Bis{[μ‐N,N′‐bis­(salicyl­idene)‐1,4‐butane­di­amine‐N,N′,O,O′‐copper(II)]‐μ‐chloro‐chloromercury(II)}

A new tetranuclear Cu^II–Hg^II–Hg^II–Cu^II complex, [Cu₂Hg₂Cl₄(C₁₈H₁₈N₂O₂)₂], has been prepared by means of a copper complex found in the literature. The molecular structure of this complex was determined by X‐ray diffraction and the Cu–Hg–Hg–Cu chain was seen to be non‐linear. The change in magnetic susceptibility with temperature was recorded for this complex and observed to abide by the Curie–Weiss law. The coordination around the Hg^II ions is square pyramidal. The Cu?Hg bridging distance is 3.5269 (7) Å.     

Synthesis and structure of [Hg2(L)2(NO3)2] (L = (4-nitrophenyl)pyridin-2-ylmethyleneamine); a theoretical study on Hg–Hg bond in this and in linear Hg2X2 (X = F, Cl, Br, I, Ph) complexes

A new binuclear mercury(I) complex, [Hg₂(L)₂(NO₃)₂] (L = (4-nitrophenyl)pyridin-2-ylmethyleneamine), 1, has been synthesized and characterized by CHN analyses, IR, UV–vis spectroscopy and X-ray crystal structure analysis. The complex contains a metal–metal bonded core, [Hg–Hg]²⁺, in which a single bidentate imine ligand is coordinated to each mercury atom. The Hg atoms have an additional interaction with the oxygen atom of the NO₃ ^? ion. Theoretical studies show that the interaction energy between the two {Hg(L)NO₃} fragments is about 45–59 kcal/mol depending on the level of calculation. The Mayer-Mulliken and Wiberg bond indices (WBI) for Hg–Hg bond at different levels of theory are about 0.75–0.88 and 0.60–0.70, respectively, and are significantly larger than that for Hg–N and Hg–O bonds. The NBO calculations by using different methods and basis sets also show that the S character in Hg–Hg bond is very large (94.65–97.81 %). All above data for this complex are compared with those for linear Hg₂X₂ (X = F,Cl, Br, I, Ph) complexes. Interestingly, the bond order for Hg–Hg bond in complex 1 is comparable with that for Hg₂F₂ and larger than those in above linear complexes. This is consistent with the experimental data indicating that the Hg–Hg bond in 1 is shorter than that in all above complexes, except Hg₂F₂.     

QM and QM/MM umbrella sampling MD study of the formation of Hg(II)–thymine bond: Model for evaluation of the reaction energy profiles in solutions with constant pH

The formation of the Hg–N3(T) bond between the 1-methylthymine (T) molecule and the hydrated Hg²⁺ cation was explored with the combined quantum mechanics/molecular mechanics (QM/MM) method including Free Energy Perturbation corrections. The thermodynamic properties were determined in the whole pH range, when these systems were explicitly investigated and considered as the QM part: (1) T + [Hg(H₂O)₆]²⁺, (2) T + [Hg(H₂O)₅(OH)]⁺, (3) T + Hg(H₂O)₄(OH)₂, and (4) N3-deprotonated T + Hg(H₂O)₄(OH)₂. The MM part contained only solvent molecules and counterions. As a result, the dependence of Gibbs-Alberty reaction free energy on pH was obtained along the reaction coordinate. We found that an endoergic reaction in acidic condition up to pH < 4–5 becomes exoergic for a higher pH corresponding to neutral and basic solutions. The migration of the Hg²⁺ cation between N3 and O4/2 positions in dependence on pH is discussed as well. For the verification, DFT calculations of stationary points were performed confirming the qualitative trends of QM/MM MD simulations and NMR parameters were determined for them.     

Preparation,Single Crystal Structure Analysis,and Thermal Behaviour of the Acidic Mercury(I) Phosphate (Hg2)2(H2PO4)(PO4)

Yellowish single crystals of acidic mercury(I) phosphate (Hg₂)₂(H₂PO₄)(PO₄) were obtained at 200 °C under hydrothermal conditions in 32% HF from a starting complex of microcrystalline (Hg₂)₂P₂O₇. Refinement of single crystal data converged at a conventional residual R[F² > 2σ(F²)] = 3.8% (C2/c, Z = 8, a = 9.597(2) Å, b = 12.673(2) Å, c = 7.976(1) Å, β = 110.91(1)°, V = 906.2(2) ų, 1426 independent reflections > 2σ out of 4147 reflections, 66 variables). The crystal structure consists of Hg₂²⁺‐dumbbells and discrete phosphate groups H₂PO₄^– and PO₄^3–. The Hg₂²⁺ pairs are built of two crystallographically independent Hg atoms with a distance d(Hg1–Hg2) = 2.5240(6) Å. The oxygen coordination sphere around the mercury atoms is asymmetric with three O atoms for Hg1 and four O atoms for Hg2. The oxygen atoms belong to the different PO₄ tetrahedra, which in case of H₂PO₄‐groups are connected by hydrogen bonding. Upon heating over 230 °C, (Hg₂)₂(H₂PO₄)(PO₄) condenses to (Hg₂)₂P₂O₇, which in turn disproportionates at higher temperatures into Hg₂P₂O₇ and elemental mercury.     

High Valent Mercury Fluoride Ions

Mercury fluoride ions formed during the laser ablation of HgF_{2( s )} show the formation of six different cluster ion series viz., HgF_n^±, Hg_nF_n–2^±, Hg_nF_n–1^±, (HgF)_n^±, Hg_nF_n+1^±, and Hg_nF_n+2^±. Among the different ion series, the observation of high valent HgF_n^±_(n^±_{=3,4; n}⁻_=6–8) indicates the existence of corresponding molecules which signify the remarkable participation of 5d Hg electrons in the chemical bonding with F atoms and thus make Hg a truly transition metal. Further, molecular orbital calculations show a large HOMO-LUMO energy gap (≥3 eV) and high electron affinity (≥5 eV) that indicates highly stable HgF_n=3,4,6,8 with super halogen properties.     

Synthese,Kristallstrukturen und Magnetismus von (Hg6As4)[MoCl6]Cl, (Hg6As4)[TiCl6]Cl und (Hg6As4)[TiBr6]Br

Polycationic Hg–As Frameworks with Trapped Anions. II Synthesis, Crystal Structure, and Magnetism of (Hg₆As₄)[MoCl₆]Cl, (Hg₆As₄)[TiCl₆]Cl, and (Hg₆As₄)[TiBr₆]Br (Hg₆As₄)[MoCl₆]Cl is obtained by reaction of Hg₂Cl₂, Hg, As, and MoCl₄ in closed, evacuated glass ampoules in a temperature gradient 450 → 400 °C in form of dark red cubelike crystals. (Hg₆As₄)[TiCl₆]Cl and (Hg₆As₄)[TiBr₆]Br are also formed in closed, evacuated ampoules from Hg₂X₂ (X = Cl, Br), Hg, As, and Ti metal at 275 °C and 245 °C in form of dark green and black crystals, respectively. All three compounds are air and light sensitive. They crystallize isotypically (cubic, Pa 3, a = 1207.8(4) pm for (Hg₆As₄)[MoCl₆]Cl, a = 1209.4(3) pm for (Hg₆As₄)[TiCl₆]Cl, a = 1230.9(3) pm for (Hg₆As₄)[TiBr₆]Br, Z = 4). The structures consist of a three‐dimensionally connected Hg–As framework which is made up of As₂ groups (As–As distance averaged 242 pm) each connected via six Hg atoms to six neighbouring As₂ groups. There are two cavities of different size in the polycationic framework. The bigger cavity is filled with [MoCl₆]^3–, [TiCl₆]^3–, and [TiBr₆]^3– ions of nearly ideal octahedral shape, the smaller cavity with discrete halide ions. The magnetic properties of the two Ti containing compounds are in accordance with a d¹ paramagnetism. The temperature dependence and the magnitude of the magnetic moment can be interpreted with consideration of the spin‐orbit coupling. The so far known representatives of this structure type can be characterised by the ionic formula (Hg₆Y₄)⁴⁺[MX₆]^3–X^– (Y = As, Sb; M = Sb³⁺, Bi³⁺, Mo³⁺, Ti³⁺; X = Cl, Br).     

The crystal structures of two Mercury Perrhenates

The mercury perrhenates with the empirical formulas HgReO₄ and Hg₂ReO₅ were prepared by annealing powdered mixtures of mercury(II)oxide and mercury(II)metaperrhenate Hg(ReO₄)₂ in sealed silica tubes. Their crystal structures were determined from single-crystal X-ray data. HgReO₄ crystallizes dimeric with nearly linear O₃Re? O? Hg? Hg? O? ReO₃ molecular units and Hg₂ReO₅ has a solid state structure, where Hg(I) and Hg(II) together with oxygen atoms form 14-membered rings, which are condensed to two-dimensionally infinite polycationic nets of composition (Hg₂²⁺ · 2 HgO)_n. These nets are separated from each other by tetrahedral ReO₄^? anions.     

A Minimal Membrane Metal Transport System: Dynamics and Energetics of mer Proteins

The mer operon in bacteria encodes a set of proteins and enzymes that impart resistance to environmental mercury toxicity by importing Hg²⁺ and reducing it to volatile Hg(0). Because the reduction occurs in the cytoplasm, mercuric ions must first be transported across the cytoplasmic membrane by one of a few known transporters. MerF is the smallest of these, containing only two transmembrane helices and two pairs of vicinal cysteines that coordinate mercuric ions. In this work, we use molecular dynamics simulations to characterize the dynamics of MerF in its apo and Hg²⁺-bound states. We find that the apo state positions one of the cysteine pairs closer to the periplasmic side of the membrane, while in the bound state the same pair approaches the cytoplasmic side. This finding is consistent with the functional requirement of accepting Hg²⁺ from the periplasmic space, sequestering it on acceptance, and transferring it to the cytoplasm. Conformational changes in the TM helices facilitate the functional interaction of the two cysteine pairs. Free-energy calculations provide a barrier of 16 kcal/mol for the association of the periplasmic Hg²⁺-bound protein MerP with MerF and 7 kcal/mol for the subsequent association of MerF's two cysteine pairs. Despite the significant conformational changes required to move the binding site across the membrane, coarse-grained simulations of multiple copies of MerF support the expectation that it functions as a monomer. Our results demonstrate how conformational changes and binding thermodynamics could lead to such a small membrane protein acting as an ion transporter. Published 2019. This article is a U.S. Government work and is in the public domain in the USA.     

Rb5Hg19: Eine neue,geordnete Defektvariante des BaAl4‐Strukturtyps

Rb₅Hg₁₉: A New Defect Variant of the BaAl₄ Structure Type The hitherto unknown, silver metallic, air sensitive Rb₅Hg₁₉ can be prepared directly from the elements. It crystallizes tetragonally with lattice constants a = 1156.1 pm, c = 1051.0 pm (Z = 2, space group I4/m, No. 87, melting temperature 467 K) in a new defect variant of the BaAl₄ structure type. The structure is based on distorted 4⁴ nets of Hg₄ rectangles and squares forming rectangular and square pyramids together with additional Hg atoms. The vertices of the pyramids point in alternate directions with respect to [001]. Opposite vertices show relatively short contacts d_Hg–Hg = 292.3 pm along [001]. The defect character of the Rb₅Hg₁₉ structure shows up by single Hg atoms substituting each fifth Hg–Hg group in an ordered way and serving as common vertices for two subsequent square pyramids along [001]. The replacement of Hg–Hg groups by single Hg atoms explains the vertical and horizontal distortions of the 4⁴ nets and explains the differences of the Rb coordination with respect to Ba (bicapped tetragonal hexagonprism) in the BaAl₄ type, in which a hypothetical RbHg₄ could eventually crystallize. The symmetry relations of Rb₅Hg₁₉ and α‐La₃Al₁₁ (the only defect variant of BaAl₄ except Rb₅Hg₁₉) to the aristo type BaAl₄ are discussed.     

Structural and Solution Studies of two Mercury(II) Complexes with [1,3‐Bis(2‐ethoxy)benzene]triazene

The reaction of [1,3‐bis(2‐ethoxy)benzene]triazene, [ HL ], with Hg(SCN)₂ and Hg(CH₃COO)₂, resulted in the formation of the complexes [Hg L (SCN)] ( 1 ) and [Hg L ₂] · CH₃OH ( 2 ). They were characterized by means of X‐ray crystallography, CHN analysis, FT‐IR, ¹H NMR, and ¹³C NMR spectroscopy. The structure of compound 1 consists of two independent complexes in which the Hg^II atoms are stacked along the crystallographic a axis to form infinite chains. Each Hg^II atom is chelated by one L ligand and one SCN ligand, whereas in compound 2 , the Hg^II atom is surrounded by two L ligands. In addition, 1D chains formed by metal–π interactions are connected to each other by C–H ··· π stacking interactions in the structure of 1 , which results in a 2D architecture. An interesting feature of compound 2 is the presence of C–H ··· π edge‐to‐face interactions.     

On Mercury(I) Oxo Compounds — Quasi‐Relativistic Computational and Experimental Studies

About 60 molecular species composed of up to 10 mercury atoms and of oxygen atoms and/or of some other elements or groups (such as halogen, OH₂, OH, H, alkali, NO₃) have been investigated quantum chemically. Different density functional approaches and the ab initio SCF‐MP2 method were applied, comparing different basis sets and different atomic core sizes. It is important not to treat the Hg 5s, p, d as inactive core shells, and to use sufficiently many polarization functions. The shape of the 〉O‐Hg‐Hg‐O〈 units is not favorable concerning the formation of lattices composed of Hg^I, O and OH only. Despite its bulkiness, the OHgHgO units can easily come into contact with each other and then disproportionate. This is prevented in the so‐called ternary M‐Hg^I oxides by the embedded oxometallate (oxoacidic) anions. Furthermore, the Hg^I and Hg^II oxide bond energies are less favorable towards the stability of Hg^I oxo compounds, as compared to Hg halidic or oxoacidic compounds. Both points are not promising concerning the search for Hg^I oxides/hydroxides, although the preparation of such compounds, including spacer groups, by topochemical reactions can still not be excluded. So far, experimental efforts towards the synthesis of such a new class of compounds have only demonstrated that Hg^II is strictly preferred over Hg^I in the formation of solids of binary Hg‐O or ternary A‐Hg‐O composition (A = electropositive metal such as alkali, in contrast to M = transition or semi‐metal). This is so even if compounds containing ‘electron rich Hg^δ— atoms’ (i.e. A‐Hg amalgams) are oxidized under mild conditions.     

A violet emission from optically excited mercury vapour. Kinetics of the formation and decay of excited dimers and trimers

A new electronic systems has been observed from excited Hg vapour, which is assigned to collisionally induced emission from the Hg₂ O^±_g first excited states of the dimer: Hg₂O^±_g + M → 2Hg(6 ¹S₀) + M + hv(γ_max 3950 A). For M = N₂, the rate coefficient is 5.3(±0.7) × 10^?19 cm³ molecule^?1 at 298 K. From time resolved measurements of the luminescence in the afterglow following pulsed excitation, the decay rate of the green emission, in an excess of N₂, is shown to be a linear function of [Hg][N₂]. It is concluded that the reaction which controls the decay of the excitation is formation of an excited trimer in a termolecular reaction; the trimer is the carrier of the green emission: Hg₂ O^±_g + Hg(6 ¹S₀ + Hg(6¹S₀ + N₂ → Hg₃³Π_u + N₂. The rate coefficient is 1.10(±0.07) × 10^?30 cm⁶ molecule^?2 s^?1 at 298 K.     

Über Caesiumtrichloromercurat(II) CsHgCl3: Lösung einer komplexen Überstruktur und Verhalten unter hohen Drücken

About Cesium Trichloromercurate(II) CsHgCl₃: Solution of a Complex Superstructure and Behaviour under High Pressure By solving the crystal structure of CsHgCl₃ a new uncommon distortion variant of the cubic perovskite type with extremely (2 + 2 + 2)‐distorted HgCl₆ octahedra has been found. The trigonal superstructure with space group P3₂ and ninefold cell contents differs from the aristotype only so far, as 2/3 of the Cl‐atoms are moved away from their ideal positions leading to 3 pairs of different Hg–Cl distances with about 2.35 Å, 2.71 Å and 3.15 Å. The cations Cs⁺ and Hg²⁺ and the chloride ions with medium Hg–Cl distance keep the ideal positions of a cubic perovskite lattice. Due to the evenly distribution of the three different bonds in the three directions of cubic space the cell shows an almost perfect cubic metric. Raman spectra and powder diffraction experiments up to pressures of 5 GPa demonstrated that the ideal perovskite arrangement is stabilized with increasing pressure. The shift of the FT‐Raman bands show in agreement with spectra simulations that the Hg–Cl bonds are equalized, leading to a regular octahedral co‐ordination of the Hg atoms. The disappearance of the Raman spectrum at P > 3.4 GPa indicates that the high pressure phase forms an ideal cubic perovskite (a = 5.204(1) Å, Hg–Cl = 2.60 Å).     

Molecular Assembly Directed by Metal–Aromatic Interactions: Control of the Aggregation and Photophysical Properties of Zn–Salen Complexes by Aromatic Mercuration

There is widespread interest in non‐covalent bonding and weak interactions, such as electrostatic interactions, hydrogen bonding, solvophobic/hydrophobic interactions, metal–metal interactions, and π–π stacking, to tune the molecular assembly of planar π‐conjugated organic and inorganic molecules. Inspired by the roles of metal–aromatic interaction in biological systems, such as in ion channels and metalloproteins, herein, we report the first example of the use of Hg²⁺–aromatic interactions to selectively control the assembly and disassembly of zinc–salen complexes in aqueous media; moreover, this process exhibited significant “turn on” fluorescent properties. UV/Vis and fluorescence spectroscopic analysis of the titration of Hg²⁺ ions versus complex ZnL¹ revealed that the higher binding affinity of Hg²⁺ ions (compared to 13 other metal ions) was ascribed to specific interactions between the Hg²⁺ ions and the phenyl rings of ZnL¹ ; this result was also confirmed by ¹H NMR spectroscopy and HRMS (ESI). Further evidence for this type of interaction was obtained from the reaction of small‐molecule analogue L¹ with Hg²⁺ ions, which demonstrates the proximity of the N‐alkyl group to the aromatic protons during Hg²⁺‐ion binding, which led to the consequential H/D exchange reaction with D₂O. DFT modeling of such interactions between the Hg²⁺ ions and the phenyl rings afforded calculated distances between the C and Hg atoms (2.29 Å) that were indicative of C? Hg bond‐formation, under the direction of the N atom of the morpholine ring. The unusual coordination of Hg²⁺ ions to the phenyl ring of the metallosalen complexes not only strengthened the binding ability but also increased the steric effect to promote the disassembly of ZnL¹ in aqueous media.     

Theoretical and Experimental Study of Pb2+ and Hg2+ Adsorption on Biopolymers, 1. Theoretical Study

Chitosan and pectic acid have been modeled as disaccharides or oligosaccharides for Hg²⁺ and Pb²⁺ adsorption. Reasonable models of both biopolymers were used. Several adsorption sites of both polysaccharides were considered, mainly NH₂ in chitosan and CO₂^– in pectic acid. Hg²⁺ has several points of anchorage on chitosan. The most important one is NH₂ . The Molecular Mechanic modeling permit us to compare in relative terms the different conformations of models of pectic acid and chitosan and their effect in heavy metal coordination. Using the Parameterized Model version 3 (PM3), we report the formation enthalpy of inter‐ and intramolecular compounds with Hg and Pb. The Extended Huckel method (EHM) results seem to indicate that electrostatic interaction (leading to adsorbed cation on NH₂ and on sites different to NH₂) could be the reason for the high uptake found for Hg²⁺ using chitosan. Besides NH₂, the OH near the amine group is the preferred site for Hg²⁺ adsorption, especially if it is ionized. In the case of Pb²⁺ adsorption, several sites of chitosan present no interaction with this cation. Only the NH₂ group and the ionized OH group mentioned above seem to be the preferred sites, following the EH modified (EHMO) results. The Hg‐ and Pb‐adsorption modeling on pectic acid permit us to conclude that the best site is the same for both metals: the bridge oxygen between monomers of galacturonic acid. the carbonyl group from carboxylate is the best second site for Hg²⁺, whereas the internal oxygen bridge is the best second site for Pb²⁺. Considering the Hg ²⁺ chemistry in aqueous solution, we evaluated the HgOH⁺ and HgCl⁺ or HgCl₃^– adsorption on both copolymers, using EHMO. The energetic of adsorption changed on both biopolymers for these species, comparing them with Hg²⁺.     

Sampling and determination of gas phase divalent mercury in the air using a KCl coated denuder

KCl coated denuders were employed for the measurement of divalent mercury (Hg²⁺) species in the air. Laboratory tests show that gaseous Hg²⁺ can be collected by the denuder with an average efficiency of 98% and elemental Hg will pass through it freely. Hg²⁺ trapped in the denuder can be quantitatively extracted by 1 mol/L HCl and analyzed by the method of SnCl₂ reduction-CVAFS determination. Hg²⁺ concentrations of 0.04–0.15 ng m^–3 corresponding to about 2–9% of the total gaseous mercury in the ambient air were determined at several sampling locations.     

Study of the Hg binding with chelation therapy agents by differential pulse voltammetry on rotating Au-disk electrode and electrospray ionization mass-spectrometry

A recently proposed electroanalytical method, using differential pulse voltammetry (DPV) on the rotating Au-disk electrode, and electrospray ionization mass-spectrometry (ESI-MS) has been applied to study the binding of the pharmaceutical chelating agents meso-2,3-dimercaptosuccinic acid (DMSA), sodium 2,3-dimercaptopropanesulfate (DMPS) and d-penicillamine (d-Pen) with Hg²⁺. From the use of voltammetric titrations it was possible to obtain a detailed picture of the complexation processes at concentrations much lower than in previous studies. Predominant species were Hg(Pen)₂, Hg₂(DMSA)₂ and Hg(DMPS)₂. For Pen, Hg(Pen) was also deduced from DPV data, while Hg₂(Pen)₄ from ESI-MS. For DMSA and DMPS, Hg₂L species were detected by DPV, and Hg₂L₃, Hg₃L₃ as well as Hg₂(DMPS)₂ and Hg(DMSA)₂ by ESI-MS. When possible, DPV data were analyzed by multivariate curve resolution with alternating least squares (MCR-ALS).     

Präparation,Kristallstruktur und thermisches Verhalten der Quecksilber(I)phosphate α-(Hg2)3(PO4)2, β-(Hg2)3(PO4)2 und (Hg2)2P2O7

Contributions on Crystal Structures and Thermal Behaviour of Anhydrous Phosphates. XXIII. Preparation, Crystal Structure, and Thermal Behaviour of the Mercury(I) Phosphates α-(Hg₂)₃(PO₄)₂, β-(Hg₂)₃(PO₄)₂, and (Hg₂)₂P₂O₇ Light-yellow single crystals of (Hg₂)₂P₂O₇ have been obtained via chemical vapour transport in a temperature gradient (500 °C → 450 °C, 23 d) using Hg₂Cl₂ as transport agent. Characteristic feature of the crystal structure (P2/n, Z = 2, a = 9,186(1), b = 4,902(1), c = 9,484(1) Å, β = 98,82(2)°, 1228 independent of 5004 reflections, R(F) = 0,066 for 61 variables, 7 atoms in the asymmetric unit) are Hg₂²⁺-units with d(Hg1–Hg1) = 2,508 Å and d(Hg2–Hg2) = 2,519 Å. The dumbbells Hg₂²⁺ are coordinated by oxygen, thus forming polyhedra [(Hg1₂)O₄] and [(Hg2₂)O₆]. These polyhedra share some oxygen atoms. In addition they are linked by the diphosphate anion P₂O₇^4– (ecliptic conformation; ∠(P,O,P) = 129°) to built up the 3-dimensional structure. Under hydrothermal conditions (T = 400 °C) orange single crystals of the mercury(I) orthophosphates α-(Hg₂)₃(PO₄)₂ and β-(Hg₂)₃(PO₄)₂ have been obtained from (Hg₂)₂P₂O₇ and H₃PO₄ (c = 1%). The crystal structures of both modifications have been refined from X-ray single crystal data [α-form (β-form): P2₁/c (P2₁/n), Z = 2 (2), a = 8,576(3) (7,869(3)), b = 4,956(1) (8,059(3)), c = 15,436(3) (9,217(4)) Å, β = 128,16(3) (108,76(4))°, 1218 (1602) independent reflections of 4339 (6358) reflections, R(F) = 0,039 (0,048) for 74 (74) variables, 8 (8) atoms in the asymmetric unit]. In the structure of α-(Hg₂)₃(PO₄)₂ three crystallographically independent mercury atoms, located in two independent dumbbells, are coordinated by three oxygen atoms each. Thus, [(Hg₂)O₆] dimers with a strongly distorted tetrahedral coordination of all mercury atoms are formed. Such dimers are present besides [(Hg₂)O₅]-polyhedra in the less dense crystal structure of β-(Hg₂)₃(PO₄)₂ (d(Hg–Hg) = 2,518 Å). The mercury(I) phosphates are thermally labile and disproportionate between 200 °C (β-(Hg₂)₃(PO₄)₂) and 480 °C (α-(Hg₂)₃(PO₄)₂) to elemental mercury and the corresponding mercury(II) phosphate.     

The Monohydrate of Basic Mercuric Nitrate, [Hg(OH)](NO3)(H2O)

Colourless single crystals of [Hg(OH)](NO₃)(H₂O) were obtained by slow evaporation of an aqueous solution of Hg(NO₃)₂ and Bi(NO₃)₃. The crystal structure (orthorhombic, Pbca, Z = 8, a = 943.2(2), b = 697.6(1), c = 1349.0(2) pm, R₁(all) = 0.0780) contains [Hg(OH)] = …OH–Hg–OH–Hg… zig zag chains (O–Hg–O angle: 168°, Hg–O–Hg angle: 112°, Hg–OH distance: 212 pm) to which one water molecule is attached loosely. The [Hg(OH)](H₂O) chains are connected via bis‐monodentate‐bridging nitrate ions to corrugated layers that are stacked in the [001] direction. Hg²⁺ has an effective 2+2+2(+1) coordination.     

Untersuchungen über das Gleichgewicht des Hg2+-Hg 2 2+ -Hg-Systems in konzentrierten Perchloratlösungen

The formal potentials of the Hg²⁺/Hg ₂ ²⁺ , Hg ₂ ²⁺ /Hg and Hg²⁺/Hg redox couples and the apparent equilibrium constants of the reaction Hg²⁺ + Hg ∝ Hg ₂ ²⁺ in conc. aqueous solutions of Mg(ClO₄)₂ and Ca(ClO₄)₂ have been determined from emf measurements performed using cells with liquid junction. Based on these data, the hydration numbers of the Hg²⁺ and Hg ₂ ²⁺ ions were estimated.