It's detected! The existence of the prototypical Zintl ions Tt44− (Tt=Group 14 element), which are isoelectronic to the P4 molecule, used to be confined to the solid state. Recently, circumstantial evidence for a solution chemistry in liquid ammonia emerged. Direct spectroscopic observation of the dissolved anions has now been achieved. In the case of Si44−, this is the first solution detection of any homoatomic silicide.

Although the chemistry of transition metal polyphosphide anions has attracted significant attention, there are few reports of studies in which such species have been synthesized directly from white phosphorus. [K(OEt ) {Co(BIAN)(cod)}] (1, BIAN=1,2-bis(2,6-diisopropylphenylimino)acenaphthene, cod=1,5-cyclooctadiene), which is readily prepared by ligand exchange from [K(thf) {Co(cod) }], reacts with P to afford [{K(thf)} {(BIAN)Co} (μ-η :η -P )] (2 a) in 61 % yield (isolated product). [{K(OEt )} {(BIAN)Co} (μ-η :η -P )] (2 b) and [K([18]crown-6)(MeCN)] [{(BIAN)Co} (μ-η :η -P )] (2 c) were obtained by recrystallizing 2 a from diethyl ether and acetonitrile (and using [18]crown-6 in case of 2 c). Oxidation of 2 a with [Cp Fe]BAr (one equivalent) and subsequent recrystallization of the product from different solvents gave [K(OEt ){(BIAN)Co} (μ-η :η -P )] (3 a) and [K(dme) ][{(BIAN)Co} (μ-η :η -P )] (3 b; dme=1,2-dimethoxyethane). Neutral [{(BIAN)Co} (μ-η :η -P )] (4) was obtained in moderate yield by oxidizing 2 a with two equivalents of [Cp Fe]BAr . The new complexes were characterized by NMR, EPR (in the case of 3 a), and UV/Vis spectroscopy, and elemental analysis. The molecular structures revealed by X-ray crystallography display planar cyclic or open-chain P units sandwiched between {(BIAN)Co} fragments.

We report on the first unambiguous detection of the elusive [HSi ] anion in solutions of liquid ammonia by various Si and H NMR experiments including chemical exchange saturation transfer (CEST). The characteristic multiplicity patterns of both the Si and H resonances together with CEST and a partially reduced H, Si coupling constant indicate the presence of a highly dynamic Si entity and a Si-H moiety with slow proton hopping. Theoretical calculations corroborate both reorganization of Si on the picosecond timescale via low vibrational modes and proton hopping. In addition, in a single-crystal X-ray study of (K(DB[18]crown-6))(K([2.2.2]crypt)) [HSi ]⋅8.5 NH , the H atom was unequivocally localized at one vertex of the basal square of the monocapped square-antiprismatic cluster. Thus experimental studies and theoretical considerations provide unprecedented insight into both the structure and the dynamic behavior of these cluster anions, which hitherto had been considered to be rigid.

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We report the first solvate structure of the silicide anion Si 4 4-, which provides circumstantial evidence of the stability of the highly charged anion in liquid ammonia solutions. The solvate Rb 1.2 K 2.8 Si 4 ·7NH 3 crystallized from a mixture of the ternary compound K 6 Rb 6 Si 17 with the transition metal complex [(C 6 H 5 ) 3 P] 2 -Ni(CO) 2 [bis(triphenylphosphine)dicarbonylnickel] in the presence of the chelating agents 18-crown-6 (1,4,7,10,13,16-hexaoxacycloocta-