Reduction of the Host Cationic Framework Charge by Isoelectronic Substitution:  Synthesis and Structure of Hg₇Ag₂P₈X₆ (X = Br, I) and Hg₆Ag₄P₈Br₆

Abstract

The first compounds, Hg(7)Ag(2)P(8)X(6) (X = Br, I) and Hg(6)Ag(4)P(8)Br(6), featuring the partial isoelectronic substitution of Hg(2+) for Ag(1+) in mercury-pnicogen frameworks have been obtained and structurally characterized. The new compounds are the supramolecular assemblies built of the covalently bonded metal-pnicogen frameworks trapping guests of different complexity. The frameworks feature the perfect ordering of Hg(2+) and Ag(1+) cations and contain P(2)(4)(-) and P(6)(6)(-) phosphorus clusters. The substitution of Hg(2+) with Ag(1+) leads to the reduction in charge of the host cluster-containing cationic matrix and concomitant replacement of the monatomic X(-) guest by a lesser amount of the AgBr(3)(2)(-) anions.

Unprecedented ∞1(P103−) band anion in the crystal structure of HgAg6P20I2

“…Hence, the title compound provides one more example of the stabilization of rare and unique phosphorus polyanions by preferable linkage of differently bonded phosphorus atoms to differently charged cations having the same coordination. The similar situation was described for some other silver mercury phosphide halides, Hg 4 Ag 5 P 8 Cl 5 , Hg 12 Ag 41 P 88 I 41 , and Hg 7 Ag 2 P 8 I 6 (Br 6 ) [6,8,9]. It should be noted that in all earlier known silver and mercury pnictide halides the coordination of silver and mercury atoms is linear, made of two phosphorus atoms, with halide atoms providing the second coordination sphere.…”

“…Ranging the annealing conditions and/or using different starting materials did not provide better yields of HgAg 6 P 20 I 2 . In all cases, silver phosphide Ag 3 P 11 is found as a main product in spite of existence of at least two more quaternary compounds in the Hg-P-Ag-I system [6]. The low yields can be explained by the close composition and similar synthesis conditions of the title compound and Ag 3 P 11 .…”

P88− Polyanion with Phosphorus Atoms in Three Different Formal Oxidation States Stabilized by a Combination of Ag+ and Hg2+ Cations

“…The crystal structures of three compounds reported earlier, [10] namely, Hg 7 Ag 2 P 8 I 6 , Hg 7 Ag 2 P 8 Br 6 , and Hg 6 Ag 3 P 8 AgBr 6 , have already provided examples of Ag + and Hg 2+ ions linked to phosphorus atoms with different oxidation numbers. In particular, mercury is bound only to the P ÀII atoms of the P 2 4À units, whereas silver prefers the P ÀI atoms of the P 6 6À rings.…”

Ferroelectric Transition in the Inorganic Supramolecular Complex (Hg6P4)(CuCl3)2

“…The HgP and PP bond lengths in the cationic moiety in 1 range from 2.409(4) to 2.434(4) Å and 2.172(7) to 2.190(5) Å, respectively, which lie in the normal ranges for HgP and PP bond lengths, in known mercury pnictide halides,16a,b respectively. The CuCl bond lengths (2.193(5)–2.681(6) Å) in the anionic guests of 1 are close to those found in literature 16c…”