Bis(cyclopentadienyl)diferrocenyl compounds of vanadium and tantalum

In the reaction of vanadocene and tantalocene dichlorides with ferrocenyl lithium (molar ra-tio 1:2) in toluene, bis(cyclopentadienyl)diferrocenyl compounds of vanadium (C5H5)2V[C5H4FeC5H5]2 (1) and tantalum (C5H5)2Ta[C5H4FeC5H5]2 (2) were obtained, yielding 43% and 48%, respectively. Black powder 1 (diff. mp 110°C) and brown crystals 2 (diff. mp 138°C), soluble in aromatic hydrocarbons and po-lar organic solvents, were identified by EPR (qi = 1.9946, Ai = 62.6 for 1 and qi = 1.9860, Ai = 102.0 for 2), IR spectroscopy (480, 494, 830, 1002, 1118, 1410 cm1 for 1 and 482, 496, 821, 1008, 1111, 1412 cm1 for 2) and elemental analysis. Thermolysis of the complexes at 200°C (3 h) in a glass evacuated ampoule led to formation of ferrocene and black non-volatile pyrophoric substances that did not contain the original bis-cyclopentadienyl structure [(C5H5)2V and (C5H5)2Ta].