Reaction of (Cp2*LnH)2 (Ln=Y, La) and Cp2*(2-C6H4CH2NMe2) with esters and amides and molecular structure of [Cp2*Y(μ-OCMe=CHC(OEt)O)]2

The activation of esters and amides by (Cp2*LnH)2 [Ln=Y (la), Ln=La (1b), Cp*=C5Me] and Cp2*Y(2-C6H4CH2NMe2) (2) is described. Compounds 1a and 1b react with ethyl acetate to form Cp2*YOEt (3a) and Cp2*LaOEt (3b). With 1a and ethyl benzoate a 1 :1 mixture of 3a and Cp2*YCH2Ph (4a) is produced and the corresponding 1 :1 mixture of 3b and Cp2*LaOCH2Ph (4b) is observed with 1b. Ethyl acrylate is polymerized rapidly by both 1a and 1b. The reaction of 1a with N,N-dimethyl-acetamide leads to a mixture of the carbonyl insertion product Cp2*Y(OCH(NMe2)Me) (5) and the aldol condensation product Cp2*Y(OC(NM2)(Me)CH2C(O)NMe2) (6). Formation of the condensation product [Cpt2*Y(μ-OCMe=CHC(OEt)O2)] (7) occurred when 2 was reacted with ethyl acetate. The molecular structure of 7 was determined by X-ray diffraction : a =10.129(1) Å, b = 10.650(1) Å, c = 12.093(1)Å, α=77.642(6)°, β=79.402(7), γ= 86.408(9), V=1252.2(2)Å3, space group P1, Z=1. Anisotropic least-squares refinement based on 4871 reflections converged to RF=0.034 and Rw = 0.041 for 428 refined parameters. The more sterically hindered ester ethyl 2-methylpropanoate reacted with 2 to produce the enolate complex Cp2*Y{OC(2-C6H4-CH2NMe2)=CMe2} (Me2CHCOOEt) (8). With N,N-dimethyl-acetamide 2 gives a clean aldol condensation to form 6.