Synthesis and characterisation of lanthanide N-trimethylsilyl and -mesityl functionalised bis(iminophosphorano)methanides and -methanediides

Abstract

We report the extension of the series of [BIPMTMSH]- (BIPMR = C[PPh2NR]2, TMS = trimethylsilyl) derived rare earth methanides by the preparation of [Ln(BIPMTMSH)(I)2(THF)] (Ln = Nd, Gd, Tb), 1a-c, in 34-50% crystalline yields via the reaction of [Ln(I)3(THF)3.5] with [Cs(BIPMTMSH)]. Similarly, we have extended the range of [BIPMMesH]- (Mes = 2,4,6-trimethylphenyl) derived rare earth methanides with the preparation of [Gd(BIPMMesH)(I)2(THF)2], 3, (49%) and [Yb(BIPMMesH)(I)2(THF)], 4, (26%), via the reaction of [Ln(I)3(THF)3.5] with [[K(BIPMMesH)]2]. Attempts to prepare dysprosium and erbium analogues of 3 or 4 were not successful, with the ion pair species [Ln(BIPMMesH)2][BIPMMesH] (Ln = Dy, Er), 5a-b, isolated in 31-39% yield. The TMEDA (N',N',N",N"-tetramethylethylenediamine) adducts [Ln(BIPMMesH)(I)2(TMEDA)] (Ln = La, Gd), 6a-b, were prepared in quantitative yield via the dissolution of [La(BIPMMesH)(I)2(THF)] or 3 in a TMEDA/THF solution. The reactions of [Ln(BIPMMesH)(I)2(THF)] [Ln = La, Ce, Pr, and Gd (3)] or 6a-b with a selection of bases did not afford [La(BIPMMes)(I)(S)n] (S = solvent) as predicted, but instead led to the isolation of the heteroleptic complexes [Ln(BIPMMes)(BIPMMesH)] (Ln = La, Ce, Pr and Gd), 7a-d, in low yields due to ligand scrambling.