Phosphino-alkoxide ligands

Isolation of the first examples of monomeric lanthanide alkoxides evidenced the importance of the a-effect . Use of a highly hindered phosphino-alkoxide ligand afforded mononuclear, 6-coordinated Ln(OCtBu2CH2PMe2)3 (Ln = Y, Nd) with facial arrangement of the bidentate ligands (Fig. 14, Table 8). The... 

Using a highly hindered phosphino-alkoxide ligand, lanthanoid metal complexes [Ln(OCBu2CH2PMe2)3l (Ln = Y or Nd) have been obtained [30], These are the first monomeric homoleptic examples of lanthanide alkoxide complexes. The bulky substituents... 

Hitchcock, P.B., Lappert, M.F., and MacKinnon, A.l. (1988) Use of a highly hindered phosphino-alkoxide ligand in the formation of monomeric homoleptic lanthanoid metal complexes X-ray structures of [Ln(r -OCBu2CH2PMe2)3] (Ln = Y or Nd). Journal of the Chemical Society, Chemical Communications, 1557-1558. 

Vinylsilane to copper transmetallation has entered the literature,93 93a,93b and a system suitable for catalytic asymmetric addition of vinylsilanes to aldehydes was developed (Scheme 24).94 A copper(l) fluoride or alkoxide is necessary to initiate transmetallation, and the work employs a copper(ll) fluoride salt as a pre-catalyst, presumably reduced in situ by excess phosphine ligand. The use of a bis-phosphine was found crucial for reactivity of the vinylcopper species, which ordinarily would not be regarded as good nucleophiles for addition to aldehydes. The highly tailored 5,5 -bis(di(3,5-di-tert-butyl-4-methoxyphenyl)phosphino-4,4 -bis(benzodioxolyl) (DTBM-SEGPHOS) (see Scheme 24) was found to provide the best results, and the use of alkoxysilanes is required. Functional group tolerance has not been adequately addressed, but the method does appear encouraging as a way to activate vinylsilanes for use as nucleophiles. 

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