HETERONUCLEAR UNBRIDGED QUADRUPLY BONDED COMPLEXES - PREPARATION AND CHARACTERIZATION OF CL2(PME2PH)2MO-W-4CL2(PME2PH)(PPH3), CL2(PME2PH)(PPH3)MO-W-4CL2(PME2PH)2, AND MO-W-4CL4(PME2PH)4

The reaction of Mo(η6-C6H5PMe2)(PMe2Ph)3and WCl4(PPh3)2in the presence of PPh3yields first Cl2(PMe2Ph)2Mo—4WCl2-(PMe2Ph)(PPh3) (1), which undergoes partial isomerization to Cl2(PMe2Ph)(PPh3)Mo—4WCl2(PMe2Ph)2(2). These complexes are the first examples of heteronuclear quadruply bonded complexes of the form Mo—4WCl4L3L′, where L and L′ are tertiary phosphines. The syntheses, 31P[H] NMR spectra, and a single-crystal X-ray structure of a mixed crystal of these complexes are reported. The complexes 1 and 2 form a solid solution in which ligand positions coincide but metal atoms are reversed. The apparent Mo-W distance is 2.2161 (7) Å. The single-crystal structure of the related complex Mo—4WCl4(PMe2Ph)4(3) is also reported. In addition to a systematic 1:1 disorder of these molecules, there is a 14% contamination by Mo2Cl4(PMe2Ph)4. The apparent Mo—4W bond length is 2.207 (3) Å. Crystal data: 1/2, C42H48Cl4P4MoW·0.5C6H14, monoclinic, space group P21/c, a = 23.345 (7) Å, b = 13.629 (3) Å, c = 15.338 (2) Å, β = 81.52 (1)°, V = 4827 (7) Å3, Z = 4, R = 0.040 for 4802 observed reflections; 3, C32H44Cl4P4[(0.57 Mo)(0.43 W)]2, monoclinic, space group C2/c, a = 17.867 (2) Å, b = 10.079 (1) Å, c = 22.354 (2) Å, β = 107.73 (0)°, V = 3834 (7) Å3, Z = 4, R = 0.039 for 2809 observed reflections. © 1990, American Chemical Society. All rights reserved.