Formation of planar-chiral alkylphosphine- and aniline-substituted cyclopentadienyl metal complexes and their reactivity toward electrophiles

A wide range of transition metal complexes containing aniline- and alkylphosphine-substituted cyclopentadienyl ligands have been synthesized: CpPIr(CH3)2 (5), CpPIr(H)(Li) (11a,b), CpPIr(H)(Sn(C6H5)3) (13a,b) (CpP=1-(2-dimethylphosphino-1,1-dimethylethyl)-3-tert-butylcyclopentadienyl), CpNIr(C2H4)2 (7), CpNIrI2 (8), CpNIr(O3SCF3)2 (9), CpN(P(CH3)3)IrI2 (10), CpN(P(CH3)3)IrH2 (2), CpN(P(CH3)3)Ir(H)(Li) (15a,b), CpN(P(CH3)3)Ir(H)(Sn(C6H5) (16a,b) (CpN=1-(2-dimethylamino)phenyl-3-tert-butylcyclopentadienyl), CpPZrCl3 (18), CpPZr(CH2Ph)3 (23), CpPZr(CH2Ph)2Cl (20), [(CpP)TiCl3]2 (22), CpNCp′ZrCl2 (Cp′=Cp (23), Cp* (24)), and CpPCp′ZrCl2 (Cp′=Cp (25), Cp* (26). The presence of the planar-chiral CpP and CpN ligands dramatically changes the reactivity at the metal center in comparison to that of the analogous unchelated and achiral pentamethylcyclopentadienyl (Cp*) complexes. Lithium salts 11 and 15 were obtained by deprotonation of dihydride 2 and the earlier prepared dihydride CpPIrH2 (1) with tert-butyllithium; these reactive species show diastereoselectivity in their reactions with Ph3SnCl to form 13a,b and 16a,b, respectively. One enantiomer of diiodide 3 was found to react selectively with (R)-binaphthol to form (R,R)-CpPIr(binaphtholate) (17a) leaving (S)-3 unreacted. Attempts to separate the enantiomers of 3 and 17a were unsuccessful, however, due to the lack of difference in their solubility. DFT calculations carried out on the two possible diastereomers 17a and 17b correctly predict the exclusive formation of 17a. The zirconium and titanium complexes catalyze the polymerization of ethylene to polyethylene and propylene to isotactic polypropylene in the presence of MAO co-catalyst. Compounds 24 and 26 can be methylated to form Cp′Cp*Zr(CH3)2 (Cp′=CpN (27), CpP (28)).