Synthesis, geometrical and absolute configuration of the tris(S-arginine)cobalt(III) trinitrate isomers and synthesis and molecular structure of (-)589-anti(N)-Δ-cis(N),cis(O)-Λ-cis(N),cis(O)-di-μ-hydroxo-tetrakis(S-arginine)dicobalt(III) tetranitrate tetrahydrate

In a direct synthesis reaction of the tris(aminocarboxylato)cobalt(III) complexes with S-arginine all four theoretically possible tris(S-arginine)cobalt(III) diastereomers were obtained as tripositive complex ions. Besides, one out of 24 theoretically possible isomers of di-μ-hydroxo-tetrakis(S-arginine)dicobalt(III) tetrapositive ion was obtained. Geometrical and absolute configurations of the tris(S-arginine)cobalt(III) isomers were determined by electronic and CD spectroscopy. The molecular structure of the (-)₅₈₉-anti(N)-Δ-cis(N),cis(O)-Λ-cis(N),cis(O)-di-μ-hydroxo-tetrakis(S-arginine)dicobalt(III) ion was solved by X-ray crystal structure analysis. The complexes obtained represent the first examples of cationic aminocarboxylato complexes of this type. For the first time the formation of the di-μ-hydroxo-tetrakis(aminocarboxylato)dicobalt(III) complex has been observed as a reaction concurrent to the formation of tris(aminocarboxylato)cobalt(III) complexes. Finally, the stereoselectivity of S-arginine in the tris(S-arginine)cobalt(III) isomers synthesis was discussed.     

New Stable Complexes of Au(III) with Biuret: X-ray Structure of cis-[Au(Biu)Br2]PPh4 and Ab Initio Investigation of cis-[Au(Biu)X2]−

Two anionic complexes of Au(III) with the bioligand biuret, cis-[Au(Biu)X₂]^? (BiuH₂=biuret, X=Cl, Br), have been synthesized and characterized. The molecular structure of cis-[Au(Biu)Br₂]PPh₄ has been determined by X-ray diffraction analysis. The complex anion has square-planar geometry with one deprotonated biuret dianion coordinated bidentately to the metal center via the terminal amino nitrogen atoms and two bromide ions in cis positions. There are no significant intermolecular Au-Au interactions in the solid state. Ab initio calculations of the geometric structure at different computational levels for biuret and both anionic complexes as well an IR study of the structures obtained are performed.     

1H n.m.r. studies of palladium(II) complexes of 2,9-dimethyl-1,10-phenanthroline and 8-hydroxyquinoline

Summary The structures in solution of a series of palladium(II) complexes have been determined by¹H n.m.r. and i.r. spectroscopy. Dicyanobis-(8-hydroxyquinoline)palladium(II) has acis-square-planar configuration, the unidentate 8-hydroxyquinoline molecules bonding to Pd through the nitrogen atoms. Dicyanobis-(2,9-dimethyl-1,10-phenanthroline)-palladium(II) has acis-square planar arrangement about Pd with respect to the nitrogen atoms of the two heterocyclic ligands. The cyanide groups bond to the two apical positions apparently giving rise to a six-coordinate PdlI atom. Dihalo-2,9-dimethyl-1,10-phenanthrolinepalladium(II) (X = Cl, Br, I) exhibits the usualcis-square-planar arrangement of Pd^II, whereas the halobis-(2,9-dimethyl-1,10-phenanthroline) - palladium(II) ion (X = Cl, Br) has a trigonal bipyramidal structure with the halogen atom in the trigonal plane.     

Palladium(II), platinum(II), rhodium(III) and iridium(III) complexes coordinated with 2-aryl-4,5-dimethyl-1,2,3-triazoles as bidentate nitrogen-carbon chelate ligands

Summary Cyclometallations of 2-aryl-4,5-dimethyl-1,2,3-triazoles [H(C-N)] occur with palladium(II), platinum(II), rhodium(III) and iridium(III) chloride. Pallaciation and platination form [MCI(C-N)]₂, and rhodation and iridation [MCI(C-N)₂]₂ species. These complexes react with monodentate ligands, L, such as pyridine and tri-n-butylphosphine to give MCl(C-N)L and MCl(C-N)₂ L complexes. Corresponding bromo and iodo complexes are prepared by metathesis with lithium bromide and iodide. Spectroscopic data suggest that MX(C-N)L compounds (X = Cl, Br or I) have a structure withtrans-C,X andtrans-N,L, while [MX(C-N)₂ L] has atrans-N,N,cis-C,C, andcis-X,L structure.Author to whom all correspondence should be directed.     

Interaction of 2-aminopyrimidine with dichloro-[1-alkyl-2-(naphthylazo) imidazole]palladium(II) complexes : Kinetic and mechanistic studies

Background  

The anticancer properties of cisplatin and palladium(II) complexes stem from the ability of the cis-MCl₂ fragment to bind to DNA bases. However, cisplatin also interacts with non-cancer cells, mainly through bonding molecules containing -SH groups, resulting in nephrotoxicity. This has aroused interest in the design of palladium(II) complexes of improved activity and lower toxicity. The reaction of DNA bases with palladium(II) complexes with chelating N,N^/donors of the cis-MCl₂ configuration constitutes a model system that may help explore the mechanism of cisplatin's anticancer activity. Heterocyclic compounds are found widely in nature and are essential to many biochemical processes. Amongst these naturally occurring compounds, the most thoroughly studied is that of pyrimidine. This was one of the factors that encouraged this study into the kinetics and mechanism of the interaction of 2-aminopyrimidine (2-NH₂-Pym) with dichloro-{1-alkyl-2-(α-naphthylazo)imidazole}palladium(II) [Pd(α-NaiR)Cl₂, 1] and dichloro-{1-alkyl-2-(β-naphthylazo)imidazole}palladium(II) [Pd(β-NaiR)Cl₂, 2] complexes where the alkyl R = Me (a), Et (b), or Bz (c).     

Hydrogen bonding interaction between ureas or thioureas and nitro-compounds

The hydrogen bonding interactions between ureas or thioureas and different nitro-compounds were studied using the MP2 method. After comparing four possible conformations, the most stable one was found, which has the typical hydrogen bonding feature of red-shift effect. Based on it, the substituent effects on both nitro-compounds and (thio) urea were researched. The results indicated that electron-withdrawing groups on ureas or thioureas and electron-donating groups on nitro-compounds can both facilitate the hydrogen bonding formation. The NBO analysis further disclosed the essence of the hydrogen bonding interaction. We also studied the cis–trans isomerization of the complexes of (thio) urea with nitroalkenes, which revealed that, for hydrogen-bonding complexes, it is necessary to take both cis and trans isomers into consideration, especially for nitroalkenes with little steric effect substituents.     

Synthesen und Strukturen von Bis(4,4′‐t‐butyl‐2,2′‐bipyridin)‐Ruthenium(II)‐Komplexen mit funktionellen Derivaten des Tetramethyl‐bibenzimidazols

Syntheses and Structures of Bis(4,4′‐t‐butyl‐2,2′‐bipyridine) Ruthenium(II) Complexes with functional Derivatives of Tetramethyl‐bibenzimidazole [(tbbpy)₂RuCl₂] reacts with dinitro‐tetramethylbibenzimidazole ( A ) in DMF to form the complex [(tbbpy)₂Ru( A )](PF₆)₂ ( 1a ) (tbbpy: bis(4,4′‐t‐butyl)‐2,2′bipyridine). Exchange of the two PF₆^? anions by a mixture of tetrafluor‐terephthalat/tetrafluor‐terephthalic acid results in the formation of 1b in which an extended hydrogen‐bonded network is formed. According to the ¹H NMR spectra and X‐ray analyses of both 1a and 1b , the two nitro groups of the bibenzimidazole ligand are situated at the periphery of the complex in cis position to each other. Reduction of the nitro groups in 1a with SnCl₂/HCl results in the corresponding diamino complex 2 which is a useful starting product for further functionalization reactions. Substitution of the two amino groups in 2 by bromide or iodide via Sandmeyer reaction results in the crystalline complexes [(tbbpy)₂Ru( C )](PF₆)₂ and [(tbbpy)₂Ru( D )](PF₆)₂ ( C : dibromo‐tetrabibenzimidazole, D : diiodo‐tetrabibenzimidazole). Furthermore, 2 readily reacts with 4‐t‐butyl‐salicylaldehyde or pyridine‐2‐carbaldehyde under formation of the corresponding Schiff base Ru^II complexes 5 and 6 . ¹H NMR spectra show that the substituents (NH₂, Br, I, azomethines) in 2 ‐ 6 are also situated in peripheral positions, cis to each other. The solid state structure of both 2 , and 3 , determined by X‐ray analyses confirm this structure. In addition, the X‐ray diffraction analyses of single crystals of the complexes [(tri‐t‐butyl‐terpy)(Cl)Ru( A )] ( 7 ) and [( A )PtCl₂] ( 8 ) display also that the nitro groups in these complexes are in a cis‐arrangement.     

Polymerization of acetylenic derivatives. XXX. Isomers of polyphenylacetylene

Cis-transoidal (orange, soluble, and of low crystallinity) and cis-cisoidal (red, insoluble, and highly crystalline) polyphenylacetylenes (PPA) were prepared by Ziegler-Natta catalysts and trans-cisoidal (yellow, soluble, and amorphous) polyphenylacetylenes were prepared by using phosphine complexes, TiCl₄ and by thermal initiation. The cis-transoidal and cis-cisoidal structures isomerize thermally in the solid state above 100°C. In solution the cis-transoidal structure isomerizes above 80°C. The polymers obtained by thermal isomerization are soluble, amorphous, and have a trans-cisoidal structure. At temperatures higher than 120°C the cis–trans isomerization is accompanied by cyclization and by scission of the polymer chain. A method was developed for determination of cis content of cis-transoidal and cis-cisoidal polyphenylacetylenes.     

Transition metal complexes with bidentate ligand 2, 11-Bis (diphenylphosphinomethyl)benzo[c]phenanthrene (1). X. Preparation and spectroscopic properties of cis-[PtCl2 (1)] trans- and cis-[PtH (PPh3) (1)] [BF4] and crystal and molecular structure of cis-[PtCl2 (1)] · CHCl3

It is shown that ligand 1 , designed to span trans-positions, under appropriate conditions also gives cis-mononuclear complexes of platinum (II). The structure of cis-[PtCl₂ (1) ] (2) has been determined by single-crystal X-ray diffraction. The major distortion from square planar coordination is the P-Pt-P angle of 104.8°. Values of valence angles within the bidentate ligand indicate that this part of the molecule is very strained. Two phenyl groups, one on each phosphorus, lie almost parallel to each other separated by ca. 3.2–3.3 Å. The ¹H-NMR. data for this compound show that the π-phenyl interactions observed in the solid state occur also in solution. The preparation and NMR.-spectroscopic properties of trans- and cis-[PtH(PPh₃) (1) ] [BF₄] are reported.     

Hydrogen Bonding 1-D Chain Network of cis-Doubly N-Confused Porphyrins

The cis-doubly N-confused porphyrin (cis-N²CP, 1) and its Cu(III) and Ag(III) complexes (1–Cu, 1–Ag) form 1-D zigzag infinite chains through hydrogen-bonding interactions between the peripheral core nitrogens (N and NH) in the solid state. Each columnar structure consists of porphyrin rings with the same chirality.     

Preparation and properties of some water-soluble cobalt (III)–poly-4-vinylpyridine complexes

Water-soluble cobalt(III) chelates having a polymeric ligand such as cis-[Co(en)_2-PVPCl]Cl₂ and cis-[Co-(trien)PVPCl]Cl₂ (PVP = poly-4-vinylpyridine) were prepared by substitution reactions between cobalt(III) chelate and PVP in water–alcohol solution. PVP of different degrees of polymerization was used as the ligand in preparation of these complexes. The PVP complexes were identified and their properties ascertained by microanalysis and by a study of the infrared, ultraviolet, visible, and PMR spectra. Most of the characteristic properties of these complexes may be ascribed to the polymeric structure of the PVP ligand.     

基于偶氮联吡啶配体的银和钴配位聚合物的构筑与性质

通过将2个4,4’-联吡啶基团用偶氮基团连接,我们合成了新的配体顺式-和反式-1,2-二（（4,4’-联吡啶）-3-氮烯）（cis-L和trans-L）,并利用trans-L与银离子和钴离子构筑了配位聚合物{[Ag₂（trans-L）（ClO₄）₂]·4CH₃CN}_n（1）和{[Co（trans-L）₂（H₂O）₂]（ClO₄）₂}_n（2）。其中1为一维梯形链,链与链之间通过π-π以及Ag…Ag相互作用堆积;2为三维无限dendrimer结构,其Co中心具有合适的氧化还原电位,在以荧光素为光敏剂的条件下,可作为光催化剂实现光解水放氢。     

Diene,Alkyne, Alkene,and Alkyl Complexes of Early Transition Metals: Structures and Synthetic Applications in Organic and Polymer Chemistry

An unprecedented series of highly reactive alkene-and diene-complexes of the early transition metals (Groups 3A–5A of the periodic system) have been isolated recently. Diene complexes of this sort (M ? Ti, Zr, Hf, Nb, Ta) prefer, besides the (η⁴-s-cis-diene)metal structure, either a novel bent η⁴-metallacyclo-3-pentene structure or the unique (η⁴-s-trans-diene)metal structure. In bis(diene)metal complexes of Nb and Ta the η⁴-s-cis-dienes assume an unusual exo-endo (supine-prone) geometry. The M? C bonds in these diene-metal complexes generally exhibit highly polarized σ-bonding along with π-bonding character. The complexes therefore undergo a variety of regio- and stereoselective carbometalations with substrates containing C? C, C? O, or C? N multiple bonds. Examples of the products that can be obtained include ketones, vinyl ketones, unsaturated primary, secondary, and tertiary alcohols, as well as diols and unsaturated acids. Mechanistic studies on the stoichiometric and catalytic conversions of unsaturated hydrocarbons provides, inter alia, some insights into the course of polymerization reactions.     

Synthesis and crystal structures of copper(II) and silver(I) complexes of a semi-rigid bipyrazolyl ligand

A semi-rigid bipyrazolyl ligand, namely 5-tert-butyl-1,3-bis[(3′,5′-diethyl-1H-pyrazol-4′-yl) methylene]benzene, and its Ag(I) and Cu(II) complexes have been prepared and structurally characterized. X-ray analysis demonstrates that the Ag(I) complex is based on a dinuclear molecular rectangle, while the Cu(II) complex displays a mono-strand helical structure. Two different conformations, namely cis,cis and cis,trans have been observed for this bipyrazolyl ligand.     

STERIC AND ELECTRONIC BALANCE IN METAL-PHOSPHINE COORDINATION: THE PHOSPHINE TWIST

Abstract

The relationship between the bite angles of cis phosphines and the electron distribution and bonding to the metal is studied by gas phase valence photoelectron spectroscopy. The complexes selected for the electronic structure comparison are cis-Mo(CO)₄(PMe₃)₂, Mo(CO)₄DMPE (DMPE = 1,2-bis dimethylphosphinotethane), Mo(CO)₄DMPM (DMPM = bis(dimethylphosphino) methane), cis-W(CO)₄(PMe₃)₂, W(CO)₄DMPE, and cis-W(CO)₄DMPM. The Mo carbonyl complexes give simple photoelectron spectra with the valence ionizations originating from the phosphine lone pairs bonding to the metals and from the metal d ⁶ configurations. The W complexes give similar spectra, but have an additional electronic spin-orbit perturbation. The ionizations from the phosphine lone pairs that donate to the metals in σ bond formation show the effects of the different bite angles of the ligands. However, the total interaction and charge distribution of the phosphines with the metals look very similar in each case. The metal-based ionizations also show very similar bonding and charge distribution in each case. The similarity of the cis-(PMe₃)₂ and DMPE spectra is interesting in light of the ～15° difference in P-M-P angles. The metal-based ionizations of the DMPM complexes are slightly different from those of the other complexes, primarily because of through-space interactions with the methylene carbon in the phosphine backbone. The similarity in electronic interactions with the metal in these complexes is traced to a twist of the phosphine coordination to the metal which adjusts for the steric or bite angle constraints of the ligands with a minimum effect on the bonding to the metal. This results in slightly bent metal-phosphorus bonds.     

Syntheses and crystal structures of diorganotin(IV) bis(2‐pyridinethiolato‐N‐oxide) complexes

The complexes di‐n‐butyldi(2‐pyridinethiolato‐N‐oxide)tin(IV) (1), diphenyldi(2‐pyridinethiolato‐N‐oxide)tin(IV) ( 2 ) and dibenzyldi(2‐pyridinethiolato‐N‐oxide)tin(IV) ( 3 ) are synthesized and characterized by elemental analyses, IR, ¹H, ¹³C, ¹¹⁹Sn NMR spectroscopy, and their structures are determined by X‐ray crystallography. In complex 1 the coordination geometry at tin is a skew‐trapezoidal bipyramid, with cis‐S,S and cis‐O,O atoms occupying the trapezoidal plane and two n‐butyl groups occupying the apical positions, which also exhibits strong π–π stacking interactions. In complexes 2 and 3 the geometry at tin is distorted cis‐octahedral, with cis‐O,O and cis‐C,C atoms occupying the equatorial plane and trans‐S,S atoms occupying the apical positions. Their in vitro cytotoxicity against two human tumour cell lines, MCF‐7 and WiDr is reported. The ID₅₀ values found are comparable to those found for cis‐platin, but lower than for many other diorganotin compounds. Copyright © 2003 John Wiley & Sons, Ltd.     

基于偶氮联吡啶配体的银和钴配位聚合物的构筑与性质

通过将2个4,4''-联吡啶基团用偶氮基团连接,我们合成了新的配体顺式-和反式-1,2-二（（4,4''-联吡啶）-3-氮烯）（cis-L和trans-L）,并利用trans-L与银离子和钴离子构筑了配位聚合物{[Ag₂（trans-L）（ClO₄）₂]·4CH₃CN}_n（1）和{[Co（trans-L）₂（H₂O）₂]（ClO₄）₂}_n（2）。其中1为一维梯形链,链与链之间通过π-π以及Ag…Ag相互作用堆积;2为三维无限dendrimer结构,其Co中心具有合适的氧化还原电位,在以荧光素为光敏剂的条件下,可作为光催化剂实现光解水放氢。     

Schiff Base Complexes of Rhodium(I) with Tridentate N-Methyl-S-methyldithiocarbazate Ligands

Schiff bases derived from the condensation of β-diketones with N-methyl-S-methyldithiocarbazates yield cis dicarbonyl complexes Rh(CO)₂ (Schiff) on reaction with [Rh(μ-Cl)(CO)₂]₂. Those derived from aromatic aldehydes form trans dicarbonyl complexes. These complexes with excess of triphenylphosphine give only Rh(CO)(PPh₃)(Schiff). cis-1,5-cyclooctadiene (COD) reacts with cis dicarbonyl complexes to yield the carbonyl-free product Rh(COD)(Schiff); similar reactions have not been observed in the case of trans-dicarbonyl complexes. Oxidative addition of bromine to these complexes yields dibromo derivative in which the Schiff base acts as bidentate chelate. Rh(PPh₃)₂(Schiff) complexes have been obtained from the reaction of above Schiff bases with Rh(PPh₃)₃Cl. The structures of these new complexes have been determined based on IR and ¹H NMR spectra.     

Stabilization of highly reactive cyclic polyolefins by coordination to iron carbonyls: cis-cyclononatetraene-iron tricarbonyl

Reaction of cis-bicyclo[6.1.0]nona-2,4,6-triene (C₉H₁₀) (I) with Fe₂(CO)₉, at room temperature, yields a number of complexes (IV)–(IX). One of the e, (IX), is the Fe₂(CO)₆ derivative of the starting polyolefin (I), whereas the others are Fe(CO)₃ or Fe(CO)₄ complexes of isomeric C₉H₁₀ polyolefins.(IV) is (h⁴-l,2,3,4-cis-8,9-dihydroindene)iron tricarbonyl, (V) is tentatively formulated as (h²-or h²-5,6-cis-bicyclo[5.2.0]nona-2,5,8-triene)iron tetracarbonyl, (VI) has been characterized only as C₉H₁₀Fe(CO)₃, and (VII) and (VIII) are the asymmetric and symmetric isomers (h⁴-cis-cyclononatetraene)iron tricarbonyl. Characterization of the complexes has been obtained through PMR, IR, and mass spectra.Peculiar features of this reaction are the promotion of the polyolefin (I) rearrangement by iron carbonyls and the stabilization of highly reactive intermediates through coordination to the metal carbonyl groups. fa]Work presented in part at the 3rd International Symposium on Reactivity and Bonding in Transition Organometallic Compounds, Venice, September 9–10, 1970.     

Rhodium(I) Tristyrylphosphine Cyclooctadiene Complexes

Rhodium complexes with unsaturated phosphines as ligands were studied by NMR spectroscopy. Tris[(E,Z,Z)-styryl)phosphine is a stronger complex-forming agent compared with tris[(Z,Z,Z)-styryl)phosphine in view of the easier accessibility of its lone electron pair. The composition of the complexes and their NMR parameters suggest a square-planar structure with cis phosphine ligands.