Isoelectronic caesium compounds: the triphosphenide Cs[tBu(3)SiPPPSitBu(3)] and the enolate Cs[OCH = CH2]

The caesium triphosphenide Cs[tBu(3)SiPPPSitBu(3)] was accessible from the reaction of CsF with the sodium triphosphenide Na[tBu(3)SiPPPSitBu(3)] in tetrahydrofuran at room temperature. In contrast to the preparation of tetrahydrofuran-solvated silanides M[SitBu(3)] (M= Li, Na, K), our efforts to synthesize the caesium silanide Cs[SitBu(3)] as a tetrahydrofuran complex failed. When tBu(3)SiBr was treated with an excess of caesium metal in tetrahydrofuran at room temperature, the caesium enolate Cs[OCH= CH2] and the supersilane tBu(3)SiH formed rather than the silanide Cs[SitBu(3)]. X-Ray quality crystals of the enolate Cs[OCH = CH2] (orthorhombic, Pnma) were obtained from tetrahydrofuran at ambient temperature. In contrast to the structures of its homologues M[tBu(3)SiPPPSitBu(3)] (M= Na, K), the caesium triphosphenide Cs[tBu(3)SiPPPSitBu(3)] features a polymer in the solid state (orthorhombic, Cmcm).