Reinterpretation of the vibrational spectroscopy of the medicinal bioinorganic synthon c,c,t-[Pt(NH3)2Cl2(OH)2]

The Pt(IV) complex c,c,t-[Pt(NH₃)₂Cl₂(OH)₂] is an important intermediate in the synthesis of Pt(IV) anticancer prodrugs and has been investigated as an anticancer agent in its own right. An analysis of the vibrational spectroscopy of this molecule was previously reported (Faggiani et al., Can. J. Chem. 60:529, 1982), in which crystallographic determination of the structure of the complex permitted a site group approach. The space group, however, was incorrectly assigned. In the present study we have redetermined at high resolution crystal structures of c,c,t-[Pt(NH₃)₂Cl₂(OH)₂] and c,c,t-[Pt(NH₃)₂Cl₂(OH)₂]·H₂O₂, which makes possible discussion of the effect of hydrogen bonding on the N–H and O–H vibrational bands. The correct crystallographic site symmetry of the platinum complex in the c,c,t-[Pt(NH₃)₂Cl₂(OH)₂] structure is used to conduct a new vibrational analysis using both group-theoretical and modern density functional theory methods. This analysis reveals the nature and symmetry of the “missing band” described in the original publication and suggests a possible explanation for its disappearance.     

Specific platinum chelation by the guanines of the deoxyhexanucleotide d(T-G-G-C-C-A) upon reaction with cis-[Pt(NH3)2(H2O)2](NO3)2

The stoichiometric reaction between d-TpGpGpCpCpA (d(T-G-G-C-C-A)) and $\text{cis}$-[Pt(NH₃)₂(H₂O)₂](NO₃)₂ (8.4 × 10^?6 to 1.3 × 10^?4M in water at pH 5.5–6) gives a single complex. High pressure gel permeation chromatography and pH-dependent ¹H NMR analyses of the nonexchangeable base protons, show that it is a platinum chelate with the $\text{cis}$-Pt^II(NH₃)₂ moiety bound to the two N7 atoms of the adjacent guanines. A 3 × 10^?3M reaction gives the same platinum chelate, via the formation of intermediate complexes, together with unsoluble adducts.     

Studies of the reaction products of adenosine with [Pt(NH3)3Cl]Cl and cis-Pt(NH3)2Cl2 by high performance liquid chromatography

The reaction products of adenosine with [Pt(NH₃)₃Cl]Cl or cis-Pt(NH₃)₂Cl₂ have been studied using high performance liquid chromatography and uv spectroscopy. The reaction of [Pt(NH₃)₃Cl]Cl with adenosine (pH = 7.0, Pt/base = 0.5) gives four products. Two of them, mononuclear complexes in which platinum is bound to adenosine through N(7) or N(1), comprise more than 90% of all the products. The N(1) and N(7) sites on adenosine indicate almost equal binding affinity for [Pt(NH₃)₃Cl]Cl. The reaction of cis-Pt(NH₃)₂Cl₂ with adenosine has been studied in the presence of a large excess of adenosine (Pt/base ? 0.05). The reaction gives four products. One is the monomeric 2:1 complex with cis-Pt(NH₃)₂²⁺ bound to two adenosine molecules through the N(7) site and the N(1) site, and another is the monomeric 2:1 complex with cis-Pt(NH₃)₂²⁺ bound to two adenosine molecules through the N(7) sites. cis-Pt(NH₃)₂Cl₂ is stronger affinity to the N(7) site than of adenosine to the N(1) site.     

Mechanism of toxicity of platinum(II) compounds in repair-deficient strains of Escherichia coli

The survival of wild-type and repair-deficient Escherichia coli treated with cis-Pt(NH₃)₂Cl₂, trans-Pt(NH₃)₂Cl₂ and [Pt(dien)Cl]Cl (dien = H₂NCH₂CH₂NHCH₂CH₂NH₂) was inversely correlated with the ability of these compounds to inhibit DNA synthesis in different bacterial strains. The relative amounts of these 3 compounds covalently bound to DNA immediately after treatment with the same dose were, respectively, 1:?2:1, their relative abilities to inhibit DNA synthesis were 6:1:0 and their relative toxicities toward the wild-type and uvrA strains were 3–5:1:0. More repair synthesis, as measured by density-gradient centrifugation techniques, was observed in wild-type bacteria after treatment with the cis than with the trans isomer whereas no repair synthesis was detected after exposure to [Pt(dien)Cl]Cl.These results are consistent with the hypothesis that cis-Pt(NH₃)Cl₂ binds to DNA and inhibits DNA synthesis thereby killing the cell. The lower toxicity of this compound toward wild-type bacteria compared with repair-deficient strains is in part a consequence of DNA repair. trans-Pt(NH₃)₂Cl₂ and [Pt(dien)Cl]Cl are less toxic than the cis isomer; this lesser toxicity is not a consequence of low levels of DNA binding or enhanced repair of the lesions but appears to reflect a weaker inhibition of DNA synthesis by these Pt-DNA adducts.     

X-ray structure of a mono(1-methylthyminato) complex of cisplatin,chloro-(1-methylthyminato-N3)-cis-diammineplatinum(II) monohydrate

The crystal structure of chloro-(1-methyltyminato- N3)-cis-diammineplatinum(II) monohydrate, cis- (NH₃)₂Pt(C₆H₇N₂O₂)Cl·H₂O, is reported. The compound crystallizes in space group P$\text{1}$ with a = 6.911(2) Å, b = 8.598(3) Å, c = 11.464(4) Å, α = 100.13(3)°, β = 120.03(3)°, γ = 93.16(3)°, Z = 2. The structure was refined to R = 0.048 and R_w = 0.057. The compound contains the deprotonated 1-methylthymine ligand coordinated to Pt through N3 (1.973(10) Å). This distance represents the shortest Pt-N3(pyrimidine-2.4-dione) bond reported so far. The two PtNH₃ bond lengths differ significantly: PtNH₃ (trans to Cl) is longer (2.052(10) Å) than PtNH₃ (trans to N3 of 1-MeT) (2.002(11) Å). The PtCl distance (2.326(3) Å) is normal, as is the large dihedral angle between the Pt coordination plane and the nucleobase (76.5°).     

N-{2-(4-methoxyphenyltelluro)ethyl}morpholine (L1) and its platinum(II) and ruthenium(II) complexes. Synthesis and crystal structure of L1 and trans-[PtCl2(L1)2]

The first tellurated derivative of morpholine, N-{2-(4-methoxyphenyltelluro)ethyl}morpholine (L¹) has been synthesized by reacting in situ generated ArTe⁻ with 4-(2-chloroethyl)morpholine hydrochloride under N₂ atmosphere. The compound L¹ gives molecular ion peak at m/z 351 and is characterized structurally. The donor atoms N and Te in compound L¹ are rightly oriented for its ligation in bidentate mode. The TeC(alkyl) is 0.02 Å longer than TeC(aryl). The complexes of ligand L¹ having composition [PtCl₂(L¹)₂] (1) and [RuCl₂(p-cymene)L¹] (2) have been synthesized. The compound 1 has been characterized structurally. The Pt has a square planar geometry in complex 1 and two molecules of ligand L¹ bonded through Te alone are trans to each other (PtTe=2.583(2) Å). The ¹³C{¹H} NMR spectrum of complex 1 is as expected. The ¹H NMR spectrum of single crystals of complex 1 shows multiplication of signals, which is supported by HETCOR experiments. The complex 2 also has ligand L¹ in a monodentate coordination mode, bonded through Te alone. This is supported by deshielded CH₂Te and ArCTe signals in ¹H and ¹³C{¹H} NMR spectra of complex 2 with respect to those of free ligand L¹. The HETCOR spectrum of complex 2 has been used to authenticate the assignments of CH₂Te group, as its two protons appear to be magnetically non-equivalent.     

Structural and reactivity studies on the ternary system guanine/methionine/trans-[PtCl2(NH3)L] (L=NH3, quinoline): implications for the mechanism of action of nonclassical trans-platinum antitumor complexes

 The present model study explores the chemistry of methionine complexes and ternary methionine-guanine adducts formed by trans-[PtCl₂(NH₃)₂] (1) and antitumor trans-[PtCl₂(NH₃)quinoline] (2) using 1D (¹H, ¹⁹⁵Pt) and 2D NMR spectroscopy. Compound 2 was substitution inert in reactions with N-acetyl-lmethionine [AcMet(H)]. Reactions of trans-[PtCl(NO₃)(NH₃)quinoline] (5) ("monoactivated" 2) with AcMetH in water and acetone at various stoichiometries point to Pt(II)-S binding that requires prior activation of the Pt-Cl bond by labile oxygen donors. Trans-[PtCl{AcMet(H)-S}(NH₃)quinoline](NO₃) (6) and trans-[Pt{AcMet(H)-S}₂(NH₃)quinoline](NO₃)₂ (7) were isolated from these mixtures. At high [Cl^–], AcMet(H) is displaced from 7, giving 6. Frozen stereodynamics in 6 at the thioether-S and slow rotation about the Pt-N_quinoline bond result in four spectroscopically distinguishable diastereomers. ¹H NMR spectra of 7 show faster exchange dynamics due to mutual trans-labilization of the sulfur donors. Substitution of chloride in trans-[PtCl(9-EtGua)(NH₃)L]NO₃ (L=NH₃, 3; L=quinoline, 4; 9-EtGua=9-ethylguanine, which mimics the first DNA binding step of 1 and 2) by methionine-sulfur proceeded ca. 2.5 times slower for the quinoline compound. Both reactions, in turn, proved to be ca. 4 times faster than binding of a second nucleobase under analogous conditions. From the resulting mixtures the ternary adducts trans-[Pt(AcMet-S)(9-EtGua-N7)(NH₃)L](NO₃, Cl) (L=NH₃, 8; L=quinoline, 9) were isolated. A species analogous to 9 formed in a rapid reaction between 6 and 5′-guanosine monophosphate (5′-GMP). From NMR data an AMBER-based solution structure of the resulting adduct, trans-[Pt(AcMet-S)(5′-GMP-N7)(NH₃)quinoline] (10), was derived. The unusual reactivity along the N7-Pt-S axis in 8–10 resulted in partial release of both 9-EtGua and AcMet at high [Cl^–]. Possible consequences of the kinetic and structural effects (e.g., trans effect of sulfur, steric demand of quinoline) observed in these systems with respect to the (trans)formation of potential biological cross-links are discussed. Received: 25 May 1998 / Accepted: 6 August 1998     

Crystal structures of trisammonium bisperoxotetrafluoroniobate(V) and analogous tantalate(V)

(NH₄)₃[Nb(O₂)₂F₄] (I) and (NH₄)₃[Ta(O₂)₂F₄] (II) are isostructural, and belong to the cubic Fm3m space group with four molecules in the unit cell. The unit cell parameters are a = 9.4442(4) (I) and a = 9.4512(4) Å (II). The structures were solved by the Patterson method and were refined by the least-squares method to the conventional R factors of 0.036 for 86 reflections (I) and 0.043 for 103 reflections (II) (in both structures having I ? 2σ(I)). The disordered distributions of fluorine and peroxo oxygens with partially occupied sites are observed. The disordered NH₄⁺ tetrahedra appear in the structures.The metal atoms exhibit an octahedral coordination with two corners of a polyhedron at the centre of the peroxo bonds. Inter-atomic distances are NbF, 1.95(2), NbO, 1.94, TaF, 1.91(4) and TaO, 2.07 Å.The structures (I, II) are composed of [M^υ(O₂)₂-F₄]^3? octahedra and two symmetrically-independent ammonium cations connected by NH?O and NH?F hydrogen bonds. These two structures are compared with the structure of (NH₄)₃Ti(O₂)F₅].     

Pt(IV) complexes as prodrugs for cisplatin

The antitumor effects of platinum(IV) complexes, considered prodrugs for cisplatin, are believed to be due to biological reduction of Pt(IV) to Pt(II), with the reduction products binding to DNA and other cellular targets. In this work we used pBR322 DNA to capture the products of reduction of oxoplatin, c,t,c-[PtCl₂(OH)₂(NH₃)₂], 3, and a carboxylate-modified analog, c,t,c-[PtCl₂(OH)(O₂CCH₂CH₂CO₂H)(NH₃)₂], 4, by ascorbic acid (AsA) or glutathione (GSH). Since carbonate plays a significant role in the speciation of platinum complexes in solution, we also investigated the effects of carbonate on the reduction/DNA-binding process. In pH 7.4 buffer in the absence of carbonate, both 3 and 4 are reduced by AsA to cisplatin (confirmed using ¹⁹⁵Pt NMR), which binds to and unwinds closed circular DNA in a manner consistent with the formation of the well-known 1, 2 intrastrand DNA crosslink. However, when GSH is used as the reducing agent for 3 and 4, ¹⁹⁵Pt NMR shows that cisplatin is not produced in the reaction medium. Although the Pt(II) products bind to closed circular DNA, their effect on the mobility of Form I DNA is different from that produced by cisplatin. When physiological carbonate is present in the reduction medium, ¹³C NMR shows that Pt(II) carbonato complexes form which block or impede platinum binding to DNA. The results of the study vis-à-vis the ability of the Pt(IV) complexes to act as prodrugs for cisplatin are discussed.     

FT-IR and 1H NMR spectroscopic evidence of sugar ring conformational change in NH4GpG on complexation to form cis-[Pt(NH3)2(GpG)]+

The conformational change of the ribose ring in NH₄GpG and cis-[Pt(NH₃)₂(GpG)]⁺ was confirmed by FT-IR spectroscopic evidence as being C2′-endo, C3′-endo, anti, gg sugar ring pucker in the solid state. These results were compared with ¹H NMR spectral data in aqueous solution. The FT-IR spectrum of NH₄GpG shows marker bands at 802 cm^?1 and 797 cm^?1 which are assigned to the C3′-endo, anti, gg sugar-phosphate vibrations of ribose (?pG) and ribose (Gp?), respectively. The FT-IR spectrum of cis-[Pt(NH₃)₂(GpG)]⁺ (with N7N7 chelation in the GpG sequence) shows a marker band at 800 cm^?1 which is assigned to the C3′-endo, and a new shoulder band at 820 cm^?1 related to a C2′-endo ring pucker. The ribose conformation of (?pG) moiety in NH₄-GpG, C3′-endo, anti, gg changes into C2′-endo, anti, gg when a platinum atom is chelated to N7N7 in the GpG sequence.     

Solution and solid-state structures of lanthanide nitrate complexes with [(MeO)2P(O)]2C(OH)R (R=Me,tBu)

The complexes Ln(NO₃)₃L^a ₂ (L^a=[(MeO)₂P(O)]₂C(OH)Me; Ln=La–Er) and Ln(NO₃)₃L^b ₂ (L^b=[(MeO)₂P(O)]₂C(OH)^tBu); Ln=La–Lu) have been synthesised. The solid-state structures examined by IR spectroscopy, single crystal X-ray diffraction and extended X-ray absorption fine structure show uniformity across the series up to Dy, the metal being ten coordinate. Solution structures have been examined by ³¹P NMR spectroscopy, conductivity, electrospray mass spectrometry and EXAFS, and results indicate that solution structures fall into two groups, one for the lighter (La–Sm) and one for the heavier (Eu–Lu) lanthanides. This structural change involves the diphosphonate ligands, which appear to be monodenate for the heavier metals, affording these a coordination number of eight.     

Ni(II), Pd(II), and Pt(II) complexes of two new ditertiary phosphines, 1-diphenylphosphino-2-bis(m- or p-fluorophenyl) phosphinoethane

New complexes of the type cis-[MX₂(PP′)] (M= Ni, Pd and Pt; X=Cl, Br, I or NCS and PP′=(m- FC₆H₄)₂PCH₂CH₂PPh₂ or (p-FC₆H₄)₂PCH₂CH₂PPh₂) have been synthesized and characterized on the basis of ³¹P{¹H}NMR¹H NMR, IR and UV spectroscopy, elemental analysis and magnetic susceptibility measurements. All these complexes are found to be low spin, diamagnetic and square planar. ³¹P{¹H} spectra of these complexes exhibit extraordinarily large downfield coordination chemical shifts, J(³¹P³¹P′) and J(¹⁹⁵pt³¹P) couplings are discussed. Ring contribution (ΔR) values for palladium and platinum complexes are calculated from ³¹P NMR data.     

A heteronuclear (Pt,Zn) complex of 1-methyluracil with different coordination geometries (square-planar and square-pyramidal) of the two metals

Reaction of cis-(NH₃)₂Pt(1-MeU)₂ (1-MeU = 1- methyluracil anion, C₅H₅N₂O₂) with ZnSO₄·7H₂O leads to the formation of a dinuclear complex of composition [(NH₃)₂Pt(C₅H₅N₂O₂)₂Zn(H₂O)₃]SO₄· 2H₂O. The compound crystallizes in space group P2₁/c with a = 10.534(1), b = 17.933(2), c = 11.490(1) Å, β=94.61(1)°, Z=4. The structure was refined to R=0.043 and R_w=0.061. In this compound, Pt is coordinated through N3 to the 1-MeU ligand, while Zn is bound through the two O4 oxygens and completes its distorted square-pyramidal coordination sphere by three aqua ligands. The positions of the two metals relative to their basal donor atoms and the shortness of the PtZn separation (2.760(1) Å) suggest a bonding interaction between the two metals. Using ¹H NMR spectroscopy, a formation constant of ca. 114 1 mol^?1 for the Pt, Zn complex has been estimated.     

Synthesis and characterization of complexes of the type [Pt(amine)4]I2 and trans-[Pt(CH3NH2)2(H3CNC(CH3)2)2]I2 by crystallography and multinuclear magnetic resonance spectroscopy

Complexes of the type [Pt(amine)₄]I₂ were synthesized and characterized mainly by multinuclear (¹⁹⁵Pt, ¹H and ¹³C) magnetic resonance spectroscopy. The compounds were prepared with different primary amines, but not with bulky amines, due to steric hindrance. In ¹⁹⁵Pt NMR, the signals were observed between −2715 and −2769 ppm in D₂O. The coupling constant ³J(¹⁹⁵Pt-¹H) for the MeNH₂ complex is 42 Hz. In ¹³C NMR, the average values of the coupling constants ²J(¹⁹⁵Pt-¹³C) and ³J(¹⁹⁵Pt-¹³C) are 18 and 30 Hz, respectively. The crystal structure of [Pt(EtNH₂)₄]I₂ was determined by X-ray diffraction methods. The Pt atom is located on an inversion center. The structure is stabilized by H-bonding between the amines and the iodide ions. The compound with n-BuNH₂ was found by crystallographic methods to be [Pt(n-BuNH₂)₄]₂I₃(n-BuNHCOO). The crystal contains two independent [Pt(CH₃NH₂)₄]²⁺ cations, three iodide ions and a carbamate ion formed from the reaction of butylamine with CO₂ from the air. When the compound [Pt(CH₃NH₂)₄]I₂ was dissolved in acetone, crystals identified as trans-[Pt(CH₃NH₂)₂(H₃CNC(CH₃)₂)₂]I₂ were isolated and characterized by crystallographic methods. Two trans bonded MeNH₂ ligands had reacted with acetone to produce the two N-bonded Schiff base Pt(II) compound.     

A new route to N(1)-5R-tetrazole complexes via azidation to nitriles coordinated to Pt(II) and Pt(IV)

New tetrazolate complexes trans-[PtCl₂(RCN₄)₂]²⁻, trans-[PtCl₄(RCN₄)₂]²⁻ with Ph₃PCH₂Ph⁺ and (CH₃)₂NH₂⁺ counterions have been obtained by azidation of nitriles coordinated to Pt(II) and Pt(IV) {trans-[PtCl₂(RCN)₂] and trans-[PtCl₄(RCN)₂] (R = Et, Ph)} and characterized. The composition and the molecular structure of the complexes obtained were established by the СHN elemental analyses, ¹Н and ¹³С NMR spectroscopy, IR spectroscopy, mass spectrometry, and X-ray diffraction. The coordination of nitriles to Pt(II) and Pt(IV) is shown significantly activate the azidation: the reaction proceeds with a higher rate and at relatively low temperature compared with the classical 1,3-dipolar addition of azides to nitriles.     

High performance liquid chromatography studies on the interactions of cis-Pt(NH3)2−(H2O)22+ with guanine and methylated g

Time dependence studies, using high performance liquid chromatography (HPLC), on the reaction between cis-diamminediaquoplatinum and guanine, N1-methylguanine, N7-methylguanine, N9-methylguanine, and N1 ,N7-dimethylguanine are reported. Each reaction gave rise to eight or more compounds; the major components have been prepared and characterization by ¹H and ¹⁹⁵Pt nuclear magnetic resonance has been attempted. Species of the form ((NH₃)₂Pt(NO₃)-(G-H)-(NO₃)-Pt(NH₃)₂)⁺, (NH₃)₂,Pt(G-H)(NO₃) monomer and (NH₃)₂Pt(G-H)(NO₃) dimer, where G-H indicates the guanine monoanion, are postulated.     

Reaction of [MCl2(CH3CN)2] (M = Pd(II), Pt(II)) compounds with N1-alkylpyridylpyrazole-derived ligands

Palladium(II) and platinum(II) complexes with N-alkylpyridylpyrazole-derived ligands, 2-(1-ethyl-5-phenyl-1H-pyrazol-3-yl)pyridine (L¹) and 2-(1-octyl-5-phenyl-1H-pyrazol-3-yl)pyridine (L²), cis-[MCl₂(L)] (M = Pd(II), Pt(II)), have been synthesised. Treatment of [PdCl₂(L)] (L = L¹, L²) with excess of ligand (L¹, L²), pyridine (py) or triphenylphosphine (PPh₃) in the presence of AgBF₄ and NaBPh₄ produced the following complexes: [Pd(L)₂](BPh₄)₂, [Pd(L)(py)₂](BPh₄)₂ and [Pd(L)(PPh₃)₂](BPh₄)₂. All complexes have been characterised by elemental analyses, conductivity, IR and NMR spectroscopies. The crystal structures of cis-[PdCl₂(L²)] (2) and cis-[PtCl₂(L¹)] (3) were determined by a single crystal X-ray diffraction method. In both complexes, the metal atom is coordinated by one pyrazole nitrogen, one pyridine nitrogen and two chlorine atoms in a distorted square-planar geometry. In complex 3, π-π stacking between pairs of molecules is observed.     

Coordination chemistry of higher oxidation states. Part 21. Platinum-195 NMR studies of platinum(II) and platinum(IV) complexes of bi- and multi-dentate phosphorus,arsenic and sulphur ligands

195-Platinum NMR spectra are reported for a series of complexes of bidentate ligands [Pt(LL)X₄] (X=Cl, Br; LL=diphosphine, diarsine, dithioether, diselenoether), [Pt(Me₂PCH₂CH₂PMe₂)₂X₂]X₂, [Pt(o-C₆H₄(AsMe₂)₂)₂X₂]X₂, and for the Pt(II) analogues. The trends in chemical shifts δ(Pt) and ¹J(PtP), ¹J(PtSe) coupling constants are discussed, and used to establish the nature of the solution species obtained by oxidation of Pt(II) complexes of some multidentate phosphorus and arsenic ligands. The [Pt(LL)I₄] materials are shown to exist as [Pt^II(LL)I₂] in dimethylsulphoxide solution, but [Pt(o-C₆H₄(AsMe₂)₂)₂I₂]²⁺ is a genuine Pt(IV) iodo-complex.     

Coordination of 9-methyladenine to [cis-Pt(NH3)2]2+ and [Pt(dien)]2+ as studied by proton NMR

Reaction products of 9-methyladenine (mAde) with [Pt(dien)Cl]Cl and cis-Pt(NH₃)₂Cl₂ have been separated using CM-Sephadex C25 cation exchange chromatography. NMR and UV characteristics are presented; the platinum binding sites were established by studying the pH dependence of the ¹H-NMR chemical shifts and of UV difference absorption. It is shown that the N 1 atom of the ligand can be protonated in Pt(mAde-N7) adducts, while the N7 atom can be protonated in Pt(mAde-N1).     

Metal-penicillamine interactions. Part 1. Preparation and crystal structure of a 1:1 complex of mercuric chloride with d-penicillamine, 2[μ3-Cl){HgSC(CH3)2CH(NH3)COO}3·3(μ2-Cl)· 2(H3O)·(H2O·Cl)3

A 1:1 complex of mercuric chloride with D-peniccillamine has been isolated and characterised as 2[(μ₃-Cl){HgSC(CH₃)₂CH(NH₃)COO}3]·3(μ₂-Cl)·2(H₃O)·(H₂O·Cl)₃. The compound crystallises in cubic space group P4₁32, with a = 18.679(5) Å and Z = 4. The structure, refined to R_F = 0.086 for 443 observed Mo-Kα diffractometer data, features a triply bridging chloride ion linking three equivalent [HgSC(CH₃)₂CH(NH₃)COO]⁺ units [Hg-Cl = 2.37(1) Å, Hg-Cl-Hg′ = 98.5(9)°]. The carboxylate groups of a pair of adjacent penicillamine ligands are strongly linked via a symmetrical O?H?O hydrogen bond of length 2.24(8) Å, and neighboring pyramidal trinuclear [μ₃-Cl){HgSC(CH₃)₂CH(NH₃)-COO}₃]²⁺ moieties are further connected by symmetrical chloride bridges [Hg-Cl = 3.06(2) Å; HgClHg′' = 79.6(7)°] to form a three-dimensional network. The voids in the lattice are filled by hydronium ions and novel planar cyclic hydrogen-bonded (H₂O·Cl^?)₃ rings of edge O-H?Cl = 2.46(4) Å.