Remetalation processes upon the formation of magnetically active heterometallic sulfide-bridged clusters

The processes of formation of antiferromagnetic heterometallic trinuclear clusters Cp₂Cr₂(-SCMe₃)₂(₃-S)₂ML _n (ML _n = Re(CO)(NO), W(NO)₂, W(NO)Cl, and W(NO)(SCMe₃)) from the antiferromagnetic binuclear chromium(iii) complex Cp₂Cr₂(-SCMe₃)₂(-S) (1) and nitrosyl-containing halide derivatives of Re^I and W⁰ were considered. It is shown that adducts of1 with ML _m (ML _m = Re(NO)(CO)₂Cl₂, W(NO)₂C1₂·1, and W₂(NO)₂(CO)₄I₂) are formed at the first stage. Then they loose the CpCrHal₂ moiety and transform into the reactive remetalation products, CpCr((-SCMe₃)₂(-S)ML _x (M = Re and W). The latter complexes join the electron-deficient CpCrS moiety to generate triangular clusters. The magnetic behavior of antiferromagnetic adducts and triangular clusters is discussed, and the existence of correlations between the energy of spin-spin exchange (–2J(Cr-Cr)) and Cr-Cr and Cr-S(sulfide) bond lengths is mentioned.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2337–2348, December, 1995.     

Synthesis, spectroscopic, and structural aspects of two trinuclear cyano-bridged heterometallic complexes

Two new cyano-bridged trinuclear heterometallic complexes [Sr₂(Phen)₄(CF₃CO₂)(H₂O)₃Fe(CN)₆]·2H₂O (1) [Ca₂(Phen)₄(CF₃CO₂)(H₂O)Co(CN)₆]·2H₂O (2) (where Phen=1,10-phenanthroline) have been synthesized and their crystal structures have been determined. The structure of complex (1) features a central [Fe(CN)₆]³⁻ unit that links a monocation, [Sr(Phen)₂(OH₂)(OOCCF₃)]⁺ and a dication, [Sr(Phen)₂(OH₂)₂]²⁺ via two trans cyanide bridges. The complex (2) features a central [Co(CN)₆]³⁻ unit that links two monocations of [Ca(Phen)₂(OH₂)(OOCCF₃)]⁺ (the positions of the trifluoro acetate and water molecules are disordered over two positions) via two trans cyanide bridges. Each metal atom is seven coordinated and achieves pentagonal bipyramidal geometry. Two cocrystallized water molecules are present in both the complexes. The presence of an extensive network of hydrogen bonding imparts the overall stability to both the systems.     

Titanium imido complexes containing 1,3,5-triazacyclohexane ligands

The syntheses of the 1,3,5-trimethyl- and tri-tert-butyl-1,3,5-triazacyclohexane-supported imido complexes [M(NR)(R′₃tach)Cl₂] (M = Ti or Zr (NMR only); R = Bu^t or 2,6-C₆H₃Prⁱ₂; R′ = Me or Bu^t) are reported, along with that of the thermally robust dibenzyl derivative [Ti(NBu^t)(Me₃tach)(CH₂Ph)₂]. The tert-butylimido ligand in [Ti(NBu^t)(Me₃tach)Cl₂] undergoes exchange with ArNH₂ (Ar = 4-C₆H₄Me or 2,6-C₆H₄Me or 2,6-C₆H₃Prⁱ₂) to form the corresponding arylimides [Ti(NAr)(Me₃tach)Cl₂]. The Me₃tach ring in [Ti(NR)(Me₃tach)Cl₂] undergoes slow exchange with Bu^t₃tach or Me₃tacn (1,4,7-trimethyl-1,4,7-triazacyclononane) to give the ring-exchanged products [Ti(NR)(Bu^t₃tach)Cl₂] and [Ti(NR)(Me₃tacn)Cl₂], respectively. The complexes [Ti(NR)(Me₃tach)X₂] (R = Bu^t or 2,6-C₆H₃Prⁱ₂; X = Cl or CH₂Ph) exhibit room-temperature dynamic NMR behaviour via an unusual trigonal twist of the facially coordinated Me₃tach ligand, and the activation parameters for these processes have been measured and are discussed. The X-ray structures of [Ti(NR)(Bu^t₃tach)Cl₂] (R = Bu^t or 2,6-C₆H₃Prⁱ₂) and [Ti(NBu^t)(Me₃tach)(X)₂] [X= Cl or CH₂Ph) are reported. Me₃tach and Bu^t₃tach = 1,3,5-trimethyl- and tri-tert-butyl-1,3,5-triazacyclohexane, respectively.     

Crystal structure and magnetic properties of heterometallic trinuclear Cu2Ni complex containing macrocyclic ligands

One novel heterometallic trinuclear complex of macrocyclic oxamide [Ni(CuL)₂(HBTC)H₂O] (I) (H₂L = 2,3-dioxo-5,6,14,15-dibenzo-1,4,8,12-tetraazacyclopentadeca-7,13-dien; H₃BTC = 1,3,5-benzenetricarboxylic acid) has been solvothermally synthesized and structurally characterized by elemental analysis, IR spectroscopy, XRD, and single-crystal X-ray diffraction. The crystals crystallize in the monoclinic system, space group P2₁/c, a = 11.435(3), b = 20.646(5), c = 18.430(5) Å, β = 94.131(4)°. The structure of I has oxamido-bridged trinuclear [Cu ₂ ^II Ni^II] units and consists of two-dimensional supramolecular architecture formed by strong intermolecular hydrogen bonds. Furthermore, the magnetic properties of complex I was investigated and discussed in detail.     

Allosteric deprogramming of a trinuclear heterometallic helicate

Two multidentate ditopic ligands L1 and L2 which contain both N-donor and crown ether units have been synthesised. The potentially octadentate ligand L1 forms a trinuclear heterometallic double helicate with Cu(I) and Zn(II) ([Zn2Cu(L1)2](5+)), whereas L2 forms a tetranuclear heterometallic double helicate with the same metal ions ([Zn2Cu2(L2)2](6+)). Both species have been characterised by (1)H NMR, ESI-MS and single crystal X-ray crystallography. Reaction of [Zn2Cu2(L2)2](6+) with Ba(2+) results in the coordination of the crown ether units giving the simple barium coordinated species [Zn2Cu2(L2)2Ba2](10+). However, reaction of [Zn2Cu(L1)2](5+) with Ba(2+) deprograms the ligand and results in the formation of a mixture of species.     

Heterobimetallic complexes as oxygen donor bidentate ligands: synthesis of early-late trinuclear complexes

The early-late heterometallic complexes [TiCp^∗((OCH₂)₂Py)(μ-O)M(COD)] (M = Rh, Ir) behave as four-electron donor ligands yielding the polynuclear cationic complexes [TiCp^∗(OCH₂)₂ Py(μ-O){M(COD)}₂]OTf (M = Rh (1), Ir (2)). The molecular structure of complex 1 has been established through an X-ray diffraction study.     

Molecular design of new magnetically active copper complexes with heteroaromatic schiff bases and azo compounds

Copper chelates with tridentate ligands containing pyridine or pyrazole ring at the azomethine or azo fragment were synthesized by chemical electrochemical methods, and their structure was characterized by the EXAFS spectra. Thermal magnetochemical analysis of the complexes revealed antiferromagnetic exchange interaction in all complexes. The exchange interaction parameter of the complex containing an N-tosylamino group in the ortho position with respect to the azomethine group is much lesser than that of the corresponding complex having an oxygen atom in the same position. The copper chelate derived from azopyrazole ligand shows low-temperature ferromagnetic phase transition.     

Computational basis for the design of PLK-2 inhibitors

Structural Chemistry - PLK-2 is a serine/threonine protein kinase and plays a crucial role in cell cycle regulation; due to its pivotal function, this enzyme is approved as cancer drug target. We...     

New magnetically active metal complexes of tridentate Schiff bases of phenylazosalicylaldehyde

The bidentate chelate Cu(II) complexes of phenylazosalicylaldehyde azomethines are synthesized for the first time and their magnetic properties are studied. The complexes with the intermetallic bridge of the nitrogen atoms are characterized by the antiferromagnetic interaction, whereas the ferromagnetic exchange is typical of analogous coordination compounds with the sulfur bridge.     

Direct synthesis of heterometallic complexes

The idea of direct synthesis of coordination compounds – use of elemental metals or their oxides as starting material – has been developed to synthesize heterometallic compounds. The advantages of this approach in obtaining polynuclear, mixed-anion and mixed-valence coordination compounds are shown, taking complexes with aminoalcohols as examples. The preparation of heterobimetallic Cu/M (Pb, Zn, Co) complexes with aminoalcohols using zerovalent copper as a starting material is presented. The main principles for the formation of heterobimetallic complexes and the most interesting crystal structures are briefly reviewed.     

Rational design of macrometallocyclic trinuclear complexes with superior pi-acidity and pi-basicity

Density functional theory (DFT) has been used to assess the pi-acidity and pi-basicity of metal-organic trimetallic macromolecular complexes of the type [M(mu-L)]3, where M = Cu, Ag, or Au and L = carbeniate, imidazolate, pyridiniate, pyrazolate, or triazolate. The organic compounds benzene, triazole, imidazole, pyrazole, and pyridine were also modeled, and their substituent effects were compared to those of the coinage metal trimers. Our results, based on molecular electrostatic potential surfaces and positive charge attraction energy curves, indicate that the metal-organic macromolecules show superior pi-acidity and -basicity compared to their organic counterparts. Moreover, the metal-organic cyclic trimers are found to exhibit pi-acidity and -basicity that can be systematically tuned both coarsely and finely by judicious variation of the bridging ligand (relative pi-basicity imidazolate > pyridiniate > carbeniate > pyrazolate > triazolate), metal (relative pi-basicity Au > Cu > Ag), and ligand substituents. These computational findings are thus guiding experimental efforts to rationally design novel [M(mu-L)]3 materials for applications in molecular electronic devices that include metal-organic field-effect transistors and light-emitting diodes.     

Bent and linear trinuclear nickel complexes with ligands derived from N -acylsalicylhydrazide ligands: structural characterization and bioactivity

Two trinuclear Ni(II) complexes Ni₃(L₁)₂(py)₂(DMF)(H₂O) (1) and Ni₃(L₂)₂(py)₂(DMF)₂ (2) with two new trianionic pentadentate ligands N-(3,5-dimethylbenzoyl)-salicylhydrazide (H₃L₁) and N-(phenylacetyl)-5-nitrosalicylhydrazide (H₃L₂) have been synthesized and characterized by X-ray crystallography. Nickel ions in the two complexes have square-planar/octahedral/square-planar coordination. Central metal ion and two terminal metal ions in the two complexes are combined by two bridging deprotonated ligands, forming a trinuclear structural unit with an M–N–N–M–N–N–M core. Studies on the trinuclear Ni(II) complexes show that the β-branched N-acylsalicylhydrazide ligands with sterically flexible Cα methylene groups yield linear trinuclear Ni(II) complexes, while α-branched N-acylsalicylhydrazide ligands tend to form bent trinuclear Ni(II) complexes. Antibacterial screening data in a previous study indicates that bent trinuclear Ni(II) compound 1 is more active than linear compound 2 and less active than a tetranuclear nickel compound.     

Comparative bonding behavior of functional cyclopentadienyl ligands and boron-containing analogues in heterometallic complexes and clusters

The reactivity of isolobal molybdenum carbonylmetalates containing a 2-boratanaphthalene, [Mo(eta5-2,4-MeC9H6BMe)(CO)3]- (5a) and [Mo(eta5-2,4-MeC9H6BNi-Pr2)(CO)3]- (5b), a 1-boratabenzene, [Mo(eta5-3,5-Me2C5H3BNi-Pr2)(CO)3]- (8), or a functionalized cyclopentadienyl ligand, the new metalate [Mo(eta5-C5H4Ph)(CO)3]- (7) and [Mo(eta5-C5H4NMe2)(CO)3]- (9), toward palladium (I and II) or platinum (I and II) complexes, such as trans-[PdCl2(NCPh)2], [Pd2(NCMe)6](BF4)2, trans-[PtCl2(PEt3)2], and [N(n-Bu)4]2 [Pt2Cl4(CO)2], has been investigated, and this has allowed an evaluation of the influence of the pi-bonded ligands on the structures and unprecedented coordination modes observed in the resulting metal-metal-bonded heterometallic clusters. The new 58 CVE planar-triangulated centrosymmetric clusters, [Mo2Pd2(eta5-C5H4Ph)2(CO)6(PEt3)2] (11), [Mo2Pd2(eta5-2,4-MeC9H6BNi-Pr2)2(CO)6] (12), [Mo(2)Pd(2)(eta5-3,5-Me2C5H3BNi-Pr2)2(CO)6] (13), [Mo2Pd2(eta5-C5H4NMe2)2(CO)6(PEt3)2] (15), [Mo2Pt2(eta5-C5H4NMe2)2(CO)6(PEt3)2] (16), and [Mo2Pt2(eta5-C5H4NMe2)2(CO)8] (20), have been characterized by single-crystal X-ray diffraction. Their structural features were compared with those of the 54 CVE cluster [Re2Pd2(eta5-C4H4BPh)2(CO)6)] (4), previously obtained from the borole-containing metalate [Re(eta5-C4H4BPh)(CO)3]- (2), in which a 2e-3c B-C(ipso)-Pd interaction involving the pi-ring was observed. As an extension of what has been observed in 4, clusters 12 and 13 present a direct interaction of the boratanaphthalene (12) and the boratabenzene (13) ligands with palladium. In clusters 11, 15, 16, and 20, the pi-ring does not interact with the palladium (11 and 15) or platinum centers (16 and 20), which confers to these clusters a geometry very similar to that of [Mo2Pd2(eta5-C5H5)2(CO)6(PEt3)2] (3b). The carbonylmetalates [Mo(pi-ring)(CO)3]- are thus best viewed as formal four electron donors which bridge a dinuclear d9-d9 unit. The orientation of this building block in the clusters influences the shape of their metal cores and the bonding mode of the bridging carbonyl ligands. The crystal structure of new centrosymmetric complex [Mo(eta5-C5H4Ph)(CO)3]2 (10) was determined, and it revealed intramolecular contacts of 2.773(4) A between the carbon atoms of carbonyl groups across the metal-metal bond and intermolecular bifurcated interactions between the carbonyl oxygen atoms (2.938(4) and 3.029(4) A), as well as intermolecular C-H...pi(Ar)(C=C) interactions (2.334(3) and 2.786(4) A) involving the phenyl substituents.     

Electron density distributions of redox active mixed valence carboxylate bridged trinuclear iron complexes

The electron density distributions (EDD) of the redox active mixed valence trinuclear oxo-centered iron carboxylate, [Fe(3)O(CH(2)ClCOO)(6)(H(2)O)(3)].3H(2)O, 1, and the oxidized form of 1, [Fe(3)O(CH(2)ClCOO)(6)(H(2)O)(2)(CH(2)ClCOO)].1H(2)O, 2, as well as of [Fe(3)O(C(CH(3))(3)COO)(6) (NC(5)H(5))(3)], 3, have been determined from accurate single-crystal X-ray diffraction data measured at 100 K (1, 2) and from extensive synchrotron radiation X-ray diffraction data measured at 28 K (3). Analysis of the EDDs shows that the central oxygen atom has a very different EDD in the mixed valence complexes (1 and 3) compared with the oxidized complex (2). Furthermore, in 1 and 3 the chemical bonds between formally identical trivalent Fe atoms and the central oxygen are fundamentally different. This is in direct contrast to the Fe(IIImicro(3)-O) bonds in the oxidized complex, which are practically identical. Analysis of the d-orbital populations on the metal sites in the three complexes shows that the extra electron density on the Fe(II) site primarily is distributed in a d(yz) orbital (z-axis toward the central oxygen, y-axis perpendicular to the Fe(3)O-plane). Presence of extra charge in the d(yz) orbital correlates with a decrease in the d(xy) population, i.e., with a depletion of charge in the equatorial region of coordination to carboxylate oxygen. The d(xy) charge depletion appears to be of importance for determining the active versus trapped Fe(III) site, and the equatorial ligands therefore have a considerable influence on the ET process. Bader topological analysis of the EDDs corroborates the conclusions drawn from the orbital population analysis, but it also provides additional knowledge about the chemical bonding in the structures. For comparison with the X-ray results, theoretical calculations were carried out for 3 in the experimental geometry. The present information about ET processes in trinuclear oxo-centered iron complexes cannot be deduced from analysis of the molecular structures (i.e., bond lengths and angles), and thus it is demonstrated that X-ray charge density analysis is able to reveal subtle new features of significant physical and chemical importance on complex molecular systems.     

Optically active rhodium complexes with indenyl-linked phosphane ligands

The optically active indenyl-linked phosphane ligands (S)-[2-(3H-inden-1-yl)-1-phenylethyl]diphenylphosphane (L₁) and (S)-[2-(4,7-dimethyl-3H-inden-1-yl)-1-phenyl-ethyl]diphenylphosphane (L₂) were synthesized in three steps from (R)-1-phenylethane-1,2-diol in excellent yields. Their lithium salts reacted with [Rh(μ-Cl)(η²-CH₂CH₂)₂]₂ at −78 °C in THF affording the planar chiral complexes (S,R_pl + S_pl)-[Rh(η⁵-indenyl-CH₂CH(Ph)PPh₂-kP)(η²-CH₂CH₂)] and (S,R_pl + S_pl)-[Rh(η⁵-4,7-dimethylindenyl-CH₂CH(Ph)PPh₂-kP)(η²-CH₂CH₂)] as 61:39 and 15:85 mixtures of diastereomers. The complexes were isolated in optically pure form by column chromatography. The stereochemical configuration of one of the diastereomers was determined by X-ray crystallography. The complexation of L₂ was studied in different solvents and with several Rh precursors and diastereomeric excesses up to 76% were achieved. The ability of the chiral ligands to control the stereochemistry at the metal center was tested by oxidative addition of methyl iodide. Diastereomeric excesses greater than 98% were observed.     

Vinyl polymerization of norbornene by mono‐ and trinuclear nickel complexes with indanimine ligands

A series of new indanimine ligands [ArN?CC₂H₃(CH₃)C₆H₂(R)OH] (Ar = Ph, R = Me ( 1 ), R = H ( 2 ), and R = Cl ( 3 ); Ar = 2,6‐i‐Pr₂C₆H₃, R = Me ( 4 ), R = H ( 5 ), and R = Cl ( 6 )) were synthesized and characterized. Reaction of indanimines with Ni(OAc)₂·4H₂O results in the formation of the trinuclear hexa(indaniminato)tri (nickel(II)) complexes Ni₃[ArN = CC₂H₃(CH₃)C₆H₂(R)O]₆ (Ar = Ph, R = Me ( 7 ), R = H ( 8 ), and R = Cl ( 9 )) and the mononuclear bis(indaniminato)nickel (II) complexes Ni[ArN?CC₂H₃(CH₃)C₆H₂(R)O]₂ (Ar = 2,6‐i‐Pr₂C₆H₃, R = Me ( 10 ), R = H ( 11 ), and R = Cl ( 12 )). All nickel complexes were characterized by their IR, NMR spectra, and elemental analyses. In addition, X‐ray structure analyses were performed for complexes 7 , 10 , 11 , and 12 . After being activated with methylaluminoxane (MAO), these nickel(II) complexes can polymerize norbornene to produce addition‐type polynorbornene (PNB) with high molecular weight M_v (10⁶ g mol^?1), highly catalytic activities up to 2.18 × 10⁷ gPNB mol^?1 Ni h^?1. Catalytic activities and the molecular weight of PNB have been investigated for various reaction conditions. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 489–500, 2008     

Organometallic building blocks with amino-substituted cyclopentadienyl and boratabenzene ligands for the synthesis of heterometallic complexes and clusters

A comparative study of the reactivity of isolobal rhenium and molybdenum carbonylmetallates containing a borole, in [Re(eta5-C4H4BPh)(CO)3]- (2), a boratanaphthalene, in [Mo(eta5-2,4-MeC9H6BMe)(CO)3]- (4a) and [Mo(eta5-2,4-MeC9H6BNi-Pr2)(CO)3]- (4b), a boratabenzene, in [Mo(eta5-3,5-Me2C5H3BNi-Pr2)(CO)3]- (6) or a dimethylaminocyclopentadienyl ligand, in [Mo(eta5-C5H4NMe2)(CO)3]- (7), toward palladium(II), gold(I), mercury(II) and platinum(II) complexes has allowed an evaluation of the role of these pi-bonded ligands on the structures and unprecedented coordination modes observed in the resulting metal-metal bonded, heterometallic complexes. The new metallate 6 was reacted with [AuCl(PPh3)], and with 1 or 2 equiv. HgCl2, which afforded the new heterodinuclear complexes [Au{Mo(eta5-3,5-Me2C5H3BNi-Pr2)(CO)3}(PPh3)] (Mo-Au) (10) and [Hg{Mo(eta5-3,5-Me2C5H3BNi-Pr2)(CO)3}Cl] (Hg-Mo) (11) and the heterometallic chain complex [Hg{Mo(eta5-3,5-Me2C5H3BNi-Pr2)(CO)3}2] (Mo-Hg-Mo) (12), respectively. Reactions of the new metallate 7 with HgCl2, trans-[PtCl2(CNt-Bu)2] and trans-[PtCl2(NCPh)2] yielded the heterodinuclear complex [Hg{Mo(eta5-C5H4NMe2)(CO)3}Cl] (Mo-Hg) (15), the heterotrinuclear chain complexes trans-[Pt{Mo(eta5-C5H4NMe2)(CO)3}2(CNt-Bu)2] (Mo-Pt-Mo) (16) and trans-[Pt{Mo(eta5-C5H4NMe2)(CO)3}2(NCPh)2] (Mo-Pt-Mo) (17), the mononuclear complex [Mo(eta5-C5H4NMe2)(CO)3Cl] (18), the lozenge-type cluster [Mo2Pt2(eta5-C5H4NMe2)2(CO)8] (19) and the heterodinuclear complex [[upper bond 1 start]Pt{Mo(eta5-C5H4N[upper bond 1 end]Me2)(CO)3}(NCPh)Cl](Mo-Pt) (20), respectively. The complexes 11, 16, 17.2THF, 18 and 20 have been structurally characterized by X-ray diffraction and 20 differs from all other compounds in that the dimethylaminocyclopentadienyl ligand forms a bridge between the metals.     

Metal complexes of biological active 2-aminothiazole derived ligands

The most imperative outcomes of extensive sterdies (synthesis, spectral, structural characterization and biological applications) of metal complexes with thiazole derived ligands are reviewed. A large number of coordination compounds are known but still there is a need of new compounds to develop various efforts in different fields for biomedical applications. The synthesis of Schiff base ligands is very important, and it has recently drawn the attention of numerous research groups, making this area constantly evolve. Authors are also synthesizing some novel biologically potent ligands and their unique complexes and complexes found more biological active agents than that of ligands against bacteria, fungi and herbs. Highlights: Schiff bases and their metal chelates catalyze reactions; Schiff bases derived from sulfane thiadiazole show toxicities against insects; Schiff bases of thiadiazole have good plant regulator activity; Phenyl ring attached to the thiazole group showed interesting structure activity.     

Synthesis of pyrazolide-bridged heterometallic binuclear complexes

A convenient synthetic procedure is described for the synthesis of heteronuclear bimetallic complexes involving platinum and one other group VIII metal with a single bridging pyrazolide group. The reagent used is the nucleophilic anion, trans-[Pt(Cl₂)(pz)(C₂H₄)]^-, (pz  C₃H₃N₂^-) generated in situ by deprotonation of the Zeise's adduct of pyrazole which will react with reasonably labile substrates to yield binuclear products. Spectroscopic and chemical properties of the products are discussed.