Syntheses and structures of some coordinatively saturated and unsaturated diruthenium carbonyl complexes

Reaction of [Ru2(CO)4(μ-DPPM)2(μ-OAc)][PF6] (1) with Et3O+BF4− in MeCN produced coordinatively saturated [Ru2(μ-CO)2(μ-DPPM)2(MeCN)4][BF4]2 (2). Upon addition of an excess amount of a uni-negative anion X− to a solution of 2 in MeCN, a series of neutral, coordinatively unsaturated adducts [Ru2(μ-CO)2(μ-DPPM)2X2] (X−=Cl−, 3a; Br−, 3b; I−, 3c; SH−, 3d; Stol−, 3e; SiPr−, 3f) were readily formed. The reaction of 3a with trimethylamine N-oxide dihydrate produced two isomeric products of [Ru2(CO)2(μ-DPPM)2Cl2(μ-H)(μ-OH)] at a ratio of 4a–4b=2.25. Treatment of 3b and 3c with dimethyl acetylenedicarboxylate produced [Ru2(μ-CO)(μ-DPPM)2(μ-MeO2CCCCO2Me)X2] (X=Br, 5a; I, 5b), whereas treating of 3e and 3f with I2 yielded [Ru2(CO)2(μ-DPPM)2I2(μ-I)(μ-SR)] (R=tol, 6a; iPr, 6b). The structures of 2, 3a, 3c, 3e, 4b, 5a and 6a were determined by X-ray crystallography. The observed RuRu distances are compared and explained in terms of both electronic and steric effects by considering the multiple metalligand (MX) bonding interactions and Alvarezʹs structural parameters including MMX pyramidal angles and the XMMX torsional angles.