Mono(pentamethylcyclopentadienyl)yttrium compounds stabilized by N,N'-bis(trimethylsilyl)benzamidinate ligands

Reaction of YCl3 . 3.5THF with Cp*K followed by [PhC(NSiMe(3))(2)]Li . OEt(2) in THF gives the surprisingly stable yttrium cyclopentadienyl-benzamidinate chloride {Cp*[PhC(NSiMe(3))(2)]Y(mu-Cl)}(2) (1). Thermally induced redistribution of the various ligands leading to disproportionation of the molecule was not observed. The dimer does not split easily, e.g., it does not react with THF to give Cp*[PhC(NSiMe(3))(2)]YCl . THF. Attempts to produce monomeric derivatives of 1 by substitution of the chloride by alkoxy, amide, or alkyl substituents using salt metathesis methodology were not successful. Reaction of 1 with 2 equiv of MeLi in the presence of TMEDA (TMEDA = N,N,N',N'-tetramethylethylenediamine) afforded the structurally characterized Cp*[PhC(NSiMe(3))(2)]Y(mu-Me)(2)Li . TMEDA (2). Compound 2 is a useful precursor for other yttrium pentamethylcyclopentadienyl-benzamidinate derivatives by controlled protolysis: with HC=CCMe(3) or HOAr it yields Cp*[PhC(NSiMe(3))(2)]Y(mu C=CCMe(3))Li . TMEDA (3) and Cp*[PhC(NSiMe(3))(2)]YOAr (4), respectively.