Four-coordinate Structure Research Articles

Intramolecular indium-nitrogen coordination. Synthesis and NMR study of four-coordinate [2-Me2NCH(Z)C6H4]Me2In and five-coordinate [2-Me2NCH(Z)C6H4]2InCl (Z = H or SMe)

Arylindium compounds of the type ArJnCl and ArMezIn, in which the Ar group is either 2-Me2NCHzC6H4 or (S)-2-Me2NCH(Me)C6H4, have been synthesized by the organolithium route and characterized by 'H and 13C NMR spectroscopy. The NMR results clearly reveal that intramolecular In-N coordination occurs in solution, resulting in fivecoordinate ArzInCl and four-coordinate ArMezIn structures. In pyridine solution, the In-N bond in the four-coordinate ArMe21n compounds weakens as the result of the formation of a five-coordinate intermediate in which the NMe2 and pyridine ligand are in axial positions.

Different behavior of sulfonamides with respect to copper-substituted bovine and human carbonic anhydrases

Spectroscopic evidences for different types of derivatives, between sulfonamides and copper-substituted carbonic anhydrases are reported. Depending on the type of sulfonamide and on the particular isoenzyme used, the ligands substitute the coordinated water molecule or bind the metal at a different site without removing the water. A four-coordinated pseudotetrahedral structure is proposed in the former case and a five-coordinated one in the latter.

Copper(II) complexes with optically active diamines. I. Synthesis and properties of copper(II) complexes wit N-benzyl andN-methyl derivatives of 1, 2-diaminopropane

The paper descrives the synthesis of N-derivatives of (R)-1, 2-diaminopropane and the results of investigations on the electrical conductivity, magnetic susceptibility and absorption spectra of their compelexes with copper. As distict from α-amino acid complexes, where the insertion of N-alkyl substituents results in their structure being changed from distorted octahedral to four-coordinate square-planar, diamine comlexes invariably preseve their distorted octahedral structure with the introduction of up to two substituents in the ligand molecule, and in the case of more overloaded ligands binuclear complexes ar formed. Even in solvents with poor coordinative capacity no four-coordinate structures could be detected, which has been explained by the coordination of anions in the axial positions of the positively charged complexes.

ChemInform Abstract: EFFECT OF CHAIN LENGTH OF ALIPHATIC DIAMINES ON THE STRUCTURE AND REACTIVITY OF DICHLORO(DIAMINE)(η‐ETHYLENE)PLATINUM(II) COMPLEXES

AbstractAnhand 1H‐NMR‐ und elektronenspektroskopischer Daten wird eine Vergleichsuntersuchung der Produkte (I) durchgeführt, die bei der Reaktion von Zeises Salz oder seinem Dimeren mit den zweizähnigen aliphatischen Diaminen entstehen.

Effect of chain length of aliphatic diamines on the structure and reactivity of dichloro(diamine)(η-ethylene)platinum(II) complexes

Bidentate aliphatic diamines react with Zeise's salt, or its dimer, to give complexes of formula [Pt(C2H4)Cl2L][L =NNN′N′-tetramethyl-ethylenediamine (Me4en), -propane-1,3-diamine (Me4pn), or -butane-1,4-diamine (Me4bn)]. In chloroform solution the Me4en complex has a five-co-ordinate structure up to the temperature (10 °C) where decomposition with release of ethylene readily occurs. The Me4pn complex (34 °C) exhibits a geometry which is intermediate between four- and five-co-ordination. On decreasing the temperature, the five-co-ordination becomes increasingly important and is attained at –30 °C. The Me4bn complex at 34 °C has a purely four-coordinate structure involving equivalent ends of the diamine (obtained by rapid head-to-tail rearrangement). On decreasing the temperature to –30 °C the four-co-ordinate η-ethylene species is still present but in equilibrium with a new species, probably formed by nucleophilic attack on ethylene of a free end of the diamine. Decomposition studies in 1,2-dichloroethane have shown that the tendency of the [Pt(C2H4)Cl2L] species to release ethylene, giving [PtCl2L], increases with increasing preference for five- relative to four-co-ordination.

Preparation and structure of organoantimony(III) derivatives containing potentially dibentate ligands. Antimony-carbon cleavage upon complex formatio

Organoantimony(III) derivatives of the tyes RSbX 2 and R 2SbX in which X represents a N, N-diethyldithiocarbamate, N, N-diethylcarbamate, oximate or tropolonate ligand have been synthesized and investigated by spectroscopic (IR, UV) methods. In the RsbX 2 compounds (R = phenyl, alkyl) the ligand X appears to be bidentate both in the solid state and in solution making the antimony pentacoordinate. The compounds RSbOx 2 are exceptional in that dissolution in benzene or chloroform causes rupture of the weak coordinate Sb bond. Compounds R 2SbX, in which R = alky, spontaneously disproportionate into a 1/1 mixture of R 3SbX 2 is connected with the much reduced electrophilic reactivity of RSbX 2 as a result of pentacoordination. In contrast, componds of the typ Ph 2SbX appear to be stable. A four-coordinate structure is observed in the solid state, but three-coordination appears to be preferred in solution.

Phosphinohydrazines. Part IV. Coordination compounds of N,N-dimethyl,N′-diphenylphosphinohydrazine and N,N-dimethyl-N′-diphenylthiophosphinatohydrazine

A study of complexes of (a) N,N-dimethyl,N′-diphenylphosphinohydrazine, DPH, viz., Pd(DPH)Cl2, Pd(DPH)2Cl2, [Pd(DPH)2Cl]ClO4, Pt(DPH)2Cl2, Pt(DPH)Cl4, Hg(DPH)Cl2; (b) N,N-dimethyl,N´-diphenylthiophosphinatohydrazine, DPS, viz., Pd(DPS)Cl2, Pt(DPS)Cl4, Ag(DPS)NO3, Zn(DPS)Cl2, Cd(DPS)Cl2, and Hg(DPS)Cl2, and (c) N,N-dimethylhydrazine, DMH, viz., Zn(DMH)2Cl2 and Cd(DMH)Cl2, has been carried out using conductivity, molecular weight, infrared, and nuclear magnetic resonance measurements. DPH functions mostly as a unidentate ligand, with the phosphorus atom as the preferred donor site. Thus Pd(DPH)Cl2 is a chlorobridged dimer in solution in weakly polar solvents, while the monomeric form in polar solvents is of uncertain structure. A trans, four-coordinate structure is consistent for Pd(DPH)2Cl2. For [Pd(DPH)2Cl]ClO4, however, one DPH ligand is chelating through the phosphorus and terminal nitrogen atoms, while the second ligand is unidentate; the compound is a monomeric uni–univalent electrolyte in nitrobenzene. The ligand DPS appears to chelate via the sulfur and central nitrogen atoms, giving four-membered ring structures; a cis configuration is suggested for Pd(DPS)Cl2. Zn(DMH)2Cl2 is monomeric in solution, with the Me2N group coordinated to the metal.

The Structure of Ice II

The stability of the high pressure ice forms discovered by Tammann and Bridgman at very low temperatures and atmospheric pressure has made it possible to obtain x-ray powder diffraction photographs of these forms. The experimental procedure is very briefly discussed. An analysis of the ice II diffraction patterns leads to a side-centered orthorhombic cell with a=7.80A, b=4.50A, and c=5.56A. This cell contains eight molecules, has the symmetry of space group V5—C2221, and gives a value for the density of 1.21. The proposed arrangement of the hydrogen atoms indicates that the transition from ice I to ice II breaks up the water molecule, and that ice II is an ionic crystal. According to the model described the effect of a pressure of 2100 atmospheres in forming ice II is: (1) To decrease the packing volume of the oxygen ion approximately three percent; (2) To break down the open ice I structure by a slipping of the oxygen ion layers relative to each other; (3) To give a four-coordinated structure where each oxygen is surrounded by a badly distorted tetrahedron of oxygen ions.