6- are isolated, H+ being the oxidizing agent. The X-ray structures of 4+PF6-.CH2Cl2, 5+PF6-·H2O, and 6+PF6- have been determined. In the monoradical 4+ the azo N-N bond lengths in the two chelate rings are 1.284(6) and 1.336(6) A, showing that the radical electron is localized in the latter ring. The half-filled extended Huckel HOMO is indeed found to be so localized, and it has a large azo character. Complexes 4-6 display radical redox couples with E(1/2) in the range -0.5 to +0.10 V vs SCE. The E(1/2) values qualitatively correlate with corresponding v(co) values (1900-2000 cm-1). The monoradicals (S = 1/2) 4+, 5, and 6 uniformly display a strong EPR signal near g = 2.00. Metal-mediated magnetic interaction makes the EPR-silent diradical 4 strongly antiferromagnetic with J = -299 cm-1. Crystal data are as follows: (4+PF6-·CH2Cl2, C40H33Cl2F6N8OP2Ru) monoclinic, space group P21/c (no. 14), a = 14.174(6) A, b = 16.451(4) A, c = 18.381(4) A, β = 98.00(3)°, Z = 4; (5+PF6-·H2O, C47H41F6N4O2P3Ru) monoclinic, space group P21/n (no. 14), a = 9.433(2) A, b = 38.914(17) A, c = 13.084(3) A, β = 103.47(2)°, Z = 4; (6+PF6-, C48H39ClF6N3OP3Ru) monoclinic, space group P21/n (no. 14), a = 10.496(5) A, b = 22.389(8) A, c = 19.720(6) A, β = 90.53(3)°, Z = 4.
