Recent studies on metal and metalloid bis(trimethylsilyl)methyls and the transformation of the bis(trimethylsilyl)methyl into the azaallyl and β-diketinimato ligands

Recent results (post-1990) on the synthesis and structures of bis(trimethylsilyl)methyls M(CHR 2 ) m (R = SiMe 3 ) of metals and metalloids M are described, including those of the crystalline lipophilic [Na(μ-CHR 2 )] ∞ , [Rb(μ-CHR 2 )(PMDETA)] 2 , K 4 (CHR 2 ) 4 (PMDETA) 2 , [Mg(CHR 2 )(μ-CHR 2 )] ∞ , P(CHR 2 ) 2 (gaseous) and P 2 (CHR 2 ) 4 , [Yb(CHR 2 ) 2 (OEt 2 ) 2 ] and [{Yb(CR 3 )(μ-OEt)(OEt 2 )} 2 ]; earlier information on other M(CHR 2 ) m complexes and some of their adducts is tabulated. Treatment of M(CHR 2 ) (M = Li or K) with four different nitriles gave the X-ray-characterized azaallyls or β-diketinimates , and (LL′ = N(R)C( t Bu)CHR, L′L′ = N(R)C(Ph)C(H)C(Ph)NR, LL″ = N(R)C(Ph)NC(H)C(Ph)CHR, R = SiMe 3 and Ar = C 6 H 3 Me 2 -2,5). The two lithium reagents were convenient sources of other metal azaallyls or β-diketinimates, including those of K, Co(II), Zr(IV), Sn(IV), Yb(II), Hf(IV) and U(VI)/U(III). Complexes having one or more of the bulky ligands [LL′] − , [L′L′] − , [LL] − , [LL″] − , [L″L‴] − , [LL‴] − and [{N(R)C( t Bu)CH} 2 C 6 H 4 -2] 2− are described and characterized (LL = N(H)C(Ph)C(H)C(Ph)NH, L″L‴ = N(R)C( t Bu)C(H)C(Ph)NR, LL‴ = N(R)C( t Bu)CHPh). Among the features of interest are (i) the contrasting tetrahedral or square-planar geometry for and , respectively, and (ii) olefin-polymerization catalytic activity of some of the zirconium(IV) chlorides.