Heterodinuclear Compounds Research Articles

Synthesis of Gold(III) Complexes with Bidentate Amino-Thiolate Ligands as Precursors of Novel Bifunctional Acyclic Diaminocarbenes.

Two neutral bis(pentafluorophenyl)thiolate gold(III) complexes with the unsymmetrical S^N ligands 2-aminothiophenol or cysteamine have been synthesized and their reactivity has been studied. Homo- and heterodinuclear compounds were obtained by their coordination to gold(I) or silver(I) derivatives through the sulfur atom. Interestingly, a tetranuclear derivative bearing short gold(I)···gold(I) and the more unusual gold(I)···gold(III) interactions has been prepared. These amino-thiolate derivatives can be used as precursors for the synthesis of novel gold(III) acyclic diaminocarbene complexes by reaction with isocyanides CNR. The nucleophilic attack of the amino group to isocyanide molecules affords the synthesis of unprecedented bidentate C^S acyclic diaminocarbene ligands. All of the complexes are air- and moisture-stable at room temperature and have been spectroscopically and structurally characterized.

Exchange Interactions Switch Tunneling: A Comparative Experimental and Theoretical Study on Relaxation Dynamics by Targeted Metal Ion Replacement.

The magnetic relaxation and magnetization blocking barriers of tailor-made homo- and heterodinuclear compounds [Dy2 (opch)2 (OAc)2 (H2 O)2 ]⋅MeOH (1) and [DyMn(opch)2 (OAc)(MeOH)(H2 O)2 ] (2), where H2 opch is (E)-N'-(2-hydroxy-3-methoxybenzylidene)pyrazine-2-carbohydrazide, were systematically investigated and the change in single-molecule magnet behavior originating from targeted replacement of one dysprosium site in the Dy2 compound with manganese was elucidated through a combination of experimental and theoretical studies. A detailed comparative study on these closely related model compounds revealed remarkable changes of the crystal-field splitting and anisotropy of the Dy site and the total exchange spectrum due to the replacement of Dy by Mn. The blocking barriers of these two compounds, which explain their different relaxation behaviors, were analyzed. The two Ising doublets arising from the magnetic interaction in the case of 1 are strongly uniaxial, with tunneling splittings smaller than 10-6 cm-1 , and this leads to magnetic relaxation at temperatures exceeding the exchange energy (2.14 cm-1 ), which involves transition via the excited states corresponding to local transitions on the excited doublet at the Dy site. The third and fourth exchange doublets in 2 (located at 2.16 and 3.25 cm-1 , respectively) show much larger tunneling splittings (of 10-4 and 10-3 cm-1 , respectively), and thus open an important path for magnetic relaxation.

Cobalt Carbonyl Hydrides with 1,1′‐Diphosphinylferrocene Ligands – Structural and Electrochemical Diversity

The reaction of Co(CO)4H with various 1,1′‐bis(diorganophosphanyl)ferrocenes (dopf) produces structurally different heterodinuclear (Co,Fe) compounds. In contrast to the P‐isopropyl and P‐cyclohexyl‐substituted complexes [Co(CO)2H(dopf)] described earlier, the P‐phenyl‐substituted analogue exhibits a structure in the crystal with the hydride in trans position to a P atom. Using the dopf precursor with bulky P‐tert‐butyl substituents, a heterotrinuclear species {(μ‐dtbpf)[Co(CO)3H]2} is obtained, in which the ferrocene‐containing ligand acts as a bridge. In addition to the comparative analysis of molecular structures the (spectro)electrochemical responses are discussed in the light of the mechanism established for the isopropyl‐substituted system.

NIR luminescent heterodinuclear [ZnII LnIII] complexes: Synthesis, crystal structures and photophysical properties

Two series of new 3d-4f heterodinuclear [ZnIILnIII] Schiff base complexes of general formula [Zn(µ-L1)(µ-CH3COO)Ln(NO3)2(S)] [Ln = Pr (1), Nd (2), Sm (3), Gd (4); S = MeOH; H2L1= N,N-bis(3-methoxysalicylidene)-1,4-diaminobutane] and [Zn(µ-L2)(µ-CH3COO)Ln(NO3)2(S)] [Ln= Pr (5), Nd (6), Sm (7), Gd (8), S= MeOH; H2L2= N,N-bis(3-ethoxysalicylidene)-1,4-diaminobutane] are synthesized and fully characterized. Complexes 1, 2, 3, 4, 5 &7 are structurally characterized by single crystal X-ray crystallography. The crystallographic investigation indicates that the complexes contain 9 and 10-coordinated LnIII ions, while the ZnII ions always display a distorted square-pyramidal geometry. The crystal structure of the complexes are stabilized by inter molecular extended hydrogen bonding and C-H····π interactions resulting in supramolecular frameworks. Luminescence studies for the heterodinuclear compounds containing NdIII & SmIII reveal that the Zn-complex moiety acts as antenna for the emission from LnIII ions. In addition to the ligand-centered emission in the UV–Vis region, complex 2 (having NdIII) exhibits emission in NIR region also, thus resulting a new NIR emitting material.

Group 11 Metal Complexes with Unsymmetrical Bifunctional Ferrocene Ligands

The reactions of two unsymmetrical P^N (L1) and P^P (L2) ferrocene (Fc) ligands towards group 11 metal complexes were studied. Ligand L1 shows different behavior with the three metals. Gold forms mononuclear derivatives with the metal center coordinated to the phosphorus atom, whereas the reactions with silver(I) or copper(I) complexes afford mononuclear or dinuclear compounds in which both donor atoms, phosphorus and nitrogen, are involved in the coordination to the metal center. The reactions of the diphosphine ligand [Fc(CH2PPh2)(PPh2)] (L2) with gold(I), gold(III), silver(I), or copper(I) complexes afford mono‐, di‐, or trinuclear derivatives. Some homo‐ and heterodinuclear compounds were obtained through the reactions of the mononuclear gold(III) complex [Au(C6F5)3{Fc(CH2PPh2)(PPh2)}] (6), in which one of the phosphorus atoms is free, with gold(I), gold(III), and silver(I) deriiivatives. Some of these derivatives were characterized by X‐ray diffraction analysis.

Tuning the Origin of Magnetic Relaxation by Substituting the 3d or Rare-Earth Ions into Three Isostructural Cyano-Bridged 3d-4f Heterodinuclear Compounds.

Three isostructural cyano-bridged 3d-4f compounds, [YFe(CN)6(hep)2(H2O)4] (1), [DyFe(CN)6(hep)2(H2O)4] (2), and [DyCo(CN)6(hep)2(H2O)4] (3), were successfully assembled by site-targeted substitution of the 3d or rare-earth ions. All compounds have been structurally characterized to display slightly distorted pentagonal-bipyramidal local coordination geometry around the rare-earth ions. Magnetic analyses revealed negligible magnetic coupling in compound 1, antiferromagnetic intradimer interaction in 2, and weak ferromagnetic coupling through dipolar-dipolar interaction in 3. Under an applied direct-current (dc) field, 1 (Hdc = 2.5 kOe, τ0 = 1.3 × 10(-7) s, and Ueff/kB = 23 K) and 3 (Hdc = 2.0 kOe, τ0 = 7.1 × 10(-11) s, and Ueff/kB = 63 K) respectively indicated magnetic relaxation behavior based on a single [Fe(III)]LS ion and a Dy(III) ion; nevertheless, 2 (Hdc = 2.0 kOe, τ0 = 9.7 × 10(-8) s, and Ueff/kB = 23 K) appeared to be a single-molecule magnet based on a cyano-bridged DyFe dimer. Compound 1, which can be regarded as a single-ion magnet of the [Fe(III)]LS ion linked to a diamagnetic Y(III) ion in a cyano-bridged heterodimer, represents one of the rarely investigated examples based on a single Fe(III) ion explored in magnetic relaxation behavior. It demonstrated that the introduction of intradimer magnetic interaction of 2 through a cyano bridge between Dy(III) and [Fe(III)]LS ions negatively affects the energy barrier and χ″(T) peak temperature compared to 3.

Synthesis, Characterization, and Antibacterial Activity of Some New Mono- and Heterodinuclear Indium Compounds

Schiff base compounds of indium [O(CH2)2N:CHC6H4OInOC6H4CH:N(R)OH] (where R = (CH2)2,(2a);C(CH3)2-CH2-(2b),CH2CH(CH3)-(2c),(CH2)3-(2d)) have been synthesized by the reactions of In(OPri)3 with corresponding Schiff base ligands in 1:2 molar ratio in refluxing benzene. Reactions of 2a–2d with hexamethyldisilazane in 2:1 molar ratio yield heterodinuclear indium compounds of the type of [O(R)N:CHC6H4OInOC6H4CH:N(R)OSiMe3] (where R = (CH2)2(3a),-C(CH3)2CH2(3b),-CH2CH(CH3)-(3c) and-(CH2)3-(3d). All these newly synthesized mono- and heterodinuclear indium compounds have been characterized by elemental analyses and molecular weight measurements. Tentative structures have been proposed on the basis of IR, NMR (1H, 13C, 29Si), and FAB-mass spectral studies. Ligands (1a–1d) and the corresponding indium compounds (2a–3d) have been screened for their antibacterial activities against gram -ve E. coli and gram -ve P. aeruginosa with promising results.

Heterometallic Derivatives of the Unsaturated Ditungsten Hydride [W2(η5-C5H5)2(H)(μ-PCy2)(CO)2

The title complex reacted with different transition-metal (M) complexes to give heterometallic clusters with W2M and W2M2 metal cores. The reaction with [Fe2(CO)9] in THF at room temperature gave a mixture of the heterodinuclear compound [FeWCp(μ-PCy2)(CO)6] and the tetrahedral clusters [Fe2W2Cp2(μ3-H)(μ-PCy2)(CO)8] (W-W = 2.704(1) Å) and [Fe2W2Cp2(μ-H)(μ-PCy2)(μ-CO)(CO)8] (W-W = 3.058(5) Å). In contrast, its reaction with [Ru3(CO)12] under ultraviolet-visible (UV-Vis) irradiation gave only the heterodinuclear complex [RuWCp(μ-PCy2)(CO)6]. The title complex also reacted readily with [M(CO)6] (M = Cr, Mo, W) in toluene solution under UV-Vis irradiation, but the main product was the known tetracarbonyl complex [W2Cp2(μ-H)(μ-PCy2)(CO)4], except in the reaction with [W(CO)6], the latter also yielding the expected 46-electron cluster [W3Cp2(μ3-H)(μ-PCy2)(CO)7] in 40% yield. The title complex reacted under visible-UV irradiation with different metal-metal bonded dimers in toluene solution, but only with [Ru2Cp2(CO)4] an heterometallic cluster was obtained, with composition [RuW2Cp3(μ-PCy2)(CO)4]. Its reaction with the tetrahydroborate complex [Cu(BH4)(PPh3)2] led to the insertion of two CuH(PPh3) fragments and release of BH3·PPh3, to give the tetranuclear cluster [Cu2W2Cp2(μ-H)3(μ-PCy2)(CO)2(PPh3)2], which exists in solution as an equilibrium mixture of two isomers.

The all non-metal homodinuclear and heterodinuclear sandwich-like compounds C2(η3-L3)2 and BN(η3-L3)2 (L = BCO, BNN and CBO)

Density functional theory studies on the all non-metal homodinuclear and heterodinuclear sandwich-like compounds C(2)(η(3)-L(3))(2) and BN(η(3)-L(3))(2) (L = BCO, BNN and CBO) have been performed. The staggered conformations of both C(2)(η(3)-L(3))(2) and BN(η(3)-L(3))(2) are predicted to be stable. The non-metal direct C-C and B-N bonds are covalent with σ interactions, which are formed by the interactions of s and p(z) orbitals of the center atoms. Different from the ionic metal-ligand bond in the traditional metal center sandwich-like compounds, the C-L, B-L, and N-L bonds are covalent in these all non-metal sandwich-like compounds. The NICS values indicate that the ligands of C(2)(η(3)-L(3))(2) and BN(η(3)-L(3))(2), as well as their bare rings, display multiple aromaticity (σ and π aromaticity). Both σ and π aromaticity of the ring ligands towards the center atoms become stronger after complexation with the center atoms, while the π aromaticity against the center atoms is reduced. The π aromaticity of the ligands bonded to different center atoms follows a trend of B > C > N, and the (CBO)(3)(+) ligands bonded to B possess the strongest π aromaticity. The dissociation reactions and possible synthetic reactions analysis show that these all non-metal sandwich-like compounds are stable, and the homodinuclear species are more stable than the heterodinuclear ones. These all non-metal binuclear sandwich-like compounds can be regarded as potential synthetic targets according to the highly negative free energies of the possible synthetic reactions. The isomerization reactions demonstrate that the CBO-based compounds should be more possible to synthesize in experiments than their BCO-based isomers.

Study of the Luminescent and Magnetic Properties of a Series of Heterodinuclear [ZnIILnIII] Complexes

Herein, we report the synthesis, structural investigation, and magnetic and photophysical properties of a series of 13 [Zn(II)Ln(III)] heterodinuclear complexes, which have been obtained employing a Schiff-base compartmental ligand derived from o-vanillin [H(2)valpn = 1,3-propanediylbis(2-iminomethylene-6-methoxy-phenol)]. The complexes have been synthesized starting from the [Zn(valpn)(H(2)O)] mononuclear compound and the corresponding lanthanide nitrates. The crystallographic investigation indicated two structural types: the first one, [Zn(H(2)O)(valpn)Ln(III)(O(2)NO)(3)], contains 10-coordinated Ln(III) ions, while in the second one, [Zn(ONO(2))(valpn)Ln(III)(H(2)O)(O(2)NO)(2)]·2H(2)O, the rare earth ions are nine-coordinated. The Zn(II) ions always display a square-pyramidal geometry. The first structural type encompasses the larger Ln ions (4f(0)-4f(9)), while the second is found for the smaller ions (4f(8)-4f(11)). The dysprosium derivative crystallizes in both forms. Luminescence studies for the heterodinuclear compounds containing Nd(III), Sm(III), Tb(III), Dy(III), and Yb(III) revealed that the [Zn(valpn)(H(2)O)] moiety acts as an antenna. The magnetic properties for the paramagnetic [Zn(II)Ln(III)] complexes have been investigated.

Mono- and heterodinuclear indium compounds of multidentate schiff bases; syntheses, characterization and their antibacterial activity

Some new indium compounds of bifunctional tridentate Schiff bases have been synthesized by the reactions of In(OPr i )3 with corresponding ligands in 1 : 2 molar ratio in refluxing benzene. Equimolar reactions of these mononuclear indium compounds with B(OPr i )3 yield heterodinuclear compounds. These newly synthesized compounds have been characterized by elemental analyses and molecular weight measurements. Their plausible structures have been proposed on the basis of IR and NMR ( 1 H, 13 C, 11 B) and FAB-Mass spectral studies. Antibacterial activities of Schiff base ligands and their corresponding mononuclear compounds have been screened against gram positive E. coli and gram negative Pseudomonas with promising results.

Construction of four 3d-4d/4d complexes based on salen-type schiff base ligands

Through a two-step synthetic strategy, four d10 Schiff-base complexes CdZn(DMF)(La)(NO3)2 (1), Cd[Zn(La)Cl]2·H2O (2) and [Cd(DMF)LbS]2·2H2O (S = NO3, 3; Cl, 4) (H2La = N,N′-bis(3-methoxy-salicylidene)phenylene-1,2-diamine, HLb = 2-(1H-benzoimidazol-2-yl)-6-methoxy-phenol) have been successfully constructed by the solvothermal reaction of Cd(NO3)2/CdCl2 with Zn(La)/Zn(Lb)2, and characterized by EA, IR, FAB-MS and TG, in which 1, 2 and 4 were confirmed by single crystal X-ray diffraction. The results reveal that 1 is the first 3d-4d hetero-dinuclear compound based on H2La, however, 2 is a CdZn2-type compound reported previously. 3 and 4 are the first examples of dinuclear compounds containing ligand HLb. Moreover, luminescence and biological activities of the four compounds and two ligands H2La/HLb are investigated.

Structural and Near‐IR Luminescent Properties of Erbium‐Containing Coordination Polymers

AbstractThe near‐IR luminescence properties of two ErIII‐containing coordination polymers, namely, [Er(btc)(H2O)5·3.5H2O]∞ [(btc)3– = 1,3,5‐benzenetricarboxylate] and [Er2(bdc)3(H2O)4]∞ [(bdc)2– = 1,4‐benzenedicarboxylate] were investigated with the aim of testing their potential use as optical materials. Because both present relatively small quantum yields and short excited‐state lifetimes, factors influencing their luminescent properties were deciphered in an effort to improve their luminescent properties. Thus, three other families of compounds were also investigated: (i) the two corresponding dehydrated compounds with respective chemical formula [Er(btc)] and [Er2(bdc)3]∞ for evaluating the importance of O–H vibrators, (ii) the heterodinuclear compounds [Er2–2xY2x(bdc)3(H2O)4]∞ (x = 0.2, 0.5, 0.8 and 0.9) for estimating the role of intermetallic quenching and (iii) the heterodinuclear compounds [Er2–2xYb2x(bdc)3(H2O)4]∞ (x = 0.2 and 0.5) for checking whether YbIII‐sensitized up‐conversion can be induced or not. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

An Unprecedented Family of Lanthanide-Containing Coordination Polymers with Highly Tunable Emission Properties

Reactions in water between mixtures of rare earth ions (Ln =Y, La-Tm, except Pm) and the sodium salt of terephthalic acid lead to an infinite family of isostructural heteropolynuclear coordination polymers. The monophasic character of the synthesized powders as well as the isostructurality of the heteropolynuclear compounds with the previously described mononuclear [Tb(2)(C(8)H(4)O(4))(3)(H(2)O)(4)](infinity) are ascertained on the basis of the X-ray powder diffraction diagrams. One family of heterodinuclear compounds has been studied in detail, that is, [(La(2-x)Y(x))(C(8)H(4)O(4))(3)(H(2)O)(4)](infinity) with 0 < or = x < or = 2. This study demonstrates the random character of the spatial distribution of the metallic ions. In order to demonstrate the high modularity of the physical properties, the solid-state luminescent properties of the compounds of general formula [(Eu(2-x)Tb(x))(C(8)H(4)O(4))(3)(H(2)O)(4)](infinity) with 0 < or = x < or = 2 have been studied and compared to those of the corresponding mixtures of [(Eu(2))(C(8)H(4)O(4))(3)(H(2)O)(4)](infinity) and [(Tb(2))(C(8)H(4)O(4))(3)(H(2)O)(4)](infinity). In order to confirm the general character of these studies, the compound containing in equal proportions all 13 rare earth ions between La and Tm (except Pm) plus Y has been synthesized and characterized. At last, the solid-state luminescent properties of compounds belonging to the ternary system [(Ce(2-x-y)Eu(x)Tb(y))(C(8)H(4)O(4))(3)(H(2)O)(4)](infinity) with x + y < or = 2 are briefly described.

Stabilizing the Elusive ortho-Quinone/Copper(I) Oxidation State Combination through π/π Interaction in an Isolated Complex

The heterodinuclear compound [(PhenQ)Cu(dppf)](BF4), PhenQ = 9,10-phenanthrenequinone and dppf = 1,1'-bis(diphenylphosphino)ferrocene, was identified structurally and spectroscopically (NMR, IR, UV-vis) as a copper(I) complex of a completely unreduced ortho-quinone. Crystallographic and DFT calculation results suggest that this stabilization of a hitherto elusive arrangement is partially owed to intramolecular pi/pi interactions phenyl/PhenQ. Intermolecular PhenQ/PhenQ pi stacking is also observed in the crystal. According to DFT calculations, the pi interactions are responsible for the considerably distorted coordination geometry at CuI with one short and one longer Cu-O and Cu-P bond, respectively, and with bond angles at copper ranging from 99 degrees to 133 degrees. Electrochemical reduction proceeds reversibly at low temperatures to yield an EPR spectroscopically characterized semiquinone-copper(I) species.

Cr(AA)(C 2O 4) 2] − and [Cu(bpca)] + as building blocks in designing new oxalato-bridged Cr IIICu II compounds [AA=2,2′-bipyridine and 1,10-phenanthroline; bpca=bis(2-pyridylcarbonyl)amide anion

The monouclear complex PPh 4[Cr(bipy)(ox) 2]·H 2O ( 1) and the heterodinuclear compounds [Cu(bpca)(H 2O)Cr(bipy)(ox) 2]·2.5H 2O ( 2) and [Cu(bpca)(H 2O)Cr(phen)(ox) 2]·2H 2O ( 3) [PPh 4 +=tetraphenylphosphonium cation, bpca=bis(2-pyridylcarbonyl)amide anion, ox=oxalate dianion, bipy=2,2′-bipyridine and phen=1,10-phenanthroline] have been synthesized and characterized by single-crystal X-ray diffraction. Discrete [Cr(bipy)(ox) 2] − mononuclear anions and tetraphenylphosphonium cations are present in 1 whereas the structures of 2 and 3 are made up neutral oxalato-bridged bimetallic Cr IIICu II units. The chromium environment is distorted octahedral in the three complexes: two nitrogen atoms from a bidentate bipy ( 1 and 2) or phen ( 3) ligand and four oxygen atoms from two oxalate groups ( 1– 3) build the coordination polyhedron around the chromium atom. The CrN(bipy) [2.055(3) and 2.078(3) Å for 1 and and 2.060(3) and 2.066(3) Å for 2] and CrN(phen) bond lengths [2.056(5) and 2.069(5) Å ( 3)] are somewhat longer than the CrO(ox) ones [values in the ranges 1.944(2)–1.955(2) ( 1), 1.948(2)–1.960(2) ( 2) and 1.945(4)–1.953(4) Å ( 3)]. The copper atom in 2 and 3 exhibits a distorted square-pyramidal surrounding: three bpca-nitrogen atoms [values of the CuN(bpca) bonds in the ranges 1.922(3)–2.017(3) ( 2) and 1.918(5)–2.004(6) Å ( 3)] and a water molecule [CuO w=1.952(3) ( 2) and 1.952(5) Å ( 3)] define the equatorial positions whereas an oxalate-oxygen atom occupies the axial site [CuO ox=2.253(2) ( 2) and 2.325(4) Å ( 3)]. The oxalate bridge in 2 and 3 exhibits a unusual bidentate/monodentate coordination mode, the metalmetal separation across this bridge being 5.283(1) ( 2) and 5.407(1) Å ( 3). Magnetic susceptibility measurements of 1– 3 in the temperature range 1.9–290 K reveal a Curie law behavior for the three complexes. The preparation of bimetallic systems by using [Cr(AA)(ox) 2] − (AA=α-diimine type ligand) as a complex ligand towards coordinatively unsaturated metal complexes is analyzed and discussed.

Concerning the question of f- and d-electron interactions in heterodinuclear compounds: synthesis, structure and 103Rh NMR investigations of LaRh-bimetallics

The reaction of the lanthanum ate-complex [{O(SiMe 2Ap) 2} 2LaLi(thf) 4] ( 1) (ApH=2-amino-4-methylpyridine, thf=tetrahydrofuran) with [(cod)RhCl] 2 (cod=cycloocta-1,5-diene) and [(C 2H 4) 2RhCl] 2 gave rise to three lanthanumrhodium bimetallic compounds: [{O(SiMe 2Ap) 2} 2LaRh(cod)] ( 2), [{O(SiMe 2Ap) 2} 2LaRh(C 2H 4)] ( 3), and [{O(SiMe 2Ap) 2} 2(thf)LaRh(C 2H 4)] ( 4). The metalmetal distances observed for 2, 3 and 4 are 3.3052(9), 3.0585(8), and 3.1598(7) Å, respectively. The structure and 103Rh NMR chemical shifts of the LaRh-bimetallics are discussed with regard to metal–metal interactions.

New heterometallic copper zinc alkoxides: synthesis, structure properties and pyrolysis to Cu/ZnO composites

The copper compound [(THF)KCu(O t Bu) 3] ∞ 1 was obtained by interaction of a 1:1 mixture of ZnCl 2/CuCl 2 with KO t Bu. Bi- and trifunctional aminoalcohols were used to synthesize the intramolecularly donor stabilized Cu(II) alkoxides Cu(OCH(R)CH 2NMe 2) 2 ( 3: R=Me, 4: =CH 2NMe 2) where 4 was structurally characterized. Lewis acid–base adduct formation with (Me 3Si) 3CZnCl gave the heterodinuclear compounds (Me 3Si) 3CZnCl · Cu(OCH(R)CH 2NMe 2) 2 ( 5: R=Me, 6: R=CH 2NMe 2), which were characterized by X-ray single-crystal structure analysis. The two metal centers Cu and Zn of 5 and 6 are bridged by two oxygen atoms to form a Cu–O–Zn core. Pyrolysis of compounds 5 and 6 in dry argon or a H 2/N 2 mixture at atmospheric pressure forms metallic copper and zinc oxide, whereas pyrolysis under O 2/Ar forms additionally oxidized copper species. Elemental analysis of the pyrolysis products showed carbon and nitrogen contamination. Scanning electron microscopy and energy dispersive X-ray analysis were performed to get information on the morphology and the chemical composition of the pyrolysis products.

Structure and Spectroelectrochemistry (UV/Vis, IR, EPR) of the Acceptor-Bridged Heterodinuclear Complex [(η5-C5Me5)ClRh(μ-bptz)Re(CO)3Cl](PF6), bptz = 3,6-Bis(2-pyridyl)-1,2,4,5-tetrazine

The title complex contains two organometallic reaction centers which are known to engage in hydride transfer catalysis (Rh) or in CO2 activation (Re), each after reductive elimination of the respective chloride ligand. The bridged heterodinuclear compound has been structurally characterized in the form where the chloride ligands are in cis-configuration relative to the bptz plane. The complex was subjected to cyclic voltammetry and spectroelectrochemical reduction to reveal an electrochemically reversible one-electron uptake by the bptz bridge, a rhodium chloride-dissociative second reduction to yield neutral [(η5-C5Me5)Rh(μ-bptz)Re(CO)3Cl], and a quasi-reversible third one-electron reduction.

Titanium σ-acetylides as building blocks for heterobimetallic transition metal complexes: synthesis and redox behaviour of π-conjugated organometallic systems

A series of related Ti σ-acetylides of the type {Ti}CCR ({Ti}=(η 5-C 5H 5) 2Ti(CH 2SiMe 3); 2: R=SiMe 3; 3: R=C 6H 3(CH 2NMe 2) 2-3,5; 4: R=C 6H 2I-4-(CH 2NMe 2) 2-3,5; 5: R=C 6H 4CN-4; 6: R=C 5H 4N-4; 7: R=Fc, Fc=(η 5-C 5H 4)Fe(η 5-C 5H 5); 8: R=C 6H 4(CC{Ti})-4) have been prepared by reacting the corresponding lithium acetylides with {Ti}Cl ( 1). The X-ray crystal structure determination of {Ti}CCSiMe 3 ( 2) is reported. This compound exhibits a one-dimensional (1D) arrangement with respect to the Ti–CC unit. The reaction of 2 with [CuCl] n afforded 1 and [CuCCSiMe 3] n ( 10) and is proposed to occur via prior formation of the dimeric intermediate [(η 2-{Ti}CCSiMe 3) 2Cu 2Cl 2]. The chemical oxidation of {Ti}CCFc, 7, with Ag[BF 4] yielded HCCFc and an undefined Ti species. Treatment of 5 or 6 with {Ru}NN{Ru} ({Ru}= mer, trans-[RuCl 2(NN′N)]; NN′N=η 3-C 5H 3N(CH 2NMe 2) 2-2,6) produced intensively coloured heterodinuclear compounds, such as [{Ti}CCC 5H 4N-4]{Ru} ( 16). In contrast, 5 and 6 react with cationic Pt compounds of the type [{Pt}·L][X] ({Pt}=[Pt(C 6H 3{CH 2NMe 2} 2-2,6] +; L=H 2O, MeCN; X=BF 4, OTf) to give product mixtures rather than defined compounds. Electrochemical studies on some of the bimetallic compounds show that the Ti(III)/Ti(IV) redox potential appears to be reversible and is shifted to a more negative value upon substitution of the Cl ligand in 1 by CCR (compounds 2– 8). Whereas the nature of R in {Ti}CCR has an influence on the Ti(III)/Ti(IV) redox potential, the attachment of a second metal onto the π-conjugated system has only negligible effect on the electrochemical properties of the Ti centre.