Anionic carbonyl complexes of the group VI transition metals with sulfur containing ligands

Anionic complexes of the type [M(CO)₄(dpet)]^? (where M is Cr, Mo or W and dpet is the anion of 2-(diphenylphosphino)ethanthiol) are readily prepared by the reaction of the Tl(dpet) and [M(CO)₅X]^? anions (X = halogen). These complex anions appear to have the normal octahedral geometry with the dpet ligand coordinated through both the P and S atoms. When treated with methyl or allyl halides, neutral complexes of the type M(CO)₄(dpet—R) are formed (where R is an allyl or methyl group now bound to the sulfur atom). By treating Tl^I salts of o-aminothiophenol (atp), o-methylmercaptophenol (nmp) and methylxanthic acid (mxt), with [M(CO)₅]^? anions, the respective complexes [M(CO)₄(atp)]^?, [M(CO)₄(mmp)]^? and [M(CO)₅(mxt)]^? are formed.     

Anionic complexes of some transition metals containing mixedβ-diketonato and alkylxanthato ligands

Summary Eleven complexes of the type K[M(acac)(Rxan)₂] and K[M(TTA)₂(Rxan)], where M=Co^II or Ni^II, acac=acetylacetonate, TTA=thenoyltrifluoroacetonate, and Rxan=alkylxanthate, R=methyl-, ethyl-, propyl-, butyl-, or cyclohexyl-, have been prepared. The magnetic and spectral data indicate that the complexes are octa-hedral and that the xanthate group is attached in a bidentate fashion to the metal ions. The conductivity data are commensurate with the ionic character in the complexes. T.g.a. were made for some of the complexes.Presented at the XXVI International Conference on Coordination Chemistry in Porto, Portugal, 28 August–2 September 1988.     

Cyanoalkyl complexes of transition metals . : II. Preparation and properties of some platinum complexes containing phosphorus as a donor atom

cis-PtCl(CH₂CN)(PPh₃)₂ was obtained by the reaction of Pt(PPh₃)₄ with ClCH₂CN in acetone. A solution of Pt(PPh₃)₄ and ClCH₂CN in benzene was heated under reflux to give trans-PtCl(CH₂CN)(PPh₃)₂. The reaction of the trans-isomer with Br^?, I^?, Ph₂PCH₂CH₂ PPh₂, Ph₂PCH₂CH₂AsPh₂ and cisPh₂PCHCHPPh₂ has been examined. The trans-influence of a ligand trans to the CH₂CN group seems to be indicated by the ²J(PtH) of the CH₂CN protons. The τ values of trans-PtX(CH₂CN)(PPh₃)₂ and PtX(CH₂ CN)(PP) (X = Cl, Br, I) are related by a linear function.     

Adducts of a palladium(II) derivatives containing a α-bonded α-diimino group with transition metals a new class of bimetallic complexes

The characterization of 1 : 1 adducts of [PdCl C(NC₂H₄OMe)(MeCNC, H₄OMe)(PPh₃)₂] and MCl₂ (M = Fe, Co, N₄, Cu and Zn) is described.     

Vinylidene complexes of transition metals : IV. The transfer of the phenylvinylidene ligand from manganese to rhenium. the novel binuclear complex Cp2MnRe(μ-CCHPh)(CO)4

The novel complex Cp₂MnRe(μ-CCHPh)(CO)₄ (I) containing the bridging phenylvinylidene ligand and MnRe bond was obtained in the reaction of CpMn(CCHPh)(CO)₂ with CpRe(CO)₂·THF. Complex I turns into CpRe(CCHPh)(CO)₂ under normal conditions. This is the first example of the transfer of the vinylidene ligand from one transition metal to another.     

Polarographic behaviour of π-allylic complexes of transition metals : II. π-allyltricarbonylcobalt and some phosphinic derivatives

The polarographic reduction in acetonitrile (ACN) of π-C₃H₅Co(CO)₃ and of the phosphinic derivatives π-C₃H₅Co(CO)₂L [L = P(OC₆H₅)₃, P(OCH₂)₃CC₂H₅, P(C₆H₅)₃, P(OC₂H₅)₃, P-n-Bu₃, P(C₆H₁₁)₃] is reported and the reduction mechanism is discussed. The dependence of the E_{$\text{1}\text{2}$} of thecomplexes on the properties of the ligands is analysed, and a linear plot of E_{$\text{1}\text{2}$} vs. ΔHNP of the ligands is observed. The pseudo first-order rate constants for the reduction of the complexes with NaBH₄ in ACN are reported.     

Mass spectrometry of π-complexes of transition metals XI. Manganese and rhenium vinylidene complexes

The mass spectra of (π-C₅H₅)_nM_n(CO)(L)₁(L′) (M = Mn, Re; L = CO, P(C₆H₅)₃, P(OC₆H₅)₃; L′ is a vinylidene ligand) are reported and characterised by strong dehydrogenation of the rhenium complexes. In bimetallic analogues, the ReRe bond is stronger than the MnMn.     

Mercury(II) complexes containing new ortho-functionalized asymmetric triazene ligands: synthesis,crystal structures,and solution studies

Synthesis of two new asymmetric ligands: 1-(2-ethoxyphenyl)-3-(2-methoxycarbonylphenyl)triazene (HL) (1) and 1-(2-methoxyphenyl)-3-(2-methoxycarbonylphenyl)triazene (HL′) (2) are reported. The prepared triazenes are functionalized by ethoxy and methoxy groups in the ortho positions, respectively. The related monomeric complexes, [HgL₂] (3) and [HgL′₂] (4), were prepared by the reacting of the corresponding ligands with Hg(NO₃)₂ salt in methanol as solvent. All compounds were characterized by CHN analysis, FT-IR, ¹H NMR, and ¹³C NMR spectroscopy. According to the crystal structures of 1 and 2, the N–N bond distances indicate the presence of alternating single and double bonds, and hence the –N=N–NH– moiety. On coordination, each triazene was deprotonated and as a result, a resonance structure is formed between nitrogens which let them to be a tridentate ligand. In the crystal structure of 3, [HgL₂], the central Hg(II) is surrounded by two N atoms from interlocked L forming linear geometry, in which the other four Hg–N and Hg–O bonds are longer and can only be regarded as weak secondary bonds. An interesting feature of 3 is also the presence of π?π [centroid–centroid distance of 3.744(3)?Å] and C–H?π interactions. The results of solution studies for the formation of 3 in methanol support its solid-state stoichiometry.     

Haloalkyl complexes of the transition metals : II. Some new chloromethyl and methoxymethyl complexes of manganese,rhenium and ruthenium

The reactions of Na[Mn(CO)₅] or Na[Mn(CO)₄(PPh₃)] with CH₂ClI yield the new chloromethyl complexes Mn(CO)₅CH₂Cl and Mn(CO)₄(PPh₃)CH₂Cl. Reaction of Na[Re(CO)₅] or Na[CpRu(CO)₂] with ClCH₂OMe yields Re(CO)₅CH₂Cl and CpRu(CO)₂CH₂Cl respectively, in addition to the corresponding methoxymethyl complexes (Cp = η⁵-C₅H₅). Reaction of CpRu(CO)₂CH₂OMe with HCl yields the corresponding chloromethyl complex.     

Chelate polymers: II. Some novel transition metals complexes with azomethine‐containing siloxanes and their polyesters

New Schiff bases of 2,4‐dihydroxybenzaldehyde with siloxane‐α,ω‐diamines having different numbers of siloxane units in the chain have been synthesized and characterized by spectroscopy, elemental and thermal analyses. These azomethines were found to form complexes readily with copper(II), nickel(II), cobalt(II), cadmium(II) and zinc(II). From IR and UV–Vis studies, the phenolic oxygen and imine nitrogen of the ligand were found to be the coordination sites. Thermogravimetric analysis (TGA) data indicate the chelates to be more stable than the corresponding ligands. The melting points increase with shortening of the siloxane segment from azomethine, as well as the result of complexation. The chelates obtained were covalently inserted in polymeric linear structures by polycondensation through the OH‐difunctionalized ligand with 1,3‐bis(carboxypropyl)tetramethyldisiloxane. Direct polycondensation, assisted either by acetic anhydride or N,N′‐dicyclohexylcarbodiimide as dehydrating agent and the complex 4‐(dimethylamino)pyridinium 4‐toluenesulfonate as catalyst, was used for the synthesis of these compound types. The structures of the polymers obtained were confirmed by IR, UV and ¹H NMR. Characterization was undertaken by TGA, solubility tests and viscosity measurements. Copyright © 2003 John Wiley & Sons, Ltd.     

Tetraamide macrocyclic complexes of transition metals with ligands derived from hydrazine

Succinic acid or phthalic acid react with hydrazine hydrate and formaldehyde in the presence of metal ions to give the macrocyclic complexes [ML1Cl2] or [ML2Cl2][M = FeII, CoII, NiII, CuII and ZnII]. The resulting cyclization has been identified, on the basis of i.r. and 1H-n.m.r. studies. The coordination of amide groups through nitrogen and the overall geometry of the complexes have been assigned on data obtained from elemental analyses i.r., u.v.-vis., magnetic moments, e.p.r and conductivity studies. All the complexes exhibit an octahedral geometry, except copper which is square planar, where the amide group coordinates through nitrogen, and are air stable. The observed low molar conductivity values suggest the non-ionic nature of all the compounds.     

QTAIM study of transition metal complexes with cyclophosphazene-based multisite ligands II. Cobalt(II) complexes

[(CoLCl)CoCl₃], [(CoMeLCl)CoCl₃], [(CoLBr)CoBr₃], [CoLBr]⁺ and [CoMeLBr₂] complexes, L = hexakis(2-pyridyloxy)cyclotriphosphazene, MeL = hexakis(4-methyl-2-pyridyloxy)cyclotriphosphazene, in the most stable high spin states are investigated at DFT level of theory using hybrid B3LYP functional. The exchange coupling parameter evaluated using a broken symmetry treatment increases with the ligands mass. Electron density is evaluated in terms of QTAIM (Quantum Theory of Atoms-in-Molecule) topological analysis of electron density. The bonds of central Co atoms with phosphazene nitrogens are shorter, stronger and more polar than with the aromatic pyridine nitrogens and their higher ellipticities may be explained by the π contribution from the phosphazene ring. The atomic charges of phosphazene nitrogens are ca. twice more negative than at the pyridine ones.     

A new method for the synthesis of oligodeoxyribonucleotides containing 4-N-alkoxycarbonyldeoxycytidine derivatives and their hybridization properties.

Oligodeoxyribonucleotides incorporating 4-N-alkoxycarbonyldeoxycytidine derivatives were synthesized on polystyrene-type ArgoPore resins having a new benzyloxy(diisopropyl)silyl linker, by use of ZnBr(2) as the detritylating agent. The first 3'-terminal thymidine could be attached to the resin by successive in situ reactions of 5'-O-DMTr-thymidine with diisopropylsilanediyl ditriflate and an ArgoPore resin containing hydroxyl groups. The use of this new silanediyl-type linker allowed release of the DNA chain from the resin by treatment with TBAF under neutral conditions. The T(m) experiments apparently showed that incorporation of 4-N-alkoxycarbonyldeoxycytidines into DNA strands resulted in higher hybridization affinity with the complementary DNA strands than that of 4-N-acyldeoxycytidines. In addition, comparable T(m) studies using oligodeoxyribonucleotides incorporating acyl (RC(O)-) groups and alkoxyacyl (RO(CH(2))(n)C(O)-) groups having the same chain length show that the latter tend to exhibit higher T(m) values than the former. It turned out that 4-N-alkoxycarbonyldeoxycytidines can form base pairs not only with deoxyguanosine but also with deoxyadenosine. Based on the ab initio calculations of the hydrogen bond energies of the possible base pairs formed between 4-N-methoxycarbonyl-1-methylcytosine and 9-methyladenine and the NMR analysis of the base-pairs of (15)N-labeled 4-N-alkoxycarbonyldeoxycytidines with deoxyadenosine derivatives, we conclude that the base pair involves two unique hydrogen bonds between the cytosyl 4-NH group and the adenyl N(1) atom and between the O atom of the ester group and the adenyl 6-NH group.     

Novel liquid-crystalline derivatives of transition metals. The effect of the molecular geometry of the ligands on the mesogenic properties of tetracoordinated copper(II) complexes

The synthesis, characterization and thermal behaviour of several new series of copper(II) complexes derived from carbonylic compounds and their Schiff's bases are reported. The complexes are of two types; [Cu(C₆H₃O(R)-C(X) = O)₂], (type I) and [Cu(C₆H₃O(R)-C(X) = N-R')₂] (type II) where R = - OOC-C₆H₄OC₁₀H₂₁-p, and the position of R is 4 or 5; R' = CH₃, n-C₁₀H₂₁, p-n-C₁₀H₂₁O(C₆H₄)-; X = H, CH₃. In type I complexes, only the compound with X = H and R in position 5 showed mesomorphism. For type II complexes, all the Schiff's bases complexes of copper(II) derived from 2,4-dihydroxybenzaldehyde showed thermotropic mesophases (smectic C and nematic), whereas the complexes derived from 2,5-dihydroxybenzaldehyde were only mesogenic when the imine was derived from methylamine. None of the complexes derived from the ketone (2,4 or 2,5-dihydroxy derivatives) showed liquid-crystalline properties. X-ray studies of four complexes of type II were carried out. The anisotropy of the magnetic susceptibility has a negative sign for complexes with R in position 4 and a positive sign for 2,5-derivative complexes. The relationship between molecular structure and mesomorphic behaviour is discussed.     

Synthesis and reactivity of transition metal complexes containing halogenated boryl ligands

The synthesis and characterization of iron and manganese complexes containing the tetrachlorocatecholboryl (BO₂C₆Cl₄) ligand are reported. Crystallographic study of the methylcyclopentadienyl derivative (η⁵-C₅H₄Me)Fe(CO)₂BO₂C₆Cl₄ allows comparison of structure and bonding with related complexes of the type (η⁵-C₅R₅)Fe(CO)₂B(OR)₂ and reveals that the relative orientation of (η⁵-C₅H₄Me)Fe(CO)₂ and BO₂C₆Cl₄ moieties is influenced by intramolecular CH?O hydrogen bonding. Additionally, an alternative route to catecholboryl complexes from dilithiocatechol is reported.     

Fullerenes as a new type of ligands for transition metals

Fullerenes are considered as ligands in transition metal π-complexes. The following aspects are discussed: metals able to form complexes with fullerenes; haptic numbers; homo-and heteroligand complexes; ligand compatibility with fullerenes for different metals, including fullerenes with a disturbed structure of conjugation.     

Vinylidene complexes of transition metals : III. Derivatives of cyclopentadienyltricarbonyl rhenium with phenylvinylidene ligands. Crystal and molecular structure of Cp(CO)2Re[CC(Ph)C(Ph)CH2]Re(CO)2Cp

The novel complexes CpRe(CCHPh)(CO)₂ and Cp₂Re₂(μ-CCHPh)(CO)₄ containing a terminal and a bridging phenylvinylidene ligand respectively and the binuclear complex Cp(CO)₂Re[CC(Ph)C(Ph)CH₂]Re(CO)₂Cp were obtained in the reaction of CpRe(CO)₃ with PhCCH.According to an X-ray study of the latter complex the unusual bridging ligand is η¹-bonded to one Re atom and η²-bonded to the other.