Synthesis and structural characterization of amido scorpionate rare earth metals complexes

Abstract

The reactivity of hybrid scorpionate/cyclopentadienyl ligands in the form of the protio derivatives as a mixture of two regioisomers, namely bpzcpH [1-{2,2-bis(3,5-dimethylpyrazol-1-yl)-1,1-diphenylethyl}-1,3-cyclopentadiene and 2-{2,2-bis(3,5-dimethylpyrazol-1-yl)-1,1-diphenylethyl}-1,3-cyclopentadiene] and bpztcpH [1-{2,2-bis(3,5-dimethylpyrazol-1-yl)-1-tert-butylethyl}-1,3-cyclopentadiene and 2-{2,2-bis(3,5-dimethylpyrazol-1-yl)-1-tert-butylethyl}-1,3-cyclopentadiene], with the tris(silylamide) precursors [M{N(SiHMe₂)₂}₃(thf)_x] of rare earth metals (including the group 3 metals scandium and yttrium) is related to the atomic radii of the metal centres. The reaction with the precursor containing the smallest ion, [Sc{N(SiHMe₂)₂}₃(thf)], did not proceed even heating at reflux temperature in toluene. The reaction with the precursors that contain a medium-sized metal ion, i.e., [M{N(SiHMe₂)₂}₃(thf)₂] (M = Y, Lu), proceeded only at high temperature and gave good yields of the silylenediamide-containing derivatives [M{κ²-NN-Me₂Si(NSiHMe₂)₂}(bpzcp)] (M = Y 1, Lu 2) and [M{κ²-NN-Me₂Si(NSiHMe₂)₂}(bpztcp)] (M = Y 3, Lu 4) by an double activation of Si–H and Si–N bonds. However, the reaction with the precursors that contained the largest metal ions, i.e., [M{N(SiHMe₂)₂}₃(thf)₂] (M = Nd, Sm), proceeded rapidly at room temperature to afford the bis(silylamide) complexes [M{N(SiHMe₂)₂}₂(bpzcp)] (M = Nd 5, Sm 6) and [M{N(SiHMe₂)₂}₂(bpztcp)] (M = Nd 7, Sm 8). Additionally, the alkyl heteroscorpionate yttrium and lutetium complexes [M(CH₂SiMe₃)₂(NNCp)] (M = Y, Lu) reacted with an excess of HN(SiHMe₂)₂ to give the mixed alkyl/amide derivatives [M{N(SiHMe₂)₂}(CH₂SiMe₃)(bpzcp)] (M = Y 9, Lu 10) and [M{N(SiHMe₂)₂}(CH₂SiMe₃)(bpztcp)] (M = Y 11, Lu 12). The structures of the complexes were determined by spectroscopic methods and the X-ray crystal structures of 1, 3 and 5 were also established.