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With tertiary phosphines the ethyl complex gives the endo-ethyl derivatives (x-C,H,) (1 -endo-EtC,H,) MoPR,CI. The complex (X-c5+t-( 6) (1 -endo-EtC,H,)MoPCIMe,Ph reacts with thallium tetrafluoroborate to give the ethyl cation [(sc-C6H5)8MoPR,Ef]+BFp-.This and related cations may also be prepared from the hydridoethylene cations and tertiary phosphine. Mechanisms for these reactions are discussed.Oxford OX1 3QRWE continue to study the chemistry of the bis(x-cyclo-pentadieny1)-molybdenum and -tungsten systems in order to unravel factors affecting reactivity and mechanism in organo-transition metal chemistry. For example, the bent bis-x-cyclopentadienyl system provides an opportunity to investigate essentially &-orientated MXR or MR, systems, which are relatively rare. Here we describe the often unexpected results of attempts to prepare such complexes. A brief communication of some of this work has been given.l Chemical Stdies.-Treatment of the dichloride ( X -C5H,),MC1, (I; M = Mo) with an excess of ethylaluminium &chloride dimer, followed by ethanolysis gives, in approximately equal yields, garnet crystals (11) and a water soluble cation isolable as a white hexafluorophosphate salt (111). The data in the Table together with a crystal structure determination shows the garnet compound to be the chloroethyl derivative (x-C,H,),MoEtCl (11). This is soluble in benzene and acetone but only very slightly soluble in light petroleum. Solutions in air show signs of decomposition after a few hours whilst 1 F.

Heating of white phosphorus, phosphorus trichloride, and cyclopentene at 220 "C gives trans-I ,2bis(dich1orophosphino)cyclopentane ( I ) , which with phenylmagnesium bromide gives trans-l,2-bis(diphenylphosphino)cyclopentane (dpcp) (2); compound (2) forms the adduct Ni(dpcp) Br2.CH2C12, which readily crystallises as a conglomerate and the pure eqantiomers may be separated by hand allowing resolution of (2), and catalytic hydrogenation of methyl(N-benzoy1)dehydrophenylalanine using resolved (2) and a rhodium catalyst gave a hydrogenated product of 100% optical purity.-179 + 4".

The reversible reaction [W(q-C,H,),(PR,)CD,]++ TREATMENT of the compound [W(q-C,H,),(C,H,)Me]+PF,-[W(q-C6HJ2(CD2PR3)D]+ and related reactions are (I) with dimethylphenylphosphine gives, as the first described ; it is proposed that they proceed via a revers-product, orange crystals of [W(q-C,H,),(CH,CH,PMe,Ph)ible equilibrium W-CH, $ W( =CH,)H. Me]+PF,-(11). The crystal structure of (11) has been

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