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Bonding Mode (bonding + mode)
Selected AbstractsTryptophan ,-Electron System Capping a Copper(I) Binding Site,A New Organometallic Bonding Mode in ProteinsCHEMBIOCHEM, Issue 11 2008Olaf Kühl Dr. ,2 -Arene coordination (dotted lines) from the aromatic tryptophan side chain to CuI (red) in the prokaryotic CuI -transport protein CusF represents a new organometallic interaction in biology. [source] Nucleophilic Addition of Water and Alcohols to Dicyanonitrosomethanide: Ligands with Diverse Bonding Modes in Magnetically Coupled d-Block ComplexesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 1 2010Anthony S. R. Chesman Abstract Ligands resulting from the transition-metal-promoted nucleophilic addition of water or an alcohol to dicyanonitrosomethanide ions (dcnm) have been utilised in the formation of a large series of polynuclear complexes. Addition of water to dcnm results in formation of carbamoylcyanonitrosomethanide (ccnm); deprotonation of this ligand gives amidocarbonyl(cyano)nitrosomethanide (acnm), which has been incorporated into the trinuclear complex [Cu3(acnm)2(dmae)2(H2O)2] [dmae = 2-(dimethylamino)ethoxide] (1) which shows strong antiferromagnetic coupling with an exchange coupling constant, J = ,500 cm,1. [Cu(acnm)(NH3)2], (2) marks the first instance of acnm facilitating the formation of a coordination polymer, namely a 1D chain with intramolecular hydrogen bonding. Attempts to synthesise 2 through different reaction conditions instead resulted in the mononuclear [Cu(acnm)(NH3)2(py)] (py = pyridine) (3). The addition of ethanol to dcnm results in cyano[imino(ethoxy)methyl]nitrosomethanide (cenm) which features in the mononuclear [Cu(cenm)2(H2O)2] (4) and polymeric {[Cu(cenm)2]2·H2O}, (5). The latter is the first example of the cenm ligand in a coordination polymer and has a highly unusual coordination mode through the nitrile groups and extremely weak antiferromagnetic coupling. {[Mn3(ccnm)2(EtOH)2(OAc)4]·2EtOH}, (6) and (Et4N)2[Cu(ccnm)4] (7) contain previously unobserved coordination modes of the ccnm ligand while the complex [Mn(cmnm)3Mn(bipy)(MeOH)](ClO4) (8) {cmnm = cyano[imino(methoxy)methyl]nitrosomethanide, bipy = 2,2,-bipyridine} displays weak antiferromagnetic coupling between manganese atoms with J = ,1.44 cm,1. A change in the solvent systems used in the synthesis of 7 results in the formation of the mononuclear complexes [Mn(bipy)2(dcnm)2] (9) or [Mn(bipy)2(H2O)(dcnm)](dcnm)·H2O (10) and [Mn(bipy)2(dcnm)(H2O)](dcnm) (11). The addition of ethlyene glycol monomethyl ether to dcnm gives cyano[imino(2-methoxyethoxy)methyl]nitrosomethanide (cgnm) and the formation of [Cu(cgnm)2(H2O)2] (12). [source] Novel Bonding Modes between Tetrathiafulvalenes (TTFs) and Transition Metal Centers: ,-Bonding and Covalent TTFSiMe2,MLn Coordination to PlatinumEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 13 2004Mathuresh N. Jayaswal Abstract Two novel strategies for coordinating TTF to transition metal centers have been developed. The reaction of tetrathiafulvalene (TTF) or 3,4-dimethyltetrathiafulvalene (o -Me2TTF) with [Pt(,2 -C2H4)(PPh3)2] leads to the , complexes [Pt(,2 -TTF)(PPh3)2] (1) and [Pt(,2 - o -Me2TTF)(PPh3)2] (2), respectively. An X-ray crystallographic study performed on 2 confirmed, that TTFs act as a , acidic ligand. NMR studies revealed the existence, in solution, of an equilibrium between free and complexed TTF. Dilithiation of o -Me2TTF and subsequent silylation with ClSiMe2H afforded 3,4-dimethyl-3,,4,-(dimethylsilyl)tetrathiafulvalene (3), which has been structurally characterized. 3 reacts by oxidative addition across [Pt(,2 -C2H4)(PPh3)2] to give [Pt{,2 - o -(SiMe2)2TTFMe2}(PPh3)2] (4), in which the TTF ligand is covalently ligated to platinum via SiMe2 bridges. The redox properties of 3 and 4 have been investigated by cyclic voltammetry. Strong cathodic shifts of the two redox processes were observed for 4, implying the TTF core. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Synthesis and Structural Characterization of Three-Coordinate MnII, FeII, and ZnII Complexes Containing a Bulky Diamide Ligand [DippN(CH2)3NDipp]2, (Dipp = 2,6- iPr2C6H3)EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 24 2004Jianfang Chai Abstract The reaction of DippNH(CH2)3NHDipp (1) (Dipp = 2,6- iPr2C6H3) with 2 equiv. of MeLi in diethyl ether resulted in the formation of the monomeric dilithium salt [(Dipp)N(CH2)3N(Dipp)][Li(OEt2)]2 (2) in high yield. Further reactions of 2 with MnCl2, FeCl2, and ZnCl2, respectively, afforded the complexes [M2{N(Dipp)(CH2)3N(Dipp)}2] [M = Mn (3), Fe (4), Zn (5)] with three-coordinate metal centers. Complexes 2,5 were characterized by X-ray structural analysis. The complexes contain a nonplanar MNMN central core. The diamide ligand in complexes 3,5 displays a boat conformation and is both chelating and bridging, so that one of the nitrogen atoms is three-coordinate and the other four-coordinate. Complexes 3,5 are the first examples with diamide ligands in such a bonding mode. The magnetic investigations of compounds 3 and 4 reveal an antiferromagnetic exchange between the metal atoms. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Synthesis and Characterization of Potassium Complexes Containing Terminal ,2 -Pyrazolato LigandsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 13 2004Wenjun Zheng Abstract The potassium complexes [K(,2 -3,5-R2pz)(,6 -18-crown-6)] (R = Ph, tBu; pz = pyrazolato) were prepared by treatment of 3,5-diphenylpyrazole or 3,5-di- tert -butylpyrazole with potassium hydride in the presence of 18-crown-6. These complexes contain ,6 -18-crown-6 and terminal ,2 -pyrazolato ligands, and constitute the first examples of group 1 metal complexes with this pyrazolato ligand coordination mode. In contrast to [K(,2 -3,5-Ph2pz)(,6 -18-crown-6)] and [K(,2 -3,5- tBu2pz)(,6 -18-crown-6)], the aqua complex [K(,2 -3,5-Me2pz)(H2O)(,6 -18-crown-6)] was obtained when 3,5-dimethylpyrazole was treated with potassium hydride and 18-crown-6 in the presence of a small amount of water. [K(,2 -3,5-Me2pz)(H2O)(,6 -18-crown-6)] contains an ,2 -pyrazolato ligand that is bent towards being co-facial with the best plane of the 18-crown-6 ligand, to allow hydrogen bonding between the pyrazolato ligand nitrogen atoms and the coordinated aqua ligand. The hydrogen bonding thus confers a novel terminal ,-facial ,2 -bonding mode to the pyrazolato ligand. All compounds were characterized by elemental analysis, NMR spectroscopy, and mass spectrometry. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Bond Orders between Molecular FragmentsCHEMISTRY - A EUROPEAN JOURNAL, Issue 8 2006Adam J. Bridgeman Dr. Abstract An extension of the Mayer bond order for the interaction between molecular fragments is presented. This approach allows the classical chemical concepts of bond order and valence to be utilised for fragments and the interactions between the fragments and symmetry-adapted linear combinations to be analysed. For high-symmetry systems, the approach allows the contribution from each irreducible representation to be assessed and provides a semiquantitative measure of the role of each bonding mode to interfragment interactions. The utility of this tool has been examined by a study of the bonding in symmetrical sandwich complexes. The validity of the frontier-orbital approach and the contributions from each frontier-orbital interaction can also be assessed within this model. As demonstrated by a study of a number of mixed-sandwich complexes, the model proves to be especially useful for low-symmetry systems in which separation of the ,, , and , roles in bonding of the ligand is difficult to assess. The fragment bond order describes the interaction between preoptimized fragment orbitals and is independent of the charges that are placed on these fragments. Although the method allows the chemist to define fragments in any way they choose, most insight is gained by using the same frontier orbitals employed so successfully in perturbational molecular-orbital approaches. The results are free from the influence of the electron-counting method used to describe fragments, such as the rings and metals in sandwich complexes. [source] The pH effects on the growth rate of KDP (KH2PO4) crystal by investigating Raman active lattice modesJOURNAL OF RAMAN SPECTROSCOPY, Issue 9 2007M. Badrouj Abstract We report on the dependence of the pH value on the growth rates of KDP single crystals. Extensive experimental work has been carried out in order to find the optimum pH ranges for growing KDP single crystals with suitable sizes and high optical quality. Different techniques including micro-Raman back-scattering spectroscopy, UV/vis/IR transmission spectroscopy and X-ray diffraction have been employed for this investigation. Deuterated substituted single crystals of KDP and DKDP also have been grown for the investigation of growth rates and Raman active mode identification purposes. The molecular vibration modes of the grown crystals, including internal modes of PO4 tetrahedrons molecular vibrations, external modes of optical phonons and hydrogen bonding modes have been determined exactly by micro-Raman back-scattering spectroscopy. The best pH values of the solution for the KDP crystal growth with reasonably higher growth rates from aqueous solutions that have been supersaturated ata temperature range of 30,50 °C have been found to be in the pH range of 3.2,5.4. Copyright © 2007 John Wiley & Sons, Ltd. [source] A novel threefold-interpenetrating primitive cubic network based on a dinuclear Zn2 nodeACTA CRYSTALLOGRAPHICA SECTION C, Issue 2 2009Yun-Peng Diao In the mixed-ligand metal,organic polymeric compound poly[[,2 -1,4-bis(imidazol-1-yl)benzene](,2 -terephthalato)dizinc(II)], [Zn2(C8H4O4)2(C12H10N4)]n or [Zn2(bdc)2(bib)]n [H2bdc is terephthalic acid and bib is 1,4-bis(imidazol-1-yl)benzene], the asymmetric unit contains one ZnII ion, with two half bdc anions and one half bib molecule lying around inversion centers. The ZnII ion is in a slightly distorted tetrahedral environment, coordinated by three carboxylate O atoms from three different bdc anions and by one bib N atom. The crystal structure is constructed from the secondary building unit (SBU) [Zn2(CO2)2N2O2], in which the two metal centers are held together by two bdc linkers with bis(syn,syn -bridging bidentate) bonding modes. The SBU is connected by bdc bridges to form a two-dimensional grid-like (4,4)-layer, which is further pillared by the bib ligand. Topologically, the dinuclear SBU can be considered to be a six-connected node, and the extended structure exhibits an elongated primitive approximately cubic framework. The three-dimensional framework possesses a large cavity with dimensions of approximately 10 × 13 × 17,Å in cross-section. The potential porosity is filled with mutual interpenetration of two identical equivalent frameworks, generating a novel threefold interpenetrating network with an ,-polonium topology [Abrahams, Hoskins, Robson & Slizys (2002). CrystEngComm, 4, 478,482]. [source] The Diversity of Difluoroacetylene Coordination Modes Obtained by Coupling Fluorocarbyne Ligands on Binuclear Manganese Carbonyl SitesCHEMISTRY - A EUROPEAN JOURNAL, Issue 22 2009Xian-mei Liu Abstract One Mn or two? The fluorocarbyne manganese carbonyl complexes [Mn(CF)(CO)n] (n=3,,4) and [Mn2(CF)2(CO)n] (n=4,7; see picture) have been investigated by density functional theory. In mononuclear complexes the CF ligand behaves very much like the NO ligand in terms of ,-acceptor strength. In binuclear complexes the two CF ligands couple in many of the low-energy structures to form a bridging C2F2 ligand derived from difluoroacetylene. Recent work has shown that the fluorocarbyne ligand CF, isoelectronic with the NO ligand, can be generated by the defluorination of CF3 metal complexes, as illustrated by the 2006 synthesis by Hughes et,al. of [C5H5Mo(CF)(CO)2] in good yield by the defluorination of [C5H5Mo(CF3)(CO)3]. The fluorocarbyne ligand has now been investigated as a ligand in the manganese carbonyl complexes [Mn(CF)(CO)n] (n=3,,4) and [Mn2(CF)2(CO)n] (n=4,7) by using density functional theory. In mononuclear complexes, such as [Mn(CF)(CO)4], the CF ligand behaves very much like the NO ligand in terms of ,-acceptor strength. However, in the binuclear complexes the two CF ligands couple in many of the low-energy structures to form a bridging C2F2 ligand derived, at least formally, from difluoroacetylene, FCCF. The geometries of such [Mn2(C2F2)(CO)n] complexes suggest several different bonding modes of the bridging C2F2 unit. These include bonding through the orthogonal ,,bonds of FCCF, similar to the well-known [R2C2Co2(CO)6] complexes, or bonding of the C2F2 unit as a symmetrical or unsymmetrical biscarbene. This research suggests that fluorocarbyne metal chemistry can serve as a means for obtaining a variety of difluoroacetylene metal complexes, thereby avoiding the need for synthesizing and handling the very unstable difluoroacetylene. [source] | ||||||||||