Synthesis and Homomolecular Metalation of Trialkylsilylphosphanides of Calcium and Barium

Metalation of triisopropylsilylphosphane with bis(tetrahydrofuran-O)calcium bis[bis(trimethylsilyl)amide] in tetrahydropyran (thp) in a molar ratio of 3:2 yields (Me3Si)2NCa[μ-P(H)SiiPr3]3Ca(thp)3 (1) containing a trigonal-bipyramidal Ca2P3 core, the metal atoms occupying apical positions. Reaction of two equivalents of triisopropylsilylphosphane or -arsane with bis(tetrahydrofuran-O)barium bis[bis(trimethylsilyl)amide] in tetrahydrofuran gives the corresponding bis(phosphanide) 2 and bis(arsanide) 3, compounds of the type (thf)3Ba[μ-E(H)SiiPr3]Ba(thf)2E(H)SiiPr3 with E = P, As. The equimolar reaction of (tri-tert-butylsilyl)phosphane with (thf)2Ba[N(SiMe3)2]2 in toluene yields heteroleptic dimeric (thf)2Ba[N(SiMe3)2][P(H)SitBu3] (4). Addition of a further equivalent of H2PSitBu3 leads to the formation of homoleptic (thf)nBa[P(H)SitBu3]2 (5). Dissolution of the latter in aromatic hydrocarbons leads to the elimination of H2PSitBu3, yielding dimeric (thf)Ba3(PSitBu3)2[P(H)SitBu3]2 (6). The inner core of 6 consists of the tetramer (BaPSitBu3)4 based on a Ba4P4 heterocubane unit, two opposite faces being capped with (thf)Ba[P(H)SitBu3]2 molecules.