Crystallochemical causes of the different thermal properties of [Cu(py)2(NCS)2] and [Cu(4-Mepy)2(NCS)2] complexes

The crystal structures and thermal behaviour of [Cu(py)₂(NCS)₂] (at 293) and [Cu(4-Mepy)₂(NCS)₂] and 180 K) complexes have been compared with their different temperature behaviour. It was found that the thermal stability of coordinated thiocyanate ligands in the course of thermal decomposition depends not only on the properties of the ligand L, but it is related to the arrangement of the thiocyanatocopper chains in the crystal structures.     

The liquid-crystalline properties of bis[N-[[4-[4-(alkoxy)benzoyloxy]2-hydroxyphenyl]methylene]alkanamino] complexes of Cu(II), Pd(II) and Ni(II). A general view

The thermotropic liquid-crystalline phase behaviour of a homologous set of bis[N-[[4-[4-(alkoxy)benzoyloxy]2-hydroxyphenyl]methylene]alkanamino] copper(II) complexes is examined. New data are reported and taken into account in addition to those previously reported in this Journal. The influence of alkoxy and alkanamine groups on the nature and stability of the mesophase is underlined. As a general trend, with some notable exception, smectic (C type) mesomorphism is favoured by longer alkoxy and alkanamine chains. Data concerning some Pd(II) and Ni(II) homologous complexes are also reported. The mesophase stability (nematic phase) is higher for palladium and nickel complexes than for the copper containing homologues.     

Antimicrobial efficiency of diorganotin(IV) bis-[3-(4-chlorophenyl)-2-methylacrylate]

Abstract

Four new diorganotin(IV) carboxylates, [n-Bu₂SnL₂] (1), [Et₂SnL₂] (2), [Me₂SnL₂] (3) and [n-Oct₂SnL₂] (4), where L?=?3-(4-chlorophenyl)-2-methylacrylate, were synthesized and characterized by elemental analysis, FT-IR, multinuclear NMR (¹H, ¹³C, and ¹¹⁹Sn) and X-ray single crystal analysis for 1. A chelating bidentate ligand and six-coordinate tin centers were confirmed in the solid state by IR for all complexes and for 1 by X-ray single crystal analysis. The NMR study has shown a decrease in the coordination number of tin in solution. The complexes were screened for their in vitro antibacterial and antifungal activities. A compromised lipo/hydrophilicity and a diffusion controlled antimicrobial activity was shown by the complexes in the order 1?>?2>3?>?4. Molecular docking studies have shown hydrogen bonding and hydrophobic interactions for 1 with the target proteins of the antimicrobial strains.     

Synthesis,and Solution and Solid-State Structures of (η3-Allyl){(4S)-4-benzyl-2-[2′-(diphenylphosphino)phenyl]- 4,5-dihydrooxazole-P,N}palladium(II) Hexafluorophosphates. Comparison with Dichloro{(4S)-2-[2′-(diphenylphosphino)phenyl]-4,5-dihydro-4-phenyloxazole-P,N}zinc(II)

Crystal and solution structures of the [Pd^II(η³-allyl)] and of the [Pd^II(η³-1,3-diphenylallyl)] complexes, 4 and 5 , respectively, with (4S)-4-benzyl-2-[2′-(diphenylphosphino)phenyl]-4,5-dihydrooxazole ( 3 ) were determined by X-ray crystallography and 2D-NMR spectroscopy. Complex 4 proved to be disordered with both diastereoisomeric complexes in the crystal. The results of X-ray and NMR experiments demonstrate a good agreement between solution and solid-state equilibria of the two isomers. A comparison with dichloro{(4S)-2-[2′-(diphenylphosphino)phenyl]-4,5-dihydro-4-phenyloxazole-P,N}zinc(II) ( 2b ) shows a surprising conformational stability of the coordinated phosphinooxazole ligand 3 .     

COPPER(II) COMPLEXES OF 1-[O-ALLYLPHENOXY]-3-[ISOPROPYLAMINO]-2-PROPANOL (ALPRENOLOL)

Abstract

Complexation of Cu(II) with the antihypertension drug Alprenolol (HAlp) under different conditions (metal/ligand ratios and solvents) results in the formation of two complexes - a binuclear green one, Cu₂Alp₂Cl₂ (1), and a mononuclear violet species CuAlp₂·2H₂O (2). Single crystals of (1) were isolated and its structure determined by X-ray diffraction. In the complex Alprenolol molecules are bidentately coordinated and each Cu atom is bound with NH, and bridged by the deprotonated OH group of the ligand to the second Cu centre. The chloride ions are coordinated to copper as terminal ligands. The mononuclear complex (2) was characterized using electronic and IR spectra, EPR, magnetochemical, calorimetric, thermogravimetric methods and elemental analysis. Copper is coordinated through O^? and N of OH and NH groups of the ligands in a distorted tetrahedral structure. The structure includes also two solvent molecules per CuAlp₂ unit.     

Calix[4]arene rhenium(V) complexes as potential radiopharmaceuticals

The calix[4]arene platform was used for the syntheses of novel rhenium(V) complexes, that may have potential applications as radiopharmaceuticals. The reaction of ReO(PPh3)2Cl3 with tetradentate N2O2-calix[4]arene ligand 8 in ethanol gave the novel mixed-ligand rhenium complex 9 with the structure ReO(N2O2-calix)OEt. The configuration was elucidated by using a number of 1H NMR techniques. In 9, the ethoxy ligand could be easily and quantitatively exchanged for another monodentate ligand to give complex 12. Tetradentate N2S2-calix[4]arene ligand 15 formed the rhenium complex 16 either via reaction with ReO(PPh3)2Cl3 in an organic solvent or by reaction with rhenium gluconate in an aqueous solution. Complex 16 showed good stability in phosphate-buffered saline solution (37 degrees C, 5 d). The crystal structures of a mono- and a bimetallic complex were determined. The bimetallic N2O2-calixarene complex dimer 11 crystallized in the monoclinic space group C2/c, with a = 38.963(5) A, b = 23.140(6) A, c = 27.382(6) A, beta = 128.456(10) degrees, V = 19,333(7) A3, Z = 8, and final R = 0.0519. The monometallic N2S2 model complex 17 crystallized in the monoclinic space group Cc, with a = 15.715(2) A, b = 12.045(2) A, c = 20.022(3) A, beta = 94.863(12) degrees, V = 3776.3(10) A3, Z = 4, and final R = 0.0342.     

Reactions of [Ru(CO)3Cl2]2 with aromatic nitrogen donor ligands in alcoholic media

The reactions of mono‐ and bidentate aromatic nitrogen‐containing ligands with [Ru(CO)₃Cl₂]₂ in alcohols have been studied. In alcoholic media the nitrogen ligands act as bases promoting acidic behaviour of alcohols and the formation of alkoxy carbonyls [Ru(N–N)(CO)₂Cl(COOR)] and [Ru(N)₂(CO)₂Cl(COOR)]. Other products are monomers of type [Ru(N)(CO)₃Cl₂], bridged complexes such as [Ru(CO)₃Cl₂]₂(N), and ion pairs of the type [Ru(CO)₃Cl₃]^? [Ru(N–N)(CO)₃Cl]⁺ (N–N = chelating aromatic nitrogen ligand, N = non‐chelating or bridging ligand). The reaction and the product distribution can be controlled by adjusting the reaction stoichiometry. The reactivity of the new ruthenium complexes was tested in 1‐hexene hydroformylation. The activity can be associated with the degree of stability of the complexes and the ruthenium–ligand interaction. Chelating or bridging nitrogen ligands suppresses the activity strongly compared with the bare ruthenium carbonyl chloride, while the decrease in activity is less pronounced with monodentate ligands. A plausible catalytic cycle is proposed and discussed in terms of ligand–ruthenium interactions. The reactivity of the ligands as well as the catalytic cycle was studied in detail using the computational DFT methods. Copyright © 2005 John Wiley & Sons, Ltd.     

Crystal Structure of 2-[2-hydroxy-3-methoxyphenyl]-3-[2-hydroxy-3-methoxybenzylamino]-1,2-dihydroquinazolin-4(3H)-one and the Synthesis, Spectral and Thermal Investigation of its Transition Metal Complexes

A new 1,2-dihydroquinazolin-4(3H)-one ligand, 2-[2-hydroxy-3-methoxyphenyl]-3-[2-hydroxy-3-methoxybenzylamino]-1,2-dihydroquinazolin-4(3H)-one (Hmpbaq), formed by the condensation of 2-aminobenzoylhydrazide with 2-hydroxy-3-methoxybenzaldehyde and its copper(II), nickel(II), cobalt(II), manganese(II), zinc(II) and cadmium(II) complexes, have been synthesized. Their structures have been elucidated on the basis of elemental analyses, conductance measurements, magnetic moments, spectral (i.r., ¹H-n.m.r., u.v.–vis., e.p.r. and FAB-mass) and thermal studies. The formation of 1,2-dihydroquinazolin-4(3H)-one rather than hydrazone in the reaction of 2-aminobenzoylhydrazide with 2-hydroxy-3-methoxybenzaldehyde is confirmed by the ¹H-n.m.r. spectra and single crystal X-ray diffraction studies. The tridentate behavior of the ligand was proposed on the basis of spectral studies. X-band e.p.r. spectra of the copper(II) and manganese(II) complexes in the polycrystalline state at room temperature and liquid nitrogen temperature were recorded and their salient features are reported. Thermal stabilities of the manganese(II) and zinc(II) complexes have been studied.     

Synthesis and characterisation of nickel(II) complexes with tripodal ligand tris[4-(3-(5-methylpyrazolyl)-3-aza-3-butenyl] amine (MPz3tren): X-ray crystal structure of [Ni(MPz3tren)](BF4)2·0.5H2O

Nickel(II) complexes of the tripodal ligand (MPz₃tren) of the general formula [Ni(MPz₃tren)]X₂·nH₂O (X=Cl, Br, NO₃, ClO₄ and BF₄; n=0 for Cl and Br; n=0.5 for NO₃, ClO₄ and BF₄) have been prepared by template methodology and characterised by elemental analyses, magnetic susceptibility and conductivity measurements at RT, IR and electronic spectra. The molar conductivities measured in MeOH for all the complexes show them to be 1:2 electrolytes. The hexadentate character of the ligand in all the complexes is inferred from IR spectral studies. The electronic spectra in solid state and in MeOH solution suggest octahedral geometry for all the complexes. The structure of [Ni(MPz₃tren)](BF₄)₂·0.5H₂O has been determined by single-crystal X-ray diffraction studies (monoclinic, c2/c). Nickel(II) is in a trigonal antiprismatic N₆ donor environment and the crystal structure is stabilised by a network of strong H-bonding.     

Synthesis and Magnetic Properties of a Copper Cube: [Cu4(OH)4(C16H18N2)4]4+ (ClO4)4 C3H6O [C16H18N2=(E)-1,6-[Di(pyridin-4-yl)hex-3-ene]

The synthesis of a Cu₄(OH)₄ cube which is coordinated by four molecules of the dipyridyl ligand 1,6-[di(pyridin-4-yl)hex-3-ene] is reported. This compound has a trans double bond which restricts the conformational freedom of the ligand and favours coordination within a unique copper cube. The structure was solved by an X-Ray single crystal structure determination and low temperature magnetic susceptibility measurements examined its magnetic properties. The cube classification corresponds to the type I classification of Mergehenn and Haase and the short/long distribution of Cu ⋅⋅⋅ Cu separations in the cube as defined by Ruiz. The magnetic susceptibility measurements show paramagnetic behaviour down to 50 K but below this the copper cube shows weak ferromagnetic exchange interactions. The low temperature magnetic susceptibility characteristics are examined in detail then modelled and compared to other similar Cu₄O₄ copper cubes.     

Complexing ability of the versatile,redox-active, 3-[3-(diphenylphosphino)propylthio]-3',4,4'-trimethyl-tetrathiafulvalene ligand

The synthesis of a ligand containing as an electroactive core a tetrathiafulvalene moiety, 3-[3-(diphenylphosphino)propylthio]-3',4,4'-trimethyl-tetrathiafulvalene, is reported. Its versatile ability to act as a bidentate or a monodentate ligand, as demonstrated by the metal carbonyl complexes obtained, is described. The novel cis-Mo(CO)(4)(P-TTF)(2) 4 and cis-W(CO)(4)(P,S-TTF) 6 complexes have been characterized by X-ray diffraction analyses and cyclic voltammetry measurements. Within complex 4, no significant influence of the two electroactive ligands on the molybdenum center was detected, whereas, in complex 6, a weak influence of the TTF redox-active core can be observed on the redox behavior of the metal center.     

M−C Bond Homolysis in Coinage‐Metal [M(CF3)4]− Derivatives

A comparative study of the homoleptic [M(CF₃)₄]^? complexes of all three coinage metals (M=Cu, Ag, Au) reveals that homolytic M?C bond cleavage is favoured in every case upon excitation in the gas phase (CID‐MS²). Homolysis also occurs in solution by photochemical excitation. Transfer of the photogenerated CF₃^. radicals to both aryl and alkyl carbon atoms was also confirmed. The observed behaviour was rationalized by considering the electronic structure of the involved species, which all show ligand‐field inversion. Moreover, the homolytic pathway constitutes experimental evidence for the marked covalent character of the M?C bond. The relative stability of these M?C bonds was evaluated by energy‐resolved mass spectrometry (ERMS) and follows the order Cu<Ag?Au. The qualitatively similar and rather uniform behaviour experimentally observed for all three coinage metals gives no ground to suggest variation in the metal oxidation state along the group.     

MONO-ORGANOMERCURY AND DIORGANOTHALLIUM DERIVATIVES OF THIOHYDANTOIN AND 5-(BENZYLIDENE)-2-THIOHYDANTOIN: THE CRYSTAL STRUCTURE OF DIMETHYL-[5-(BENZYLIDENE)-2-THIOHYDANTOINATO]-THALLIUM(III)

Abstract

The complexes [TlR₂(Td)], [TlR₂(BTd)], [HgR(Td)] and [HgR(BTd)] (R = Me, Ph; HTd = thiohydantoin; HBTd = 5-(benzylidene)-2-thiohydantoin) were prepared by reacting the appropriate ligand with the appropriate diorganothallium hydroxide or mono-organomercury acetate. They have been studied in the solid state (by vibrational spectroscopy and mass spectrometry) and in solution (by using NMR). In addition, the crystal structure of [TlMe₂(BTd)] has been determined by X-ray diffraction. The crystals have a polymeric structure in which each thallium atom is coordinated to the two methyl C atoms, the S and N atoms of one BTd ligand. the S atom of another and the O atom of a third. The coordination modes of the two ligands in the other complexes are discussed on this basis in the light of spectroscopic data.     

Properties of [Fe(Salten)Cl] Being a Precursor for Spin-Crossover Compounds in Polycrystals and Vitrified Acetonitrile Solutions

The complexes of precursor with pentadentate Salten ligand has been shown to have high-spin state (S = 5/2) in a single crystal and polycrystalline phase and contain both high-spin and low-spin (S = 1/2) fractions in vitrified acetonitrile solutions. A correlation between ESR spectrum shape and crystallinity degree has been tracked for polycrystalline phase. The majority of complexes in crystals has been found to form exchange-coupled clusters. The ESR spectra of vitrified solutions have shown several types of high-spin centers and two kinds of low-spin complexes with different g-factors. On the basis of quantum chemical calculations, conclusion was drawn for the most likely structural form of the precursor in single crystal and polycrystalline samples and possible supramolecular associates in frozen solutions.     

Crystal Structure of 2-thiophene-2-yl-3(thiophene-2-carboxylideneamino)-1, 2-dihydroquinazolin-4(3H)-one and the Synthesis, Spectral and Thermal Studies of its Transition Metal(II) Complexes

The synthesis of manganese(II), cobalt(II), nickel(II), copper(II), zinc(II) and cadmium(II) complexes of a new ligand 2-thiophene-2-yl-3(thiophene-2-carboxylidene-amino)-1,2-dihydroquinazolin-4(3H)-one (TTCADQ) is described. The ligand and metal complexes were characterized by elemental analysis, conductivity measurements, spectral (u.v.–vis., i.r., 1D n.m.r., 2D hetcor and e.p.r.) and thermal studies. The formation of 1,2-dihydroquinazolin-4(3H)-one rather than hydrazone, in the reaction of aromatic aldehyde and o-aminobenzoylhydrazide is proved by single crystal X-ray diffraction and 2D hetcor n.m.r. studies. On the basis of elemental analysis, u.v.–vis.spectroscopy and magnetic moment studies, six coordinate geometry for all the complexes was proposed. The i.r. spectral studies reveal the bidentate behaviour of the ligand.     

Bis[1,1'-N,N'-(2-picolyl)aminomethyl]ferrocene as a redox sensor for transition metal ions

The compound bis[1,1'-N,N'-(2-picolyl)aminomethyl]ferrocene, L(1), was synthesized. The protonation constants of this ligand and the stability constants of its complexes with Ni(2+), Cu(2+), Zn(2+), Cd(2+) and Pb(2+) were determined in aqueous solution by potentiometric methods at 25 degrees C and at ionic strength 0.10 mol dm(-3) in KNO(3). The compound L(1) forms only 1:1 (M:L) complexes with Pb(2+) and Cd(2+) while with Ni(2+) and Cu(2+) species of 2 [ratio] 1 ratio were also found. The complexing behaviour of L(1) is regulated by the constraint imposed by the ferrocene in its backbone, leading to lower values of stability constants for complexes of the divalent first row transition metals when compared with related ligands. However, the differences in stability are smaller for the larger metal ions. The structure of the copper complex with L(1) was determined by single-crystal X-ray diffraction and shows that a species of 2:2 ratio is formed. The two copper centres display distorted octahedral geometries and are linked through the two L(1) bridges at a long distance of 8.781(10) Angstrom. The electrochemical behaviour of L(1) was studied in the presence of Ni(2+), Cu(2+), Zn(2+), Cd(2+) and Pb(2+), showing that upon complexation the ferrocene-ferrocenium half-wave potential shifts anodically in relation to that of the free ligand. The maximum electrochemical shift ([capital Delta]E(1/2)) of 268 mV was found in the presence of Pb(2+), followed by Cu(2+)(218 mV), Ni(2+)(152 mV), Zn(2+)(111 mV) and Cd(2+)(110 mV). Moreover, L(1) is able to electrochemically and selectively sense Cu(2+) in the presence of a large excess of the other transition metal cations studied.     

Zum Komplexbildungsverhalten der 5,6-Dihydroxy-7-oxa-bicyclo[2.2.1]heptan-2,3-dicarbonsäure gegenüber 3 d-Übergangsmetallen

Complex Formation of 5,6-Dihydroxy-7-oxa-bicyclo[2.2.1]heptane-2,3-dicarboxylic Acid with 3 d-Transition Elements Binary carboxylate complexes of bivalent 3 d-transition metal ions with 5-exo,6-cis-dihydroxy-7-oxabicyclo[2.2.1]heptane-2-exo,3-cis-dicarboxylic acid ( 2 ) have been synthesized in aqueous solution and characterized by elementary analysis, infrared and electronic spectra and magnetic susceptibility measurements. The coordination compounds have been found to undergo thermal decomposition with loss of water molecules, followed by the organic ligand to give metal oxides. The stability constants of the complexes have been determined by potentiometric measurements. It could be shown by X-ray analysis, that the dicarboxylate anion of 2 has different coordination behaviour in complexes [NiL²(H₂O)₃] · H₂O ( 2 c ) and [CuL²(H₂O)₂] · 2 H₂O ( 2 d ), respectively. In 2 c it acts as a tridentate chelating ligand forming together with three water molecules an only slightly distorted octahedral coordination sphere and its hydroxyl groups are coordinatively inactive. In 2 d , however, the oxygen atom of one hydroxyl group is included in coordination and by its interaction with a Cu atom of a neighboring molecule a polymeric chain structure is built up in the crystal. Two corners of the tetragonally extended coordination octahedron are occupied by water molecules. In both complexes the molecular packing is stabilized by a network of hydrogen bonds in which also the crystal water molecules are included.     

Synthesis, luminescence and ion-binding properties of palladium(II) complexes with 1,2-bis[di(benzo-15-crown-5)phosphino]ethane (dbcpe)

A series of palladium(II) complexes with 1,2-bis[di(benzo-15-crown-5)phosphino]ethane ligand (dbcpe), [Pd(dbcpe)X2] (X = Cl 1, Br 2 and I 3), have been successfully synthesised and characterised. The X-ray crystal structure of dbcpe has also been determined. The cation-binding properties of the complexes have been studied and the stability constants with alkali metal cations determined. The crown-free analogue of dbcpe, 1,2-bis[bis(3,4-dimethoxyphenyl)phosphino]ethane (ddmppe), and the related complexes have also been prepared and comparison studies have been made.     

Coinage metal complexes of tris(pyrazolyl)methanide [C(3,5-Me2pz)3]-: kappa3-coordination vs. backbone functionalisation

Tris(pyrazolyl)methanides, [C(3,5-R2pz)3]-, contain an unassociated tetrahedral carbanionic centre in the bridgehead position. In addition to nitrogen donor centres for transition metal coordination, an accessible reactive site for further manipulations is available in the backbone of the ligand. The coordination variability of the ambidental C-/N ligand [C(3,5-Me2pz)3]- was elucidated by investigating its coinage metal complexes. Two principle coordination modes were found for complexes of general formula [LMPR3] (with M = Cu(I), Ag(I), Au(I); L =[C(3,5-Me2pz)3]-; R = Ph, OMe). While for Cu(I) (2,3) and Ag(I) (4) complexes the anionic ligand acts as a face-capping, six electron N3-donor, gold(I) (5) is coordinated by the bridging carbanion yielding a two coordinate Au(I) complex comprising a covalent Au-C bond. The complexes featuring the kappa3-coordinated N3-donor ligand were investigated by 31P CP (MAS) NMR in the solid state.     

Syntheses of aluminum and zinc alkyl complexes of a highly fluorinated tris(pyrazolyl)borate using [HB(3,5-(CF3)2Pz)3]Ag(THF) as the ligand transfer agent

Dimethylaluminum or ethylzinc complexes of highly fluorinated tris(pyrazolyl)borate ligand [HB(3,5-(CF(3))(2)Pz)(3)](-) can be obtained in excellent yield from the reaction between the silver adduct [HB(3,5-(CF(3))(2)Pz)(3)]Ag(THF) and the metal alkyl reagent Me(3)Al or Et(2)Zn. The X-ray crystal structure of [HB(3,5-(CF(3))(2)Pz)(3)]AlMe(2) shows that the tris(pyrazolyl)borate ligand coordinates to the aluminum center in kappa(2)-fashion. [HB(3,5-(CF(3))(2)Pz)(3)]ZnEt features the typical kappa(3)-bonded ligand.