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Friedelane triterpenes from the stem bark of Caloncoba glauca
1993
Further investigation of the stem bark of Caloncoba glauca has yielded three minor (D:A)-friedo-oleanane derivatives. These have been identified, on the basis of NMR studies, as the known compound kokoonol [3-oxo-(D:A)-friedo-olean-27-ol] and the novel natural products kokoonal [3-oxo-(D:A)-friedo-olean-27- al] and 3β,21β-dihydroxy-30-nor-(D:A)-friedo-olean-27-oic acid.
Synthesis and Structural Characterization of a Cyclen-Derived Molecular Cage
2015
Reaction of a tetrafunctionalized cyclen derivative containing four aldehyde groups with an appropriate diamine followed by reduction and demetalation highly efficiently affords a bis(cyclen)-derived molecular cage. Potentiometric investigations show that this compound forms dimetallic complexes with copper(II), with the two metal ions selectively coordinated to the cyclen units. X-ray crystallography indicates that these complexes could give rise to new cascade complexes after incorporation of anions between the metal centers.
Remarkably Robust Group 4 Metal Half-Sandwich Complexes Containing Two Higher Alkyl Ligands: X-ray Structure and Reactivity of the Di-n-butyl Comple…
1997
The reaction of LiR with M(η5:η1:η1-C5Me4SiMe2NCH2CH2OMe)Cl2 (1, M = Zr (a), Hf (b)) gives the isolable, thermally stable complexes M(η5:η1:η1-C5Me4SiMe2NCH2CH2OMe)R2 (R = Et (2), nPr (3), nBu(4)), which contain two alkyl ligands with β-hydrogen atoms.
Bimetallic Cyanide-Bridged Complexes Based on the Photochromic Nitroprusside Anion and Paramagnetic Metal Complexes. Syntheses, Structures, and Physi…
2000
The synthesis, crystal structure, and physical characterization of the coordination compounds [Ni(en)2]4[Fe(CN)5NO]2[Fe(CN)6]x5H2O (1), [Ni(en)2][Fe(CN)5NO]x3H2O (2), [Mn(3-MeOsalen)(H2O)]2[Fe(CN)5NO] (3), and [Mn(5-Brsalen)]2[Fe(CN)5NO] (4) are presented. 1 crystallizes in the monoclinic space group P2(1)/n (a = 7.407(4) A, b = 28.963(6) A, c = 14.744(5) A, alpha = 90 degrees, beta = 103.26(4) degrees, gamma = 90 degrees, Z = 2). Its structure consists of branched linear chains formed by cis-[Ni(en)2]2+ cations and ferrocyanide and nitroprusside anions. The presence of two kinds of iron(II) sites has been demonstrated by Mossbauer spectroscopy. 2 crystallizes in the monoclinic space group …
Organocyanide coordination chemistry: Syntheses, structural characterisations and magnetic properties of copper (II) complexes with a di-imine/pyridi…
2005
Abstract The reactions between the copper (II) salts [CuXL]PF6 (L: 2,6-[1-(2,6-diisopropylphenylimino)ethyl]pyridine) (X = Cl 1, X = Br 2) and LiTCNQ, in a DMF/water mixture, or Et3NH(TCNQ)2, in acetone, produced the new complexes [CuXL(TCNQ)] (X = Cl 3, X = Br 4). For both compounds, crystallographic studies have clearly evidenced the existence of dimeric complexes [{CuClL}(TCNQ)]2 owing to π–π overlap between two adjacent TCNQ − radical anions. Compound 1 reacted with Et4N(C10N7) to afford the mononuclear derivative [CuClL(C10N7)] (5), while its reaction with K2C10N6 produced the dinuclear complex [(CuClL)2(C10N6)] (6). The crystal structures of complexes 5 and 6 have been determined by X…
Computational Analysis of n→π* Back-Bonding in Metallylene–Isocyanide Complexes R2MCNR′ (M = Si, Ge, Sn; R = tBu, Ph; R′ = Me, tBu, Ph)
2013
A detailed computational investigation of orbital interactions in metal–carbon bonds of metallylene–isocyanide adducts of the type R2MCNR′ (M = Si, Ge, Sn; R, R′ = alkyl, aryl) was performed using density functional theory and different methods based on energy decomposition analysis. Similar analyses have not been carried out before for metal complexes of isocyanides, even though the related carbonyl complexes have been under intense investigations throughout the years. The results of our work reveal that the relative importance of π-type back-bonding interactions in these systems increases in the sequence Sn < Ge ≪ Si, and in contrast to some earlier assumptions, the π-component cannot be …
Synthesis of a tetradentate piperazine ligand and a structural study of its coordination compounds
1999
Abstract A tetradentate ligand N,N′-bis(2-pyridylmethyl)piperazine (L1) and seven structures of its transition metal coordination compounds are described. Most of the compounds are of the general formula [M(L1)(NO3)2], with M=Cu2+, Co2+, Mn2+and Cd2+. In addition, a dimeric copper(II) compound, [Cu2(L1)(Ac)4](H2O)3, and polymeric silver(I) compounds, [Ag(L1)]n(NO3)n(EtOH)n and [Ag(L1)]n(SO3CF3)n, were formed. The overall structure of L1 in the metal complexes A–G varies with the size and electronic properties of the metal ions. Mononuclear complex A is a five-coordinated, B is a six-coordinated, and C and D are eight-coordinated metal complexes. The dinuclear Cu complex, E, is four-coordina…
Synthesis and characterisation of polymeric metal-ion carboxylates from benzene-1,3,5-tricarboxylic acid with Mn(II), Co(II) or Zn(II) and 2,2-bipyri…
2001
A total of 13 new co-ordination solids have been prepared of composition [Co(HBTC)(PHEN)(H2O)] (12), [Mn-3(BTC)(2)(PHEN)(3)] (13), [Mn(HBTC)(6)(H2O)] (14), [Mn(HBTC)(7)(H2O)] (15), [Zn-3(BTC)(2)(6)(3)(H2O)(3)]. 4H(2)O (16), [Zn-(HBTC)(6)(H2O)] (17), [Zn(H2BTC)(2)(6)] (18), [Zn(HBTC)(7)(H2O)] (19), [Zn(HBTC)(8)(H2O)] (20), [Zn-2(HBTC)(2)(9)(2)]. 2H(2)O (21), [Zn(HBTC)(10)(H2O)].H2O (22), [Co(HBTC)(10)(H2O)].H2O (23) and [Co(HBTC)(11)(H2O)] (24) 6 = pyridine-2-(1-methyl-1H-pyrazol-3-yl); 7 = pyridine-2-(1-methyl-4-bromo-1H-pyrazol-3-yl); 8 = pyridine-2-(1-methyl-4-nitro-1H-pyrazol-3-yl); 9 = pyridine-2-(1-methyl-5-trifluoromethyl-1H-pyrazol-3-yl); 10 = pyridine-2-(1-methyl-5-tert-butyl-1H-pyr…
Generation of [2×2] Grid Metallosupramolecular Architectures from Preformed Ditopic Bis(acylhydrazone) Ligands and through Component Self‐Assembly
2007
Ditopic bis(acylhydrazone) ligands, derived from the reactions of carbohydrazides with 2-phenylpyrimidine-4,6-dicarbaldehyde and designed for grid formation with octahedrally coordinating transition-metal ions, exhibit a varied coordination chemistry depending upon the degree of their deprotonation. The neutral acylhydrazones are relatively poor ligands and are seemingly involved in multiple, labile complexation equilibria varying with the solvent and the particular metal salt in solution; nevertheless, grid complexes of different forms can be isolated in the solid state. Although only limited study has been made of the singly deprotonated ligands, grid species appear to be much more readil…
Syntheses, crystal structures and magnetic properties of a series of μ-phenoxo-μ1,1-carboxylato-μ1,3-carboxylato trinickel(II) compounds.
2014
The work in this report describes the syntheses, characterization, crystal structures and magnetic properties of eight linear trinickel(ii) compounds of the composition [Ni(II)3(L(sal-pyr))2(propionate)4] (), [Ni(II)3(L(sal-pyr))2(benzoate)4]·CH3CN (), [Ni(II)3(L(sal-pip))2(acetate)4]·2CH3CN (), [Ni(II)3(L(sal-pip))2(propionate)4] (), [Ni(II)3(L(sal-pip))2(benzoate)4]·CH2Cl2 (), [Ni(II)3(L(sal-mor))2(propionate)4] (), [Ni(II)3(L(sal-mor))2(benzoate)4]·3CH2Cl2 () and [Ni(II)3(L(sal-mor))2(o-Cl-benzoate)4]·2CH3CN·2H2O (), where HL(sal-pyr), HL(sal-pip) and HL(sal-mor) are the 1 : 1 condensation products of salicylaldehyde and 1-(2-aminoethyl)-pyrrolidine, 1-(2-aminoethyl)-piperidine and 4-(2-…