Structural Diversity in Alkaline Earth Metal Complexes of a Phosphine-Borane-Stabilized 1,3-Dicarbanion
作者:Keith Izod、Corinne Wills、Salima El-Hamruni、Ross W. Harrington、Paul G. Waddell、Michael R. Probert
DOI:10.1021/om501183p
日期:2015.6.8
The reaction between (4-tBuC(6)H(4)CH(2))(2)Cri. and one equivalent of PhP(BH3)(CH2SiMe3)(2) (1) in diethyl ether gives the dimeric complex [[PhP(BH3)CH(SiMe3)}(2)]-Ca(OEt2)](2) (2) in good yield. Similar reactions between 1 and one equivalent of either (PhCH2)(2)Sr(THF) or (PhCH2)(2)Ba yield the corresponding drillers [[PhP(BH3)CH(SiMe3)}(2)]-Sr(THF)(1.75)(OEt2)(0.25)](2) (3) and [[PhP(BH3)CH(SiMe3)}Ba(OEt2)(1.75)(THF)(0.25)](2) (4), respectively. Unexpectedly, an. attempt to prepare 3 from a one-pot reaction between SrI2, 1, and two equivalents of PhCH2K gave the complex [[PhP(BH3)CH(SiMe3)}(2)](2)Sr3K2(OEt2)(THF)(2)](2)center dot Et2O (5) in low yield. While superficially similar, compounds 2, 3, and 4 crystallize with distinct structures, which differ either in the chirality of the carbanion centers or in the nature of the bridging group. Compounds 2, 3, and 4 decompose slowly in THF solution to give ethylene, Ae(OEt)(2) (or Ae(OCH=CH2)(2)), and the monocarbanion derivatives [PhP(BH3)CH(SiMe3)}CH2SiMe3}](2)Ae(THF)(n), according to NMR spectroscopy [Ae = Ca, Sr, Ba].