Synthesis and spectral studies on Ni(II) complexes involving N-furfuryl-N-substituted benzyldithiocarbamates and PPh3: Anagostic and C–H…π(chelate) interactions in (N-furfuryl-N-(4-fluorobenzyl)dithiocarbamato-S,S′)(thiocyanato-N)(triphenylphosphine)nickel(II)

Twelve new nickel(II) complexes of functionalized dithiocarabamates [Ni(S₂CNRR')₂](1-6) and [Ni(S₂CNRR')(NCS)(PPh₃)](7-12) [where R=furfuryl; R'=2-hydroxy benzyl (1,7), 3-hydroxy benzyl (2,8), 4-hydroxy benzyl (3,9), 4-methoxy benzyl (4,10), 4-fluoro benzyl (5,11), 4-chloro benzyl (6,12)] have been prepared and characterized by elemental analysis, IR, UV-Vis and NMR (¹H and ¹³C) spectroscopy. IR spectra of the complexes support the bidentate coordination of dithiocarbamate ligands. Electronic spectral studies on complexes 1-12 indicate square planar geometry around the nickel(II) central atom. In the ¹³C NMR spectra, the upfield shift of NCS₂ carbon signal for heteroleptic complex (7-12) compared to homoleptic complexes (1-6) is due to the effect of PPh₃ on the mesomeric drift of electron density toward nickel through thioureide C-N bond. Single crystal X-ray structural analysis of complex 11 confirms that the coordination geometry about the Ni(II) is distorted square planar. A rare intramolecular anagostic interaction C–H^…Ni [Ni???H=2.804 Å] is observed. The packing of complex 11 is stabilized by non-conventional C–H^…S, C–H?F and C–H?π(chelate, NiS₂C) bonding interactions.     

Structural variations of nickel complexes in NiS4 and NiS2PN coordination environments: spectral and single-crystal X-ray structural studies on bis(4-methylpiperidinecarbodithioato-S,S′)nickel(II) and (4-methylpiperidinecarbodithioato-S,S′)(thiocyanato-N)(triphenylphosphine)nickel(II)

Abstract  

[Ni(4-mpipdtc)₂] and [Ni(4-mpipdtc)(PPh₃)(NCS)] (4-mpipdtc = 4-methylpiperidinecarbodithioate anion) have been characterized by electronic, IR, and NMR spectroscopy, single crystal X-ray analysis, and cyclic voltammetry. IR spectra of the complexes show the contribution of the thioureide form to the structures. ¹H NMR spectra show the deshielding of α-CH₂ protons on complexation. ¹³C NMR spectra shows interesting differences between the N¹³CS₂ carbon signals of the parent complex [Ni(4-mpipdtc)₂] and the mixed ligand complex [Ni(4-mpipdtc)(PPh₃)(NCS)]. The N¹³CS₂ carbon signal for [Ni(4-mpipdtc)(PPh₃)(NCS)] is observed at 204.85 ppm with an upfield shift of about 3.8 ppm compared with that found in [Ni(4-mpipdtc)₂] (201.06 ppm). The observed shielding in [Ni(4-mpipdtc)(PPh₃)(NCS)] indicates the effect of PPh₃ on the mesomeric drift of electron density toward nickel through the thioureide C–N bond. Single crystal X-ray analysis of [Ni(4-mpipdtc)₂] and [Ni(4-mpipdtc)(PPh₃)(NCS)] confirms the presence of four-coordinated nickel in a distorted square-planar arrangement with the NiS₄ and NiS₂PN chromophores, respectively. The C–N (thioureide) bond lengths of [Ni(4-mpipdtc)(PPh₃)(NCS)] are shorter than those found in [Ni(4-mpipdtc)₂], because of the presence of the π-acid (triphenylphosphine) in [Ni(4-mpipdtc)(PPh₃)(NCS)]. Significant asymmetry in Ni–S bond distances was observed in Ni(4-mpipdtc)(PPh₃)(NCS)] (2.162(2) and 2.211(2) ?). This observation clearly supports the less effective trans effect of SCN^– over PPh₃. The piperidine ring in the dithiocarbamate fragment is in the normal chair conformation.     

Hydrogen-bonded and π-stacked nickel(II) thiosemicarbazone complexes: Synthesis,spectral and structural studies

Transition Metal Chemistry - Mixed ligand Ni(II) complexes were synthesized from triphenylphosphine and S-methyl- or S-ethyl-isothiosemicarbazone ligands derived from...     

Synthesis and crystal structure of a dinuclear zinc(II)-dithiocarbamate complex,bis {[(μ 2-pyrrolidinedithiocarbamato-S,S′)(pyrrolidinedithiocarbamato-S,S′)zinc(II)]}

A new zinc(II) complex of pyrrolidinedithiocarbamate (PDTC), bis[(μ ²-pyrrolidinedithiocarbamato-S,S′)(pyrrolidinedithiocarbamato-S,S′)zinc(II)], [Zn₂(PDTC)₄] (1) has been prepared by reaction of ZnCl₂ with ammonium pyrrolidinedithiocarbamate in 1 : 1 and 1 : 2 ratio, respectively. The complex has been characterized by IR, NMR and X-ray crystallography. Compound 1 crystallizes in the triclinic space group P 1 in the form of a centrosymmetric dimer. The solid-state structure contains two crystallographically equivalent Zn⁺² centers in a tetrahedrally distorted ion sphere. A mixed-ligand complex, [Zn(PDTC)(MSC)]^? (MSC = mercaptosuccinate) was also prepared but the structure of the resulting complex was found to be the same as 1, suggesting that the thiolate ligand was replaced on addition of PDTC.     

Mercury(II) complexes of pyrrolidinedithiocarbamate,crystal structure of bis{[μ2-(pyrrolidinedithiocarbamato-S,S ′)(pyrrolidinedithiocarbamato-S,S ′)mercury(II)]}

Mercury(II) complexes of pyrrolidinedithiocarbamate (PDTC) having the general formula [Hg(PDTC)X] (X = Cl^?, SCN^?, and CN^?) and [Hg(PDTC)₂] have been prepared and characterized by elemental analysis, IR, and NMR. The crystal structure of [Hg(PDTC)₂] has also been determined by X-ray crystallography, showing that the complex is a centrosymmetric dimer, [Hg₂(PDTC)₄] (bis[µ²-(pyrrolidinedithiocarbamato-S,S′)(pyrrolidinedithiocarbamato-S,S′)mercury(II)]) (1). The solid-state structure of 1 contains two crystallographically equivalent Hg(II) centers in a distorted tetrahedron.     

Synthesis and spectral studies on mixed ligand complexes of Cd(II) dithiocarbamates with nitrogen donors: single crystal X-ray structure of bis (4-methylpiperidinecarbodithioato-S,S′)(1,10-phenanthroline)cadmium(II)

The current article describes the synthesis and characterization of the following adducts: [Cd(2-mpipdtc)₂(1,10-phen)], [Cd(2-mpipdtc)₂(bipy)], [Cd(4-mpipdtc)₂(1,10-phen)], [Cd(4-mpipdtc)₂(bipy)] (where 2-mpipdtc^? = 2-methylpiperidinecarbodithioate anion, 4-mpipdtc^? = 4-methylpiperidinecarbodithioate anion, 1,10-phen = 1,10-phenanthroline and bipy = 2,2′-bipyridine). A single crystal X-ray structural analysis was carried out for [Cd(4-mpipdtc)₂(1,10-phen)]. IR spectra of the complexes show the contribution of the thioureide form to the structures. Reduction in ν_C–N(thioureide) for the mixed ligand complexes is attributed to the change in coordination number from four to six and the steric effect exerted by 1,10-phenanthroline or 2,2′-bipyridine. Deshielding of the protons adjacent to nitrogen in the ¹H NMR spectra is attributed to drift of electrons from the nitrogen of NR₂, forcing electron density towards sulfur via the thioureide π-system. Single crystal X-ray structural analysis of [Cd(4-mpipdtc)₂(1,10-phen)] showed that the cadmium is in a distorted octahedral environment with a CdS₄N₂ chromophore. The presence of 1,10-phenanthroline in the coordination sphere of Cd(dtc)₂ increases the Cd–S distances and decreases the S–Cd–S angles. VBS analysis supports the determined structure.     

Synthesis,crystal structure and equilibrium studies on the novel bidentate amine adducts of bis[S-benzyl-β-N(p-nitrophenyl)methyldithiocarbazide]nickel(II)

The novel adducts [Ni(SN)2L] formed from chelating bidentate diamines and the square-planar bis[S-benzyl--N(p-nitrophenyl)methyldithiocarbazide]nickel(II) complex [Ni(SN)2] have been prepared and characterized. The bidentate diammines are 1,10-phenanthroline (phen), 2,2-bipyridine (bipy), 5-nitro-1,10-phenanthroline (NO2phen), 4,4-methyl-2,2-bipyridine(Mebipy) and 4,5-diazafluoren-9-one (diafo). The addition equilibrium constants, K, determined by u.v.-vis. spectrophotometry in CH2Cl2, were influenced by the coordinating ability of the added ligands in the order: Kphen >; KNO2phen >; Kdiafo; and KMebipy >; Kbipy >; Kdiafo. The structure of the phenanthroline adduct was determined in order to study the mechanism of the addition processes and the [Ni(SN)2phen] complex has been characterized by X-ray crystal structure analysis. The coordination geometry of the nickel atom is distorted octahedral. The four nitrogen atoms of the two SN ligands and the phenanthroline form an equatorial plane with a Ni-N distance of ca. 2.10 AÅ, and the two sulfur atoms are located at the axial position with an average Ni-S distance of 2.40 AÅ. From the results of the structural determination and the addition equilibrium studies, a possible addition mechanism is also discussed.     

Synthesis, structural characterisation and thermal decomposition studies of some 2,4′-bipyridyl complexes with cobalt(II), nickel(II) and copper(II)

2,4-Bipyridyl (2,4-bipy orL) complexes with cobalt(II), nickel(II) and copper(II) of the formulae M(2,4-bipy)₂(CH₃COO)₂·2H₂O (M(II) = Co, Ni, Cu), Co(2,4-bipy)₂SO₄·3H₂O or Ni(2,4-bipy)₂SO₄·4H₂O have been prepared and their IR and electronic (VIS) spectra are discussed. The thermal behaviour of the obtained compounds has also been studied. The intermediate products of decomposition at different temperatures have been characterized by chemical analysis and X-ray diffraction.We thank dr. A. Malinowska for performing VIS spectra. This work was supported by the KBN project No. PB 0636/P3/93/04.     

Functionalized zinc(II) dithiocarbamate complexes: Synthesis,spectral and molecular structures of bis(N-cyclopropyl-N-4-methoxybenzyldithiocarbamato-S,S′)zinc(II) and (2,2′-bipyridine)bis(N-cyclopropyl-N-4-methoxybenzyldithiocarbamato-S,S′)zinc(II)

Two new zinc and dithiocarbamate integrated metal complexes such as bis(N-cyclopropyl-N-4-methoxybenzyldithiocarbamato-S,S′)zinc(II) (1) and (2,2′-bipyridine)bis(N-cyclopropyl-N-4-methoxybenzyldithiocarbamato-S,S′)zinc(II) (2) have been synthesized and their spectral investigations viz., FT-IR, ¹H and ¹³C NMR as well as single crystal X-ray diffraction studies have been accomplished. Single crystal X-ray analysis of the complex 1 reveals the presence of distorted trigonal bipyramidal and tetrahedral coordination geometry around the zinc. The dithiocarbamate motif acts as bidentate chelating and bidentate bridging ligands between the zinc ions furnishing centrosymmetric dimeric molecules. In the complex 2, the zinc is in a distorted octahedral environment with a ZnS₄N₂ chromophore. The supramolecular frameworks in the complexes 1 and 2 have been sustained by CH?S, CH?O and CH?π (ZnCS₂, and chelate) interactions. Computational studies on complexes 1 and 2 have been executed utilizing DFT-B3LYP/ LANL2DZ method. In both the cases, the HOMO-LUMO calculations imply the occurrence of effective charge transfer within the molecule. Further, the MEP analysis of 1 and 2 implies the negative potential sites are sulfur of NCS₂ and oxygen of OCH₃ and the positive potential sites are nitrogen of NCS₂ in both the complexes along with 2,2′-bipyridine for complex 2. The former sites are susceptible for electrophilic reactions while the latter for nucleophilic reactions.     

Synthesis, characterization and antimicrobial studies of mixed ligand silver(I) complexes of triphenylphosphine and heterocyclic thiones: Crystal structure of bis[{(μ-diazinane-2-thione)(diazinane-2-thione)(triphenylphosphine)silver(I) nitrate}]

Mixed ligand silver(I) complexes of triphenylphosphine and heterocyclic thiones (imidazolidine-2-thione (Imt), diazinane-2-thione (Diaz) and 2-mercaptopyridine (Mpy)) having the general formulae [(Ph₃P)Ag(thione)₂]NO₃ and [(Ph₃P)₂Ag(thione)]NO₃ were prepared and characterized by elemental analysis, IR and NMR (¹H, ¹³C and ³¹P) spectroscopic methods. The crystal structure of one of the complexes, [Ag(Ph₃P)(Diaz)₂]₂(NO₃)₂ (1) was determined by X-ray crystallography. The title complex (1) is dinuclear, having each silver atom coordinated to three thione sulfur atoms of Diaz and to one phosphorus atom of PPh₃ in a nearly tetrahedral environment, with an average P-Ag-S bond angle of 108.5°. The spectral data of the complexes are consistent with sulfur coordination of the thiones to silver(I). Antimicrobial activities of the complexes were evaluated by minimum inhibitory concentrations and the results showed that the complexes exhibit a wide range of activity against two gram-negative bacteria (E. coli, P. aeruginosa) and molds (A. niger, P. citrinum), while the activities were poor against yeasts (C. albicans, S. cerevisiae).     

EPR on bis(1,2-dithiosquarato)cuprate(II) in the bis(1,2-dithiosquarato)nickelate(II) host lattice — structure and spectroscopy‡

EPR spectroscopy is a well suited analytical tool to monitor the electronic situation around paramagnetic metal centres as copper(II) and therefore the structural influences on the paramagnetic ion. 1,2-Dithiosquaratometalates are available by direct synthesis from metal salts with dipotassium-1,2-dithiosquarate and the appropriate counter cations. Synthesis and characterisation of bis(benzyltributylammonium)1,2-dithiosquaratonickelate(II), (BzlBu₃N)₂[Ni(dtsq)₂], and bis(benzyltributylammonium)1,2-dithiosquaratocuprate(II), (BzlBu₃N)₂[Cu(dtsq)₂], with benzyltributylammonium as the counter ion is reported and the X-ray structures of two complexes, (BzlBu₃N)₂[Ni(dtsq)₂] and (BzlBu₃N)₂[Cu(dtsq)₂], are presented. Both complexes, crystallising in the monoclinic space group P2₁/c, are isostructural with only small differences in the coordination sphere due to the different metal ions. The diamagnetic nickel complex is therefore well suited as a host lattice for the paramagnetic Cu(II) complex to measure EPR for additional structural information.     

Synthesis,spectral, magnetic,electrochemical and catalytic studies of cyclam-based copper(II) and nickel(II) complexes–effect of N-substitution

New N-substituted cyclam ligands 1,8-[bis(3-formyl-2-hydroxy-5-methyl)benzyl]-1,4,8,11-tetraazacyclotetradecane, 1,8-[bis(3-formyl-2-hydroxy-5-methyl)benzyl]-4,11-dimethyl-1,4,8,11-tetraazacyclotetradecane, 1,8-[bis(3-formyl-2-hydroxy-5-bromo)benzyl]-1,4,8,11-tetraazacyclotetradecane, and 1,8-[bis(3-formyl-2-hydroxy-5-bromo)benzyl]-4,11-dimethyl-1,4,8,11-tetraazacyclotetradecane (L¹–L⁴) were synthesized and mononuclear copper(II) and nickel(II) complexes prepared. The ligands and complexes were characterized by elemental analysis, electronic, IR, ¹H NMR and ¹³C NMR spectral studies. N-alkylation causes red shifts in the λ_max values of the complexes. Copper(II) complexes show one-electron, quasi-reversible reduction waves in the range ?1.04 to ?1.00 V. The nickel(II) complexes show one-electron, quasi-reversible reduction waves in the range ?1.18 to ?1.30 V and one-electron, quasi-reversible oxidation waves in the range +1.20 to +1.40 V. The reduction potential of the copper(II) and nickel(II) complexes of the ligands L¹ to L² and L³ to L⁴ shift anodically on N-alkylation. The ESR spectra of the mononuclear copper(II) complexes show four lines, characteristic of square-planar geometry with nuclear hyperfine spin 3/2. All copper(II) complexes show a normal room temperature magnetic moment value μ_eff?=?1.70–1.74 BM which is close to the spin only value of 1.73 BM. Kinetic studies on the oxidation of pyrocatechol to o-quinone using the copper(II) complexes as catalysts and on the hydrolysis of 4-nitrophenylphosphate using the copper(II) and nickel(II) complexes as catalyst were carried out. The tetra-N-substituted complexes have higher rate constants than the corresponding disubstituted complexes.     

Substituent and solvent effects on electronic structure and spectral property of ReCl(CO)3(N∧N) (N∧N = glyoxime): DFT and TDDFT theoretical studies

The ground- and excited-state structures of five Re(I) halide glyoxime complexes ReCl(CO)(3)(N(∧)N) (N(∧)N = glyoxime (DHG 1), dimethylglyoxime (DMG 2), cyclohexane dione glyoxime (CHDG 3), dibromoglyoxime (DBG 4), and dimethylformylgloxime (DMFG 5)) have been studied with density functional theory (DFT) and configuration interaction with single excitations (CIS) methods. Time-dependent density functional theory/polarized continuum model (TDDFT/PCM) was carried out to predict the absorption and emission spectra in different media. The effect of substituent and solvent has been researched. It is found that electron-donating groups increase the lowest unoccupied molecular orbital (LUMO) energy resulting in the increased highest occupied molecular orbital (HOMO)-LUMO energy gap. The change leads to their absorption spectra blue shifts in the order 1 > 2 > 3, which arises from the HOMO-1 → LUMO. Just the opposite, electron-withdrawing groups lead to the spectra red shifts (5 > 4 > 1) because of the decreased HOMO-LUMO energy gap. The reorganization energy (λ) calculations show that the relatively balanceable charges transfer abilities of 2 will result in the higher efficiency of organic light emitting devices (OLEDs). In addition, both the absorption and the emission spectra display red shifts in different extents with the decrease of solvent polarity.     

Humidity-sensing and DNA-binding ability of bis(4-benzylpiperazine-1-carbodithioato-k2 S,S′)nickel(II)

Bis(4-benzylpiperazine-1-carbodithioato-k² S,S?)nickel(II), 1, was prepared by metathesis of sodium salt of 4-benzylpiperazine-1-carbodithioate with nickel(II) chloride in 2?:?1 ratio. Complex 1 was characterized by analytical techniques including elemental analysis, FT-IR, UV–visible spectroscopy, and X-ray single-crystal analysis. The latter technique confirmed square-planar geometry around Ni with the formation of NiS₄ core with two shorter and two longer Ni–S bonds. The packing diagram revealed a supramolecular chain structure mediated by unconventional H?H dihydrogen bonds that resulted in a chair and a ladder-like structure when viewed along the a-axis and c-axis, respectively. The thin-film coating resulted in a microporous film with a band gap of 1.69 eV. Complex 1-based sensor was fabricated to check the humidity-sensing properties of the material. Resistance of the device decreased by two orders of magnitude and capacitance was enhanced with the increase of relative humidity. The DNA binding study proved 1 to be a good DNA binder with binding constant value of 1.4 × 10⁴ M^?1.     

Thiobis(β-diketonato)-bridged binuclear ruthenium(III) complexes containing triphenylphosphine or triphenylarsine. Synthetic,spectral, catalytic and antimicrobial studies

Hexacoordinated binuclear ruthenium(III) complexes of the type {[RuX₂(EPh₃)₂]₂(bis--dk)} [X = Cl or Br; bis--dk = thiobis(-diketone)] have been prepared by reacting [RuCl₃(PPh₃)₃], [RuCl₃(AsPh₃)₃], [RuBr₃(AsPh₃)₃] or [RuBr₃(PPh₃)₂(MeOH)] with thiobis(-diketones) in a 2:1 molar ratio in benzene, and characterized by analytical, spectroscopic (i.r., electronic e.p.r.) and cyclic voltammetric data. An octahedral structure has been proposed. The complexes are effective catalysts for the oxidation of PhCH₂OH and cyclohexanol to PhCHO and cyclohexanone respectively using N-methylmorpholine-N-oxide as co-oxidant. Some of the complexes have been subjected to antifungal activity studies.     

Synthesis, reactivity and structural studies of (η-methylcyclopentadienyl)(η-tetraphenylcyclobutadiene)cobalt and its derivatives

(η⁵-methylcyclopentadienyl)(η⁴-tetraphenylcyclobutadiene)cobalt (1) and its derivatives, [(1-acetyl-2-methyl)η⁵-cyclopentadienyl](η⁴-tetraphenylcyclobutadiene)cobalt (2) [(1-acetyl-3-methyl)η⁵-cyclopentadienyl](η⁴-tetraphenylcyclobutadiene)cobalt (3) [(1-carbomethoxy-2-methyl)η⁵-cyclopentadienyl](η⁴-tetraphenylcyclobutadiene)cobalt (4) and [(1-carbomethoxy-3-methyl)η⁵-cyclopentadienyl](η⁴-tetraphenylcyclobutadiene) cobalt (5) have been prepared in yields varying from 11% to 28% by introducing the substituents on the cyclopentadienyl ring of methylcyclopentadienyl sodium and then reacting with diphenylacetylene and CoCl(PPh₃)₃. The carboxylic acids [(1-carboxy-2-methyl)η⁵-cyclopentadienyl](η⁴-tetraphenylcyclobutadiene)cobalt (6), [(1-carboxy-3-methyl)η⁵-cyclopentadienyl](η⁴-tetraphenylcyclobutadiene)cobalt (7) have been prepared after ester hydrolysis of compounds 4 and 5 using KOH/ethanol. [(1-dimethylaminomethyl-3-methyl)η⁵-cyclopentadienyl](η⁴-tetraphenylcyclobutadiene) cobalt (8), was prepared selectively by direct substitution on the cyclopentadienyl ring of (η⁵-methylcyclopentadienyl)(η⁴-tetraphenylcyclobutadiene)cobalt in 65% yield. The 1,2-isomer was formed only in traces in this reaction. Reactivity of (η⁵-methylcyclopentadienyl)(η⁴-tetraphenylcyclobutadiene)cobalt and its carbomethoxy derivative have been compared with (η⁵-cyclopentadienyl)(η⁴-tetraphenylcyclobutadiene)cobalt. All new compounds were characterized by ¹H and ¹³C NMR, FT-IR, mass spectra and CHN analysis. Compounds 2, 4, 6 and 8 have also been structurally characterized by single crystal X-ray structural analysis.     

Chloro(η-dihydropentalenyl)bis(triphenylphosphine)ruthenium(II): synthesis, structural characterization and catalytic activity in the dimerization of phenylacetylene

Reactions between HRuCl(PPh₃)₃ and 1,3- or 1,5-cyclooctadiene yield the 1,2-dihydropentalenyl complex (η⁵-C₈H₉)Ru(PPh₃)₂Cl through a series of steps including olefin insertion and electrocyclization. The reaction is accompanied by the loss of two equivalents of hydrogen. The product crystallizes in the monoclinic space group (No. 2). (η⁵-C₈H₉)Ru(PPh₃)₂Cl catalyzes the dimerization of phenylacetylene to a ≈2:1 mixture of Z:E 1,4-diphenyl-1-buten-3-yne. Comparison of the catalytic activity of (η⁵-C₈H₉)Ru(PPh₃)₂Cl with (η⁵-C₅H₅)Ru(PPh₃)₂Cl, (η⁵-C₅Me₅)Ru(PPh₃)H₃ and {η⁵-HB(pz)₃}Ru(PPh₃)₂Cl suggests that the more electron-rich η⁵ ligands favor formation of the Z isomer.     

Synthesis,structural, and spectral studies of diorganotin(IV) complexes with 2–hydroxy-5-methylbenzaldehyde-N(4)-cyclohexylthiosemicarbazone

Three new diorganotin(IV) complexes, [Me₂Sn(L)] (2), [Bu₂Sn(L)] (3), and [Ph₂Sn(L)] (4) [where H₂L (1) = 2-hydroxy-5-methylbenzaldehyde-N(4)-cyclohexylthiosemicarbazone] have been synthesized by reacting the corresponding diorganotin(IV) dichloride with H₂L (1) in absolute methanol in the presence of potassium hydroxide. All the compounds have been characterized by CHN analyses, UV–vis, FT-IR, ¹H, ¹³C, and ¹¹⁹Sn NMR spectroscopy. The molecular structures of H₂L (1) and 2 have been confirmed by single crystal X-ray diffraction analysis. H₂L (1) is found to be in the thiol tautomeric form. The X-ray structure of 2 showed that H₂L is a tridentate ligand and binds to the tin(IV) atom via the phenolic oxygen, azomethine nitrogen, and thiolate sulfur. Complex 2 has a triclinic structure and the coordination geometry of tin(IV) is distorted trigonal bipyramidal. The sulfur and oxygen are in axial positions while the azomethine nitrogen of 1 and two methyl groups occupy the equatorial positions. The C-Sn-C angles determined from ¹J(¹¹⁹Sn, ¹³C) for 2, 3, and 4 are 124.35°, 123.11°, and 123.82°, respectively. The values of δ(¹¹⁹Sn) for 2, 3, and 4 are ?153.4, ?180.59, and ?158.3 ppm, respectively, indicating five-coordinate tin(IV). From NMR data a distorted trigonal-bipyramidal configuration at each tin is proposed.     

Synthesis,spectroscopy, magnetism and X-ray structure of μ-(bipyrimidine)-bis[aqua(bipyrimidine)(saccharinato)copper(II)] bis(saccharinate) tetrahydrate

The compound [Cu₂(bipym)₃(sac)₂(H₂O)₂](sac)₂(H₂O)₄ (bipym = 2,2-bipyrimidine and sac = saccharin) crystallizes in the space group P-1, with a = 10.710(3), b = 10.725(3), c = 13.637(5) Å, a = 70.07(3), = 80.31(2), g = 82.87(3)° and Z = 2. The geometry in the centrosymmetric dinuclear complex around each Cu^II ion is a distorted octahedron, in which the equatorial plane is formed by a nitrogen atom of a bis-didentate bridging bipym ligand, two nitrogen atoms of a didentate bipym ligand, and the nitrogen atom of a coordinating sac ligand. The axial positions in the octahedron are occupied by a second nitrogen of the bis-didentate bridging bipym ligand and a water molecule. The lattice contains two saccharinate anions and four water molecules held together in a hydrogen-bonded network. The i.r vibrations of the bipym ligand are found as a quasi-symmetric doublet at 1558 and 1580 cm^–1, while the most important i.r vibrations of the sac ligand are observed at 1629 and 1644 cm^–1 (carbonyl vibrations) and at 1285 and 1159 cm^–1 (sulfonyl vibrations). The magnetic exchange interactions between the Cu ions is very weak and is ferromagnetic (J < 0.1 cm^–1).