Abstract
The reaction between (4-tBuC6H4CH2)2Ca 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)2Sr(THF) or (PhCH2)2Ba yield the corresponding dimers [[PhP(BH3){CH(SiMe3)}2]Sr(THF)1.75(OEt2)0.25]2 (3) and [[PhP(BH3){CH(SiMe3)}2]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]2Sr3K2(OEt2)(THF)2]2.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}]2Ae(THF)n, according to NMR spectroscopy [Ae = Ca, Sr, Ba].