Homobimetallic Complexes Research Articles

Di-Mesoionic Carbene-Bridged Complexes of Rh2, Ir2, and RhIr: A Stepwise Metalation Strategy for the Synthesis of di-MIC-Bridged Mixed-Metal Systems

A meta-substituted benzene-bridged ditriazolium salt has been prepared using copper-catalyzed azide–alkyne cycloaddition (CuAAC or “click” chemistry) and methylation protocols. Metalation of this dicationic species by basic-ligand-containing [Rh(μ-OMe)(COD)]2 and [Ir(μ-OMe)(COD)]2 precursors provides homobimetallic complexes of Rh and Ir bridged by a 1,2,3-triazol-5-ylidene-type di-mesoionic carbene (di-MIC) via an “internal-base” strategy. By using only 1/2 equiv of the internal-base precursor, mononuclear MIC-anchored/pendent-triazolium intermediates have been isolated, in which only one end of the ditriazolium salt has been deprotonated and attached to Rh or Ir. Reaction of these pendent intermediates with another 1/2 equiv of an internal-base precursor affords either the aforementioned homobimetallic products or an analogous di-MIC-bridged, mixed-metal Ir/Rh complex.

Magnetic properties of structurally characterized binuclear lanthanide complexes bridged by 2,2′-bipyrimidine

A family of five homobimetallic complexes with magnetically-active trivalent lanthanides of the second half of the series with general formula [{Ln(tta)3}2(μ-bpm)] (Ln=Gd, Tb, Dy, Ho, Er, tta=2-thenoyltrifluoroacetonato, bpm=2,2′-bipyrimidine) has been structurally characterized by X-ray diffraction and the magnetic properties of these complexes are reported. The two lanthanide ions are coordinated to the bridging bpm ligand which connects the two metallic centers. The magnetic behavior of these complexes has been investigated. It revealed that a weak antiferromagnetic coupling is observed with the TbIII, DyIII, HoIII, and ErIII ions while a very weak ferromagnetic exchange between the two GdIII ions was observed.

Homobimetallic complexes containing Sn(IV) with acetylene dicarboxylic acid: their syntheses and structural interpretation by spectroscopic, semi-empirical, and DFT techniques

Homobimetallic carboxylates with general formulae (R3Sn)2 L (where R = Me, n‐Bu, Ph and L = acetylene dicarboxylate dianion) have been synthesized by refluxing disodium salt of acetylene dicarboxylic acid with triorganotin chlorides in 1 : 2 (L : M) molar ratio in methanol under reflux. These complexes have been characterized by elemental analyses, FTIR, and multinuclear NMR (1H, 13C) spectroscopies. DFT calculations have been performed for structural elucidation and results were compared with semi‐empirical data. FTIR data indicate bidentate chelation of the ligand with tin and the complexes exhibit five‐coordinate geometry in the solid state. Such coordination behavior is also supported by DFT and semi‐empirical studies. NMR data confirm four‐coordinate geometry in solution.

Homobimetallic complexes of ligand having O- and S-donor sites with same and different di- and trialkyl/aryltin(IV) moiety: their synthesis, spectral characterization and biological activities

Homobimetallic complexes with oxygen and sulphur donor ligand have been synthesized at room temperature under stirring conditions using R2SnCl2 (R = Me, n-Bu) and R3SnCl (R = Me, n-Bu, Ph) in 1:1 molar ratio. The synthesized complexes have been characterized by elemental analysis, IR and multinuclear NMR (1H, 13C) spectroscopy. These complexes have also been screened for their biological activities. IR data show that the ligand acts in a bidentate manner and exhibits trigonal bipyramidal geometry in solid state which is also confirmed by semi-empirical study. NMR data show that reported complexes exhibit tetrahedral geometry in solution. Results of antimicrobial screening activities indicated that complexes (6) and (7) are very effective antibacterial and antifungal agents, respectively, and they might indeed be a potential source of antimicrobial agents, while the complex (3) exhibits significant free radical scavenging ability with lower IC50 value of 99.47 ± 1.2 μg/mL. Results of cytotoxicity/haemolytic activity showed the significant value of % haemolysis for complex (7) (18.101 ± 2.3), while complex (4) was found to be least cytotoxic (5.733 ± 1.0). Only a few colonies are observed in mutagenicity testing by Ames test.

Homo- and hetero-bimetallic complexes of TTHA

The preparation is described of bimetallic complexes of the multidentate ligand, H6TTHA – triethylenetetraamine-N,N′,N″,N‴-hexaacetic acid. Attempts to use a stepwise approach systematically to prepare heterobimetallic complexes were unsuccessful and led in most cases to homobimetallic complexes or to heterobimetallic complexes whose stoichiometry did not reflect the stoichiometry of the preparation. Nonetheless, on one occasion a monodisperse heterobimetallic complex of rhodium and zinc was isolated, which represents the first properly characterised heterobimetallic complex of TTHA.

Magneto-structural and photophysical investigations on a dinuclear Sm(III) complex featuring 2,2′-bipyrimidine

A homobimetallic complex, [{Sm(tta)3(MeOH)}2(μ-bpm)]·1bpm (tta=2-thenoyltrifluoroacetonato, bpm=2,2′-bipyrimidine) has been synthesized and structurally characterized by single-crystal X-ray diffraction. Magnetic measurements (between 5 and 295K) show that the two metal centers bridged by the bpm connector are magnetically almost isolated. The SmIII emission is observed upon excitation in a wide range of wavelengths going from the UV to the visible (250–500nm).

Structures and Electronic Spectroscopy of Rhodium-Based Complexes: a Theoretical Study on Promising Optical Materials

A series of rhodium-based complexes were explored theoretically to understand their application in optical materials and potential photocatalytic activity. Better structural description of [RhAu(CNH)2(PH2CH2PH2)2]2+ (1) were achieved with the ab initio MP2, XαVWN, and SVWN methods. To fine-tune the electronic spectroscopy, two analogues of 1 were taken into account by varying its Au metal center and bridging bidentate ligand. The experimental spectra were well reproduced by our TD-DFT calculations. It was shown that the lowest-energy absorption of homobimetallic Rh-Rh complex occurs in lower-energy region than those of heterobimetallic Rh-Au complexes.

Different coordination behavior of a catechol phosphine and its sulfide: Formation of an unprecedented dinuclear rhodium complex with a non-coordinated P[dbnd]S unit

Sulfurization of 3-[(diphenylphosphinyl)methyl]benzene-1,2-diol 1 produced phosphine sulfide 3. Both ligands reacted easily to form gold(I) and rhodium(I) complexes which were characterized by analytical and spectroscopic data, and single-crystal X-ray diffraction studies. Whereas the phosphine prefers to form complexes with a metal-to-ligand ratio of 1:2 with both metals, the phosphine sulfide exhibits a reduced donor power and yields only a 1:1 complex with AuCl. With rhodium(I), formation of a homobimetallic complex with a metal-to-ligand ratio of 2:1 was found. This complex displays an unusual coordination of both metal atoms to the catechol moiety whereas the phosphine sulfide moiety remains inactive.

Synthesis and structures of homo- and heterobimetallic rhodium(i) and/or iridium(i) complexes of binucleating bis(1-pyrazolyl)methane ligands

The synthesis of a series of Rh(I) and Ir(I) homobimetallic complexes using three different linking scaffolds is described. The cyclooctadiene (COD) complexes [M(2)(COD)(2)(L(scaffold))][BAr(F)(4)](2) (2-7) where M = Rh(I) or Ir(I), and L(scaffold) = bis(1-pyrazolyl)methane ligands, p-C(6)H(4)[CH(pz)(2)](2) (1a), m-C(6)H(4)[CH(pz)(2)](2) (1b) and the anthracene-bridged 1,8-C(14)H(8)[CH(pz)(2)](2) (1c) were synthesized. The COD co-ligands of 2-7 were replaced with the carbonyl co-ligands to form the analogous homobimetallic complexes, [M(2)(CO)(4)(L(scaffold))][BAr(F)(4)](2) (8-13). The solid-state structures of the dicationic homobimetallic complexes 2, 3, 5, 6, 9, and 10, as well as cationic monometallic complexes 15 and 22 of ligands 1b and 1c respectively, were characterized using X-ray crystallography. The solid-state XRD structures of the resulting dirhodium and diiridium complexes with the para- and meta-phenylene and anthracene scaffolds show that there are distinct differences between structures of complexes 2-10 due to the variation in the scaffold structures, in particular the relative positions of the two metal centres. Heterobimetallic RhIr complexes of the m-C(6)H(4)[CH(pz)(2)](2) ligand were also synthesized using a stepwise approach, and the observed exchange of the metal centres in the heterobimetallic complexes was found to be dependent on the nature of the coligand.

The use of 1,2-dipiperidinoacetylene for the preparation of monometallic diaminoacetylene and homo- or heterobimetallic diaminodicarbene ruthenium(ii) complexes

The reaction of the ynediamine 1,2-dipiperidinoacetylene (1) with [(η(2)-COE)Cr(CO)(5)], [(THF)W(CO)(5)] and [RuCl(2)(η(6)-cymene)](2) afforded homobimetallic complexes 2a, 2b and 3, in which the diaminoacetylene 1 acts as a bis(aminocarbene) ligand by bridging two complex fragments Cr(CO)(5) (in 2a), W(CO)(5) (in 2b) and RuCl(2)(η(6)-cymene) (in 3). The reaction of 1 with [RuCl(2)(PPh(3))(3)] gave trans-[(1)RuCl(PPh(3))(2)]Cl, [4]Cl, in which the alkyne 1 coordinates as a 4-electron donor ligand. The cation 4 represents a rare example of a square-planar Ru(II) complex with a low-spin ground state (S = 0), and its stability can be ascribed to the strong alkyne-metal π-interaction as confirmed by DFT calculations. Treatment with one or two equivalents of NaBPh(4) in acetonitrile gave [4]BPh(4) and the dicationic [(1)Ru(PPh(3))(2)(CH(3)CN)(2)](BPh(4))(2), [5](BPh(4))(2). [4]Cl can be used for the preparation of heterobimetallic Ru-Pd bis(aminocarbene) complexes by reaction with [(MeCN)(2)PdCl(2)], resulting in the formation of bimetallic 6 and tetrametallic 7.

A homobimetallic complex of chromium(0) with a σ-borane component

The synthesis, characterization, and reactivity of a chromium(0) complex bearing an amine-borane moiety (η(6)-C(6)H(5)CH(2)NMe(2)·BH(3))Cr(CO)(3) (2) is reported. Photolysis of complex 2 results in the elimination of a CO ligand followed by the formation of an intramolecular σ-borane complex (η(1)-(η(6)-C(6)H(5)CH(2)NMe(2)·BH(2)-H))Cr(CO)(2) (3). This species was characterized in solution by NMR spectroscopy. Reaction of complex 2 with photochemically generated (OC)(5)Cr(THF) affords a novel homobimetallic σ-borane complex (OC)(3)Cr(η(6)-C(6)H(5)CH(2)NMe(2)·BH(2)-H-Cr(CO)(5)) (4), wherein one of the BH moieties is bound to the chromium center in an η(1)-fashion. The σ-borane complex 4 was isolated in moderate to good yield (72%). The BH(3) fragment in the complexes 3 and 4 are highly dynamic involving exchange of the BH hydrogen bound to the metal with the terminal BH hydrogen atoms. The dynamics has been studied using variable-temperature NMR spectroscopy. Complexes 2 and 4 have been characterized by X-ray crystallography.

Homobimetallic Ruthenium−Arene Complexes Bearing Vinylidene Ligands: Synthesis, Characterization, and Catalytic Application in Olefin Metathesis

Five new arylvinylidene complexes with substituents ranging from electron-donating to strongly withdrawing (p-OMe, p-Me, p-Cl, p-CF3, and m-(CF3)2) were isolated in high yields by reacting [(p-cymene)Ru(μ-Cl)3RuCl(η2-C2H4)(PCy3)] (3) with the corresponding phenylacetylene derivatives. The known phenylvinylidene complex [(p-cymene)Ru(μ-Cl)3RuCl(═C═CHPh)(PCy3)] (5) was also obtained from [RuCl2(p-cymene)]2, tricyclohexylphosphine, and phenylacetylene under microwave irradiation. The influence of the remote aryl substituents on structural features was investigated by IR, NMR, and XRD spectroscopies. A very good linear relationship was observed between the chemical shift of the vinylidene α-carbon atom and the Hammett σ-constants of the aryl group substituents. The catalytic activity of the six homobimetallic complexes was probed in various types of olefin metathesis reactions. Unsubstituted phenylvinylidene compound 5 served as a lead structure for these experiments. Its reaction with norbornene afforded hig...

The shortest metal‐metal bond

The synthesis and isolation of stable bimetallic complexes that contain formally quintuply bonded transition metals is a novel and emerging field of science. Efforts have been undertaken in designing and tuning the ligands to achieve a very short (actually the shortest) metal-metal bond. The motivation for these efforts arose from the expectation that an increasing bond order may go along with a shortening of the bond length. In consequence, formally quintuply bonded bimetallics could have shorter metal-metal distances than quadruply bonded ones. A chromium homo-bimetallic complex with a Cr-Cr bond length of 1.7293(12) Å has been synthesized, and a formal bond order of five was assigned. This compound holds the record for the shortest metal-metal bond in a stable molecule to date. At this stage, there is no evidence that additional shortening is impossible.

Synthesis of Oxygen- and Sulfur-Bridged Dirhodium Complexes and Their Use As Catalysts in the Chemoselective Hydrogenation of Alkenes

Oxygen-bridged and sulfur-bridged rhodium homobimetallic complexes were synthesized as air-stable crystals by using 2,6-bis(phosphanylmethyl)phenolate and -thiophenolate as the ligands, respectively. The oxygen-bridged dirhodium complex has a symmetrical structure where the carbon atom at the ipso position, oxygen, and two rhodium atoms are located in the same plane. It is thermally stable compared to the sulfur-bridged dirhodium complex and shows catalytic activity for hydrogenation of alkenes with high chemoselectivity.

Synthesis, physico-chemical and spectral investigations of novel homo-bimetallic mixed-ligand complexes: 57Fe Mössbauer parameters of [Fe2(imda)2(H2O)3Cl

The newly prepared homo-bimetallic complexes [M(2)(imda)(2)(H(2)O)(4)], [M(2)(imda)(2)(Bipy)(2)] (M=Co, Ni or Cu) and [Fe(2)(imda)(2)(H(2)O)(3)Cl] (H(2)imda=iminodiacetic acid and Bipy=2,2'-bipyridine) have been studied employing IR, FAB-mass, (1)H and (13)C NMR, EPR and ligand field spectra, which indicated a high-spin state of metal ion with hexa-coordinate environment. (57)Fe Mössbauer data of the homo-bimetallic complex [Fe(2)(imda)(2)(H(2)O)(3)Cl] confirm a high-spin configuration with Fe (+/-3/2-->1/2) nuclear transitions and the presence of Kramer's double degeneracy. At RT, the spin-spin interactions of the neighbouring nuclei (Fe(3+)-Fe(3+)=S(5/2)-S(5/2)) are anti-ferromagnetically coupled. However, at LNT, the complex acquires a mixed-valent [Fe(III)-Fe(II)] composition corroborated from the X-band EPR data. CV studies indicated the presence of quasi-reversible redox Cu(II/I), Cu(II/III), Fe(III/II), Fe(III/I) and Fe(II/I) couples.

Synthesis, characterization and photophysics of bimetallic manganese(I) and ruthenium(II) complexes

A series of new manganese(I) and ruthenium(II) monometallic and bimetallic complexes made of 2,2′-bipyridine and 1,10-phenanthroline ligands, [Mn(CO) 3(NN)(4,4′-bpy)] +, [{(CO) 3(NN)Mn} 2(4,4′-bpy)] 2+ and [(CO) 3(NN)Mn(4,4′-bpy)Ru(NN) 2Cl] 2+ (NN = 2,2′-bipyridine, 1,10-phenanthroline; 4,4′-bpy = 4,4′-bipyridine) are synthesized and characterized, in addition to already known ruthenium(II) complexes [Ru(NN) 2Cl(4,4′-bpy)] + and [Cl(NN) 2Ru(4,4′-bpy)Ru(NN) 2Cl] 2+. The electrochemical properties show that there is a weak interaction between two metal centers in Mn–Ru heterobimetallic complexes. The photophysical behavior of all the complexes is studied. The Mn(I) monometallic and homobimetallic complexes have no detectable emission. In Mn–Ru heterobimetallic complexes, the attachment of Mn(I) with Ru(II) provides interesting photophysical properties.

Synthesis and Characterization of Proximal Dinuclear Complexes of Palladium Supported by 2,6-Bis(arylimino)phenoxy (aryl = 2,6-diisopropylphenyl and 2,4,6-tri-tert-butylphenyl) and 3,6-Bis(imino(2,6-diisopropylphenyl))pyridazine Ligands

Two kinds of binucleating ligands, 2,6-bis(arylimino)phenoxy (1a: aryl = 2,6-diisopropylphenyl; 1b: aryl = 2,4,6-tri-tert-butylphenyl) and 3,6-bis(imino(2,6-diisopropylphenyl))pyridazine (2), were prepared, and their proximal complexation with two palladium atoms was studied. Treatment of the sodium compounds of 1a,b with 2 equiv of PdCl2(PhCN)2 and PdMeCl(cod) afforded the corresponding homobimetallic complexes, [2,6-bis(arylimino)phenoxy][RPd(μ-Cl)PdR] (4a: R = Cl, aryl = 2,6-diisopropylphenyl; 4b: R = Cl, aryl = 2,4,6-tri-tert-butylphenyl; 7a: R = Me, aryl = 2,6-diisopropylphenyl; 7b: R = Me, aryl = 2,4,6-tri-tert-butylphenyl), whose structures were characterized spectroscopically and crystallographically. In the reaction between the sodium compound of 1a with 1 equiv of PdCl2(PhCN)2, we detected the NaCl adduct of mononuclear palladium species 5a, which, upon release of NaCl, formed a dimeric complex, ([2,6-bis(2,6-diisopropylphenylimino)phenoxy](PdCl])2 (4a), as confirmed by X-ray analysis. Complexation of 2 with 2 equiv of PdCl2(PhCN)2 and PdMeCl(cod) in the presence of 1 equiv of AgBF4 resulted in the formation of the corresponding cationic complexes ([3,6-bis(imino(2,6-diisopropylphenyl))pyridazine][RPd(μ-Cl)PdR])(BF4) (9a: R = Cl; 9b: R = Me), whose RPd(μ-Cl)PdR skeletons (R = Cl and Me) were revealed spectroscopically and crystallographically.

A phosphine complex of copper (I) bromide as single-source precursor for the aerosol-assisted chemical vapour deposition of phosphide

A new homobimetallic complex [Cu 2(tpp) 2(dppm)Br 2] ( 1) of copper(I) bromide with triphenylphosphine (tpp) and bis-diphenylphosphinomethane (dppm) has been synthesized and charaterized by m.p., elemental analysis, FT-IR, 1H NMR, mass spectrometry, thermal studies and single crystal X-ray analysis. The solid-state molecular structure of 1, belonging to the monoclinic crystal system with space group P2 1/ n, describes it as a neutral dinuclear species in which two copper atoms are bridged together through two bromides and a dppm ligand and each copper atom possesses a distorted tetrahedral geometry. Complex 1 was studied as a single-source precursor for the fabrication of phase pure thin films of Cu 3P by aerosol-assisted chemical vapour deposition. The films have been characterized by PXRD, SEM and ED-XRF analyses and found to exhibit the particles size range 200−400 nm with high purity and surface uniformity.

Multimetallic arrays: Symmetrical bi-, tri- and tetrametallic complexes based on the group 10 metals and the functionalisation of gold nanoparticles with nickel-phosphine surface units

Homobimetallic complexes of nickel, palladium and platinum, [(L2M)2(S2CNC4H8NCS2)]2+, are formed on reaction of the piperazine bis(dithiocarbamate) linker, KS2CNC4H8NCS2K, with [MCl2L2] (M=Ni, L2=dppe, dppf; M=Pd, L2=dppf; M=Pt, L=PEt3, PMePh2, PPh3, L2=dppf). [{Pd(C,N-C6H4CH2NMe2)}2(S2CNC4H8NCS2)] can be obtained in the same way. On reaction of [MCl2L2] (M=Pd, Pt) with the zwitterion S2CNC4H8NH2, a symmetrisation process occurs to yield a mixture of the complexes [M(S2CNC4H8NH2)L2]2+ and [(L2M)2(S2CNC4H8NCS2)]2+. However, the monometallic complexes [L2Ni(S2CNC4H8NH2)]2+ (L2=dppe, dppf) and [(L2Ni)2(S2CNC4H8NCS2)]2+ can be prepared without ready symmetrisation. Starting from the previously reported [(dppm)Ru(S2CNC4H8NH2)]2+, the heterotrimetallic products [(dppm)Ru(S2CNC4H8NCS2)M(dppf)]2+ (M=Pd, Pt) can be prepared without symmetrisation occurring. The crystal structures of five complexes are reported. The metalla-dithiocarbamate complexes [L2Ni(S2CNC4H8NCS2)] (L2=dppe, dppf) were used to functionalise the surface of gold nanoparticles by the displacement of a citrate shell to yield NiAu and FeNiAu materials.

Novel homo-bimetallic complexes of [N 10] macrocyclic ligand modified with tetrapeptide function: Biological activities, spectral and cyclic voltammetric studies

The bimetallic complexes [M 2LCl 4] (M = Cr, Co, Ni, Cu) prepared via metal template cyclization reactions were characterized by physico-chemical and spectroscopic methods. L is a 30-membered [N 10] macrocycle with tetraamide functions bind metal ions through aza donors forming hexa-coordinate geometry. The perspective view and important structural parameters have been computed from the molecular model (MOPAC) method. The electrochemical studies indicate existence of quasi-reversible redox couples in solution. The metal complexes were screened (in vitro) against a few pathogenic fungi and bacteria to assess their growth inhibiting potential.