Tantalocene complexes as bidentate metalloligands: (C5Me5) (C5H4X)Ta(H-2)(PPh2) (C5Me5) (C5H4X)Ta(CO)(PPh2) (X = PPh2, CH2CH2NMe2)

The synthesis of new bidentate metalloligands derived from tantalocene (C5M e5)(C5H4X)Ta(H-2)(PPh2) (X = PPh2, 2P; X = CH2CH2NMe2 2N) and (C5Me5)(C5H4X )Ta(CO)(PPh2) 4(P,N) is described. When opposed to chromium unsaturated fra gments the phosphino functionalised complexes 2P and 4P act as chelating bi dentate ligands affording Ta(V) (C5Me5)(C5H4PPh2)Ta(H-2) (mu-PPh2)Cr(CO)(4) or Ta(III) (C5Me5)(C5H4PPh2)Ta(CO)(mu-PPh2)Cr(CO)(4) bimetallic complexes. The same reaction carried out starting from 2N gives rise to a mu-phosphid o, mu-hydrido dibridged complex Cp*(C5H4CH2CH2NMe2)TaH(mu-H)(mu-PPh2)Cr(CO) (4). (C) Academie des sciences/Elsevier, Paris.