Synthesis and catalytic potential of molybdenum(VI) complexes with hydrazone ligand obtained from 5-nitrosalicylaldehide and benzhydrazide ; Choosing demonstration for homogenous catalysis

Ovaj diplomski rad sastoji se od dvije cjeline: istraživačkog i metodičkog dijela. U istraživačkom dijelu pripravljen je hidrazonski ligand izveden iz 5-nitrosalicilaldehida i benzhidrazida (H2L). Reakcijom [MoO2(acac)2] i hidrazonskog liganda (H2L), pripravljeni su kompleksni spojevi molibdena(VI). Mononuklearni kompleksni spojevi, [MoO2(L)(MeOH)], [MoO2(L)(H2O)], [MoO2(L)(EtOH)], dobiveni su iz metanolne, acetonitrilne i etanolne otopine, a dinuklearni, [(MoO2(L))2(4,4'-bipiridin)], iz acetonitrilne otopine uz dodatak 4,4'-bipiridina. Kompleksni spojevi su karakterizirani i identificirani metodom infracrvene spektroskopije, elementnom i termogravimetrijskom analizom. Difrakcijom rentgenskog zračenja na jediničnom kristalu određena je molekulska i kristalna struktura mononuklearnih i dinuklearnog kompleksnog spoja molibdena(VI). Katalitička aktivnost pripravljenog mononuklearnog spoja [MoO2(L)(MeOH)], ispitana je u reakciji (ep)oksidacije cikloheksena i transcikloheksan-1,2-diola uz vodikov peroksid kao oksidacijsko sredstvo s ciljem dobivanja adipinske kiseline. Metodički dio rada usmjeren je na paramatre koji su bitni pri odabiru pokusa koji će biti temelj nastavnog sata učenja otkrivanjem na temu katalize. Poseban osvrt dan je na pokus koji se desetljećima u međunarodnoj literaturi navodi kao primjer homogene katalize – na potencijalnu reakciju tartaratnih iona s molekulama vodikovog peroksida u prisustvu kobaltovih(II) iona. Na temelju detaljne analize dostupne literature i provedenih pokusa ovu kemijsku promjenu bolje je opisati terminom sparene reakcije nego je navoditi kao primjer katalitičkog pokusa.This Diploma thesis consists of two parts: the research part and the methodical part. In the research part a hydrazone ligand derived from 5-nitrosalicyaldehyde and benzhydrazide (H2L) was prepared. By the reaction of [MoO2(acac)2] and hydrazone ligand (H2L), complexes of molybdenum(VI) were synthesized. Mononuclear complexes [MoO2(L)(MeOH)], [MoO2(L)(H2O)], [MoO2(L)(EtOH)], were syntesised from methanol, acetonitrile and ethanol solutions, and dinuclear one, [(MoO2(L))2(4,4'- bipyridine)], from an acetonitrile solution with the addition of 4,4'-bipyridine. All complexes were characterized and identified by infrared spectroscopy, element and thermogravimetric analysis. The molecular and crystal structure of mononuclear and dinuclear molybdenum(VI) complex was determined by the single crystal X-ray diffraction. Catalytic activity of mononuclear complex [MoO2(L)(MeOH)], was tested in the (ep)oxidation reaction of cyclohexene and trans-cyclohex-1,2-an diole, with hydrogen peroxide as an oxidant, with the aim of obtainig apidic acid. Methodological part of the thesis is focused on parameters that should be addressed when one is choosing a demonstration experiment that should serve as a basis to design a lesson based on guided inquiry learning on the subject of catalysis. Special attention is given to the experiment that is for decades quoted in international literature as an example of homogenous catalysis – potential reaction of tartarate ions and hydrogen peroxide molecules in presence of cobalt(II) ions. Detailed analysis of available literature and conducted experiments showed that it would be better to consider this chemical change as an example of coupled reactions than to use it as demonstration of homogenous catalysis