Hydrolytic ring opening reactions of anhydrides for first row transition metal dicarboxylate complexes

Ring opening reactions of 2,3-pyridine dicarboxylic anhydride are studied with hydrated salts of cobalt, nickel and zinc. The hydrated metal salts preferentially hydrolyze 2,3-pyridine dicarboxylic anhydride rather than causing esterification in methanol medium. Hydrolytic opening of 2,3-pyridine dicarboxylic anhydride by hydrated cobalt(II) acetate and nickel(II) acetate resulted in the corresponding chelate complexes of monodeprotonated 2,3-pyridine dicarboxylic acid. The reaction of copper acetate with pyromellitic dianhydride in the presence of 1,10-phenanthroline gives a dinuclear copper complex whereas a similar reaction with copper(II) chloride gives a mononuclear copper complex.     

Recent advancements in the anticancer potentials of first row transition metal complexes

The frequently severe effects of currently utilized platinum-based complexes have prompted researchers to develop less toxic transition metal based anticancer drugs. Transition metal complexes have recently gained considerable attention as promising anticancer agents due to their efficient drug design and fast optimisation. Some transition metal complexes displayed better anticancer activity than cis-platin. This led to the transition metal complexes for clinical application of chemotherapeutic drugs for cancer therapy. Cytotoxicity of the complexes has been evaluated on the basis of their IC₅₀ values. In this review, we have focussed on recent findings about the anticancer mechanism of action of first row transition metal complexes during the last ten years.     

The hapticity of cyclooctatetraene in its first row mononuclear transition metal carbonyl complexes: Several examples of octahapto coordination

The two cyclooctatetraene metal carbonyls that have been synthesized are the tetrahapto derivative (η⁴-C₈H₈)Fe(CO)₃ and the hexahapto derivative (η⁶-C₈H₈)Cr(CO)₃ using the reactions of cyclooctatetraene with Fe(CO)₅ and with fac-(CH₃CN)₃Cr(CO)₃, respectively. Related C₈H₈M(CO)_n (M = Ti, V, Cr, Mn, Fe, Co, Ni; n = 4, 3, 2, 1) species have now been investigated by density functional theory in order to explore the scope of cyclooctatetraene metal carbonyl chemistry. In this connection, the existence of octahapto (η⁸-C₈H₈)M(CO)_n species is predicted as long as the central metal M does not exceed the 18-electron configuration by receiving eight electrons from the η⁸-C₈H₈ ring. Thus the lowest energy structures (η⁸-C₈H₈)Ti(CO)_n (n = 3, 2, 1), (η⁸-C₈H₈)M(CO)_n (M = V, Cr; n = 2, 1), and (η⁸-C₈H₈)Mn(CO) all have octahapto η⁸-C₈H₈ rings. An exception is (η⁶-C₈H₈)Fe(CO), with a hexahapto η⁶-C₈H₈ ring and thus only a 16-electron configuration for the iron atom. Hexahapto (η⁶-C₈H₈)M(CO)_n structures are predicted for the known (η⁶-C₈H₈)Cr(CO)₃ as well as the unknown (η⁶-C₈H₈)Ti(CO)₄, (η⁶-C₈H₈)V(CO)₃, (η⁶-C₈H₈)Mn(CO)₂, and (η⁶-C₈H₈)Fe(CO)₂ with 18, 18, 17, 17, and 18 electron configurations, respectively, for the central metal atoms. There are two types of tetrahapto C₈H₈M(CO)_n complexes. In the 1,2,3,4-tetrahapto (η⁴-C₈H₈)M(CO)_n complexes two adjacent CC double bonds, forming a 1,3-diene unit similar to butadiene, are bonded to the metal atom. In the 1,2,5,6-tetrahapto (η^2,2-C₈H₈)M(CO)₃ derivatives two non-adjacent CC double bonds of the C₈H₈ ring are bonded to the metal atom. The known (η⁴-C₈H₈)Fe(CO)₃ is a 1,2,3,4-tetrahapto complex. The unknown isomeric 1,2,5,6-tetrahapto complex (η^2,2-C₈H₈)Fe(CO)₃ is predicted to lie ∼15 kcal/mol above (η⁴-C₈H₈)Fe(CO)₃. The related 1,2,5,6-tetrahapto complexes (η^2,2-C₈H₈)Cr(CO)₄, (η^2,2-C₈H₈)Mn(CO)₄, [(η^2,2-C₈H₈)Mn(CO)₃]⁻, (η^2,2-C₈H₈)Co(CO)₂, and (η^2,2-C₈H₈)Ni(CO)₂ are all predicted to be low-energy structures.     

Calculations of rate constants for reactions of first and second row cations

Calculations of rate constants for 35 reactions of first and second row monocations with different neutrals are presented. A combined rotationally adiabatic capture and centrifugal sudden approximation is used. The majority of predicted rate constants are in good agreement with the experimental measurements. An exploration of energetics of the potential energy surface for some of those cases in which prediction fails has been done using ab initio G2 theory. These cases usually correspond to situations in which the reaction is not as exothermic as the application of capture approximation requires or secondary barriers exist in the reaction path. Second row cations present these kind of problems due to their smaller electronegativity with respect to cations of the first row. Received: 12 April 1997 / Accepted: 27 June 1997     

Mononuclear homoleptic allyl complexes of the first row transition metals: species with unusual metal electronic configurations

A number of evanescent unsubstituted homoleptic allyl derivatives M(C(3)H(5))(n) of the first row transition metals have been reported in the literature. In addition, the much more thermally stable silylated derivatives M[C(3)H(3)(SiMe(3))(2)](2) (M = Cr, Fe, Co, Ni) are reported to survive vacuum sublimation without significant decomposition. In this connection, the complete series of homoleptic allyl derivatives M(C(3)H(5))(n) (n = 2, 3; M = Sc, Ti, V, Cr, Mn, Fe, Co, Ni) have been studied theoretically using density functional theory. In most of the lowest energy predicted M(C(3)H(5))(n) structures all of the allyl groups are bonded as trihapto η(3)-C(3)H(5) ligands and the metals have considerably less than the normally favored 18-electron configuration. Such ligands can be considered formally as bidentate ligands with the metal atom connected to the centers of the two C-C bonds of the η(3)-C(3)H(5) group. The later transition metal diallyls M(C(3)H(5))(2) (M = Cr, Mn, Fe, Co, Ni) form two stereoisomers of similar relative energies, namely the C(2h) staggered isomer and the C(2v) eclipsed isomer with the orientation of the η(3)-C(3)H(5) groups corresponding to square planar metal coordination of the bidentate η(3)-C(3)H(5) ligands. The staggered and eclipsed Ni(C(3)H(5))(2) isomers have been observed experimentally by NMR. Less symmetrical M(C(3)H(5))(2) structures are found for the earlier transition metals Sc, Ti, and V in which the orientation of the allyl groups corresponds to tetrahedral metal coordination. The triallylmetal derivatives M(C(3)H(5))(3) are predicted to be thermodynamically viable with respect to allyl loss to give the corresponding diallylmetal derivatives, except for triallylnickel. The lowest energy Ni(C(3)H(5))(3) structure has two trihaptoallyl ligands and one monohaptoallyl ligand, whereas the lowest energy Mn(C(3)H(5))(3) structures have only one trihaptoallyl ligand and two monohaptoallyl ligands. Otherwise, the M(C(3)H(5))(3) complexes have structures with three trihaptoallyl ligands corresponding formally to octahedral metal coordination. The M(C(3)H(5))(3) complexes (M = Cr, Co) thus correspond to a well-known series of "classical" octahedral coordination complexes, namely, those of the d(3) Cr(III) and the d(6) Co(III), respectively.     

Coordination polymers of glutaraldehyde with glycine metal complexes: synthesis,spectral characterization,and their biological evaluation

Glycine metal complexes were prepared by the reaction of glycine with Mn(II), Co(II), Ni(II), Cu(II), and Zn(II) in 1?:?2 molar ratio. Thereafter their condensation polymerization was done with glutaraldehyde to obtain polymer metal complexes. All the synthesized polymer metal complexes were characterized by elemental analysis, FT-IR, ¹H-NMR, and UV-Vis spectrometry, magnetic susceptibility, and thermogravimetric studies. The analytical data of all the polymers agreed with 1?:?1 molar ratio of metal complex to glutaraldehyde and magnetic moment data suggest that PGG–Mn(II), PGG–Co(II), PGG–Ni(II), and PGG–Cu(II) have an octahedral geometry around the metal atom, whereas the tetrahedral geometry was proposed for PGG–Zn(II) polymer. The PGG–Mn(II) and PGG–Cu(II) showed octahedral geometry. Thermal behavior of the polymer metal complexes was obtained at a heating rate of 10°C?min^?1 under nitrogen atmosphere from 0°C to 800°C. The antimicrobial activities of synthesized polymers were investigated against Streptococcus aureus, Escherichia coli, Bacillus sphaericus, Salmonella sp. (Bacteria), Fusarium oryzae, Candida albicans, and Aspergillus niger (Yeast).     

Spectral, magnetic and biological studies of 1,4-dibenzoyl-3-thiosemicarbazide complexes with some first row transition metal ions

The ligand 1,4-dibenzoyl-3-thiosemicarbazide (DBtsc) forms complexes [M(DBtsc-H)(SCN)] [M = Mn(II), Co(II) or Zn(II)], [M(DBtsc-H) (SCN)(H₂O)] [M = Ni(II) or Cu(II)], [M(DBtsc-H)Cl] [M = Co(II), Ni(II), Cu(II) or Zn(II)] and [Mn(DBtsc)Cl₂], which have been characterized by elemental analyses, magnetic susceptibility measurements, UV/Vis, IR,¹H and¹³C NMR and FAB mass spectral data. Room temperature ESR spectra of the Mn(II) and Cu(II) complexes yield <g> values, characteristic of tetrahedral and square planar complexes respectively. DBtsc and its soluble complexes have been screened against several bacteria, fungi and tumour cell lines.     

New chelate ring opening reactions leading to the synthesis of novel mixed ligand complexes of the octahedral metal carbonyls

Reactions of the four-membered ring chelate CH₃N(PF₂)₂Cr(CO)₄ with trivalent phosphorous ligands (L) at 80°C leads to facile opening of the chelate ring to give the mixed ligand complexes trans-CH₃N(PF₂)₂Cr(CO)₄L (L=C₆H₅)₃P or monodentate C₆H₅N(PF₂)₂) containing a monodentate CH₃N(PF₂)₂ ligand.     

Functionalization of white phosphorus in the coordination sphere of transition metal complexes

This review highlights the stoichiometric functionalization of both white phosphorus and naked P_n fragments derived from the metal-mediated demolition of the P₄ tetrahedron. In a first section, the alkylation of P_n ligands is discussed giving specific examples such as: (i) the electrophilic alkylation of η³-P₃ or, μ,η³-P₃ ligands: (ii) the transfer of a methyl group from molybdenum to η⁵-P₅ ligands to yield a norbornadiene-like μ₃,η⁴:η¹:η¹-MeP₇ ligand; (iii) the formation of P-C or P-H bonds mediated by rhodium and iron complexes; (iv) the use of ammonium salts to transfer an alkyl to polyphosphido clusters. Different methods to functionalise white phosphorus or other P_n ligands, including the cyclization of acrolein with diphosphenes and the insertion of CO or carbenes across P-P, P-M bonds, and P-E bonds (E = S, Se), are illustrated in appropriate sections. Finally, the last part of the article, reports on the astounding coupling of alkynes and phosphalkynes with P_n ligands which is a versatile, not yet completely explored, method to form an unprecedented variety of carbon-phosphorus heterocycles.     

第一过渡系金属M(II)的联吡啶配合物电子光谱的研究——谱带归属、D~q、B、β、ζ~3~d、λ

我们合成了[M(bpy)~3]X~p(X为SO^2^-~4、Cl^-或ClO^-~4, P=1或2。M为V、Cr、Mn、Fe、Co, Ni、Cu、Zn)。测定了其电子光谱, 指认了各谱带的归属, 并预计了未能显示的谱带的位置。求得了八面体场的参数: D~q, Racah参数B、电子云扩展系数β、M的单电子的旋-轨偶合参数ξ~a~d和配合物的旋--轨偶合参数λ, 指出了与[M(bpy)~3]^2^+的电子光谱相关的电子跃迁。     

Nonprecious metal catalysts for fuel cell applications: electrochemical dioxygen activation by a series of first row transition metal tris(2-pyridylmethyl)amine complexes

A series of divalent first row triflate complexes supported by the ligand tris(2-pyridylmethyl)amine (TPA) have been investigated as oxygen reduction catalysts for fuel cell applications. [(TPA)M(2+)](n+) (M = Mn, Fe, Co, Ni, and Cu) derivatives were synthesized and characterized by X-ray crystallography, cyclic voltammetry, NMR spectroscopy, magnetic susceptibility, IR spectroscopy, and conductance measurements. The stoichiometric and electrochemical O(2) reactivities of the series were examined. Rotating-ring disk electrode (RRDE) voltammetry was used to examine the catalytic activity of the complexes on a carbon support in acidic media, emulating fuel cell performance. The iron complex displayed a selectivity of 89% for four-electron conversion and demonstrated the fastest reaction kinetics, as determined by a kinetic current of 7.6 mA. Additionally, the Mn, Co, and Cu complexes all showed selective four-electron oxygen reduction (<28% H(2)O(2)) at onset potentials (~0.44 V vs RHE) comparable to state of the art molecular catalysts, while being straightforward to access synthetically and derived from nonprecious metals.     

Redox reactions involving low-valence transition metal complexes: Palladium and platinum phosphinecarbonyl clusters in the synthesis of binuclear compounds

Conclusions The heterobinuclear complex, PtPdCl₂(₂-CO)(PPh₃)₃ was obtained by the redox addition of Pd₄(CO)₅(PPh₃)₄, and Pt₄(CO)₅(PPh₃)₄, to MCl₂(PPh₃)₂, where M=Pd and Pt, as a single isomer containing the two PPh₃ ligands at the platinum atom.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2360–2362, October, 1987.     

Synthesis,crystal structures and characterization of late first row transition metal complexes derived from thiosemicarbazone hub: DNA binding/cleavage studies

Air‐ and moisture‐stable coordination compounds of late first row transition metals, i.e. Co(III), Ni(II), Cu(II) and Zn(II), derived from the ligand (E)‐4‐(4‐chlorophenyl)‐1‐(1‐hydroxypropan‐2‐ylidene)thiosemicarbazide were prepared and successfully characterized using various spectro‐analytical techniques. The molecular structures of the ligand LH and complexes C1 and C2 were determined using single‐crystal X‐ray diffraction. The complexes C1 and C2 are stabilized by weak intermolecular CH???π stacking interactions: C1 between phenyl rings (C2–H21???C2) with a contact distance of 2.855 Å and C2 between phenyl ring and thione sulfur (C13???S1) with a contact distance of 3.366(6) Å. Complex C3 is found to be electrochemically active in the working potential range, showing a quasi‐reversible redox process. The interactions of all the compounds with calf thymus DNA were comprehensively investigated using electronic absorption spectroscopy, viscosity and thermal denaturation studies. Cleavage studies of Escherichia coli DNA were monitored using agarose gel electrophoresis. The results show that LH and complex C4 bind to calf thymus DNA through partial intercalation, while remaining complexes bind electrostatically. Further, C1, C2 and C4 complexes show better cleavage potential towards E. coli DNA. Copyright © 2015 John Wiley & Sons, Ltd.     

Investigation of the interaction of olefin-bonded transition metal complexes by gas chromatography. II. Phosphine complexes of Cu(II)

Summary Packings consisting of chemically bonded diphenylphosphine complexes with CuCl₂ and CuBr₂ were synthesized and their retention parameters determined. The packings investigated are capable of specific interactions with electron-donating compounds and are characterized by particularly high selectivity in relation to cis and trans isomers allowing their complete separation.Part 1: see ref. [1]     

A new dinuclear chiral salen complexes for asymmetric ring opening and closing reactions: Synthesis of valuable chiral intermediates

A new dinuclear chiral Co(salen) complexes bearing group 13 metals have been synthesized and characterized. The easily prepared complexes exhibited very high catalytic reactivity and enantioselectivity for the asymmetric ring opening of epoxides with H₂O, chloride ions and carboxylic acids and consequently provide enantiomerically enriched terminal epoxides (>99% ee). It also catalyzes the asymmetric cyclization of ring opened product, to prepare optically pure terminal epoxides in one step. The homogeneous dinuclear chiral Co(salen) have been covalently immobilized on MCM-41. The potential benefits of heterogenization include facilitation of catalyst separation and recyclability requiring very simple techniques. The system described is very efficient.     

Metal-assisted transformation of N-benzoyldithiocarbazate to 5-phenyl-1,3,4-oxadiazole-2-thiol in the presence of ethylenediamine,and its first row transition metal complexes

The reaction of metal complexes of the type [M(HL)Cl] or [M(HL)₂] [where M = Cu(II), Ni(II), Mn(II), Co(II) and Zn(II) and H₂L = N-benzoyldithiocarbazate] with an excess of ethylenediamine (en) in CHCl₃–MeOH medium leads to ring closure by desulfurisation to yield unique mixed-ligand complexes 1–4, [Cu(en)₂](pot)₂(pot = 5-phenyl-1,3,4-oxadiazole-2-thiol), [M(en)₂(pot)₂] [M = Ni(II), Mn(II)] and [Zn(en)(pot)₂]. The metal complexes have been characterized by various physicochemical methods. The molecular structure of [Cu(en)₂](pot)₂ has been determined by a single crystal X-ray diffraction study. In the centrosymmetric unit of [Cu(en)₂](pot)_2, the metal ion has a square planar arrangement of four symmetry related N-atoms of two en groups and is ionically bonded to two pot anions. Weak interaction studies on the complex reveal the presence of a hydrogen-bonded network in the molecule involving non-coordinating donor atoms of the pot anion with en resulting in the formation of an extended three-dimensional network. The arrangement of the [Cu(en)₂]²⁺ units, at a dihedral angle of 49.43° to pot⁻, provides a network of intermingled chains leading to a π–π stacked 3-dimensional framework.     

A chiral probe for the asynchronous transition state of diels-alder reactions with acetylenedicarboxylate

Diels-Alder reactions took place with modest diastereoselectivity between dimethylcyclo-hexadiene derivative 3a and di-(−)-menthyl acetylenedicarboxylate, whereas the dimethylcyclohexadiene 2 showed no selectivity whatsoever. These results can be rationalized in terms of a complete lack of any endo-exo preference for the carboxylate groups and a more synchronous addition with 3a than with 2.