Synthesis of monomeric permethylyttrocene derivatives. The crystal structures of Cp2*YN(SiMe3)2 and Cp2*YCH(SiMe3)2

Abstract

The reactions of Cp*2YCl·THF (2) with NaN(SiMe3)2 and LiCH(SiMe3)2 yield the monomeric complexes Cp*2YN(SiMe3)2 (3) and Cp*2YCH(SiMe3)2 (4), respectively. The crystal structures of 3 and 4 were determined by X-ray diffraction methods. The crystals of 3 are monoclinic, space group P21/c, with a = 11.466 (2) Å, b = 15.684 (8) Å, c = 31.557 (9) Å, β = 96.36 (2)°, and Z = 8. The structure was refined to R = 0.044. The molecular structures of this complex feature remarkably short Y-N distances (2.274 (5) and 2.253 (5) Å) and Y-methyl contacts. Crystals of 4 are monoclinic, space group I2/c, with a = 17.998 (8) Å, b = 21.758 (8) Å, c = 14.591 (4) Å, β = 92.39 (3)°, and Z = 8. The structure was refined to R = 0.073. The molecular structure exhibits besides a short Y-methyl contact an "α-agostic Y···CH interaction". The yttrium-methyl interactions were also studied by solid-state CP 13C NMR. At room temperature 3 shows two and 4 shows three separate resonances of methyl groups bonded to silicon, supporting the conclusion that in 4 the methyl-yttrium interaction is stronger than in 3. A convenient synthesis of Cp*Na (1) is described.