Synthesis and structural analysis of the mixed-ligand seven-coordinate complexes [MI2(CO)(2){P(OR)(3)} {Ph2P(CH2)(n)PPh2}] (M = Mo, R = Me, Et, n=1; R = Et, Pr-i, Ph, n=2; M = W, R = Ph, n=1; R = Me, Et, Pr-i, n=2). A systemwhere the ligand cone angle and ligand 'bite' angle do not affect the coordination geometry

Reaction of [MI2(CO)(3)(NCMe)(2)] with an equimolar amount of Ph2P(CH2)(n)P Ph2 in CH2Cl2 at room temperature gave [MI2(CO)(3) {Ph2P(CH2)(n)PPh2)], whi ch, followed by an in situ reaction with one equivalent of P(OR)(3), afford ed the mixed-ligand seven-coordinate complexes [MI2(CO)(2){P(OR)(3)} (Ph2P( CH2)(n)PPh2}] (M = Mo, R = Me, Et, n = 1; R = Et, 'Pr, Ph, n = 2; M = W, R = Ph, n = 1; R = Me, Et, 'Pr, n = 2) (1-9) in good yield. All nine complexe s have been crystallographically characterised, and they all have surprisin gly very similar capped octahedral geometries with a carbonyl group capping an octahedral face containing a carbonyl, the phosphite ligand and one of the phosphorus atoms of the bidentate phosphine ligand. It appears that the different steric effects of the phosphite ligands and angle of bite of the bidentate phosphines do not cause any significant structural differences. (C) 1999 Elsevier Science S.A. All rights reserved.