Crystal and molecular structure of(η 5-C 5H 5)W[C 3(CME 3) 2Me](PME 3)Cl 2, a species with a tetrahedral WC 3, core formed from a tungstenacyclobutadiene complex via attack on tungsten by a phosphorus-donor ligand

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The complex (η 5-C 5H 5)W[C 3(CMe 3) 2Me](PMe 3)Cl 2, prepared previously by the reaction of the tungstenacyclobutadiene complex (η 5-C 5H 5) W[C(Ph)C(CMe 3)C (Ph)]Cl 2 with PMe 3, has been subjected to a single-crystal X-ray diffraction study. This complex crystallizes in the centrosymmetric monoclinic space group P2 1/ c (C 2h 5; No. 14) with a 10.302(3) Å, b 15.314(3) Å, c 14.130(2) Å, β 98.036(16)°, V 2207.4(8) Å 3 and Z = 4. Diffraction data (Mo- K α, 2θ 4.5–50.0°) were collected with a Syntex P2 1 automated four-circle diffractometer and the structure was refined to R 4.7% for all 3919 independent reflections ( R 3.4% for those 3290 data with | F 0| > 3σ(| F 0|)). The molecular geometry approximates that of a “four-legged piano stool” with the tungsten atom surrounded by an η 5-cyclopentadienyl ligand, two chloride ligands (WCl(1) 2.538(2) Å, WCl(2) 2.504(2) Å) a trimethylphosphine ligand (WP 2.600(2) Å) and an η 3-[C 3(CMe 3) 2Me] ligand. The three carbon atoms of the C 3 ring are tightly bound to tungsten (WC(1) 2.139(5) Å, WC(2) 2.150(6) Å WC(3) 2.200(6) Å) and the WC 3 core of the molecule is closer to a “tungstenatetrahedrane” moiety than to the more familiar η 3-cyclopropeniumtungsten (i.e., C 3H 3 +) representation; the C 3 ring is perhaps best termed an η 3-cyclopropenyl system.