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

Abstract

The Ru(II) complex cis, trans-[Ru(Me 2NCH 2CH 2PPh 2- P, N) 2Cl 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 Å; β = 104.556°. 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 Å), but the Ru-N bonds (2.37–2.42 Å) are 0.2 Å longer than typical values for Ru-N trans to phosphorus. The Cl-Ru-Cl bond angles of 1 are 171.78 and 173.14°. 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 × 10 −4 s −1 for the first step, and 3.29 ± 0.03 × 10 −5 s −1 for the second step accompanied by a colour change from red to green. 1H and 31P{ 1H} 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.