C. J. Groenenboom

CYCLOPENTADIENYLCYCLOHEPTATRIENYLTITANIUM - SUBSTITUTION-REACTIONS AND CHARGE-DISTRIBUTION

Abstract Metallation of (C 5 H 5 )Ti(C 7 H 7 ) occurs much more readily than that of (C 5 H 5 )V(C 7 H 7 ) and (C 5 H 5 )Cr)C 7 H 7 ). Analysis of the products obtained after addition of CH 3 I shows that metallation of (C 5 H 5 )Ti(C 7 H 7 ) has taken place predominantly in the seven-membered ring; this is in contrast to the behaviour of the corresponding vanadium (and chromium) compounds, which are preferentially metallated in the five-membered ring. These observations are discussed in terms of qualitative molecular orbital considerations on the charge distribution in (C 5 H 5 )M(C 7 H 7 )(M = Cr, V, Ti).

ALLYL COMPLEXES OF DICYCLOPENTADIENYL-NIOBIUM(III) AND DICYCLOPENTADIENYL-TANTALUM(III)

Abstract The synthesis and the properties of the complexes Cp2TaCl2, Cp2M(allyl), Cp2M(1-methylallyl) and Cp2M(2-methylallyl) with M  Nb, Ta are described. The complex Cp2TaCl2 has one unpaired electron per tantalum atom, while the allyl complexes are diamagnetic. The IR and PMR spectra indicate that the allyl group is π-bonded to the metal. The mass spectra of the complexes are discussed; the thermal stability of the Cp2Nb- and Cp2Ta-(allyl) complexes was investigated by differential thermal analysis. The properties of the niobium and tantalum complexes are compared with those of the corresponding titanium complexes.

ELECTRON-SPECTROSCOPY OF SOME CYCLOPENTADIENYLCYCLOHEPTATRIENYLMETAL COMPOUNDS

Abstract X-ray photoelectron spectra of (C5H5)M(C7H7) with M = Ti, V, Cr and some related compounds are reported. Data show that the oxidation state of the metal increases in the sequence Cr

Charge distribution in cyclopentadienylcyclooctatetraenetitanium

Metallation of (C5H5)Ti(C8H8) is much more difficult than that of (C5H5)-Ti(C7H7). Analysis of the products obtained after addition of CH3I shows that substitution of (C5H5)Ti(C8H8) takes place predominantly in the C5H5 ring, whereas (C5H5)Ti(C7H7) is metallated preferentially in the C7H7 ring. These results indicate that in (C5H5)Ti(C8H8) the C5H5 ring is more negatively charged than the C8H8 ring, which is in agreement with the results of ESCA measurements. The difference in the behaviour of (C5H5)Ti(C7H7 and (C5H5)Ti(C8H8) is discussed.