Download or read book Synthesis of Low-coordinate Transition Metal Bis(alkoxide) Complexes and Their Reactivity Toward Small Molecules written by Maryam Yousif and published by . This book was released on 2017 with total page 217 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation focused on the synthesis of new transition metal complexes in bis(alkoxide) ligand environments and the investigation of their reactivity in nitrene-group transfer catalysis and small molecule activation. Treatment of Cr(N(SiMe3)2)2(THF)2 with two equivalents of HOR (OR = OCtBu2Ph) led to the formation of the chromium(II) alkoxide dimer, Cr2(OR)4. Upon the reaction with bulky aryl and alkyl azides, Cr2(OR)4 led to the stable Cr(IV) mono(imido) complexes, Cr(OR)2(NR), featuring trigonal planar metal centers. In contrast, less bulky aryl azides led to the formation of chromium (VI) bis(imido) complexes Cr(OR)2(NR)2, independent of the amount of azide used. Chromium(IV) mono(imido) species Cr(OR)2(NR) is capable of nitrene transfer to isocyanides to form asymmetric carbodiimides (RNCNR'). When excess isocyanide is added to Cr(OR)2(NR), a new chromium(II) complex, Cr(OR)2(CNR2)4, was identified by X-ray crystallography. This tetrakis(isocyanide) chromium(II) complex is also capable of forming carbodiimide when azide is introduced. Efficient catalytic formation of carbodiimides was obtained using 2.5 mol% of Cr2(OR)4 for the mixtures of bulky organoazides and isocyanides; no catalytic reactivity was observed for the non-bulky aryl azides. DFT calculations suggest that trigonal CrIV(OR)2(NR) intermediate is the key species in the reaction mechanism as, due to it coordinative unsaturation, it allows isocyanide binding to the metal, which enables subsequent C-N bond formation. A bulkier alkoxide ligand HOR' (R = CtBu2(3,5-Ph2Ph)) was synthesized by lithium halogen exchange reaction. The protonolysis of the metal complexes, M(N(SiMe3)2(THF)x, with HOR' enabled an easy isolation of new bis(alkoxide) precursors M(OR')2(THF)2 (where M = Cr, Co, Fe) featuring cis-divacant octahedral geometry. The chemistry of the iron bis(alkoxide) compound Fe(OR')2(THF)2 with the variety of aryl azides was investigated.