Structural studies in the [M(bidentate ligand)(unidentate ligand)₅] system. A new co-ordination type for [MI₂(CO)₃{Ph₂P(CH₂) _nPPh₂}] (M = Mo or W; n = 1-3)

The crystal structures of [Mol₂(CO)₃{Ph₂P(CH₂) ₂PPh₂}]·CH₂Cl₂ (1), [Mol₂(CO)₃{Ph₂P(CH₂) ₃PPh₂}] (2), and [WI₂(CO)₃[{Ph₂P(CH₂)PPh ₂}] (3) have been determined by single-crystal X-ray methods at 295 K and refined by least squares to residuals of 0.082, 0.061, and 0.051 for 7 358, 4 572, and 4 522′ observed' reflections respectively. Crystals of (1) are monoclinic, space group P2₁/n, with a = 19.338(6), b = 14.674(6), c = 11.577(5) Å, β = 92.39(3)°, and Z = 4; (2) is monoclinic, space group P2₁/n, with a = 20.85(1), b = 14.64(2), c = 10.510(4) Å, β = 104.11 (5)°, and Z = 4; (3) is monoclinic, space group P2₁/c, with a = 20.880(5), b = 8.646(5), c = 16.706(6) Å, β = 104.17(2)°, and Z = 4. For compounds (1) and (2), with bidentate ligands of large bite, the metal-atom stereochemistry is that usually found for complexes of this type, a capped trigonal prism with the bidentate ligand spanning one of the prism edges. For (3), in which the ligand has only one methylene group bridging the two phosphorus atoms, the bite is smaller and a novel stereochemistry is observed, a pentagonal bi-pyramid with the bidentate ligand spanning one of the pentagonal edges.