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1.
A novel supramolecular strategy to prepare bidentate ligands via the assembly of functionalised monomeric ligands on a dimeric zinc(II) porphyrin template is presented; the assembled bidentate ligands show chelating behaviour and their rhodium complexes display enhanced selectivity in the hydroformylation compared to the non-template analogue. 相似文献
2.
Slagt VF van Leeuwen PW Reek JN 《Dalton transactions (Cambridge, England : 2003)》2007,(22):2302-2310
Selective metal-ligand interactions have been used to prepare supramolecular bidentate ligands by mixing monodentate ligands with a suitable template. For these assemblies pyridine phosphorus ligands and a zinc(II) porphyrin dimer were used. In the rhodium-catalysed hydroformylation of 1-octene and styrene improved selectivities have been obtained for some of the assembled bidentate ligand systems. In the palladium catalysed asymmetric allylic alkylation similar effects were observed; the enantioselectivity increased by using a bisporphyrin template. The preparation of supramolecular catalyst systems was also explored using tin-oxygen interactions. Dihydroxotin(IV) porphyrin and carboxylic phosphorus ligands assemble into supramolecular ligands and the phosphorus donor atom coordinates to transition metals. The stronger oxygen-tin bond, compared to pyridine-zinc does not result in a better performance of the catalyst. 相似文献
3.
《Journal of Inorganic and Nuclear Chemistry》1976,28(9):1605-1609
Transition metal ion complexes of the potentially bidentate ligand 2-pyridylcarbinol N-oxide have been prepared. They are characterized and identified by chemical analysis and physical measurements. Their IR and electronic spectra are discussed with regard to monodentate or bidentate bonding of the ligand. The Cr(III) and Fe(III) complexes each contain two 2-pyridylcarbinol N-oxide ligands and a conjugate base of the carbinol in their coordination spheres. The remaining metal ions crystallized with either four (Mn(II), Ni(II), Cu(II), Zn(II)) or six (Co(II)) neutral ligands. 相似文献
4.
《Journal of Coordination Chemistry》2012,65(2):335-347
Abstract Mn(II) cations in the crystals of trisaquobis(μ-thiophen-2-carboxylato-O,O′)(thiophen-2-carboxylato-O)manganese(II) monohydrate are bridged by oxygen atoms donated by bidentate carboxylic groups of two thiophen-2-carboxylate ligands. In addition, each Mn(II) ion is coordinated by an oxygen atom of a monodentate carboxylic group of this ligand and three oxygen atoms of water molecules. The coordination around the Mn(II) cation is octahedral. The bridging of the ligands results in molecular ribbons propagating in the c-direction of the crystal held together by C?H…O hydrogen bonds. The crystal structure of diaquobis(μ-furan-3-carboxylato-O,O′)di(μ-furan-3-carboxylato-O,O)(μ-aqua-O)manganese(II) consists of dinuclear structural units. In each molecule Mn(II) cations are O,O′ bridged by oxygen atoms of bidentate carboxylic groups of two furan-3-carboxylate ligands and have a water located between the Mn cations. The units are O,O′ bridged to Mn(II) ions located in adjacent units by bidentate oxygen atoms, forming molecular ribbons extending in the c-direction. Octahedral coordination around each Mn(II) ion is completed by two water molecules. The octahedra around two adjacent metal ions in the unit share a common apex - the bridging oxygen atom of the water molecule. The ribbons are held together by C?H…O hydrogen bonds between furan ring oxygen atoms and the carbon atoms of adjacent furan rings. 相似文献
5.
Slagt VF Röder M Kamer PC Van Leeuwen PW Reek JN 《Journal of the American Chemical Society》2004,126(13):4056-4057
We report a new strategy for the preparation of chelating bidentate ligands, which involves just the mixing of two monodentate ligands functionalized with complementary binding sites. In the current example, the assembly process is based on selective metal-ligand interactions, using phosphite zinc(II) porphyrins 1-6 and the nitrogen donor ligands b-i. From only 16 monodentate ligands, a library of 60 palladium catalysts based on 48 bidentate ligand assemblies has been prepared. The relatively small catalyst library gave a large variety in the selectivity of the alkylation of rac-1,3-diphenyl-2-propenyl acetate. Importantly, small variations in the building blocks lead to large differences in the enantioselectivity imposed by the catalyst (up to 97% ee). 相似文献
6.
The synthesis and evaluation of the liquid crystalline properties of non-conventional liquid crystals, consisting of two non-identical mesogenic segments interconnected via a paraffinic chain spacer, are of considerable current interest. In particular, chiral dimesogens possessing a cholesteryl ester unit as the chiral entity joined to other aromatic mesogens through a polymethylene spacer have shown unique and interesting thermal behaviour. In continuation of our investigations on this topic, here we present the synthesis and characterization of the first examples of cholesterol-based unsymmetrical dimesogenic bidentate ligands and their Cu(II) and Pd(II) metal-organic systems (metallomesogens). Our studies reveal that the dimesogenic bidentate ligands exhibit multiple mesophases, whereas their metal complexes stabilize only the mesophase. 相似文献
7.
《Liquid crystals》2001,28(3):351-355
The synthesis and evaluation of the liquid crystalline properties of non-conventional liquid crystals, consisting of two non-identical mesogenic segments interconnected via a paraffinic chain spacer, are of considerable current interest. In particular, chiral dimesogens possessing a cholesteryl ester unit as the chiral entity joined to other aromatic mesogens through a polymethylene spacer have shown unique and interesting thermal behaviour. In continuation of our investigations on this topic, here we present the synthesis and characterization of the first examples of cholesterol-based unsymmetrical dimesogenic bidentate ligands and their Cu(II) and Pd(II) metal-organic systems (metallomesogens). Our studies reveal that the dimesogenic bidentate ligands exhibit multiple mesophases, whereas their metal complexes stabilize only the mesophase. 相似文献
8.
Hydrothermal reactions of 5-sulfoisophthalic acid (HO(3)SC(6)H(3)-1,3-(CO(2)H)(2), H(3)L) with M(II) carbonate (or oxide) and 4,4'-bipyridine (4,4'-bipy) (or 2,2'-bipyridine, 2,2'-bipy) resulted in three new metal carboxylate-sulfonate hybrids, namely, [CdL(H-4,4'-bipy)] (1) and [Cd(3)L(2)(2,2-bipy)(4)(H(2)O)(2)].2H(2)O (2) with layered structures and [ZnL(H-4,4'-bipy)(H(2)O)].2H(2)O (3), whose structure features a one-dimensional double chain. The cadmium(II) ion in complex 1 is seven-coordinated by five carboxylate oxygen atoms and one sulfonate oxygen atom from four ligands and a unidentate 4,4'-bipyridine. The interconnection of the cadmium(II) ions through bridging carboxylate-sulfonate ligands resulted in the formation of a <002> double layer with the bipyridyl rings orientated toward the interlayer space. Complex 2 has a different layered structure. Cd(1) is seven-coordinated by two bidentate chelating carboxylate groups from two ligands, a bidentate chelating 2,2'-bipy and an aqua ligand, and Cd(2) is octahedrally coordinated by two bidentate chelating 2,2'-bipy's, a sulfonate oxygen, and an aqua ligand. The coordination geometry around Cd(3) is similar to that of Cd(1) with the aqua ligand being replaced by an oxygen atom from the sulfonate group. The carboxylate-sulfonate ligand acts as pentadentate ligand, bridging with three cadmium(II) ions. The bridging of cadmium(II) ions through the carboxylate-sulfonate ligands resulted in the formation of <006> and <003> layers; the 2,2'-bipy molecules and [Cd(2)(2,2'-bipy)(2)(H(2)O)] cations are orientated to the interlayer space. Complex 3 features a 1D metal carboxylate-sulfonate double chain along the diagonal of the a- and b-axes. The zinc(II) ion is octahedrally coordinated by four carboxylate O atoms from three ligands, a unidentate 4,4'-bipy, and an aqua ligand. Each pair of zinc(II) ions is bridged by two carboxylate groups from two ligands to form a dimer, and such dimeric units are interconnected by bridging ligands to form a double chain. The sulfonate group of the carboxylate sulfonate ligand remains noncoordinated and forms a number of hydrogen bonds with aqua ligands as well as lattice water molecules. 相似文献
9.
C. V. YELAMAGGAD UMA S. HIREMATH S. ANITHA NAGAMANI D. S. SHANKAR RAO S. KRISHNA PRASAD NOBUO IYI 《Liquid crystals》2013,40(6):681-690
The synthesis and characterization of cholesterol-based dimesogenic bidentate ligands and their Cu(II) and Pd(II) metallomesogens are reported in detail. To understand structure-property relationships in these materials the terminal alkoxy chains and the central metal atom have been varied. Our studies reveal that chiral dimesogenic bidentate ligands with n-butyloxy chains exhibit smectic A (SmA), twist grain boundary and chiral nematic (N*) mesophases while substitution with either n -decyloxy or 3,7-dimethyloctyloxy chains also show a ferroelectrically switchable chiral smectic C (SmC*) mesophase. The metal complexes with n-butyloxy chains show only the SmA phase whereas higher chain length derivatives exhibit N* phase irrespective of the metal atom present. The ligands are thermally stable whereas their metal complexes, especially Pd(II) systems, seem to be heat sensitive. Spontaneous polarization, response time and tilt angle measurements have been carried out in the smectic C* phase of the two ligands. 相似文献
10.
C. V. Yelamaggad S. Anitha Nagamani Geetha G. Nair D. S. Shankar Rao S. Krishna Prasad A. Jakli 《Liquid crystals》2002,29(9):1181-1185
The first achiral bent-core banana-shaped bidentate ligands and their Cu(II) and Pd(II) metal complexes have been synthesized and investigated for mesomorphic behaviour. The bidentate ligands exhibit only one enantiotropic mesophase. The ligand having C 6 -alkoxy chains shows a mesophase that has been assigned as a two-dimensional B 1 phase while the C 8 and C 10 homologues stabilize the fluid B 2 mesophase showing antiferroelectric switching characteristics. In constrast, their corresponding Cu(II) and Pd(II) metal complexes are non-mesomorphic. 相似文献
11.
C. V. Yelamaggad S. Anitha Nagamani Geetha G. Nair D. S. Shankar Rao S. Krishna Prasad A. Jakli 《Liquid crystals》2013,40(9):1181-1185
The first achiral bent-core banana-shaped bidentate ligands and their Cu(II) and Pd(II) metal complexes have been synthesized and investigated for mesomorphic behaviour. The bidentate ligands exhibit only one enantiotropic mesophase. The ligand having C6 -alkoxy chains shows a mesophase that has been assigned as a two-dimensional B1 phase while the C8 and C10 homologues stabilize the fluid B2 mesophase showing antiferroelectric switching characteristics. In constrast, their corresponding Cu(II) and Pd(II) metal complexes are non-mesomorphic. 相似文献
12.
Squires C Baxter CW Campbell J Lindoy LF McNab H Parkin A Parsons S Tasker PA Wei G White DJ 《Dalton transactions (Cambridge, England : 2003)》2006,(16):2026-2034
Monosulfonyl derivatives of simple 1,2- and 1,3-diamines (R2HN-R-NHSO2R1 = L) have been shown to be easily deprotonated to give neutral 2:1 complexes, [M(L - H)(2)], with Co(II), Ni(II), Cu(II) or Zn(II). The Ni(II) and Cu(II) complexes with deprotonated N-tosyl-1,2-diaminoethane have a planar N4(2-) donor set and a 14-membered pseudo-macrocyclic structure based on head-to-tail S=O...H-N((amine)) bonding between the two bidentate ligands. In the related tetrahedral Zn(II) complex the ends of the mutually perpendicular bidentate N2- units are too far apart to form a cyclic H-bonded system. X-Ray structure determinations on five free ligands provide evidence for extensive inter-molecular H-bonding, which in the case of N-tosyl-1,3-diaminopropane and its N'-tert-butyl derivative involves formation of dimeric 16-membered pseudo-macrocycles. Despite favourable inter-ligand H-bonding in the neutral 2:1 complexes, these ligands are relatively weak extractants, showing >50% loading of Cu(II) in "pH-swing" equilibria, 2L(org)+ M2+ = [M(L - H)2](org)+ 2 H+, only when the pH of the aqueous phase is raised above 4. 相似文献
13.
C. V. Yelamaggad Uma S. Hiremath S. Anitha Nagamani D. S. Shankar Rao S. Krishna Prasad Nobuo Iyi Taketoshi Fujita 《Liquid crystals》2003,30(6):681-690
The synthesis and characterization of cholesterol-based dimesogenic bidentate ligands and their Cu(II) and Pd(II) metallomesogens are reported in detail. To understand structure-property relationships in these materials the terminal alkoxy chains and the central metal atom have been varied. Our studies reveal that chiral dimesogenic bidentate ligands with n -butyloxy chains exhibit smectic A (SmA), twist grain boundary and chiral nematic (N * ) mesophases while substitution with either n -decyloxy or 3,7-dimethyloctyloxy chains also show a ferroelectrically switchable chiral smectic C (SmC * ) mesophase. The metal complexes with n -butyloxy chains show only the SmA phase whereas higher chain length derivatives exhibit N * phase irrespective of the metal atom present. The ligands are thermally stable whereas their metal complexes, especially Pd(II) systems, seem to be heat sensitive. Spontaneous polarization, response time and tilt angle measurements have been carried out in the smectic C * phase of the two ligands. 相似文献
14.
Spectrophotometric studies of the reactions of iron(II), copper(I) and cobalt(II) with 33 new compounds have demonstrated that the chromogenic properties of diazyl groups are inferior to those of triazyl or pyridyl groups when incorporated into the ferroin chromophore group. The metal complexes of the diazyl derivatives are less stable than those of the corresponding pyridyl and triazyl derivatives. Conditional formation constants of the iron(II) chelates of some representative diazyl derivatives indicate that pyridazyl groups impart greater stabilities than pyrimidyl or pyrazyl groups. Five of the new chromogens have structures that suggest they can chelate iron(II) without steric hindrance, either as bidentate or as terdenate ligands. Although the terdentate mode would ordinarily be expected, two of the five were found to act preferably as bidentate ligands. 相似文献
15.
Mixed ligand complexes of Zn(II) and Co(II) with cysteine, histidine, cysteinemethylester, and histidinemethylester have been
synthesized and characterized by elemental analysis, conductivity, magnetic susceptibility measurements, and infrared,1H NMR, TGA and FAB mass spectra. In these complexes, histidine, and histidinemethylester act as bidentate ligands involving
amino and imidazole nitrogens in metal coordination. Similarly, cysteine, and cysteinemethylester also act as bidentate ligands
coordinating through thiol sulphur and amino nitrogen. Tetrahedral geometry has been proposed for Zn(II) and Co(II) complexes
based on experimental evidence. 相似文献
16.
《Journal of organometallic chemistry》2011,696(26):4215-4220
The asymmetric hydroarsination reactions between diphenylarsine and 3-diphenylphosphanyl-but-3-en-1-ol and 2-diphenylphosphanyl-prop-2-en-1-ol have been achieved using the organopalladium complex containing ortho-metallated (R)-[1-(dimethylamino)ethylnaphthalene as the chiral reaction template in high stereoselectivities under mild conditions. Hydroarsination of 3-diphenylphosphanyl-but-3-en-1-ol with diphenylarsine generated only one stereoisomer as five-membered As–P bidentate chelate on chiral naphthylamine palladium template. Using the same chiral metal template, similar hydroarsination reaction was carried out on 2-diphenylphosphanyl-prop-2-en-1-ol which gave two different products in the ratio of 2.6 to 1. The major isomer was identified as the expected five-membered As–P bidentate ligand and the minor isomer was identified as the elimination product. The naphthylamine auxiliary could be removed chemoselectively by treatment with concentrated hydrochloric acid. Optically pure As–P ligands containing the hydroxy groups at the chiral carbon centres were prepared by ligand displacement. The absolute configuration and coordination properties of the complexes have been established by single crystal X-ray analysis. 相似文献
17.
Yuen Lin Cheow Sumod A. Pullarkat Yongxin Li Pak-Hing Leung 《Journal of organometallic chemistry》2012,696(26):4215-4220
The asymmetric hydroarsination reactions between diphenylarsine and 3-diphenylphosphanyl-but-3-en-1-ol and 2-diphenylphosphanyl-prop-2-en-1-ol have been achieved using the organopalladium complex containing ortho-metallated (R)-[1-(dimethylamino)ethylnaphthalene as the chiral reaction template in high stereoselectivities under mild conditions. Hydroarsination of 3-diphenylphosphanyl-but-3-en-1-ol with diphenylarsine generated only one stereoisomer as five-membered As–P bidentate chelate on chiral naphthylamine palladium template. Using the same chiral metal template, similar hydroarsination reaction was carried out on 2-diphenylphosphanyl-prop-2-en-1-ol which gave two different products in the ratio of 2.6 to 1. The major isomer was identified as the expected five-membered As–P bidentate ligand and the minor isomer was identified as the elimination product. The naphthylamine auxiliary could be removed chemoselectively by treatment with concentrated hydrochloric acid. Optically pure As–P ligands containing the hydroxy groups at the chiral carbon centres were prepared by ligand displacement. The absolute configuration and coordination properties of the complexes have been established by single crystal X-ray analysis. 相似文献
18.
《Journal of Coordination Chemistry》2012,65(4):301-308
Abstract Crystals of monoaquo(μ-5-methylpyrazine-2-carboxylato-N,O,O′), (5-methylpyrazine-2-carboxyato-N,O)di(μ-aquo-O,O)calcium(II) contain molecular ribbons in which two adjacent calcium(II) ions are bridged by two bidentate oxygen atoms donated by two ligand molecules on one side and bidentate oxygen atoms of two water molecules on the other. The coordination polyhedron around the Ca(II) ion is a pentagonal bipyramid. The vertices of its pentagonal base are composed of two bridging water oxygen atoms, two carboxylate oxygen atoms of two ligand molecules and a nitrogen atom belonging to one of the bridging ligands. A coordinated water molecule constitutes the apex of the pyramid on one side of the base, while the N, O bonding moiety of a second ligand molecule makes two apices on the other side of the base. The ribbons are held together by a system of hydrogen bonds. 相似文献
19.
Joost N.H. Reek Marc Röder P. Elsbeth Goudriaan Paul C.J. Kamer Piet W.N.M. van Leeuwen Vincent F. Slagt 《Journal of organometallic chemistry》2005,690(20):4505-4516
Herein, we report a new strategy for the preparation of chelating bidentate ligands, which involves the mixing of two mondentate ligands functionalized with complementary binding sites. The assembly process is based on selective metal-ligand interactions employing phosphite zinc(II) porphyrins 1-6 and the nitrogen-containing phosphorus ligands b-i (Scheme 1). Only 14 monodentate ligands were utilized to generate a library of 48 palladium catalysts based on supraphos-type bidentate ligands. The characterization of rhodium complexes based on representative Supramolecular bidentate ligands and the comparison of their performance in the hydroformylation of styrene will be presented. The current library of catalysts was tested in the asymmetric palladium-catalyzed alkylation of rac-1,3-diphenyl-2-propenyl acetate, which resulted in a large variety in the observed enantioselectivity for the different catalysts. Importantly, small variations in the supraphos building blocks, lead to large differences in the enantioselectivity imposed by the catalyst, the most selective catalyst producing 97% ee. 相似文献
20.
Aucagne V Berna J Crowley JD Goldup SM Hänni KD Leigh DA Lusby PJ Ronaldson VE Slawin AM Viterisi A Walker DB 《Journal of the American Chemical Society》2007,129(39):11950-11963
A synthetic approach to rotaxane architectures is described in which metal atoms catalyze covalent bond formation while simultaneously acting as the template for the assembly of the mechanically interlocked structure. This "active-metal" template strategy is exemplified using the Huisgen-Meldal-Fokin Cu(I)-catalyzed 1,3-cycloaddition of azides with terminal alkynes (the CuAAC "click" reaction). Coordination of Cu(I) to an endotopic pyridine-containing macrocycle allows the alkyne and azide to bind to metal atoms in such a way that the metal-mediated bond-forming reaction takes place through the cavity of the macrocycle--or macrocycles--forming a rotaxane. A variety of mono- and bidentate macrocyclic ligands are demonstrated to form [2]rotaxanes in this way, and by adding pyridine, the metal can turn over during the reaction, giving a catalytic active-metal template assembly process. Both the stoichiometric and catalytic versions of the reaction were also used to synthesize more complex two-station molecular shuttles. The dynamics of the translocation of the macrocycle by ligand exchange in these two-station shuttles could be controlled by coordination to different metal ions (rapid shuttling is observed with Cu(I), slow shuttling with Pd(II)). Under active-metal template reaction conditions that feature a high macrocycle:copper ratio, [3]rotaxanes (two macrocycles on a thread containing a single triazole ring) are also produced during the reaction. The latter observation shows that under these conditions the mechanism of the Cu(I)-catalyzed terminal alkyne-azide cycloaddition involves a reactive intermediate that features at least two metal ions. 相似文献