Structure-Property Relationships in Polynuclear mu-O Bridged Aqua Clusters: Effect of M-muO bond covalency

The extent of M-mu O bond covalency is the dominant factor controlling the M-mu O distance, the terminal water pK(a) and exchange mechanism within a range of polynuclear oxo-bridged aqueous clusters. These effects lead to limiting associative/dissociative mechanisms for water exchange on the polynuclear species.</p

Transition Metals in Selective Hydrocarbon Oxygenation Catalysis : Kinetic Studies of the Reactions of Cyclohexylhydroperoxide under Gif Conditions

Iron(III) chloride in the presence of excess H2O2 in 10:1 pyridine-acetic acid catalyses the clean conversion of cyclohexylhydroperoxide to cyclohexanone on the same time scale (hours) as observed for the latter stages of the Barton GoAggII system for the oxygenation of cyclohexane. The addition of one equivalent of picolinic acid/Fe-III causes a significant increase (10 fold) in the conversion rate (no change in products) paralleling the rate enhancing effect observed in the Fe-III-picolinate-H2O2 (GoAggIII) oxygenating system. The Fe-III catalysed reaction in the absence of H2O2, however, is totally different with evidence of a linear induction period before the onset of product autocatalysis by the ketone. Here only a very slight rate enhancement is seen on adding picolinic acid and a different mechanism may be relevant. These and other observations have implications for the nature of reactions taking place in typical 'Gif' systems.</p

Structural parameters for the incomplete cuboidal cluster cation: [Nb₃(µ₃-Cl)(µ-O)₃(OH₂)₉]⁴+ in solutions of acid hydrolysed trivalent niobium from Niobium K edge EXAFS

A niobium K edge EXAFS study on the green solutions obtained following hydrolysis of NbCl3(dme) in aqueous non-oxidising strong acids has shown that the major species resulting in these solutions is the incomplete cuboidal chloride-capped triangular niobium cation, [Nb-3(mu(3)-Cl)(mu-O)(3)(OH2)(9)](4+).</p

Transition Metals in Selective Hydrocarbon Oxygenation Catalysis : Kinetic Studies of the Reactions of Cyclohexylhydroperoxide under Gif Conditions

Iron(III) chloride in the presence of excess H2O2 in 10:1 pyridine-acetic acid catalyses the clean conversion of cyclohexylhydroperoxide to cyclohexanone on the same time scale (hours) as observed for the latter stages of the Barton GoAggII system for the oxygenation of cyclohexane. The addition of one equivalent of picolinic acid/Fe-III causes a significant increase (10 fold) in the conversion rate (no change in products) paralleling the rate enhancing effect observed in the Fe-III-picolinate-H2O2 (GoAggIII) oxygenating system. The Fe-III catalysed reaction in the absence of H2O2, however, is totally different with evidence of a linear induction period before the onset of product autocatalysis by the ketone. Here only a very slight rate enhancement is seen on adding picolinic acid and a different mechanism may be relevant. These and other observations have implications for the nature of reactions taking place in typical 'Gif' systems.</p

Structural parameters for the incomplete cuboidal cluster cation: [Nb₃(µ₃-Cl)(µ-O)₃(OH₂)₉]⁴+ in solutions of acid hydrolysed trivalent niobium from Niobium K edge EXAFS

A niobium K edge EXAFS study on the green solutions obtained following hydrolysis of NbCl3(dme) in aqueous non-oxidising strong acids has shown that the major species resulting in these solutions is the incomplete cuboidal chloride-capped triangular niobium cation, [Nb-3(mu(3)-Cl)(mu-O)(3)(OH2)(9)](4+).</p