(Phosphine)gold(I) Complexes of Benzenedithioles. Crystal structures of 1,2-benzenedithiolato-bis[triphenyl-phosphinegold(I)] and bis(triethylphosphine)gold(I) bis(1,2-benzenedithiolato)gold(III)

The reaction of 1,2- and 1,3-benzenedithiol C₆H₄(SH)₂ with chloro(phosphine)gold(I) complexes R₃PAuCl (R = Et, Ph) in the presence of triethylamine in tetrahydrofuran gives stable gold(I) complexes 1,2-C₆H₄(SAuPR₃)₂ [R = Et ( 1 ) and Ph ( 2 )] or 1,3-C₆H₄(SAuPPh₃)₂ ( 3 ), respectively, in high yield. The compounds have been characterized by analytical and NMR spectroscopic data. From the reaction of 1,2-C₆H(SH)₂ with Et₃P? AuCl a by-product [(Et₃P)₂Au]⁺ [Au(1,2? C₆H₄S₂)₂]^? ( 4 ) has also been isolated in low yield. The crystal structures of compounds 2 and 4 have been determined by single crystal X-ray diffraction. The gold(I) atoms in complex 2 are two-coordinate with bond angles S? Au? P of 175.2(1) and 159.5(1)°, Au? S bond distances of 2.304(1) and 2.321(1) å, and a short Au…?Au contact of 3.145(1) Å. The gold(I) atom in the cation of complex 4 is also linearly two-coordinate with a P? Au? P angle of 170.1(1) Å and Au? P distances of 2.296(3) and 2.298(3) Å. The geometry of the anion in 4 shows a square-planar coordination of gold(III) by two chelating 1,2-benzenedithiolate ligands with Au? S distances between 2.299(3) and 2.312(3) Å (for two crystallographically independent, centrosymmetrical anions in the unit cell).     

Nitrene Insertion into CC and CH Bonds of Diamide Diimine Ligands Ligated to Chromium and Iron

The impact of redox non‐innocence (RNI) on chemical reactivity is a forefront theme in coordination chemistry. A diamide diimine ligand, [{‐CH?N(1,2‐C₆H₄)NH(2,6‐iPr₂C₆H₃)}₂]ⁿ (n=0 to ?4), (dadi)ⁿ, chelates Cr and Fe to give [(dadi)M] ([ 1 Cr(thf)] and [ 1 Fe]). Calculations show [ 1 Cr(thf)] (and [ 1 Cr]) to have a d⁴ Cr configuration antiferromagnetically coupled to (dadi)^2?*, and [ 1 Fe] to be S=2. Treatment with RN₃ provides products where RN is formally inserted into the C? C bond of the diimine or into a C? H bond of the diimine. Calculations on the process support a mechanism in which a transient imide (imidyl) aziridinates the diimine, which subsequently ring opens.     

Syntheses and crystal structures of four lanthanide complexes based on two tri-protonated hexacarboxylic acids of 1,2,3,4,5,6-cyclohexane-hexacarboxylic acid and mellitic acid

Four lanthanide complexes with two tri-protonated hexacarboxylic acids [1,2,3,4,5,6-cyclohexane-hexacarboxylic acid (H₆chhc) and mellitic acid (H₆Mel)], [Pr(H₃chhc)(DMF)₃(H₂O)]·H₂O (1), Nd(H₃chhc)(DMF)₃ (2), [Er(H₂O)₈]·(H₃Mel)·9(H₂O) (3), and [Yb(H₂O)₈]·(H₃Mel)·8.5(H₂O) (4), have been synthesized in solution at room temperature and characterized by elemental analysis, IR spectrum, and single-crystal X-ray diffraction. The crystal structures of 1 and 2 are made up of a (4⁴, 6²) 2-D network extended infinitely parallel to the (1?0?0) plane. The H₃chhc^3? anions assume a cis-e,a,e,a,e,a-conformation with the central ring in chair-shaped configuration. In 3 and 4, the H₃Mel^3? as counter ions are interconnected by hydrogen bonds to form 2-D organic supramolecular layers. The coordination modes and abilities of H₆chhc and mellitic acid are discussed and compared. The luminescences of 1–4 have been investigated.     

Prediction of 195Pt NMR chemical shifts of dissolution products of H2[Pt(OH)6] in nitric acid solutions by DFT methods: how important are the counter‐ion effects?

¹⁹⁵Pt NMR chemical shifts of octahedral Pt(IV) complexes with general formula [Pt(NO₃)_n(OH)_{6 ? n}]^2?, [Pt(NO₃)_n(OH₂)_{6 ? n}]^{4 ? n} (n = 1–6), and [Pt(NO₃)_{6 ? n ? m}(OH)_m(OH₂)_n]^{?2 + n ? m} formed by dissolution of platinic acid, H₂[Pt(OH)₆], in aqueous nitric acid solutions are calculated employing density functional theory methods. Particularly, the gauge‐including atomic orbitals (GIAO)‐PBE0/segmented all‐electron relativistically contracted–zeroth‐order regular approximation (SARC–ZORA)(Pt) ∪ 6–31G(d,p)(E)/Polarizable Continuum Model computational protocol performs the best. Excellent second‐order polynomial plots of δ_calcd(¹⁹⁵Pt) versus δ_exptl(¹⁹⁵Pt) chemical shifts and δ_calcd(¹⁹⁵Pt) versus the natural atomic charge Q_Pt are obtained. Despite of neglecting relativistic and spin orbit effects the good agreement of the calculated δ ¹⁹⁵Pt chemical shifts with experimental values is probably because of the fact that the contribution of relativistic and spin orbit effects to computed σ^{iso 195}Pt magnetic shielding of Pt(IV) coordination compounds is effectively cancelled in the computed δ ¹⁹⁵Pt chemical shifts, because the relativistic corrections are expected to be similar in the complexes and the proper reference standard used. To probe the counter‐ion effects on the ¹⁹⁵Pt NMR chemical shifts of the anionic [Pt(NO₃)_n(OH)_{6 ? n}]^2? and cationic [Pt(NO₃)_n(OH₂)_{6 ? n}]^{4 ? n} (n = 0–3) complexes we calculated the ¹⁹⁵Pt NMR chemical shifts of the neutral (PyH)₂[Pt(NO₃)_n(OH)_{6 ? n}] (n = 1–6; PyH = pyridinium cation, C₅H₅NH⁺) and [Pt(NO₃)_n(H₂O)_{6 ? n}](NO₃)_{4 ? n} (n = 0–3) complexes. Counter‐anion effects are very important for the accurate prediction of the ¹⁹⁵Pt NMR chemical shifts of the cationic [Pt(NO₃)_n(OH₂)_{6 ? n}]^{4 ? n} complexes, while counter‐cation effects are less important for the anionic [Pt(NO₃)_n(OH)_{6 ? n}]^2? complexes. The simple computational protocol is easily implemented even by synthetic chemists in platinum coordination chemistry that dispose limited software availability, or locally existing routines and knowhow. Copyright © 2016 John Wiley & Sons, Ltd.     

Two new CdII and ZnII coordination polymers incorporating 1‐aminobenzene‐3,4,5‐tricarboxylic acid: synthesis,crystal structure and characterization

Aminobenzoic acid derivatives are widely used in the preparation of new coordination polymers since they contain O‐atom donors, as well as N‐atom donors, and have a rich variety of coordination modes which can lead to polymers with intriguing structures and interesting properties. Two new coordination polymers incorporating 1‐aminobenzene‐3,4,5‐tricarboxylic acid (H₃abtc), namely, poly[(μ₃‐1‐amino‐5‐carboxybenzene‐3,4‐dicarboxylato)diaquacadmium(II)], [Cd(C₉H₅NO₆)(H₂O)₂]_n, (I), and poly[[bis(μ₅‐1‐aminobenzene‐3,4,5‐tricarboxylato)triaquatrizinc(II)] dihydrate], {[Zn₃(C₉H₄NO₆)₂(H₂O)₃]·2H₂O}_n, (II), have been prepared and structurally characterized by single‐crystal X‐ray diffraction. In polymer (I), each tridentate 1‐amino‐5‐carboxybenzene‐3,4‐dicarboxylate (Habtc^2?) ligand coordinates to three Cd^II ions to form a two‐dimensional network structure, in which all of the Cd^II ions and Habtc^2? ligands are equivalent, respectively. Polymer (II) also exhibits a two‐dimensional network structure, in which three crystallographically independent Zn^II ions are bridged by two crystallographically independent pentadentate 1‐aminobenzene‐3,4,5‐tricarboxylate (abtc^3?) ligands. This indicates that changing the metal ion can influence the coordination mode of the H₃abtc‐derived ligand and further influence the detailed architecture of the polymer. Moreover, the IR spectra, thermogravimetric analyses and fluorescence properties were investigated.     

Three-dimensional porous metal-radical frameworks based on triphenylmethyl radicals

Lanthanide coordination polymers {[Ln(PTMTC)(EtOH)₂H₂O] ? x H₂O, y EtOH} [Ln=Tb ( 1 ), Gd ( 2 ), and Eu ( 3 )] and {[Ln(αH? PTMTC)(EtOH)₂H₂O] ? x H₂O, y EtOH} [Ln=Tb ( 1′ ), Gd ( 2′ ), and Eu ( 3′ )] have been prepared by reacting Ln^III ions with tricarboxylate‐perchlorotriphenylmethyl/methane ligands that have a radical (PTMTC^3?) or closed‐shell (αH? PTMTC^3?) character, respectively. X‐ray diffraction analyses reveal 3D architectures that combine helical 1D channels and a fairly rare (6,3) connectivity described with the (4².8)?(4⁴.6².8⁵.10⁴) Schäfli symbol. Such 3D architectures make these polymers porous solids upon departure of the non‐coordinated guest‐solvent molecules as confirmed by the XRD structure of the guest‐free [Tb(PTMTC)(EtOH)₂H₂O] and [Tb(αH? PTMTC)(EtOH)₂H₂O] materials. Accessible voids represent 40 % of the cell volume. Metal‐centered luminescence was observed in Tb^III and Eu^III coordination polymers 1′ and 3′ , although the Ln^III‐ion luminescence was quenched when radical ligands were involved. The magnetic properties of all these compounds were investigated, and the nature of the {Ln–radical} (in 1 and 2 ) and the {radical–radical} exchange interactions (in 3 ) were assessed by comparing the behaviors for the radical‐based coordination polymers 1 – 3 with those of the compounds with the diamagnetic ligand set. Whilst antiferromagnetic {radical–radical} interactions were found in 3 , ferromagnetic {Ln–radical} interactions propagated in the 3D architectures of 1 and 2 .     

Lead(II) coordination frameworks with 3-fluorophthalic acid: hydrothermal synthesis,crystal structure,and luminescence

Hydrothermal reactions of Pb(NO₃)₂ and 3-fluorophthalic acid (H₂Fpht) in the absence or presence of 2,2′-bipyridine (bpy) gave two coordination polymers: Pb₅(Fpht)₄(Fba)₂ (1) and [Pb₂(Fpht)₂(bpy)(H₂O)]·3H₂O (2). The 3-fluorobenzoic acid (HFba) results from an in situ decarboxylation of H₂Fpht. Solid 1 displays a 2-D structure, comprising center-related hexanuclear [Pb₃(COO)₆]₂ units. There are three crystallographically different Pb(II) ions and two different ligands, Fpht and Fba. The Fpht ligands adopt μ_6?:?η⁵η³ and μ_6?:?η³η⁴ unusual bridging coordination modes. A 3-D supramolecular architecture is formed via C–H?F hydrogen bonds. Solid 2 possesses a 1-D chain structure, comprising center-related tetranuclear [Pb₂(COO)₄]₂ units. There are two crystallographically different Pb(II) ions. The Fpht ligands adopt μ_3?:?η²η³ and μ_4?:?η³η³ bridging coordination. The free water molecules form (H₂O)₃ clusters to link the 1-D chain by hydrogen bonds. A 3-D supramolecular assembly is constructed via hydrogen bonds between the free water and the F of Fpht ligands. Fluorescence of the complexes originates from π*–π transitions of the ligands.     

An iron(III) 18-metallacrown-6 complex: synthesis,crystal structure,and bioactivity

A macrocyclic hexanuclear iron(III) 18-metallacrown-6 complex, [Fe₆(C₉H₆BrN₂O₃)₆(CH₃OH)₄(H₂O)₂]?·?7CH₃OH?·?4H₂O, has been prepared using a trianionic pentadentate ligand N-acetyl-5-bromosalicylhydrazidate, abshz^3–, and characterized by X-ray diffraction. The crystal structure contains a neutral 18-membered metallacrown ring consisting of six Fe(III) and six abshz^3– ligands. The 18-membered metallacrown ring is formed by combination of six structural moieties, [Fe(III)–N–N]. Due to meridional coordination of ligand to Fe³⁺, the ligand enforces the stereochemistry of the Fe³⁺ ions as a propeller configuration with alternating Δ/Λ forms. Methanol and water are linked with Fe1, Fe1A, Fe,3 and Fe3A. The ratios of methanol to water are 0.76?:?0.24 for Fe1 and Fe1A, and 0.30?:?0.70 for Fe3 and Fe3A, which results in four component crystals of metallacrown rings with ratio of 0.168?:?0.072?:?0.532?:?0.228. Antibacterial screening data showed that the iron metallacrown has moderate antimicrobial activity against Bacillus subtilis.     

Synthesis,crystal structure and cytotoxic activity of tricyclohexyltin complexes of benzenedioxyacetic acids

Two new bis(tricyclohexyltin)benzenedioxyacetates, 1,x‐C₆H₄[OCH₂CO₂Sn(c‐C₆H₁₁)₃]₂ ( 1 : x = 3; 2 : x = 4), have been synthesized and characterized by means of elemental analysis, infrared and NMR (¹H, ¹³C and ¹¹⁹Sn) spectra and single‐crystal X‐ray diffraction. Compound 1 ?H₂O?CH₃OH is a binuclear tin complex containing a four‐coordinated tin and a five‐coordinated tin and linked by an R₃³(16) hydrogen bond into a one‐dimensional supramolecular chain. Compound 2 is a two‐dimensional coordination polymer which is formed as a result of anisobidentate bridging coordination action of the two carboxylate units of the ligand. Interestingly the two‐dimensional coordination polymer contains 34‐membered macrocycles each of which is comprised of four tricyclohexyltin units. Both compounds have potent in vitro cytotoxic activity against three human tumor cell lines: HeLa, MCF‐7 and CoLo 205. Copyright © 2015 John Wiley & Sons, Ltd.     

Synthesis,structures and thermal stabilities of three 1-D coordination polymers based on flexible polycarboxylates

Three new coordination polymers, [Cu(butca)_0.5(bipy)(H₂O)] _n · 2nH₂O (1), [Zn(H₂butca) (phen)(H₂O)] _n · nH₂O (2), and [Cd(H₂chhca)_0.5(phen)(H₂O)] _n · 2nH₂O (3) (H₄butca =1,2,3,4-butanetetracarboxylic acid, H₆chhca = 1,2,3,4,5,6-cyclohexanehexacarboxylic acid), were prepared and characterized by EA, IR, TG, and X-ray crystallography. Complex 1 is a 1-D double-chain coordination polymer in which tetradentate butca^4? coordinates to four Cu(II) ions through four monodentate carboxylates. Complex 2 is a 1-D chain with tridentate H₂butca^2? coordinating to two Zn(II) ions through monodentate and chelating carboxylates. Complex 3 is a 1-D double-chain coordination polymer. H₂chhca^4? is octadentate coordinating to four Cd(II) ions through four chelating carboxylates. Hydrogen bonds and π–π stacking interactions play important roles in the formation of supramolecular architectures. The thermal stabilities of 1–3 show dehydrated coordination polymers are thermally stable in the range 260–400°C.     

A three‐dimensional ZnII coordination network based on 5,5′‐methylenebis(2,4,6‐trimethylisophthalic acid) and 2,7‐bis(1H‐imidazol‐1‐yl)fluorene: synthesis,structure and luminescence properties

In recent years, coordination polymers constructed from multidentate carboxylate ligands and N‐containing ligands have attracted much attention since these ligands can adopt a rich variety of coordination modes which can lead to crystalline products with intriguing structures and interesting properties. A new coordination polymer, namely poly[[diaqua[μ‐2,7‐bis(1H‐imidazol‐1‐yl)fluorene‐κ²N³:N^3′][μ‐5,5′‐methylenebis(3‐carboxy‐2,4,6‐trimethylbenzoato)‐κ²O¹:O^1′]zinc(II)] hemihydrate], {[Zn(C₂₃H₂₂O₈)(C₁₉H₁₄N₄)(H₂O)₂]·0.5H₂O}_n, 1 , was prepared by the self‐assembly of Zn(NO₃)₂·6H₂O with 5,5′‐methylenebis(2,4,6‐trimethylisophthalic acid) (H₄BTMIPA) and 2,7‐bis(1H‐imidazol‐1‐yl)fluorene (BIF) under solvothermal conditions. The structure of 1 was determined by elemental analysis, single‐crystal X‐ray crystallography, powder X‐ray diffraction, IR spectroscopy and thermogravimetric analysis. Each Zn^II ion is six‐coordinated by two O atoms from two H₂BTMIPA^2? ligands, by two N atoms from two BIF ligands and by two water molecules, forming a distorted octahedral ZnN₂O₄ coordination geometry. Adjacent Zn^II ions are linked by H₂BTMIPA^2? ligands and BIF ligands, leading to the formation of a two‐dimensional (2D) (4,4)‐ sql network, and intermolecular hydrogen‐bonding interactions connect the 2D layer structure into the three‐dimensional (3D) supramolecular structure. Each 2D layer contains two kinds of helices with the same direction, which are opposite in adjacent layers. The luminescence properties of complex 1 in the solid state have also been investigated.     

Two complexes based on 1H-1,2,3-triazole-4,5-dicarboxylic acid: hydrothermal synthesis,crystal structures and spectral properties

[Zn₃(tda)₂(bipy)₂(H₂O)_2?·?4H₂O] _n (1) and [Co₂(Htda)₂(H₂O)₆·5H₂O] (2) have been synthesized and characterized structurally by X-ray diffraction, where H₃tda?=?1H-1,2,3-triazole-4, 5-dicarboxylic acid and 2,2′-bipy?=?2,2′-bipyridine. Their solid-state structures have been characterized by elemental analysis and IR spectroscopy. The molecular unit of 1 consists of two crystallographically unique Zn(II) ions assuming different coordination geometries, the tda^3? exhibits a hexadentate binding mode chelating three Zn(II) ions; neighboring Zn–Zn distances through tda^3? bridges are 5.910(6), 5.888(5), and 6.279(3)?Å, respectively. In 2, two neighboring Co(II) ions are bridged by two Htda^2? ligands, forming a binuclear structure, with Co–Co distance of 4.091?Å and is further linked to generate a 3-D structure via hydrogen bonds. Fluorescent of 1 was investigated.     

Gadolinium(III)‐Hydroxy Ladders Trapped in Succinate Frameworks with Optimized Magnetocaloric Effect

Two kinds of inorganic gadolinium(III)‐hydroxy “ladders”, [2×n] and [3×n], were successfully trapped in succinate (suc) coordination polymers, [Gd₂(OH)₂(suc)₂(H₂O)]_n ? 2n H₂O ( 1 ) and [Gd₆(OH)₈(suc)₅(H₂O)₂]_n ? 4n H₂O ( 2 ), respectively. Such coordination polymers could be regarded as alternating inorganic–organic hybrid materials with relatively high density. Magnetic and heat capacity studies reveal a large cryogenic magnetocaloric effect (MCE) in both compounds, namely (ΔH=70 kG) 42.8 J kg^?1 K^?1 for complex 1 and 48.0 J kg^?1 K^?1 for complex 2 . The effect of the high density is evident, which gives very large volumetric MCEs up to 120 and 144 mJ cm^?3 K^?1 for complexes 1 and 2 , respectively.     

1H, 13C, 15N and 195Pt NMR studies of Au(III) and Pt(II) chloride organometallics with 2‐phenylpyridine

¹H, ¹³C, ¹⁵N and ¹⁹⁵Pt NMR studies of gold(III) and platinum(II) chloride organometallics with N(1),C(2′)‐chelated, deprotonated 2‐phenylpyridine (2ppy*) of the formulae [Au(2ppy*)Cl₂], trans(N,N)‐[Pt(2ppy*)(2ppy)Cl] and trans(S,N)‐[Pt(2ppy*)(DMSO‐d₆)Cl] (formed in situ upon dissolving [Pt(2ppy*)(µ‐Cl)]₂ in DMSO‐d₆) were performed. All signals were unambiguously assigned by HMBC/HSQC methods and the respective ¹H, ¹³C and ¹⁵N coordination shifts (i.e. differences between chemical shifts of the same atom in the complex and ligand molecules: Δ^1H_coord = δ^1H_complex ? δ^1H_ligand, Δ^13C_coord = δ^13C_complex ? δ^13C_ligand, Δ^15N_coord = δ^15N_complex ? δ^15N_ligand), as well as ¹⁹⁵Pt chemical shifts and ¹H‐¹⁹⁵Pt coupling constants discussed in relation to the known molecular structures. Characteristic deshielding of nitrogen‐adjacent H(6) protons and metallated C(2′) atoms as well as significant shielding of coordinated N(1) nitrogens is discussed in respect to a large set of literature NMR data available for related cyclometallated compounds. Copyright © 2009 John Wiley & Sons, Ltd.     

The synthesis,NMR (1H, 13C, 119Sn) and IR spectral studies of some di‐ and tri‐organotin(IV) sulfonates: X‐ray crystal structure of [(n‐C4H9)2Sn(OSO2C6H4CH3‐4)2·2H2O]

A number of alkyltin(IV) paratoluenesulfonates, R_nSn(OSO₂C₆H₄CH₃‐4)_4?n (n = 2, 3; R = C₂H₅, n‐C₃H₇, n‐C₄H₉), have been prepared and IR spectra and solution NMR (¹H, ¹³C, ¹¹⁹Sn) are reported for these compounds, including (n‐C₄H₉)₂Sn(OSO₂X)₂ (X = CH₃ and CF₃), the NMR spectra of which have not been reported previously. From the chemical shift δ(¹¹⁹Sn) and the coupling constants ¹J(¹³C, ¹¹⁹Sn) and ²J(¹H, ¹¹⁹Sn), the coordination of the tin atom and the geometry of its coordination sphere in solutions of these compounds is suggested. IR spectra of the compounds are very similar to that observed for the paratoluenesulfonate anion in its sodium salt. The studies indicate that diorganotin(IV) paratoluenesulfonates, and the previously reported compounds (n‐C₄H₉)₂Sn(OSO₂X)₂ (X = CH₃ and CF₃), contain bridging SO₃X groups that yield polymeric structures with hexacoordination around tin and contain non‐linear C? Sn? C bonds. In triorganotin(IV) sulfonates, pentacoordination for tin with a planar SnC₃ skeleton and bidentate bridging paratoluenesulfonate anionic groups are suggested by IR and NMR spectral studies. The X‐ray structure shows [(n‐C₄H₉)₂Sn(OSO₂C₆H₄CH₃‐4)₂·2H₂O] to be monomeric containing six‐coordinate tin and crystallizes from methanol–chloroform in monoclinic space group C2/c. The Sn? O (paratoluenesulfonate) bond distance (2.26(2) Å) is indicative of a relatively high degree of ionic character in the metal–anion bonds. Copyright © 2003 John Wiley & Sons, Ltd.     

Revealing the structural chemistry of the group 12 halide coordination compounds with 2,2′-bipyridine and 1,10-phenanthroline

The coordination compounds of group 12 halides with 2,2′-bipyridine (bpy) and 1,10-phenanthroline (phen), 2[CdF₂(bpy)₂]·7H₂O (1), [ZnI(bpy)₂]⁺·I₃^? (2), [CdI₂(bpy)₂] (3), [Cd(SiF₆)H₂O(phen)₂]·[Cd(H₂O)₂(phen)₂]²⁺·F^–·0.5(SiF₆)^2–·9H₂O (4), [Hg(phen)₃]²⁺·(SiF₆)^2–·5H₂O (5), [ZnBr₂(phen)₂] (6), 6[Zn(phen)₃]²⁺·12Br^–·26H₂O (7) and [ZnI(phen)₂]⁺·I^– (8), have been synthesized and characterized by X-ray crystallography, IR spectroscopy, elemental and thermal analysis. Structural investigations revealed that metal?:?ligand stoichiometry in the inner coordination sphere is 1?:?2 or 1?:?3. A diversity of intra- and intermolecular interactions exists in structures of 1–8, including the rare halogen?halogen and halogen?π interactions. The thermal and spectroscopic properties were correlated with the molecular structures of 1–8. Structural review of all currently known coordination compounds of group 12 halides with bpy and phen is presented.     

Self-assembly of 1-D, 2-D,and 3-D transition-metal coordination polymers based on a T-shaped tripodal ligand 4-(4,5-dicarboxy-1H-imidazol-2-yl)pyridine 1-oxide

Three coordination polymers, {[Co(C₁₀H₅N₃O₅)(H₂O)₂]·H₂O}_n (1), {[Mn₃(C₁₀H₅N₃O₅)₂Cl₂(H₂O)₆]·2H₂O}_n (2), and {[Cu₃(C₁₀H₄N₃O₅)₂(H₂O)₃]·4H₂O}_n (3), based on a T-shaped tripodal ligand 4-(4,5-dicarboxy-1H-imidazol-2-yl)pyridine 1-oxide (H₃DCImPyO), were synthesized under hydrothermal conditions. The polymers showed diverse coordination modes, being characterized by elemental analysis, infrared spectroscopy, and single-crystal X-ray structure analysis. In 1, the HDCImPyO^2? generated a 1-D chain by adopting a μ₂-kN, O : kN′, O′ coordination mode to bridge two Co(II) ions in two bis-N,O-chelating modes. In 2, the HDCImPyO^2? adopted a μ₃-kN, O : kO′, O′′ : O′′′ coordination mode to bridge two crystallographically independent Mn(II) ions, forming a 2-D hcb network with {6³} topology. In 3, by adopting μ₄-kN, O : kO′, O′′ : kN′′, O′′′ : O′′′′ coordination, DCImPyO^3? bridged three crystallographically independent Cu(II) ions to form a 3-D framework having the stb topology.     

Dihydrogen Catalysis of the Reversible Formation and Cleavage of CH and NH Bonds of Aminopyridinate Ligands Bound to (η5‐C5Me5)IrIII

This study focuses on a series of cationic complexes of iridium that contain aminopyridinate (Ap) ligands bound to an (η⁵‐C₅Me₅)Ir^III fragment. The new complexes have the chemical composition [Ir(Ap)(η⁵‐C₅Me₅)]⁺, exist in the form of two isomers ( 1⁺ and 2⁺ ) and were isolated as salts of the BAr_F^? anion (BAr_F=B[3,5‐(CF₃)₂C₆H₃]₄). Four Ap ligands that differ in the nature of their bulky aryl substituents at the amido nitrogen atom and pyridinic ring were employed. In the presence of H₂, the electrophilicity of the Ir^III centre of these complexes allows for a reversible prototropic rearrangement that changes the nature and coordination mode of the aminopyridinate ligand between the well‐known κ²‐N,N′‐bidentate binding in 1⁺ and the unprecedented κ‐N,η³‐pseudo‐allyl‐coordination mode in isomers 2⁺ through activation of a benzylic C?H bond and formal proton transfer to the amido nitrogen atom. Experimental and computational studies evidence that the overall rearrangement, which entails reversible formation and cleavage of H?H, C?H and N?H bonds, is catalysed by dihydrogen under homogeneous conditions.     

Synthesis and characterization of a two-dimensional calcium complex with (1,3,4-thiadiazole-2,5-diyldithio)diacetic acid

A two-dimensional coordination polymer {[Ca₂(tzda)₂(H₂O)₄]?·?3H₂O} _n , where H₂tzda is a flexible carboxylate ligand (1,3,4-thiadiazole-2,5-diyldithio)diacetic acid, was synthesized and characterized by X-ray crystallography, IR, TGA and photoluminescence. The results show that there are two crystallographically independent Ca atoms in the structure, which are both seven-coordinate, but with different coordination environments. Two kinds of tzda^2? ligands with identical coordination mode exist in {[Ca₂(tzda)₂(H₂O)₄]?·?3H₂O} _n . The η ²-bridging O3 and O8 atoms link the Ca1 atoms into a 1-D chain, which are further connected by the tzda^2? ligands forming a 2-D network. A series of hydrogen bonds link the 2-D network to form a 3-D architecture. The solid state luminescence behavior of {[Ca₂(tzda)₂(H₂O)₄]?·?3H₂O} _n exhibits one intense emission band at 375?nm upon excitation at 315?nm which can be attributed to the intraligand emission.     

Synthesis and characterization of di‐n‐butyltin(IV) complexes with 4′/2′‐nitrobiphenyl‐2‐carboxylic acids: X‐ray crystal structures of [{(n‐C4H9)2Sn(OCOC12H8NO2−4′)}2O]2 and (n‐C4H9)2Sn{OCOC12H8NO2−4′}2

Reactions of di‐n‐butyltin(IV) oxide with 4′/2′‐nitrobiphenyl‐2‐carboxylic acids in 1 : 1 and 1 : 2 stoichiometry yield complexes [{(n‐C₄H₉)₂Sn(OCOC₁₂H₈NO₂?4′/2′)}₂O]₂ ( 1 and 2 ) and (n‐C₄H₉)₂Sn(OCOC₁₂H₈NO₂?4′/2′)₂ ( 3 and 4 ) respectively. These compounds were characterized by elemental analysis, IR and NMR (¹H, ¹³C and ¹¹⁹Sn) spectroscopy. The IR spectra of these compounds indicate the presence of anisobidentate carboxylate groups and non‐linear C? Sn? C bonds. From the chemical shifts δ (¹¹⁹Sn) and the coupling constants ¹J(¹³C, ¹¹⁹Sn), the coordination number of the tin atom and the geometry of its coordination sphere have been suggested. [{(n‐C₄H₉)₂Sn(OCOC₁₂H₈NO₂?4′)}₂O]₂ ( 1 ) exhibits a dimeric structure containing distannoxane units with two types of tin atom with essentially identical geometry. To a first approximation, the tin atoms appear to be pentacoordinated with distorted trigonal bipyramidal geometry. However, each type of tin atom is further subjected to a sixth weaker interaction and may be described as having a capped trigonal bipyramidal structure. The diffraction study of the complex (n‐C₄H₉)₂Sn(OCOC₁₂H₈NO₂?4′)₂ ( 3 ) shows a six–coordinate tin in a distorted octahedral frame containing bidentate asymmetric chelating carboxylate groups, with the n‐Bu groups trans to each other. The n‐Bu? Sn? n‐Bu angle is 152.8° and the Sn? O distances are 2.108(4) and 2.493(5) Å. The oxygen atom of the nitro group of the ligand does not participate in bonding to the tin atom in 1 and 3 . Crystals of 1 are triclinic with space group P1 and of that of 3 have orthorhombic space group Pnna. Copyright © 2003 John Wiley & Sons, Ltd.