η1- and η5-Indenyl and Cyclopentadienyl Tri-tert-Butylphosphoraneiminatotitanium Complexes

The compounds (indenyl)Ti(NP-t-Bu3)Cl2 (4), Cp2Ti(NP-t-Bu3)Cl (6), (indenyl)2Ti(NP-t-Bu3)Cl (7), Cp(indenyl)Ti(NP-t-Bu3)Cl (8), Cp3Ti(NP-t-Bu3) (9), (indenyl)3Ti(NP-t-Bu3) (10), and Cp(indenyl)2Ti(NP-t-Bu3) (11) are readily derived from reaction with (dme)NaCp or Li(indenyl) with CpTi(NP-t-Bu3)Cl2 (1) or 4 in the appropriate stoichiometry. X-ray crystallography studies of (indenyl)Ti(NP-t-Bu3)Me2 (5) and 7−11 are reported. In the case of 6 and 9 two cyclopentadienyl rings are bound to the metal in a η5 -bonding mode, whereas in 7, 8, 10, and 11 one of the cyclopentadienyl or indenyl ligands is bound in an η5 mode and the remainder in an η1-fashion. In the case of 10, temperature-dependent 1H NMR spectra infer a η5-η1 ligand exchange process with an approximate barrier of 8−9 kcal/mol. Steric crowding appears to be the major factor determining the binding modes of the cyclopentadienyl and indenyl ligands. These structural data result in a view of the phosphoraneiminato ligand as a sterically demanding, fou...