in tetrahydrofuran all operations performed under Ar or in vac., slight heating; evapn., mixture of at least 2 compds., Cp2TaCl2 identified by X-ray anal.;

in tetrahydrofuran all operations performed under Ar or in vac., standing for 20-30 min; evapn., mixture of at least 2 compds., Cp2TaCl2 identified by X-ray anal.;

in benzene Ar; 65°C; 15 h; 4 equiv. PMe3;; elem. anal.;;