Synthesis and characterization of bis-benzyl and bis-allyl complexes of titanium(III) and vanadium(III); Catalytic isomerization of alkenes with CpV(η3-C3H5)2

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 .