Showing papers in "Transition Metal Chemistry in 1976"

A π-acceptor series for phosphines from51V N.M.R. data on [η5-CpV(CO)3L] complexes

Abstract: Qualitative molecular orbital considerations of the complexes [η5-CPV(CO)3 L] (L = substituted phosphane, SbPh3, AsPh3, CN−) suggest that s' V chemical shift parameters (τ) obtained for these compounds should correlate with the π-acceptor abilities of L. Based on observed r-values, the ligands are arranged in sequence of their π-acceptor ability, which lies in the order P(OR)3 > CN− > PR'33 ∼ SbPh3 ∼ PPhF2 > P(i-Bu)3 ∼ P(NR 2 ″ )3 > PPh3 > AsPh3 Nuclear spin-spin coupling constants J (51V-31 P), line widths Δ H and i.r. data in the ν(CO) region are also presented.

Reactions of carbon monoxide with transition metal-carbon bonds

Abstract: Insertions of carbon monoxide into transition metal-carbon bonds are among the most selective methods for the catalytic introduction of oxygen into organic compounds A variety of processes are known today and most of them are of great industrial importance Depending on the nature of the organic substrate, the catalyst and additional reaction components products range from aldehydes, alcohols, and acids to esters, anhydrides, acid chlorides, amides etc An attempt is made here to show that all these reactions proceed by similar mechanisms

Synthesis of copper(II) and nickel(II) triazacycloalkane complexes

Abstract: Copper(II) and nickel(II) complexes of triazacycloalkanes (pqr-cy), with p, q, r = 2–6, have been prepared and characterized by means of electronic and i.r. spectroscopy, and by magnetic measurements. With nickel(II) mononuclear octahedral complexes [Ni(pgr-cy)2](CI04)2 are formed, but for copper(II) mononuclear octahedral complexes were obtained only for 222-cy and 223-cy. The other ligands gave copper(II) complexes of the type [Cu(pgr-cy)CI]CIO4, [Cu(pgr-cy)OH]ClO4, Or [Cu(pgr-cy)CI1/2OH1/2]ClO4. The hydroxy complexes have low magnetic moments and binuclear hydroxy bridged structures are proposed.

Tricarbonylbis(η-cyclopentadienyl)diiron and iododicarbonyl(η-cyclopentadienyl)iron amine complexes

Abstract: The monodentate ligands, L, ethylamine, butylamine, cyclohexylamine, benzylamine, piperidine and morpholine, and bidentate ligands, L, 1,10-phenanthroline and 2,2′-bipyridyl react with tetracarbonylbis(η-cyclopentadienyl)diiron to give monosubstituted derivatives, (η-C5H5)2Fe2(CO)3L, and with iododicarbonyl(η-cyclopentadienyl)iron to yield ionic products, [(η-C5H5)Fe(CO)2L]I. I.r. spectral studies suggest that two isomeric (η-C5H5)2-Fe2(CO)3L molecules exist.

The mechanism of catalyst formation from tungsten hexachloride and cocatalyst in olefin metathesis

Abstract: The mechanism of the catalyst formation in hept-2-ene metathesis was investigated by gas chromatographic analysis of the products from reactions of tungsten hexachloride with R4Sn(R = Ph, n-Bu), RLi, RMgl (R = n-Bu) or R3Al(R = Et) as cocatalyst. The products are chiefly RH, RCl and RR species, and the highest catalytic activity is observed for an equimolar ratio of products to tungsten hexachloride. The facts suggested that the active catalyst, a WCl4 species, is formed by the elimination of two R groups from R2WCl4 and/or one R group and chlorine from RWCl5. The total quantity and composition of the products varies with the cocatalyst:WCl6 ratio, and the difference between the behavior of tetra-n-butylstannane and n-butyllithium in the catalyst formation is explainable on the basis of their relative nucleophilicities. Gas chromatographic analysis of the organotin compounds resulting from the WCl6:: Bu4Sn system shows that tetra-n-butylstannane provides only one butyl group per mole of WCl6.

Equilibrium constants of some protonated, nonprotonated and hydroxo complexes of uranium(VI) with xylenol orange

Abstract: The species, UO2H3L−, UO2H2L2−, UO2HL3−, UO2L4−, UO2(OH)L5− and UO2(OH)2L6− are found in the equilibria between uranyl ions and 3,3′-bis[N,N′-di(carboxymethyl)-aminomethyl]-o-cresolsulphonphthalein (H6L; xylenol orange; dcac) in aqueous solution. The equilibria have been studied by the potentiometric method at 25° and at an ionic strength of 0.1M (KNO3). New algebraic equations have been employed to evaluate the equilibrium constants.

Extrusion of halogens from aromatic compounds by transition metal complexes. Reaction of IrCl(CO)(PPh3)2 with halogenated benzaldehydes

Abstract: The chlorobenzaldehydes, 2-bromo-4-tolualdehyde and 2-iodobenzaldehyde react with IrCl(CO)(PPh3)2 at 190 to 220° to give PhIrCl2(CO)(PPh3)2,p-tolyl IrBr2(CO)(PPh3)2 and PhIrCl2(CO)(PPh3), respectively Iodo-and bromobenzene form PhIrCl(Hal)(CO)(PPh3)2 complexes, whereas chlorobenzene does not react under these conditions Halogen transfer from the aromatic to the metal atom in the reaction of halobenzaldehydes, and halogen extrusion in various homogeneously catalyzed processes, are assumed to follow similar reaction patterns

Electrophilic substitution in phenanthroline coordinated to transition metal ions. Rates of nitration of some rhodium(III) and cobalt(III) complexes

Abstract: The rates of nitration in sulphuric acid of 1,10-phenanthroline coordinated to rhodium(III) and cobalt(Ill) in a number of complexes have been measured and found to be much greater in these complexes than in free phenanthroline under the same conditions. Relative rates are generally higher in those complexes which bear the smaller overall positive charges, but these charges may be modified by protonation of the other ligands in the complexes.