cis-Dichlorido(1,3-dimesitylimidazolidin-2-ylidene)(2-formylbenzylidene-κ2C,O)ruthenium diethyl ether solvate

The title compound, [RuCl2(C8H6O)(C21H26N2)]·C4H10O, contains a catalytically active ruthenium carbene complex of the `second-generation Grubbs/Hoveyda' type with Ru in a square-pyramidal coordination, the apex of which is formed by the benzylidene carbene atom with Ru=C 1.827 (2) Å. The complex shows the uncommon cis, rather than the usual trans, arrangement of the two chloride ligands, with Ru—Cl bond lengths of 2.3548 (6) and 2.3600 (6) Å, and a Cl—Ru—Cl angle of 89.76 (2)°. This cis configuration is desirable for certain applications of ring-opening metathesis polymerization (ROMP) of strained cyclic olefins. The crystalline solid is a diethyl ether solvate, which is built up from a porous framework of Ru complexes held together by π–π stacking and C—H...Cl and C—H...O interactions. The disordered diethyl ether solvent molecules are contained in two independent infinite channels, which extend parallel to the c axis at x,y = 0,0 and x,y = {1over 2},{1over 2} and have solvent-accessible void volumes of 695 and 464 Å3 per unit cell