The synthesis, characterization, and catalytic activity of a series of unprecedented ruthenium-based metathesis catalysts bearing a cis-dichloro arrangement, an N-heterocyclic carbene, and a chelating carbene ligand derived from 2-vinylbenzaldehyde or 2-vinylbenzoic acid ester are presented.

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The title compound, [RuCl 2 (C 8 H 6 O)(C 21 H 26 N 2)]ÁC 4 H 10 O, 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 bystacking and C-HÁ Á ÁCl and C-HÁ Á ÁO 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 = 1 2 , 1 2 and have solvent-accessible void volumes of 695 and 464 Å 3 per unit cell. Related literature For the synthesis and application of the title compound in ring-opening metathesis polymerization (ROMP), see: Slugovc et al. (2004); Burtscher et al. (2006). For thermally switchable initiators for olefin metathesis polymerization, see: Gstrein et al. (2007); Szadkowska & Grela (2008). For a recent authoritative review on ruthenium-based heterocyclic carbene-coordinated olefin metathesis catalysts, see: Vougioukalakis & Grubbs (2010). Experimental Crystal data [RuCl 2 (C 8 H 6 O)(C 21 H 26 N 2)]Á-C 4 H 10 O M r = 670.66 Tetragonal, P4c2 a = 19.8603 (4) Å c = 15.6582 (7) Å V = 6176.1 (3) Å 3 Z = 8 Mo K radiation = 0.71 mm À1 T = 100 K 0.43 Â 0.25 Â 0.22 mm Data collection Bruker SMART APEX CCD diffractometer Absorption correction: multi-scan (SADABS; Bruker, 2003) T min = 0.78, T max = 0.86 90504 measured reflections 8992 independent reflections 7306 reflections with I > 2(I) R int = 0.058 Refinement R[F 2 > 2(F 2)] = 0.029 wR(F 2) = 0.067 S = 1.01 8992 reflections 322 parameters H-atom parameters constrained Á max = 0.42 e Å À3 Á min = À0.31 e Å À3 Absolute structure: Flack (1983), 4175 Friedel pairs Flack parameter: À0.02 (2) Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: BT5164). metal-organic compounds m154 Slugovc et al.