Platinum complexes of oxopurines: cis‐bis(theophyllinato‐N7)bis(triphenylphosphine)platinum(II) and cis‐chloro(theobrominato‐N1)bis(triphenylphosphine)platinum(II) ethanol hemisolvate

The syntheses and structures of two mixed‐ligand complexes of platinum(II) with deprotonated oxopurine bases and tri­phenyl­phosphine are reported, namely the theophyllinate complex cis‐bis(1,2,3,6‐tetra­hydro‐1,3‐di­methyl­purine‐2,6‐dionato‐κN⁷)­bis(tri­phenyl­phosphine‐κP)­platinum(II), [Pt(C₇H₇N₄O₂)₂(C₁₈H₁₅P)₂], (I), and the theobrominate complex cis‐chloro(1,2,3,6‐tetrahydro‐3,7‐dimethylpurine‐2,6‐dionato‐κN¹)­bis(tri­phenyl­phosphine‐κP)­platinum(II) ethanol hemisolvate, [PtCl(C₇H₇N₄O₂)(C₁₈H₁₅P)₂]·0.5C₂H₅OH, (II). In (I), the coordination geometry of Pt is square planar, formed by the two coordinating N atoms of the theophyl­linate anions in a cis arrangement and two P atoms from the tri­phenyl­phosphine groups. In (II), there are two crystallographically independent mol­ecules. They both exhibit a square‐planar coordination geometry around Pt involving one Cl atom, the coordinating N atom of the theobrominate anion and two P atoms from the tri­phenyl­phosphine groups. The two tri­phenyl­phosphine groups are arranged in a cis configuration in both structures. The heterocyclic rings are rotated with respect to the coordination plane of the metal by 82.99 (8) and 88.09 (8)° in complex (I), and by 85.91 (16) and 88.14 (18)° in complex (II). Both structures are stabilized by intramolecular stacking interactions involving the purine rings and the phenyl rings of adjacent tri­phenyl­phosphine moieties.     

Thermal decomposition of trans-chloro(2-allylphenyl)bis(triethylphospine)nickel(II)

Thermolysis of trans-chloro(2-allylphenyl)bis(triethylphosphine)nickel(II), I, in tetrachloroethylene has afforded indene as the major hydrocarbon product along with lesser amounts of allylbenzene and trans-β-methylstyrene. Organonickel products were trans-chloro(trichlorovinyl)bis(triethylphosphine)nickel(II), II, chloro[2-(trans-propenyl)phenyl]bis(triethylphosphine)nickel(II), III, and trans-dichlorobis(triethylphosphine)nickel(II). Compound III was the major product from thermolysis of I in benzene. Chloro[2-(cis-propenyl)phenyl]bis(triethylphosphine)nickel(II), IV, and III could be synthesized independently by treatment of chloro-2-(cis-propenyl)benzene and chloro-2-(trans-propenyl)benzene, respectively, with nickel acetylacetonate and triethylaluminium in the presence of triethylphosphine. Thermolysis of I in benzene containing allylbenzene led to the formation of trans-β-methylstyrene. The thermolysis of I in benzene in the presence of cis-1,4-hexadiene caused the skeletal rearrangement of the diene to trans-2-methyl-1,3-pentadiene. A catalyst derived from ethylenebis(triphenylphosphine)nickel(0) and hydrogen chloride isomerized allylbenzene to trans-β-methylstyrene.     

Crystallization experiments with the dinuclear chelate ring complex di‐μ‐chlorido‐bis[(η2‐2‐allyl‐4‐methoxy‐5‐{[(propan‐2‐yloxy)carbonyl]methoxy}phenyl‐κC1)platinum(II)]

Crystallization experiments with the dinuclear chelate ring complex di‐μ‐chlorido‐bis[(η²‐2‐allyl‐4‐methoxy‐5‐{[(propan‐2‐yloxy)carbonyl]methoxy}phenyl‐κC¹)platinum(II)], [Pt₂(C₁₅H₁₉O₄)₂Cl₂], containing a derivative of the natural compound eugenol as ligand, have been performed. Using five different sets of crystallization conditions resulted in four different complexes which can be further used as starting compounds for the synthesis of Pt complexes with promising anticancer activities. In the case of vapour diffusion with the binary chloroform–diethyl ether or methylene chloride–diethyl ether systems, no change of the molecular structure was observed. Using evaporation from acetonitrile (at room temperature), dimethylformamide (DMF, at 313 K) or dimethyl sulfoxide (DMSO, at 313 K), however, resulted in the displacement of a chloride ligand by the solvent, giving, respectively, the mononuclear complexes (acetonitrile‐κN)(η²‐2‐allyl‐4‐methoxy‐5‐{[(propan‐2‐yloxy)carbonyl]methoxy}phenyl‐κC¹)chloridoplatinum(II) monohydrate, [Pt(C₁₅H₁₉O₄)Cl(CH₃CN)]·H₂O, (η²‐2‐allyl‐4‐methoxy‐5‐{[(propan‐2‐yloxy)carbonyl]methoxy}phenyl‐κC¹)chlorido(dimethylformamide‐κO)platinum(II), [Pt(C₁₅H₁₉O₄)Cl(C₂H₇NO)], and (η²‐2‐allyl‐4‐methoxy‐5‐{[(propan‐2‐yloxy)carbonyl]methoxy}phenyl‐κC¹)chlorido(dimethyl sulfoxide‐κS)platinum(II), determined as the analogue {η²‐2‐allyl‐4‐methoxy‐5‐[(ethoxycarbonyl)methoxy]phenyl‐κC¹}chlorido(dimethyl sulfoxide‐κS)platinum(II), [Pt(C₁₄H₁₇O₄)Cl(C₂H₆OS)]. The crystal structures confirm that acetonitrile interacts with the Pt^II atom via its N atom, while for DMSO, the S atom is the coordinating atom. For the replacement, the longest of the two Pt—Cl bonds is cleaved, leading to a cis position of the solvent ligand with respect to the allyl group. The crystal packing of the complexes is characterized by dimer formation via C—H…O and C—H…π interactions, but no π–π interactions are observed despite the presence of the aromatic ring.     

Three isomorphous two‐dimensional coordination polymers generated from a benzimidazole bridging ligand and ZnX2 (X = Cl,Br and I)

A novel bridging asymmetric benzimidazole ligand, 4‐{2‐[3‐(pyridin‐4‐yl)phenyl]‐1H‐benzimidazol‐1‐ylmethyl}benzoic acid, was used to construct three isomorphous two‐dimensional coordination polymers, namely catena‐poly[chlorido(μ₃‐4‐{2‐[3‐(pyridin‐4‐yl)phenyl]‐1H‐benzimidazol‐1‐ylmethyl}benzoato)zinc(II)], [Zn(C₂₆H₁₈N₃O₂)Cl]_n, (I), and the bromide, (II), and iodide, (III), analogues. Neighbouring two‐dimensional networks are stacked into three‐dimensional frameworks via interlayer π–π interactions. The luminescent properties of (I)–(III) were investigated and they display an obvious red‐shift in the solid state at room temperature.     

Four NiII complexes with the new cyclam–methylimidazole ligand 1‐[(1‐methyl‐1H‐imidazol‐2‐yl)methyl]‐1,4,8,11‐tetraazacyclotetradecane

Although it has not proved possible to crystallize the newly prepared cyclam–methylimidazole ligand 1‐[(1‐methyl‐1H‐imidazol‐2‐yl)methyl]‐1,4,8,11‐tetraazacyclotetradecane (L^Im1), the trans and cis isomers of an Ni^II complex, namely trans‐aqua{1‐[(1‐methyl‐1H‐imidazol‐2‐yl)methyl]‐1,4,8,11‐tetraazacyclotetradecane}nickel(II) bis(perchlorate) monohydrate, [Ni(C₁₅H₃₀N₆)(H₂O)](ClO₄)₂·H₂O, (1), and cis‐aqua{1‐[(1‐methyl‐1H‐imidazol‐2‐yl)methyl]‐1,4,8,11‐tetraazacyclotetradecane}nickel(II) bis(perchlorate), [Ni(C₁₅H₃₀N₆)(H₂O)](ClO₄)₂, (2), have been prepared and structurally characterized. At different stages of the crystallization and thermal treatment from which (1) and (2) were obtained, a further two compounds were isolated in crystalline form and their structures also analysed, namely trans‐{1‐[(1‐methyl‐1H‐imidazol‐2‐yl)methyl]‐1,4,8,11‐tetraazacyclotetradecane}(perchlorato)nickel(II) perchlorate, [Ni(ClO₄)(C₁₅H₃₀N₆)]ClO₄, (3), and cis‐{1,8‐bis[(1‐methyl‐1H‐imidazol‐2‐yl)methyl]‐1,4,8,11‐tetraazacyclotetradecane}nickel(II) bis(perchlorate) 0.24‐hydrate, [Ni(C₂₀H₃₆N₆)](ClO₄)₂·0.24H₂O, (4); the 1,8‐bis[(1‐methyl‐1H‐imidazol‐2‐yl)methyl]‐1,4,8,11‐tetraazacyclotetradecane ligand is a minor side product, probably formed in trace amounts in the synthesis of L^Im1. The configurations of the cyclam macrocycles in the complexes have been analysed and the structures are compared with analogues from the literature.     

Hydro­gen‐bonding patterns in two structural isomers of 3,6‐bis(2‐chloro­phenyl)‐1,4‐di­hydro‐1,2,4,5‐tetrazine

Two structural isomers, 3,6‐bis(2‐chloro­phenyl)‐1,4‐di­hydro‐1,2,4,5‐tetrazine, (I), and 3,5‐bis(2‐chloro­phenyl)‐4‐amino‐1H‐1,2,4‐triazole, (II), both C₁₄H₁₀Cl₂N₄, form chain‐like structures in the solid state, stabilized by N—H⋯N and N—H⋯Cl hydrogen bonds. A contribution from weak interactions to the strong hydrogen‐bond network is observed in both structures. The secondary graph sets for intermolecular hydrogen bonds [(11) for (I) and (12) for (II)] indicate the similarity between the networks.     

Oxidative addition of tetrabromo-1,2-benzoquinone totrans-carbonylchlorobis(triphenylphosphine)rhodium andtrans-carbonyliodiobis(triphenylphosphine)rhodium

Summary The oxidative addition of tetrabromo-1,2-benzoquinone to Rh(CO)X(PPh₃)₂ (X = Cl or I) has been studied. With the square planar complex Rh(CO)Cl(PPh₃)₂, two new isomeric hexacoordinated compounds; withcis andtrans PPh₃ ligands, have been isolated and their structures are discussed on the basis of spectroscopic data. Thecis isomer in acetone solution quickly converts into thetrans. Such a conversion presumably proceeds through the dissociation of a triphenylphosphine molecule as seems indicated by the isolation of the pentacoordinated intermediate species Rh(CO)I(PPh₃)(1,2-O₂C₆Br₄), which has been identified by elemental analysis and spectroscopically characterized.     

A monomeric gold(I) carbanion complex with an uncoordinated thioether: [2‐(methylsulfanyl)phenyl](triphenylphosphine)gold(I)

The title compound, [Au(C₇H₇S)(C₁₈H₁₅P)], is conformationally chiral and crystallizes from benzene–hexane as individually enantiopure crystals. This mononuclear compound has the Au^I atom linearly bound to a triphenylphosphine P atom and to a phenyl C atom of a 2‐(methylsulfanyl)phenyl group. The angle at the Au^I atom is 175.9 (2)°. The linear ligand coordination about the Au^I atom has geometric parameters inside the remarkably narrow range found for gold complexes bound by a phosphine ligand and by the ortho‐C atom of a substituted phenyl group. This is the first example of gold(I) attached to a methylsulfanyl aromatic carbanion.     

Aluminium(III) amidinates formed from reactions of `AlCl' with lithium amidinates

The disproportionation of AlCl(THF)_n (THF is tetrahydrofuran) in the presence of lithium amidinate species gives aluminium(III) amidinate complexes with partial or full chloride substitution. Three aluminium amidinate complexes formed during the reaction between aluminium monochloride and lithium amidinates are presented. The homoleptic complex tris(N,N′‐diisopropylbenzimidamido)aluminium(III), [Al(C₁₃H₁₉N₂)₃] or Al{PhC[N(i‐Pr)]₂}₃, (I), crystallizes from the same solution as the heteroleptic complex chloridobis(N,N′‐diisopropylbenzimidamido)aluminium(III), [Al(C₁₃H₁₉N₂)₂Cl] or Al{PhC[N(i‐Pr)]₂}₂Cl, (II). Both have two crystallographically independent molecules per asymmetric unit (Z′ = 2) and (I) shows disorder in four of its N(i‐Pr) groups. Changing the ligand substituent to the bulkier cyclohexyl allows the isolation of the partial THF solvate chloridobis(N,N′‐dicyclohexylbenzimidamido)aluminium(III) tetrahydrofuran 0.675‐solvate, [Al(C₁₉H₂₇N₂)₂Cl]·0.675C₄H₈O or Al[PhC(NCy)₂]₂Cl·0.675THF, (III). Despite having a twofold rotation axis running through its Al and Cl atoms, (III) has a similar molecular structure to that of (II).     

Synthesis,characterization, and crystal structures of organonickel(II) complexes coordinated to novel 1‐bromo‐2,6‐bis{[(λ5‐phosphanylidene)imino]methyl}benzene NCN‐pincer ligands

A novel family of four 1‐bromo‐2,6‐bis{[(λ⁵‐phosphanylidene)imino]methyl}benzene ligands has been synthesized and characterized. The phosphiniminomethyl substituents are decorated with either three phenyl groups, two phenyl and one cyclohexyl group, one phenyl and two cyclohexyl groups, or three cyclohexyl groups. Each ligand was metallated using zero‐valent nickel through an oxidative addition to form a family of organonickel(II) complexes, namely (2,6‐bis{[(triphenyl‐λ⁵‐phosphanylidene)imino]methyl}phenyl‐κ³N,C¹,N′)bromidonickel(II) dichloromethane hemisolvate, [NiBr(C₄₄H₃₇N₂P₂)]·0.5CH₂Cl₂, (2,6‐bis{[(cyclohexyldiphenyl‐λ⁵‐phosphanylidene)imino]methyl}phenyl‐κ³N,C¹,N′)bromidonickel(II) diethyl ether hemisolvate, [NiBr(C₄₄H₄₉N₂P₂)]·0.5C₄H₁₀O, (2,6‐bis{[(dicyclohexylphenyl‐λ⁵‐phosphanylidene)imino]methyl}phenyl‐κ³N,C¹,N′)bromidonickel(II), [NiBr(C₄₄H₆₁N₂P₂)], and (2,6‐bis{[(tricyclohexyl‐λ⁵‐phosphanylidene)imino]methyl}phenyl‐κ³N,C¹,N′)bromidonickel(II), [NiBr(C₄₄H₇₃N₂P₂)]. This family of complexes represents a useful opportunity to investigate the impact of incrementally changing the steric characteristics of a complex on its structure and reactivity.     

Cobalt(II) chloride adducts with acetonitrile,propan‐2‐ol and tetrahydrofuran: considerations on nuclearity,reactivity and synthetic applications

High‐spin cobalt(II) complexes are considered useful building blocks for the synthesis of single‐molecule magnets (SMM) because of their intrinsic magnetic anisotropy. In this work, three new cobalt(II) chloride adducts with labile ligands have been synthesized from anhydrous CoCl₂, to be subsequently employed as starting materials for heterobimetallic compounds. The products were characterized by elemental, spectroscopic (EPR and FT–IR) and single‐crystal X‐ray diffraction analyses. trans‐Tetrakis(acetonitrile‐κN )bis(tetrahydrofuran‐κO )cobalt(II) bis[(acetonitrile‐κN )trichloridocobaltate(II)], [Co(C₂H₃N)₄(C₄H₈O)₂][CoCl₃(C₂H₃N)]₂, (1), comprises mononuclear ions and contains both acetonitrile and tetrahydrofuran (thf) ligands, The coordination polymer catena‐poly[[tetrakis(propan‐2‐ol‐κO )cobalt(II)]‐μ‐chlorido‐[dichloridocobalt(II)]‐μ‐chlorido], [Co₂Cl₄(C₃H₈O)₄], (2′), was prepared by direct reaction between anhydrous CoCl₂ and propan‐2‐ol in an attempt to rationalize the formation of the CoCl₂–alcohol adduct (2), probably CoCl₂(HOⁱPr)_m . The binuclear complex di‐μ‐chlorido‐1:2κ⁴Cl :Cl‐dichlorido‐2κ²Cl‐tetrakis(tetrahydrofuran‐1κO )dicobalt(II), [Co₂Cl₄(C₄H₈O)₄], (3), was obtained from (2) after recrystallization from tetrahydrofuran. All three products present cobalt(II) centres in both octahedral and tetrahedral environments, the former usually less distorted than the latter, regardless of the nature of the neutral ligand. Product (2′) is stabilized by an intramolecular hydrogen‐bond network that appears to favour a trans arrangement of the chloride ligands in the octahedral moiety; this differs from the cis disposition found in (3). The expected easy displacement of the bound solvent molecules from the metal coordination sphere makes the three compounds good candidates for suitable starting materials in a number of synthetic applications.     

The trans influence of the pyridine ligand on ruthenium(II)–porphyrin–carbene complexes

In the two ruthenium(II)–porphyrin–carbene complexes ­(di­benzoyl­carbenyl‐κC)(pyridine‐κN)(5,10,15,20‐tetra‐p‐tolyl­porphyrinato‐κ⁴N)­ruthenium(II), [Ru(C₁₅H₁₀O₂)(C₅H₅N)(C₄₈H₃₆N₄)], (I), and (pyridine‐κN)(5,10,15,20‐tetra‐p‐tolyl­porphyrinato‐κ⁴N)[bis(3‐tri­fluoro­methyl­phenyl)­carbenyl‐κC]­ruthenium(II), [Ru(C₁₅H₈F₆)(C₅H₅N)(C₄₈H₃₆N₄)], (II), the pyridine ligand coordinates to the octahedral Ru atom trans with respect to the carbene ligand. The C(carbene)—Ru—N(pyridine) bonds in (I) coincide with a crystallographic twofold axis. The Ru—C bond lengths of 1.877 (8) and 1.868 (3) Å in (I) and (II), respectively, are slightly longer than those of other ruthenium(II)–porphyrin–carbene complexes, owing to the trans influence of the pyridine ligands.     

Hydrogen bonding and π–π interactions in the cocrystal salt [Fe(bpe)2(H2O)4](TCEP)2·2(bpe) [bpe is trans‐1,2‐bis(pyridin‐4‐yl)ethene and TCEP is 1,1,3,3‐tetracyano‐2‐ethoxypropenide]

The cocrystal salt tetraaquabis[trans‐1,2‐bis(pyridin‐4‐yl)ethene‐κN]iron(II) bis(1,1,3,3‐tetracyano‐2‐ethoxypropenide)–trans‐1,2‐bis(pyridin‐4‐yl)ethene (1/2), [Fe(C₁₂H₁₀N₂)₂(H₂O)₄](C₉H₅N₄O)₂·2C₁₂H₁₀N₂, is a rare example of a mononuclear Fe^II compound with trans‐1,2‐bis(pyridin‐4‐yl)ethane (bpe) ligands. The complex cation resides on a crystallographically imposed inversion center and exhibits a tetragonally distorted octahedral coordination geometry. Both the symmetry‐independent bpe ligand and the cocrystallized bpe molecule are essentially planar. The 1,1,3,3‐tetracyano‐2‐ethoxypropenide counter‐ion is nonplanar and the bond lengths are consistant with significant electron delocalization. The extended structure exhibits an extensive O—H…N hydrogen‐bonding network with layers of complex cations joined by the cocrystallized bpe. Both the coordinated and the cocrystallized bpe are involved in π–π interactions. Hirshfeld and fingerprint plots reveal the important intermolecular interactions. Density functional theory was used to estimate the strengths of the hydrogen‐bonding and π–π interactions, and suggest that the O—H…N hydrogen bonds enhance the strength of the π‐interactions by increasing the polarization of the pyridine rings.     

Comparative X‐ray study of three nickel(II)–thio­cyanate compounds

Three cis nickel–di­thio­cyanate (SCN) complexes with different N,N′‐bidentate bases have been prepared and their crystal structures determined: bis(2,2′‐bi­pyridine‐N,N′)­bis­(thio­cyan‐­ato‐N)­nickel(II), [Ni(SCN)₂­(C₁₀H₈N₂)₂], bis(1,10‐phen­anthroline‐N,N′)­bis­(thio­cyanato‐N)­nickel(II), [Ni(SCN)₂­(C₁₂H₈N₂)₂], and bis(2,9‐di­methyl‐1,10‐phenanthroline‐N,N′)­bis­(thiocyanato‐N)nickel(II) mono­hydrate, [Ni(SCN)₂­(C₁₂H₈N₂)₂]·H₂O. Distortions due to ligand size are discussed.     

1,2,3‐Trimethoxy‐4‐[(E)‐2‐phenylvinyl]benzene and (E,E)‐1,4‐bis(2,3,4‐trimethoxyphenyl)buta‐1,3‐diene

The stilbene derivative 1,2,3‐trimethoxy‐4‐[(E)‐2‐phenylvinyl]benzene, C₁₇H₁₈O₃, (I), and its homocoupling co‐product (E,E)‐1,4‐bis(2,3,4‐trimethoxyphenyl)buta‐1,3‐diene, C₂₂H₂₆O₆, (II), both have double bonds in trans conformations in their conjugated linkages. In the structure of stilbene (I), the aromatic rings deviate significantly from coplanarity, in contrast with coproduct (II), the core of which is rigorously planar. The deviation in stilbene (I) seems to be driven by intermolecular electrostatic interactions. Diene (II) sits on a crystallographic inversion centre, which bisects the conjugated linkage.     

Chloro­(phenyl)(1H‐pyrazole‐κN2)(tri­phenyl­phosphine‐κP)­palladium(II)

In the title compound, [Pd(C₆H₅)Cl(C₃H₄N₂){P(C₆H₅)₃}], the phenyl and Cl ligands lie mutually trans. The compound is the first structurally characterized complex with four mono­dentate Cl, P, N and (non‐carbenoid) C ligands in a square‐planar four‐coordinate palladium(II) environment. The pyrazole ligand is coplanar with the latter array. The pyrazole NH group forms a bifurcated hydrogen bond to Cl, with an intra‐ and intermolecular component.     

Metal complexes with chloride and triazole‐based ligands: investigation of a well‐resolved up–up–down–down (uudd) cyclic water tetramer and X—H...Cl (X = O and C) hydrogen‐bonding interactions

The crystal structure of the title complex, trans‐dichloridotetrakis[1‐phenyl‐3‐(1H‐1,2,4‐triazol‐1‐yl‐κN⁴)propan‐1‐one]copper(II) hexahydrate, [CuCl₂(C₁₁H₁₁N₃O)₄]·6H₂O, is isomorphous with that of the corresponding nickel and cobalt compounds. The complex has crystallographic inversion symmetry with the Cu^II atom on an inversion centre. Each Cu^II atom is six‐coordinated by one N atom from each of the four 1‐phenyl‐3‐(1H‐1,2,4‐triazol‐1‐yl)propan‐1‐one ligands in the equatorial plane and by two chloride ligands in axial positions. The structure includes a centrosymmetric irregular up–up–down–down (uudd) water tetramer cluster and O—H...Cl hydrogen bonds. Intermolecular C—H...Cl hydrogen bonds exist between adjacent molecules, resulting in a three‐dimensional supramolecular network.     

Unusual 4‐arsonoanilinium cationic species in the hydrochloride salt of (4‐aminophenyl)arsonic acid and formed in the reaction of the acid with copper(II) sulfate,copper(II) chloride and cadmium chloride

Structures having the unusual protonated 4‐arsonoanilinium species, namely in the hydrochloride salt, C₆H₉AsNO₃⁺·Cl⁻, (I), and the complex salts formed from the reaction of (4‐aminophenyl)arsonic acid (p‐arsanilic acid) with copper(II) sulfate, i.e. hexaaquacopper(II) bis(4‐arsonoanilinium) disulfate dihydrate, (C₆H₉AsNO₃)₂[Cu(H₂O)₆](SO₄)₂·2H₂O, (II), with copper(II) chloride, i.e. poly[bis(4‐arsonoanilinium) [tetra‐μ‐chlorido‐cuprate(II)]], {(C₆H₉AsNO₃)₂[CuCl₄]}_n , (III), and with cadmium chloride, i.e. poly[bis(4‐arsonoanilinium) [tetra‐μ‐chlorido‐cadmate(II)]], {(C₆H₉AsNO₃)₂[CdCl₄]}_n , (IV), have been determined. In (II), the two 4‐arsonoanilinium cations are accompanied by [Cu(H₂O)₆]²⁺ cations with sulfate anions. In the isotypic complex salts (III) and (IV), they act as counter‐cations to the {[CuCl₄]²⁻}_n or {[CdCl₄]²⁻}_n anionic polymer sheets, respectively. In (II), the [Cu(H₂O)₆]²⁺ ion sits on a crystallographic centre of symmetry and displays a slightly distorted octahedral coordination geometry. The asymmetric unit for (II) contains, in addition to half the [Cu(H₂O)₆]²⁺ ion, one 4‐arsonoanilinium cation, a sulfate dianion and a solvent water molecule. Extensive O—H…O and N—H…O hydrogen bonds link all the species, giving an overall three‐dimensional structure. In (III), four of the chloride ligands are related by inversion [Cu—Cl = 2.2826 (8) and 2.2990 (9) Å], with the other two sites of the tetragonally distorted octahedral CuCl₆ unit occupied by symmetry‐generated Cl‐atom donors [Cu—Cl = 2.9833 (9) Å], forming a two‐dimensional coordination polymer network substructure lying parallel to (001). In the crystal, the polymer layers are linked across [001] by a number of bridging hydrogen bonds involving N—H…Cl interactions from head‐to‐head‐linked As—O—H…O 4‐arsonoanilinium cations. A three‐dimensional network structure is formed. Cd^II compound (IV) is isotypic with Cu^II complex (III), but with the central CdCl₆ complex repeat unit having a more regular M —Cl bond‐length range [2.5232 (12)–2.6931 (10) Å] compared to that in (III). This series of compounds represents the first reported crystal structures having the protonated 4‐arsonoanilinium species.     

Conformational change induced by hydration: trans‐dichloro­bis­[(1R,2R,3R,5S)‐(–)‐isopinocampheylamine]palladium(II) and trans‐dichloro­bis[(1S,2S,3S,5R)‐(+)‐isopinocampheylamine]palladium(II) hemihydrate

The title compounds, trans‐dichloro­bis[(1R,2R,3R,5S)‐(−)‐2,6,6‐trimethyl­bicyclo­[3.1.1]heptan‐3‐amine]palladium(II), [PdCl₂(C₁₀H₁₉N)₂], and trans‐dichloro­bis[(1S,2S,3S,5R)‐(+)‐2,6,6‐trimethyl­bicyclo­[3.1.1]heptan‐3‐amine]palladium(II) hemihydrate, [PdCl₂(C₁₀H₁₉N)₂]·0.5H₂O, present different arrangements of the amine ligands coordinated to Pd^II, viz. antiperiplanar in the former case and (−)anticlinal in the latter. The hemihydrate is an inclusion compound, with a Pd coordination complex and disordered water mol­ecules residing on crystallographic twofold axes. The crystal structure for the hemihydrate includes a short Pd⋯Pd separation of 3.4133 (13) Å.     

Two isomorphous imidazole (Him) complexes: [MCl2(Him)2(H2O)2] (M = Co and Ni)

The structures of aqua­di­chloro­bis(1H‐imidazole)­cobalt(II), [CoCl₂(Him)₂(H₂O)₂] (Him is 1H‐imidazole, C₃H₄N₂), (I), and aqua­di­chloro­bis(1H‐imidazole)­nickel(II), [NiCl₂(Him)₂(H₂O)₂], (II), are isomorphous and consist of monomers with inversion symmetry. The three monodentate ligands (imidazole, chlorine and aqua), together with their symmetry equivalents, define almost perfect octahedra. Hydro­gen‐bonding interactions via the imidazole and aqua H atoms lead to a three‐dimensional network.