Synthesis of Alkylidene-Bridged Cp/Phosphido Group 4 Metal ComplexesPrecursors of the “(CpCPR)M−Constrained-Geometry” Catalyst Family

Phosphide [PHR 1 ]Li (R 1 = cyclohexyl, phenyl) addition to the fulvenes (C 5 H 4 )CMe 2 ( 1 ) and (C 5 H 4 )CHCMe 3 ( 2 ) yields the corresponding phosphinoalkyl-substituted cyclopentadienides. Subsequent deprotonation at phosphorus with LDA followed by transmetalation of the resulting [(C 5 H 4 )CR 2 R 3 PR 1 ]Li 2 dianion equivalents to Cl 2 Ti(NMe 2 ) 2 or Cl 2 Zr(NEt 2 ) 2 (THF) 2 yields the corresponding [“CpCPR 1 ”MX 2 ] “constrained-geometry” systems (eight examples, 11 − 18 ). These systems contain a chiral phosphorus center that is characterized by a low inversion barrier (Δ G ⧧ inv ranging from ca. 7.5 to 10.0 kcal mol - 1 ). The structural and some spectroscopic features of the (CpCPR)Ti and Zr complexes were investigated by DFT calculations. Treatment with a large excess of methylalumoxane gave ethene/1-octene copolymerization catalysts. The [(C 5 H 4 )CMe 2 PR 1 ]ZrX 2 systems gave the most active catalysts in this series.