Mer Configuration Research Articles

Anionic Fischer-type carbene complexes as bidentate (N,O) ligands.

New polynuclear complexes, (L1)3M2 [M2 = Cr(III) (4a,4b), Fe(III) (5), Co(III) (8)], (L1)2M2(L2)2 [M2 = Co(II) (7), Ni(II) (9)], (L1)2M2(O)L2 [M2 = V(IV) (6)] and L1M2Cp2 [M2 = Ti(III) (10)] with L1 = (CO)5M1=C[C=NC(CH3)=CHS](O-)(M1 = Cr or W) and L2 = 4-methylthiazole or THF, are described. The molecular structures of these complexes determined by X-ray diffraction show that the Fischer-type carbene complexes act as bidentate ligands towards the second metal centre, coordinating through C(carbene)-attached O-atoms and imine N-atoms of the thiazolyl groups to form five-membered chelates with the oxygen atoms in the mer configuration. Isostructural complexes have similar characteristic band patterns in their far-IR spectra. Cyclic voltammetry of selected complexes reveals the oxidation of the carbene complex ligand between 1.01 and 1.29 V. Oxidation of the central metal (M2) takes place at 0.56 and 0.86 V for 7 and 9, respectively. Three stepwise reductions of Cr(III) to Cr(0) occur for 4a and 4b in the region -0.51 to -1.58 V. These new ligand types and other variants thereof should find application in ligand design with the first metal -- and other ligands attached thereto -- in the carbene complex ligand, playing an important role.

A New Class of S-Bridged CoIIIMCoIII (M = NiII, PdII) Trinuclear Complexes with Mixed Aliphatic and Aromatic Thiolate Ligands: Synthesis, Characterization, and Stereochemistry

Abstract Treatments of a mixture of CoCl2·6H2O, HL (Hpyt = 2-pyridinethiol, Hpymt = 2-pyrimidinethiol), and triethylamine with [Ni(aet)2] (aet = 2-aminoethanethiolate) in methanol led to the isolation of novel S-bridged CoIIINiIICoIII trinuclear complexes, [Ni{Co(aet)2(pyt)}2]2+ ([1]2+) and [Ni{Co(aet)2(pymt)}2]2+ ([2]2+), in which a NiII ion is coordinated by four aet S atoms from two tris(thiolato)-type [Co(aet)2(pyt or pymt)] units. The NiII ion in both [1]2+ and [2]2+ was replaced by a PdII ion through the reaction with Na2[PdCl4] in water, giving the corresponding CoIIIPdIICoIII trinuclear complexes, [Pd{Co(aet)2(pyt)}2]2+ ([3]2+) and [Pd{Co(aet)2(pymt)}2]2+ ([4]2+). The related CoIIIPdIICoIII trinuclear complexes composed of one [Co(aet)2(pyt or pymt)] and one [Co(aet)2(en)]+ units, [Pd{Co(aet)2(pyt)}{Co(aet)2(en)}]3+ ([5]3+) and [Pd{Co(aet)2(pymt)}{Co(aet)2(en)}]3+ ([6]3+), were also prepared by the reactions of a 1:1 mixture of [Ni{Co(aet)2(pyt or pymt)}2]2+ and [Ni{Co(aet)2(en)}2]4+ with Na2[PdCl4] in water, followed by the column chromatographic separation. The electronic absorption, CD, and NMR spectroscopies indicated that these CoIIIMCoIII trinuclear complexes produce only the racemic (ΔΔ⁄ΛΛ) isomer, in which each [Co(aet)2(pyt or pymt)] unit adopts a mer(S) configuration with two aet N atoms at the apical positions. For [1]2+, [2]2+, [3]2+, and [4]2+, another geometrical isomerism of syn–anti, which arises from the arrangement of the two terminal pyt or pymt S atoms, was identified.

Synthesis and characterisation of new homoleptic rhenium thiosemicarbazone complexes

A series of new rhenium(III) complexes, [ReL2]+, where LH = a 2-formylpyridine thiosemicarbazone have been synthesised and characterised. The complexes have been synthesised from the Re(V) starting material [ReOCl3(PPh3)2] and from [ReO4]− in the presence of triphenylphosphine. All of the new compounds have been characterised by X-ray crystallography, NMR and mass spectroscopy. In all cases the Re atom is in a distorted octahedral environment with two tridentate deprotonated thiosemicarbazones binding as monoanionic ligands through the sulfur, pyridyl nitrogen and azamethinic nitrogen in a mer (azomethine nitrogen atoms trans) configuration. Electrochemical measurements show that the complexes undergo two reversible reductions at biologically accessible potentials. Under certain conditions the 2-formylpyridine thiosemicarbazone ligands undergo reductive cleavage of the hydrazinic N–N bond resulting in the formation of a rhenium complex of methyl(2-pyridyl)methyleneimine which has been characterised by X-ray crystallography.

Preparation and structural characterization of six new diorganotin(IV) complexes of the R 2Sn(SaleanH 2) and R 2Sn(SalceanH 2) type (R=Me, nBu, Ph)

Six new diorganotin(IV) complexes have been prepared from R 2SnO (R=Me, n Bu, Ph) and the Salan ligands SaleanH 4 (SaleanH 4= N, N′-bis( o-hydroxybenzyl)-1,2-diaminoethane) and SalceanH 4 (SalceanH 4= N, N′-bis( o-hydroxybenzyl)-1,2-diaminocyclohexane) in order to determine the preferred coordination mode of these ligands in dependence of their flexibility and basicity as well as the steric bulk of the organic groups attached to the tin(IV) atom. The present NMR spectroscopic and X-ray crystallographic study shows that the SaleanH 2 and SalceanH 2 ligands prefer a fac– fac configuration when coordinated to a diorganotin(IV) fragment, in which the nitrogen atoms are located trans to the organic groups. Depending on the steric bulk of the organic substituents, the conformation of the coordinated ligand can vary with respect to the orientation of the benzyloxy phenyl rings. In the solution state there may exist a rapid equilibrium between these possible conformations. For related R 2Sn(Salen) complexes so far only structures with trans configurations have been reported, however, for SalanH 2 complexes with other metal ions both examples with fac– fac and fac– mer configurations are known. In the solid state structure of one of the complexes studied in here an interesting CH⋯π intermolecular contact between a chloroform molecule and an aromatic ring has been detected.

Stereochemical Analysis of Cobalt(III) Complexes with Tridentate Imino- and Amino-Oxime Ligands

The stereochemistry of a new class of models of the vitamin B12 system, containing tridentate pyridyl-imino-oxime [C6H5N(CH2)nNC(CH3)C(CH3)NO−; n = 1, L1; n = 2, L2] and pyridyl-amino-oxime [C6H5N(CH2)nNHCH(CH3)C(CH3)NO−; n = 1, L3; n = 2, L4] ligands, has been investigated through molecular mechanics calculations based on a specific force field. It is shown that, among all the possible diastereomers of the imino complexes [Co(L1,2)2]+, the minimum strain energy is exhibited in a mer configuration. For the amino complexes [Co(L3,4)(HL3,4)]2+, the minimum is exhibited in a fac configuration, with the amino nitrogen atoms all having the same chirality, opposite to that of the adjacent carbon atoms. Furthermore, comparison of the effect of five- (L1, L3) or six-membered (L2, L4) chelate rings on the complexes indicates that the strain energy decreases upon passing from L1 to L2 complexes, while it increases upon passing from L3 to L4 complexes. The effect of rotation around the axial pyridyl Co−N bond on the coordination geometry has also been studied through a conformational analysis of the methyl (R = Me) and adamantyl (R = Adam) organocobalt derivatives [RCo(L4)(HL4)]+. The most important result is that the rotation is rather hindered in the case of the bulky Adam group, while in the Me case the pyridyl group can rotate across a wide angular range. In both cases, the rotation causes a significant change in the Co−N bond length, while the Co−C distance is almost unaffected. It is also shown that the aromatic base is oriented with respect to the equatorial ligand in a fashion quite different from other B12 models. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

Synthesis and Characterization of Nitrato-Triamine-Metal(II) Complexes. Conglomerate Crystallization Part 55. Crystal Structure of [Ni(dien)(O2NO)(ONO2)] (I), {[Cu(dien)-(μ-ONO2)]NO3}∞ (II), [Zn(dien)(O2NO)(ONO2)] (III), [Ni(Medpt)(O2NO)(ONO2)] (IV) and [Cu(Medpt)(ONO2)2] (V)

In absolute ethanol and in the presence of triethylorthoformate, reactions of metal(II) nitrates with linear tridentate amines afforded metal complexes of the formula M(NNN)(NO3)2, where M = Ni2+, Cu2+ and Zn2+, and NNN = dien and Medpt. The compounds fall into three categories in accordance with their stereochemistry and mode of binding of the nitrato ligands. Compounds I, [Ni(dien)(O2NO)(ONO2)] and III, [Zn(dien)(O2NO)(ONO2)] are isomorphous and isostructural. They crystallize in the monoclinic space group P21/n with nearly identical cell constants. The stereochemistry of these two compounds is such that the terdentate dien ligand forms a fac MN3 moiety with the two oxygens of the bidentate nitrato ligand trans to the terminal NH2. These ligands form the base of the octahedral arrangement in which the sixth position, trans to the secondary nitrogen of the dien, is an oxygen of the monodentate nitrato ligand. Compound IV, [Ni(Medpt)(O2NO)(ONO2)] falls into the same category as I and III despite the fact that the two rings in the Ni-Medpt moiety are six-membered rings, unlike those in compounds I and III which are five-membered rings. Nevertheless, the nickel-amine arrangement is fac. The bidentate nitrato-oxygens are trans to the terminal NH2 of the amine ligand, and the oxygen of the monodentate nitrato ligand is trans to the tertiary amine-nitrogen. Such stereochemistry is prevalent for nickel and zinc compounds. Interestingly, compound IV crystallizes as a conglomerate (space group P212121). Compound II, {[Cu(dien)(μ-ONO2)]NO3}∞ belongs to the second category and has a polymeric structure. The repeating fragment in the polymeric chain is a Cu(dien)-O fragment with the monodentate nitrato ligand occupying an equatorial position of the base. A second oxygen of the equatorial nitrate becomes an axial ligand for an adjacent Cu-N3O fragment. In this way the substance propagates into an infinite chain. The repeating unit has an effective square pyramidal, five-coordinate, configuration. Finally, the compound crystallizes as a racemate. The second nitrate necessary for charge compensation of this copper(II) compound is ionic and its function is to hold the infinite chains of the lattice. The third category represented by compound V, [Cu(Medpt)(ONO2)2] contains two molecules in the asymmetric unit of the racemic lattice (monoclinic, space group P21/a). The structure of Cu-Medpt is unlike that of IV in that both species present in the asymmetric unit have the amine ligand in a mer configuration which together with a monodentate oxygen of a nitrato ligand form a base plane of a square pyramid. The fifth ligand of both Cu2+ ions is a second monodentate nitrato ligand. The stereochemical differences between the two Cu2+ ions are insignificant for the Cu-Medpt fragment, which share the same conformation and configuration. The major difference between the two species is the torsional angles defined by the Cu-O-N-O angles. The difference arises from variation in the hydrogens of the primary amine moieties selected by nitrato-oxygens to form intramolecular hydrogen bonds. Finally, there is a little variation in the equatorial Cu-ONO2 stereochemistry because of steric hindrance, imposed by the Medpt, preventing large torsional angles by these nitrato ligands. This is evident by comparing the two copper species shown in Finally, nitrate-to-Br ligand exchange was found to take place when KBr pellets are prepared for IR spectral measurements.

Synthesis and spectroscopic characterisation of cobalt(III) complexes with S-benzyl-β- N-(5-methylpyrazole-3-yl)methylenedithiocarbazate (H 2L): X-ray structures of [Co(HL) 2]NO 3·EtOH ( 1) and [Co(HL)(L)]·H 2O ( 2)

Two new cobalt(III) complexes with S-benzyl-β- N-(5-methylpyrazole-3-yl)methylenedithiocarbazate (H 2L), [Co(HL) 2]NO 3·EtOH ( 1) and [Co(HL)(L)]·H 2O ( 2), have been synthesised and characterised using single-crystal X-ray diffraction and spectroscopic (electronic, IR and NMR) techniques. The structure of 1 consists of [Co(HL) 2] + cation and NO 3 − anion linked by an ethanol solvent molecule, that of 2 consists of neutral monomeric species [Co(HL)(L)] with one mole water of crystallisation where the two ligand molecules are uniquely non-equivalent. In both the complexes the coordination geometry about cobalt is distorted octahedral and the two ligands are in the mer configuration (S and tertiary N atom cis to each other and the iminic N atoms trans).

Conversion of azomethine moiety to carboxamido group at cobalt(III) center in model complexes of Co-containing nitrile hydratase.

The Co(III) complex of the Schiff base ligand N-2-mercaptophenyl-2'-pyridylmethyl-enimine (PyASH), namely, [Co(PyAS)(2)]Cl (1), has been synthesized via an improved method and its structure has been determined by X-ray crystallography. The two deprotonated ligands are arranged in mer configuration around the Co(III) center and the overall coordination geometry is octahedral. The coordinated azomethine function in 1 is rapidly converted into carboxamido group upon reaction with OH(-). The product is the bis carboxamido complex (Et(4)N)[Co(PyPepS)(2)] (2), reported by us previously. Reaction of H(2)O(2) with 1 in DMF affords [Co(PyASO(2))(PyPepSO(2))] (3), a species with mixed imine and carboxamido-N donor centers as well as S-bound sulfinates. Further reaction with H(2)O(2) in the presence of NaClO(4) converts 3 into the previously reported bis carboxamido/sulfinato complex Na[Co(PyPepSO(2))(2)] (4). The reaction conditions for the various transformation reactions for complexes 1-4 and the structure of 3 are also reported. The mechanism of the -CH=NR + [O] --> -C(=O)NHR transformation has been discussed. The reactions reported here provide convenient alternate routes for the syntheses of Co(III) complexes with coordinated carboxamide, thiolate, and/or sulfinate donors as models for the Co-site in the Co-containing nitrile hydratase(s).

Transition metal complexes with thiosemicarbazide-based ligands. Part XLI. Two crystal structures of cobalt(III) complexes with salicylaldehyde S-methylisothiosemicarbazone and theoretical study on orientations of coordinated pyridines

Two compounds, [Co III(L)(py) 3][Co II(py)Cl 3]·EtOH and [Co III(L)(py) 3]I 3 (H 2L=salicylaldehyde S-methylisothiosemicarbazone, py=pyridine), were synthesized and the crystal structures determined by single-crystal X-ray diffraction. In both structures the geometries of the cation are very similar to a thiosemicarbazide-based ligand coordinated in the mer configuration. The axial pyridines are in mutual perpendicular orientation, the angles between the planes being 85.3(2) and 82.5(2)°. The plane of the equatorial pyridine is tilted with respect to the equatorial plane by about 40°. The orientations of the pyridines were studied in model systems by quantum chemistry calculations. It was shown that the interactions between axial and equatorial pyridines are responsible for the orientation of pyridines in the complex cation; consequently, there are very similar geometries of the complex cation in both crystal structures. The compounds were also characterized by elemental analysis, molar conductivity, magnetic susceptibility and electronic absorption spectra.

Products derived from the reaction of [M(CN)4O(H2O)]2− with pentane-2,4-dione. X-ray crystal structure of (Ph4P)2[M(CN)3O(acac)], M = Mo or W

The reaction of pentane-2,4-dione (Hacac) with [M(CN)4O(H2O)]2− ion (M = Mo, W) gave complexes which were isolated as their tetraphenylphosphonium salts (Ph4P)2[M(CN)3O(acac)], and were characterised by X-ray crystal structure determination, by u.v.–vis. and 1H-n.m.r. spectroscopy, cyclic voltammetry, and thermogravimetric and differential thermal analysis. The structure determination showed the complexes to have an approximately octahedral geometry, with the three cyanides in the mer configuration. Results are compared with those of other [M(CN)3O(LL)]n− ions containing bidentate ligands LL.

Bidentate phosphinophenol ligands. Preparation and electrochemistry of the Re(III) complexes of 2-(diphenylphosphinomethyl)-4-methylphenol (P 1OH) and 2-diphenylphosphinophenol (P 2OH). Crystal and molecular structure of mer-Re[P 1O] 3

The reaction of 2-(diphenylphosphinomethyl)-4-methylphenol (P 1OH) and 2-diphenylphosphinophenol (P 2OH) on ReCl 3(MeCN)(PPh 3) 2 in a 3:1 ratio leads to the formation of the homoleptic Re(III) complexes Re(P 1O) 3 ( 1) and Re(P 2O) 3 ( 2) in high yield. 1 is reasonably stable in air in the solid state and in solution, which is not the case for 2. Orange–red crystals of 1 contain distorted octahedral Re entities in which the metal is coordinated to three bidentate phosphinophenolato ligands in the mer configuration. Cyclic voltammetry of 1 and 2 shows two well defined monoelectronic quasi-reversible redox waves, one reductive attributed to the Re(III)/Re(II) couple and one oxidative due to the Re(III)/Re(IV) one. A second oxidative wave, attributed to the Re(IV)/Re(V) couple, is reversible only for 1, indicating the lower stability of 2 toward oxidation. In agreement with this, 2 gives, in air, the Re(V)-oxo species ReO(OP 2O)(P 2O) 2 ( 3) quantitatively, whose structure is confirmed by X-ray diffraction.

Titanium and Zirconium Complexes That Contain the Tridentate Diamido Ligands [(i-PrN-o-C6H4)2O]2-([i-PrNON]2-) and [(C6H11N-o-C6H4)2O]2-([CyNON]2-)

A variety of five- and six-coordinate titanium and zirconium dialkyl complexes that contain the [(i-PrN-o-C6H4)2O]2- ([i-PrNON]2-) ligand have been prepared, among them [i-PrNON]Ti(CH2CHMe2)2, [i-PrNON]Ti(CH2CMe3)2, [i-PrNON]Zr(CH2CH3)2, and [i-PrNON]Zr(CH2CHMe2)2. These species serve as sources of complexes such as {[i-PrNON]Ti(PMe3)2}2(μ-N2), [i-PrNON]Ti(CHCMe3)(PMe3)2, [i-PrNON]Zr(CH2CHMe2)2(PMe3), and [i-PrNON]Zr(H2CCMe2)(PMe3)2. The reaction between [i-PrNON]Ti(CH2CMe3)2 and Me2PCH2CH2PMe2 in the absence of dinitrogen yields (i-PrNC6H4)(i-PrNC6H4O)Ti(dmpe), a pseudooctahedral species in which one aryl−oxygen bond has been cleaved. In all structurally characterized complexes in which the [i-PrNON]2- ligand is intact, it adopts a mer configuration in which the donor oxygen atom is planar. Analogous dialkyl complexes [CyNON]MR2 (Cy = cyclohexyl; M = Zr, R = Me, Et, i-Bu, CH2CMe3, allyl; M = Ti, R = Me, CH2CMe3, i-Bu) have also been prepared. Decomposition of [i-PrNON]Zr(CH2CH3)2 in the absence of phosph...

Pyridine adducts of arylbismuth(III) halides

A range of bismuth trihalide and arylbismuth(III) halide complexes with pyridine ligands has been prepared and structurally characterised. The complex [BiI3(py)3] (py = pyridine) is octahedral with the iodide and pyridine ligands arranged in a mer configuration. A seven-co-ordinate complex [BiCl3(py)4] is also described. The compounds [BiCl2Ph(4-Mepy)2] (4-Mepy = 4-methylpyridine), [BiBr2Ph(4-Mepy)2], [BiBr2Ph(4-Butpy)2] (4-Butpy = 4-tert-butylpyridine) and [BiI2Ph(4-Butpy)2] all have a five-co-ordinate, square-based pyramidal bismuth centre in which the phenyl group occupies the apical position with two trans halides and two trans pyridine ligands residing in the basal plane. In the solid state these moieties are dimerised through a pair of weak asymmetric halide bridging interactions. The complexes [BiBr2Ph(py)2] and [BiI2Ph(4-Mepy)2] have similar monomeric units but in the former case these are weakly associated into polymeric chains rather than dimers whereas, for the latter, dimers are formed through a single bridging iodide. In the structure of the ionic compound [4-ButpyH][BiCl3Ph(4-Butpy)] the [BiCl3Ph(4-Butpy)]– anion is monomeric with a square-based pyramidal structure in which the phenyl group is in an apical site whilst the three chlorides and 4-Butpy ligand occupy the basal positions. An example of a diphenylbismuth halide complex is seen in the structure of [BiIPh2(4-Mepy)], the monomeric unit of which contains a four-co-ordinate bismuth centre with a geometry based on an equatorially vacant trigonal bipyramid in which the two phenyl groups are equatorial and the iodide and 4-methylpyridine ligand are axial. A weak association into polymeric chains occurs through long Bi· · ·I interactions approximately trans to one phenyl group. All compounds are discussed in terms of their structure and bonding and compared with related materials previously characterised.

Base hydrolysis of [Co(triamine)(diamine)Cl] 2+ and epimerization of [Co(triamine)(diamine)OH] 2+: studies on resolved cobalt(III) complexes of 3-aza-hexane-1,6-diamine (2,3-tri)

The kinetics and stereochemistry of base hydrolysis have been investigated for the 12 systems endo- and exo- mer-[Co(triamine)(diamine)Cl] 2+ where the triamine is 2,2, 2,3 or 3,3-tri (2,3-tri = NH 2(CH 2) 2NH(CH 2) 3NH 2) and the diamine is en or tn. Some of these complexes are the `missing mer isomers' in the series of complexes known for some years. The complete series of mer-aqua and azido complexes have been isolated as well; these are all new. The 2,3-tri complexes are chiral on the sec-NH centre and all four have been optically resolved for the first time. These mer-chloro complexes base-hydrolyse with complete retention of the mer configuration, but with some inversion at the sec-NH site. For the dien systems (2,2-tri), the steric course of base hydrolysis has been determined for all four isomers ( fac and mer) for both tn and en systems, and the results substantiate the edge displacement principle. Endo-/ exo-epimerization rates have been measured for the [Co(triamine)(diamine)OH] 2+ ions. For the resolved 2,3-tri complexes, azide competition is observed, and the common racemic exo- and endo-product distribution indicates a common trigonal bipyramidal intermediate with a `flat' deprotonated sec-amine. The endo- and exo- mer-[Co(2,3-tri)(diamine)OH] 2+ complexes are rapidly anated by the azide ion to give the same (kinetic) endo-/ exo- mer-[Co(2,3-tri)(diamine)N 3] 2+ distribution, at pH-independent rates, and it is shown that these complexes react via an internal conjugate base complex where the sec-NH is deprotonated and water is the leaving group. The epimerization rates for [Co(triamine)(diamine)OH] 2+ and base hydrolysis rates for [Co(triamine)(diamine)Cl] 2+ are discussed in terms of topology, N-configuration and ring size. The exo- mer-[Co(3,3-tri)(tn)Cl] 2+ ion is established to be the fastest-reported hydrolysing pentaaminecobalt(III) complex, and it is shown to aquate in acid without exchange at any of the NH sites, nor inversion at the sec-NH, thereby excluding a conjugate base pathway where the base is water (rather than OH −).

Oxidative addition of chlorinated solvents (e.g. CH2Cl2 and CHCl3) with rhodium(I) complexes; crystal structure of mer-[Rh(py)3(CH2Cl)Cl2

Common chlorinated solvents (e.g. CH2Cl2 and CHCl3) readily reacted with [Rh2(C8H14)4(µ-Cl)2] (C8H14 = cyclooctene), in the presence of a monodentate, nitrogen donor ligand (L = py or 4-Butpy), to give the oxidative addition product [RhL3RCl2] (R = CH2Cl, CHCl2 or CH2Ph) which for R = CH2Cl and CH2Ph has been shown by X-ray analysis to adopt the mer configuration. NMR Spectroscopic measurements (13C and 15N) in solution were consistent with this configuration, although these NMR data cannot unambiguously distinguish between the mer and fac isomers.

Synthesis and characterization of the new complex tris[(2-oxazolinyl)phenolato] manganese (III) and its use as a catalyst in oxidation reactions

A new managanese complex, Mn(phox), (Hphox = 2-(2′-hydroxyphenyl)oxazoline, was synthesized and charaacterized. The X-ray structure shows the complex to be in a mer configuration with a significant Jahn-Teller distortion. Preliminary results show that this complex is a promising catalyst for the epoxidation of styrene with H 2O 2.

Synthesis, characterization and crystal structure of trans-aquatrichlorobis (5,7-dimethyl1,2,4triazolo1,5- apyrimidine- N3)ruthenium(III) monohydrate

The synthesis and characterization of trans-aquatrichlorobis(5,7-dimethyl1,2,4triazolo1,5- apyrimidine- N 3)ruthenium(III) monohydrate ( 1) are described. Complex 1 has been analysed spectroscopically and the crystal structure has been obtained by X-ray diffraction analysis, with an R w value of 0.032. Crystals of 1, trans-RuCl 3(H 2O)(dmtp) 2 · H 2O, are monoclinic and belong to the space group C2/ m with a = 14.160(3), b = 17.115(3) and c = 8.550(2) Å, β = 98.51(2)° and Z = 4. The three chloride ions coordinate on the ruthenium(III) ion in a mer configuration, while the two dmtp molecules coordinate in a trans configuration. The coordinated water molecule stabilizes the parallel ‘face-to-face’ trans orientation of the dmtp ligands by hydrogen bonds of both its protons with the two N(3) nitrogens of the pyrimidine rings. Compound 1 is interesting for its structural similarity to the first hydrolysis product of ruthenium(III) complexes that are currently under investigation for applications in antitumour chemotherapy. Substitution reactions in coordinating solvents like acetonitrile and dimethylsulfoxide were followed in time with conductometry, UV—Vis absorption and proton NMR spectroscopy, and show the formation of neutral trichloro complexes which are formed by substitution of the coordinated water molecule in 1 by a solvent molecule.

Synthesis and spectroscopic characterization of copper, nickel and cobalt complexes with N-( N″, N″-disubstituted-aminothiocarbonyl)- N′-substituted benzamidines

A series of copper(II), nickel(II) and cobalt(III) complexes with N-( N″, N″-disubstituted-aminothiocarbonyl)-N′-substitutedbenzamides have been synthesized and characterized. 1H and 13C NMR spectra have shown a mer configuration for the CoL 3 compounds. The NiL 2 complexes have a square-planar structure. Electron spin resonance spectra have shown that the presence of a bulky substituent on the nitrogen donor atom generates a large tetrahedral distortion around the copper in CuL 2 compounds. Cyclic voltammetry has revealed irreversible redox waves corresponding to the Cu(III)Cu(II) and Cu(II)Cu(II) couples.

Fac-Tris(6-methyl-2-mercaptopyridinato)cobalt(III) at 150K

The title compound, tris(6-methylpyridine-2-thiolato-N,S)cobalt(III), [Co(C6H6NS)3], has been isolated and characterized as the fac isomer. However, several closely related Co and Fe complexes which have been characterized previously all adopt the mer configuration.

Nitrosyl ruthenium complexes with general formula [RuCl 3(NO)(PP)] (PP = {PPh 2(CH 2) nPPh 2}, n = 1–3 and {PPh 2-CHPPh 2}). X-ray structure of [RuCl 3(NO){PPh 2(CH 2) 3PPh 2}

Ruthenium(II) complexes with general formula [RuCl 3(NO)(PP)] were obtained in the solid state, where PP = PPh 2(CH 2) n PPh 2 ( n = 1) and PPh 2-Ch = CH-PPh 2. The 31P NMR spectra of these compounds measured in CH 2Cl 2 showed only singlets, consistent with a fac configuration containing two equivalent phosphorus atoms. However the X-ray diffraction data show that the [RuCl 3(NO){PPh 2(CH 2) 3PPh 2}] complex crystallizes in a mer configuration, where one of the phosphorus atoms is trans to the NO group, in a slightly distorted octahedral geometry.