Haloalkyl complexes of the transition metals. Part 5. The synthesis and reactions of some new pentamethylcyclopentadienyl halomethyl and methoxymethyl complexes of molybdenum(II) and tungsten(II) and the X-ray crystal structure of the cationic ylide complex [η-C 5Me 5W(CO) 3CH 2PPh 3

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Synthetic routes are described for the new halo- methyl complexes of the type [η-C 5Me 5M(CO) 3- CH 2X]. The complexes where M = Mo, X = Cl or OMe and M = W, X = Cl, I, OMe have been fully characterized. Reaction of [η-C 5Me 5Mo(CO) 3CH 2Cl] with PPh 3 in methanol under reflux or acetonitrile at room temperature gives [η-C 5Me 5Mo(CO) 2(PPh 3)- Cl], whereas reaction of [η-C 5Me 5W(CO) 3CH 2I] with PPh 3 under similar conditions gives the cationic phosphorus ylide complex [η-C 5Me 5W(CO) 3CH 2- PPh 3]I. The structure of this ylide complex has been determined by X-ray crystallography. The complex crystallizes with half a molecule of CH 2Cl 2 in the monoclinic space group P2 1/ n with a = 16.616- (8), b = 11.738(6), c = 18.126(9) Å, β = 101.74(2)° and Z = 4. The structure was solved and refined to R = 0.076. It confirms the formulation of the compound and the presence of the ylide ligand, WC ylide 2.34(2) Å, PC ylide 1.82(2) Å and the WC ylideP angle of 119(1)°.