Isoelectronic caesium compounds: the triphosphenide Cs[tBu3SiPPPSitBu3] and the enolate Cs[OCHCH2]

Abstract

The caesium triphosphenide Cs[tBu₃SiPPPSitBu₃] was accessible from the reaction of CsF with the sodium triphosphenide Na[tBu₃SiPPPSitBu₃] in tetrahydrofuran at room temperature. In contrast to the preparation of tetrahydrofuran-solvated silanides M[SitBu₃] (M = Li, Na, K), our efforts to synthesize the caesium silanide Cs[SitBu₃] as a tetrahydrofuran complex failed. When tBu₃SiBr was treated with an excess of caesium metal in tetrahydrofuran at room temperature, the caesium enolate Cs[OCHCH₂] and the supersilane tBu₃SiH formed rather than the silanide Cs[SitBu₃]. X-Ray quality crystals of the enolate Cs[OCHCH₂] (orthorhombic, Pnma) were obtained from tetrahydrofuran at ambient temperature. In contrast to the structures of its homologues M[tBu₃SiPPPSitBu₃] (M = Na, K), the caesium triphosphenide Cs[tBu₃SiPPPSitBu₃] features a polymer in the solid state (orthorhombic, Cmcm).