Ligand-field photolysis of [Mo(CN)8]4- in aqueous hydrazine: trapped Mo(II) intermediate and catalytic disproportionation of hydrazine by cyano-ligated Mo(III,IV) complexes.
The substitutional photolysis of K4[Mo(CN)8].2H2O in 98% N2H4.H2O has been investigated in detail. A molybdenum(II) intermediate, K5[Mo(CN)7].N2H4, is isolated in the primary stage of the reaction that involves the oxidation of N2H4 to N2, as evidenced by the analysis of evolving gases. The powder X-ray crystal structure of K5[Mo(CN)7].N2H4 indicates the pentagonal bipiramidal geometry of the anion and the presence of N2H4 in proximity to the CN(-) ligands. The salt is characterized by means of EDS, IR, UV-vis, and EPR spectroscopy as well as cyclic voltammetry measurements. The secondary stages of photolysis, involving the catalytic decomposition of N2H4 into NH3 and N2, lead to the formation of a molybdenum(IV) complex, [Mo(CN)4O(NH3)]2-. The monitoring of the amounts of evolving gases combined with UV-vis and EPR spectroscopic measurements at various stages of photolysis indicate that the molybdenum(III,IV) couple is catalytically active. The scheme of the catalytic decomposition of hydrazine is presented and discussed.
Szklarzewicz
Janusz
J
Faculty of Chemistry, Jagiellonian University, Kraków, Poland. szklarze@chemia.uj.edu.pl
Matoga
Dariusz
D
Kłyś
Agnieszka
A
Lasocha
Wiesław
W
D002384:Catalysis; D003486:Cyanides / Q000737:chemistry*; D006834:Hydrazines / Q000737:chemistry*; D008024:Ligands; D008855:Microscopy, Electron, Scanning; D008956:Models, Chemical; D008982:Molybdenum / Q000737:chemistry*; D010782:Photolysis; D014867:Water / Q000737:chemistry*
D003486:Cyanides; D006834:Hydrazines; D008024:Ligands; D014867:Water; C029424:hydrazine; D008982:Molybdenum