RECENT STUDIES ON METAL AND METALLOID BIS(TRIMETHYLSILYL) METHYLS ANDTHE TRANSFORMATION OF THE BIS(TRIMETHYLSILYL) METHYL INTO THE AZAALLYL AND BETA-DIKETINIMATO LIGANDS

Recent results (post-1990) on the synthesis and structures of bis(trim ethylsilyl)methyls M(CHR(2))(m) (R = SiMe(3)) of metals and metalloids M are described, including those of the crystalline lipophilic [Na(mu -CHR(2))](?)(infinity), [Rb(mu-CHR(2))(PMDETA)](2), K-4(CHR(2))(4)(PMD ETA)(2), [Mg(CHR(2))(mu-CHR(2))](m), P(CHR(2))(m) (gaseous) and P-2(CH R(2))(4), [Yb(CHR(2))(2)(OEt(2))(2)] and [{Yb(CR(3))(mu-OEt)OEt(2))}(2 )]; earlier information on other M(CHR(2))(m) complexes and some of th eir adducts is tabulated. Treatment of M(CHR(2)) (M = Li or K) with fo ur different nitriles gave the X-ray-characterized azaallyls or beta-d iketinimates [Li(LL')](2), [Li(LL')](2) and [K(LL '')(NCAr)](2) (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 reag ents were convenient sources of other metal azaallyls or beta-diketini mates, including those of K, Co(II), Zr(lV), Sn(IV), Yb(II), Hf(IV) an d 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}2C6H4-2](2-) are described and characterized (LL = N(H )C(Ph)C(H)C(Ph)MI, L '' L''' = N(R>Ct(Bu>C(H)C(Ph>NR, LL''' = N(R)C((t )Bu)CHPh). Among the features of interest are (i) the contrasting tetr ahedral or square-planar geometry for [Co(L'L')(2)] and [Co(LL)(2)], r espectively, and (ii) olefin-polymerization catalytic activity of some of the zirconium(IV) chlorides.