Synthesis and characterisation of the bidentately attached linear triphos complexes [MXY(CO)(L-P,P ')(eta(2)-RC2R)] {M = Mo, W; X, Y = Cl, Br, I; L =PhP(CH2CH2PPh2)(2); R = Me, Ph}. X-ray crystal structures of [WX2(CO)(L-P,P ')(eta(2)-PhC2Ph)] (X = Br and I) and [MoI2(O){Ph2P(CH2)(2)PPh(CH2)(2)POPh2-P,P ',O}]

Reaction of equimolar quantities of [MXY(CO)(NCMe)(eta(2)-RC2R)(2)] and L { L = PhP(CH2CH2PPh2)(2)} in CH2Cl2 at room temperature gives the bidentately coordinated triphos complexes [MXY(CO)(L-P,P')(eta(2)-RC2R)] (M = Mo, X = Y = I, R = Me or Ph; M = W, X = Y = Pr, R = Me or Ph; M = W, X = Pr, Cl, Y = I, R = Me or Ph) (1-8) in high yield. The molecular structures of [WX2(CO )(L-P,P')(eta(2)-PhC2Ph)] (X = Br, I) have been determined crystallographic ally and are equivalent. The coordination geometry about the tungsten atom in both complexes is distorted octahedral with two adjacent phosphorus atom s in the triphos ligand, a halide and a carbonyl ligand occupying the equat orial plane, with the diphenylacetylene and the other halide atom occupying the axial positions. The C-13-NMR spectrum of WBr2(CO)(L-P,P')eta(2)-PhC2P h (4) shows the diphenylacetylene ligand is donating four electrons to the metal. Refluxing a slightly wet acetonitrile solution of [MoI2(CO)(L-P,P')( eta(2)-MeC2Me)] for 24 h affords the unusual crystallographically character ised molybdenum(IV) oxidised triphos complex [MoI2(O){Ph2P(CH2)(2)PPh(CH2)( 2)POPh2-P,P',O}] (9). (C) 1999 Elsevier Science S.A. All rights reserved.