Henri Arzoumanian

Reaction of molybdenum−molybdenum triple bonded compounds with group VIII peroxo-transition metal complexes

Abstract The reaction of (t-butyl-NC) 2 NiO 2 with (C 5 Me 5 ) 2 Mo 2 (CO) 4 results in complete decarbonylation with retention of the metal—metal bond and formation of one oxo and one μ-oxo group per molybdenum. The structure has been established from spectral data and a single crystal X-ray study.

Arylalkane oxidation by dioxo[4,4′-di(tert-butyl)-2,2′-bipyridyl]molybdenum(VI) complexes

Arylalkanes are oxidized by dithiocyanato- and dibromo-[4,4′-di(tert-butyl)-2,2′-bipyridyl]molybdenum(VI) dioxo complexes either thermally or under UV irradiation.

A kinetic study of the catalytic decomposition of cyclohexenyl hydroperoxide by RhCl(PPh3)3

Abstract The study of the catalytic decomposition of cyclohexenyl hydroperoxide shows that the reaction occurs by a free-radical process which can be described by a monoelectronic Haber-Weiss mechanism involving rhodium(I), rhodium(II) and rhodium(III) species. The validity of the proposed mechanism was tested by simulating it on a digital computer and comparing the observed and calculated rate constants. Good agreement between kinetic results obtained from the decomposition study and a previously performed autoxidation study was also verified.

Preparation and x-ray structure determination of penta-and tetracyano-oxomolybdenum(IV) anions. The influence of water on their reactivity

SummarySeveral penta-and tetracyanooxomolybdenum(IV) anions have been synthesized containing different numbers of H2O molecules, either coordinated or present as crystallisation molecules. The influence of these molecules on the reactivity of the complex, especially towards O2, is discussed. Three compounds were characterized by x-ray structure determination. [Mo(O)(CN)5(H2O)2(MeCN)2][PPh4]4Cl belongs to triclinic space group P-1 witha=13.146(3) Å,b=16.944(5) Å,c=21.761(6) Å, α=84.72(2)°, β=87.15(2)° and γ=85.25(2)°. The volume of the unit cell is 4678(6)Å3 withz=2. The structure was refined to R=6.5%. [Mo(O)(CN)4(H2O)·6H2O][PPh4]2 belongs to monoclinic space group P21/n witha=15.313(2)Å,b=19.983(3)Å,c=17.006(2)Å, β=100.51(2)°. The volume of the unit cell is 5117(3)Å3 withz=4. The structure was refined to R=8.7%. [Mo(O)(CN)4(MeCN)](PH3)2N]2 belongs to triclinic space group P-1 witha=13.770(4)Å,b=16.292(5)Å,c=16.889(5)Å, α=73.23(2)°, β=72.02(2)° and γ=71.57(2)°. The volume of the unit cell is 3342(3)Å3 withz=2. The structure was refined to R=7.2%.

Metalloporphyrin-catalyzed oxidations [1] 2. Inhibition and re-activation of metalloporphyrin catalysts. A simple model for hormone action

Abstract Cobalt(III) and iron(III) porphyrins have been found to catalyse the autoxidation of cyclohexene to allylic hydroperoxides which then decomposed to give 2-cyclohexenone as the main product. If molybdenum of vanadium complexes (porphyrinates of acetylacetonates) were added in equimolar amounts to the cobalt or iron porphyrins, the reaction was stopped. Addition of steroids, deazaflavin or chrysene, led to a re-activation of the iron and cobalt porphyrin catalysts. With lanosterol equimolar amounts were sufficient to produce this effect. The main oxidation product of cyclohexene was again 2-cyclohexenone. Reactivation could also be achieved with high concentrations of cumene. In this case a 1|1 mixture of cyclohexane epoxide and 2-cyclohexenol were formed. The possible bearing of the findings on the action of steroid hormones in nature is briefly discussed.

An unusual route to the isopolymolybdates; Octamolybdate β-[Mo8O26]4− and hexamolybdate [Mo6O19]2−. Reaction of dioxomolybdenum complexes with triphenylphosphonium ylides. Crystal structures of the salts [PPh3CH2COOEt]+2[NH2Et]+2 [Mo8O26]4−, [PPh3CH2COOEt]+2 [Mo6O19]2−, and [PPh3CH2Ph]+2 [Mo6O19]2−

Abstract Isopolymolybdate anions with various counterions have been obtained from the reaction of dioxomolybdenum(VI) compounds and the triphenylphosphonium ylides RCHPPh 3 (R = Ph, COOEt, H) in dichloromethane. The polyoxoanions are of two types, β-[Mo 8 O 26 ] 4− and [Mo 6 O 19 ] 2− , depending on the starting molybdates. X-ray structure determinations have been performed on the salts [PPh 3 CH 2 COOEt] + 2 [NH 2 Et] + 2 [Mo 8 O 26 ] 4− , [PPh 3 CH 2 COOEt] + 2 [Mo 6 O 19 ] 2− , and [PPh 3 CH 2 Ph] + 2 [Mo 6 O 19 ] 2− .

Solid—liquid phase transfer and cobalt catalyzed synthesis of but-2-enolide

Abstract Tris dioxa-3,6-heptylamine (TDA) is an effective solid—liquid phase transfer catalyst for the synthesis of hydroxybut-2-enolide from alkyne and benzyl bromide under CO atmosphere.

Catalytic hydrocyanation of α-ketoalkynes by Ni(CN)2/CO/KCN system in alkaline aqueous media: Identification of the active species

Abstract 5-Hydroxy-3-pyrrolin-2-ones are regioselectively synthesized in a good yield under very mild conditions by tetracyanonickelate (0) ion catalyzed hydrocyanation of α-ketoalkynes, in the absence of hydrogen cyanide. The catalyst is prepared in situ in a basic aqueous medium by reduction of Ni(CN) 2 with CO in the excess of KCN. From the IR spectroscopy studies and by evaluation of catalytic activity of some cyanonickelates it is proposed that [Ni(CN) 4 ] −4 anion is the active species in the process. A possible mechanism is suggested for the conversion of nickel cyanide to [Ni(CN) 4 ] −4 . The effect of the reaction variables, e.g.: reaction time, temperature, absorption of carbon monoxide, the concentration of potassium cyanide, water, substrate, and sodium hydroxide were also examined.

Synthesis and Characterisation of a Dioxo‐μ‐Oxo Molybdenum Dimer: An Unusual case of a μ‐Oxo Conformational Equilibrium

A new thiocyanatomolybdenum(VI) dioxo-μ-oxo complex dimer bearing a 4,4′-di-tert-butyl-2,2′-bipyridine ligand (2) is shown to exist in the crystal cell unit as a meso (Mo-O–Mo angle of 180°) and d,l, pair (Mo–O–Mo angle of 155.7°). These conformers are in equilibrium in solution and have been observed clearly by 1H NMR spectroscopy.

Palladium and phase transfer catalyzed carbonylation of propargyl derivatives

Abstract The palladium catalyzed carbonylation of propargyl derivatives in the presence of phosphines and under phase transfer conditions leads to the formation of allenic acids and olefinic diacids with good yields and very high selectivity.