Synthesis and Characterisation of Lanthanide N-Trimethylsilyl and -Mesityl Functionalised Bis(iminophosphorano)methanides and -Methanediides

We report the extension of the series of {BIPMH} (BIPM = C{PPh2NR}2, TMS = trimethylsilyl) derived rare earth methanides by the preparation of [Ln(BIPMH)(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(BIPMH)]. Similarly, we have extended the range of {BIPMH} (Mes = 2,4,6-trimethylphenyl) derived rare earth methanides with the preparation of [Gd(BIPMH)(I)2(THF)2], 3, (49%) and [Yb(BIPMH)(I)2(THF)], 4, (26%), via the reaction of [Ln(I)3(THF)3.5] with [{K(BIPMH)}2]. Attempts to prepare dysprosium and erbium analogues of 3 or 4 were not successful, with the ion pair species [Ln(BIPMH)2][BIPMH] (Ln = Dy, Er), 5a–b, isolated in 31–39% yield. The TMEDA (N',N',N",N"-tetramethylethylenediamine) adducts [Ln(BIPMH)(I)2(TMEDA)] (Ln = La, Gd), 6a–b, were prepared in quantitative yield via the dissolution of [La(BIPMH)(I)2(THF)] or 3 in a TMEDA/THF solution. The reactions of [Ln(BIPMH)(I)2(THF)] [Ln = La, Ce, Pr, and Gd (3)] or 6a–b with a selection of bases did not afford [La(BIPM)(I)(S)n] (S = solvent) as predicted, but instead led to the isolation of the heteroleptic complexes [Ln(BIPM)(BIPMH)] (Ln = La, Ce, Pr and Gd), 7a–d, in low yields due to ligand scrambling. OPEN ACCESS Inorganics 2013, 1 47