Chelate ring-opening ruthenium complexes: X-ray crystal structure and solution studies of cis,trans-bis(2-dimethyl-aminoethyl)diphenylphosphino(dichloro)ruthenium(II)

The Ru(II) complex cis,trans-[Ru(Me(2)NCH(2)Ch(2)PPh(2)-P,N)(2)Cl-2] (1) has been characterized in the solid state and in solution. X-ray crystallography showed that complex 1 is monoclinic, space group C-2/c; a = 36.0421, b = 11.4866, c = 31.0540 Angstrom; beta = 104.556 degrees. The structure refined to R = 0.0925 and Rw = 0.223. There are two independent molecules in the unit cell, with normal Ru-P bonds (2.24-2.26 Angstrom), but the Ru-N bonds (2.37-2.42 Angstrom) are 0.2 Angstrom longer than typical values for Ru-N trans to phosphorus. The Cl-Ru-Cl bond angles of 1 are 171.78 and 173.14 degrees. Complex 1 is stable in methylene chloride solution and cyclic voltammetry showed that it undergoes a fully reversible one-electron oxidation at 0.326 V. In methanol, however, 1 (both in air or under N-2) undergoes a two-stage ionization/solvolysis with first order constants at 293 K: 5.40 +/- 0.02 X 10(-4) s(-1) for the first step, and 3.29 +/- 0.03 X 10(-5) s(-1) for the second step accompanied by a colour change from red to green. H-1 and P-31{H-1} NMR spectroscopic studies suggest that the solvolysis is accompanied by P,N-chelate ring-opening. These processes are inhibited by the presence of excess of lithium chloride.