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Reactions of CpTiCl 2 (Cp = η 5-C 5 H 5) with RMgX (X = Cl, Br) yield the complexes CpTiR 2 (R = CH 2 Ph, η 3-C 3 H 5). The complex Cp Ti(η 3-C 3 H 5) 2 (Cp = η 5-C 5 Me 5) was prepared analogously from Cp TiCl 2 (THF). CpVCl 2 (PEt 3) 2 and Cp´VCl 2 (PEt 3) 2 (Cp´ = η 5-C 5 H 4 Me) were used for the preparation of CpV(CH 2 Ph) 2 , CpV(η 3-C 3 H 5) 2 , CpV(η 3-1-MeC 3 H 4) 2 and Cp´V(η 3-C 3 H 5) 2 , respectively. The corresponding Cp V derivatives could not be obtained. The reaction of CpCrCl 2 (thf) with C 3 H 5 MgCl gives a dimeric complex [CpCr(C 3 H 5)] 2 , probably via intermediate formation of CpCr(C 3 H 5) 2. CpV-bis-allyl complexes are active in the catalytic isomerization of alkenes; a 1,3-hydride shift via a π-allylmetal hydride species is proposed. In contrast no activity in isomerization was observed for CpTi(C 3 H 5) 2 and Cp Ti(C 3 H 5) 2. CpMX 2 L n + 2 RM´ CpMR 2 L m +(nm)L + 2 M´X (1)

Reduction of C P V X~(P R~)~ (X = C1, R = Me, Et; X = Br, R = Et) with A1 or Zn in THF gives dimeric vanadium(I1) complexes [CpVX(PR,)],. Methylcyclopentadienyl compounds are accessible by the same method. Treating the dimers with an exceas of PR, gives CpVx(PF&J,, and treating the dimers with bidentate phosphines, CpVCl(DMPE) and CpVCl(DPPE) are obtained. All compounds are paramagnetic with, in principle, three unpaired electrons on the metal atom. ' H NMR spectra of the complexes show large downfield shifts of the cyclopentadienyl protons (range of 64-250 ppm). The phosphine ligands show smaller shifts, varying between-3.0 and 4.60 ppm for the dimers [CpVX(PR3)], and between-25.5 and-17.0 ppm for CpVCl(DMPE). The complexes are very reactive and their reactions with a variety of substrates, e.g., dioxygen, cyclohexene oxide, alkynes, and carbon monoxide, proceed easily. With a-olefins no reaction (hydrogenation, isomerization, or oligomerization) was observed.

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