Reductive nitrosylation of tetraoxometallates. part V1. single pot and A virtually single step synthesis of chromium(l) cyanonitrosyl derivatives directly from chromate(VI) in aqueous-aerobic media.

Cyanonitrosyl complexes and their derivatives of the types [Cr(NO)(CN)₄]^2?, [Cr(NO)(CN)₃H₂O]^? and [Cr(NO)(CN)₂ LL] [LL = 2,2′ bipyridine (bipy) or 1, 10-Phenanthroline (phen)] are synthesised directly from CrO₄^2? using NH₂OH.HCl, OH^? and CN^? and other appropriate ligands, virtually in a single step process in an aqueous aerobic medium. The compounds are characterised by IR, molar conductance, magnetic susceptibility, e.s.r, electronic spectra and thermoanalytical data.     

Reductive nitrosylation of tetraoxometallates—XI. Molybdate hydroxylamine reaction in the presence of cyanide: Synthesis of mono- and dinitrosyl cyan

The new molybdenum cyanonitrosyl complexes, R₂[Mo(NO)(CN)₅]·2H₂O (R = Ph₄P and Bu₄N) and [Mo(NO)(CN)₃(L-L)]·H₂O [L-L =     

Molecular fragmentations: Part VIII. Structures and energies of mass spectral fragments derived from tetraphosphorus trisulphide

Molecular structures and energies have been calculated in the MNDO approximation, for P₄S₃ and its molecular ion P₄S₃⁺, and for the mass spectral fragment pairs: (P₃S₃⁺ + P), (P₃S₂⁺ + PS), (P₃S⁺ + PS₂), (P₂S₃⁺ + P₂), (P₂S₂⁺ + P₂S), (P₂S⁺ + P₂S₂), (P₂S₂), PS₃⁺ + P₃), (PS₂⁺ + P₃S), (PS⁺ + P₃S₂), and (PS⁺ + P₂S + PS). Three distinct energy minima were found for each of P₂S₂⁺ and P₂S₂, and two minima for each of P₂S⁺, P₂S, PS₃⁺, PS₃⁺, PS₂⁺, PS₂, P₃⁺ and P₃. The fragments arising from P₄ and P₄⁺ were also investigated. The structures are discussed in terms of the Jahn—Teller effect, whose predictions are fulfilled without exception.     

Photochemical production of chromate(VI) ions from some chromium(Ill) complexes

Complexes of the type [Cr(CN)_6-X(OH)_X]^3- were found to produce the chromate(VI) ions upon exposure to UV radiation in alkaline medium. The quantum yields are reported and possible mechanism is discussed.     

An electrochemical study of redox indicators : Part I. Substituted chrysoidines

The electrochemical oxidation of various substituted chrysoidines was studied by cyclic voltammetry, to determine which have stable oxidation products. Only 4-hydroxy-chrysoidine has a stable product; the apparent oxidation potential is 0.779 V vs. NHE. 4-Methoxy- and 4-ethoxy-chrysoidine rapidly lose methanol or ethanol, respectively, so that the 4-hydroxychrysoidine wave appears on subsequent scans. All the other chrysoidines studied are irreversible. The results indicate that a hydroxy group in the 4-position is necessary for stability; the 4-alkoxychrysoidines can achieve the stable quinoidal structure by cleavage of the alkoxy group after nucleophilic attack.     

An answer to the spiro versus ansa dilemma in cyclophosphazenes: Part I. N3P3Cl4[NH(CH2)3NH]

Structural investigation, mainly by mass spectrometry and X-ray crystallography, of the product obtained from the reaction of propylenediamine and N₃P₃Cl₆ shows it to have a monospiro structure. It is demonstrated that in this case data collected through indirect structural methods such as IR or NMR spectroscopy could not provide a priori the right answer.     

Semiempirical molecular orbital studies on the electronic structure of molecules in excited states: The INDO/2-VN— 1 potential model: Part I.

The performance of the V_N—1 potential model at the INDO/2 level of approximation in the calculation of transition energy, singlet—triplet splitting, change in molecular structure, inversion barrier and electron-density distribution in the excited electronic states of a few simple carbonyls is analysed. The method turns out to be reasonably successful in many ways.     

Metal template synthesis of chromium(III) complexes

Chromium(III) complexes of Schiff bases resulting from the condensation of one mole of diacetyl with two moles of ethylene-diamine or 1,3 diaminopropane has been isolated by metal template reaction. The isolated complexes have been assigned cis configurations.     

Analytical applications of copper(II) and copper(I) in acetonitrile: potentiometric and spectrophotometric determination of dithiocarbamates

The use of copper(II) perchlorate and tetra-acetonitrilocopper(I) perchlorate (in acetonitrile) for the potentiometric and spectrophotometric determination of dithiocarbamates in acetonitrile medium is described. The proposed methods are simple, accurate and reliable and show promise of wide applicability. They are recommended for routine determination of dithiocarbamates. Their advantages over the carbon disulphide evolution method, commonly employed for the determination of these compounds, are discussed.     

Photophysical studies of uranyl complexes: VIII. Luminescence spectra of UO2SO4 · 312H2O and two polymorphs of bis(urea) uranyl sulfate

The photoluminescence spectra of hydrated and anhydrous uranyl sulfates have been studied under conditions of high resolution at cryogenic temperatures. All uranyl sulfate systems were found to yield nonequivalent spectra: the energies for the electronic and vibronic origins were found to vary with the system, and certain uranyl vibrational frequencies exhibited a dependence on environment. These differences must reflect the various ways in which the uranyl centers are linked by the bridging sulfate groups, as this linking is the main difference between the various structures.     

1-pyrazolyliridium(I) derivatives; x-ray evidence for monodentate pyrazolato ligands

An X-ray crystal structure determination has shown that trans-(Ph₃P)₂Ir(CO)-(pyrazolato-N), obtained from the chloride and potassium pyrazolate, contains a monodentate azolato ligand.     

Molecular fragmentations: Part VII. Structures and energies of mass spectral fragments derived from benzene

Molecular structures and energies have been calculated, using MINDO/3, of the mass spectral ions arising from benzene: (C₆H₆)⁺ (three non-valence isomers); (C₆H₅⁺); (C₅H₃⁺) (four isomers); (C₄H₄)⁺ (three isomers); (C₄H₃)⁺ (two isomers); (C₄H₂)⁺ (four isomers); (C₃H₃)⁺; and (C₂H₂)⁺. Calculations have been made for the conjugate neutral fragments, allowing calculation of appearance potentials, and also for the ion (C₆H₇)⁺.     

Mass spectrometry of π-complexes of transition metals XIX. Cymantrene-cyclopentadienylmetal carbonyl derivatives

Mass spectra of the complexes π-C₅H₅M(CO)_nXC₅H₄Mn(CO)₃ have been studied. The presence of intense ions C₅H₅M(CO)_nMn⁺ suggests that synthesis of new compounds with charged bivalent manganese of π-C₅H₅W(CO)₃Mn⁺X^? type is possible. In addition, the presence of these ions indicates preferential loss of the first three carbonyl groups from the manganese atom.     

Identification of Cu(II)/Cu(III) couples in binuclear copper(II) complexes

A new series of binuclear copper(II) complexes were synthesised and studied by magnetic, spectral, ESR and cyclic voltammetry methods. The μ_eff values per copper atom correspond to the values observed for mononuclear copper(II) complexes. ESR spectral data in solution indicate weak interactions resulting from the electron delocalisation through the ligand system. Two nearly reversible red-ox couples are identified at $\text{+}\text{?}$0.50 V and $\text{+}\text{?}$0.75 V vs SCE. They correspond to Cu(II)αCu(III) red-ox processes, successively occurring at the two copper sites in the binuclear complexes.     

Molecular fragmentations: Part IX. Structures and energies of mass spectral fragments derived from xanthan hydride, 5-amino-1,2,4-dithiazolin-3-thione

Structures and energies have been calculated, in the MNDO approximation, for xanthan hydride (C₂H₂N₂S₃) and its molecular cation, and for the mass spectral fragment ions H₂NCNCS⁺, HNCNCS⁺, CS₂⁺, H₂N₂CS⁺ (two isomers), HN₂CS⁺, S₂⁺, H₂NCS⁺ (three isomers), HNCS⁺ (two isomers), H₃N₂C₂⁺ (four isomers), CS⁺ and HNCS⁺² (two isomers), together with the corresponding neutral fragments.     

Cyclic voltammetric studies of copper(II) dipeptide complexes. Evidence for copper(I) dipeptide complexes in aqueous media

The reduction of the title complexes was studied by cyclic voltammetry in aqueous media. It proceeds through a one-electron process generating intermediate copper(I) dipeptide complexes. The copper(I) dipeptide complexes are found to be short-lived and undergo transformations eventually generating Cu⁰ at the mercury electrode. The unchanged fraction of the copper(I) species is re-oxidised to the copper(II) complexes. The Cu⁰ generated undergoes a two-electron oxidation at a more anodic potential than the copper(I) complexes. pH-dependence of the title complexes is also investigated by cyclic voltammetry.     

Cationic carbonyl complexes of manganese (I) with nitriles and dinitriles

The reaction of Mn(CO)₅OClO₃ with nitriles,L, and dinitriles,L-L, in a wide variety of conditions affords cationic pentacarbonyls, [Mn(CO)₅(L)] ClO₄ and [Mn (CO)₅(L-L)] ClO₄ and fac-tricarbonyls, [Mn (CO)₃ (L)₃] ClO₄ and [(CO) ₃Mn (μ L-L) ₃Mn (CO)₃] (ClO₄)₂     

Generation of reactive cyclopentadienylcobalt(I) derivatives by reduction of dicyclopentadienyldicobalt tetraiodide

Reduction of [(C₅H₅)CoI₂]₂ by sodium amalgam in toluene in the presence of 1,3-butadiene, 1,3-cyclohexadiene or 1,5-cyclooctadiene affords the corresponding cyclopentadienylcobalt(I) diolefin complexes in high yields. Reduction of [(C₅H₅)CoI₂]₂ in the presence of 2-butyne yields the binuclear metallocyclic compound (C₅H₅)₂Co₂(C₄(CH₃)₄), previously characterized as a structurally fluxional catalyst for alkyne cyclotrimerisation, as the major product; a trinuclear dicarbyne compound, (C₅H₅)₃Co₃(C-CH₃)₂, is obtained as a minor product. With diphenylacetylene, the analogous phenylcarbyne derivative (C₅H₅)₃Co₃(C-C₆H₅)₂, previously obtained from thermal reaction with (C₅H₅)Co(CO)₂, is obtained along with the major product, the tetraphenylcyclobutadiene complex (C₅H₅)Co(C₄(C₆H₅)₄). Pathways and intermediates for these reactions are discussed.     

Molecular fragmentations: Part VI. Structures and energies of the valence isomers of benzene,and their molecular cations and anions

Molecular structures and energies have been calculated, in the MINDO/3 approximation, for neutral singlets and triplets, and for molecular cations and anions of benzene and seven of its valence isomers.