CYCLOPENTADIENYL, INDENYL AND BIS(CYCLOPENTADIENYL) TITANIUM IMIDO COMPOUNDS

The titanium tert-butyl imido compounds [Ti(NBu(t))Cl-2(NC(5)H(4)R-4)( n)] (R = H, n = 2 or 3; R = Bu(t), n = 2) have been found to be entry points to the half-sandwich eta(5)-cyclopentadienyl derivatives [Ti(et a(5)-C(5)R'(4)R '')(NBu(t))Cl(NC(5)H(4)R-4)] (R = Bu(t), R' = R '' = H or Me; R = H, R' = H, R '' = H, Me or Pr-i; R = H, R' = Me, R '' = Me , Et or C4H7), the eta(5)-1,2,3 -trimethylindenyl species [Ti(eta(5)-C (9)H(4)Me(3)) (NBu(t))Cl(NC(5)H(4)Bu(t)-4)] and the bis(eta(5) 5-cyclo pentadienyl) compound [Ti(eta(5)-C5H5)(2)(NBu(t)(NC5H5)], the crystal structure of which has been determined. The complex [Ti(eta(5)-C5H5)(N Bu(t))Cl(NC5H5)] readily loses pyridine under vacuum in the solid Stat e to form the binuclear complex [Ti-2(eta(5)-C5H5)(2)(mu-NBu(t))(2)Cl- 2]. Treatment of [Ti(eta(5)-C(5)Me(4)R)(NBu(t))Cl(NC5H5)] (R = Me or E t) with Na[C5H5] gives the corresponding mixed-ring sandwich derivativ es eta(5)-C5H5)(eta(5)-C(5)Me(4)R)(NBu(t))Cl(NC5H5)]. Addition of Li[C 9H7] to [Ti(eta(5)-C5H5)(NBu(t))Cl(NC5H5)] gave the eta(5)-cyclopentad ienyl, eta(3)-indenyl mixed-ring analogue [Ti(eta(5)-C5H5)(eta(3)-C9H7 )(NBu(t))(NC5H5)]. The complex [Ti(eta(5)-C5H5)(2)(NBu(t))(NC5H)] unde rgoes a room-temperature cyclopentadienyl ligand-redistribution reacti on with [Ti(NBu(t))Cl-2(NC5H5)(2)] forming [Ti(eta(5)-C5H5)(NBu(t))Cl( NC5H5)] in quantitative yield. Variable-temperature NMR spectra for th e half-sandwich complexes show that the co-ordinated pyridine exchange s with free pyridine via an associative mechanism. The compound i(eta( 5)-C5H5)(eta(5)-C(5)Me(4)Et)(NBu(t))(NC5H5)] is also fluxionaI and exh ibits reversible pyridine dissociation at higher temperatures and rest ricted rotationabout the Ti-N (pyridine) bond at lower temperatures.