טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
Ph.D Thesis
Ph.D StudentMolev Gregory
SubjectParamagnetic Metallosilanes
DepartmentDepartment of Chemistry
Supervisor ? 18? Yitzhak Apeloig
Full Thesis textFull thesis text - English Version


Abstract

The main goal of this research was to prepare and characterize novel paramagnetic transition metal silyl complexes - a group of compounds previously unknown. We aimed to answer basic questions regarding the structure, bonding and reactivity of these very important species.

The research included the synthesis and characterization of radicals of the types LnM.SiR3 (silyl substituted metal centered radicals) and LnMSi.R2 (metal substituted silicon centered radicals) and the study of their chemistry. We concentrated on Pt-silyl complexes because of their importance as catalysts, but Rh and Hf silyl complexes were also studied. A major challenge was the synthesis of the precursors for these radicals. The target radicals were generated by two methods: (a) irradiation of the corresponding metallo-silyl-mercury compounds and (b) radical hydrogen abstraction from the corresponding metallosilanes.

The main achievements of this research are:

(a) A new insertion reaction of a Pt0 complex, (dmpe)Pt(PEt3)2, into a Si-Hg bond of various mercurio-silanes was discovered and studied in some detail. Insertion of a Pt0 complex into a Si-Hg bond is faster than its insertion into a Si-H bond. Several novel platinum silyl complexes were isolated and their structures were determined by X-ray crystallography; two of them exhibit unusual coordinative Pt-Hg bonds.

(b) Two new mercurio-silyllithium reagents were synthesized. Their reactions with metal electrophiles were studied and novel rhodium and hafnium mercurio-silyl complexes were isolated and characterized by X-ray crystallography.

(c) The first neutral platinum centered radical was generated and characterized by EPR spectroscopy, DFT calculations and a trapping experiment. The kinetics of its decay and the structures of its decomposition products were determined.

(d)  The first platinum substituted silyl radical was generated and characterized by EPR spectroscopy and by DFT calculations which are in good agreement with experiment.

(e) New platinum silyl complexes with bulky silyl substituents were synthesized and characterized by X-ray crystallography.

(f)  A radical hydrogen abstraction reaction from platinum silyl complexes was demonstrated for the first time.

(g) Two novel cyclic platinum silanes: a platinum trisilacyclobutane and a platinum tetrasilacyclopentane, were isolated and characterized by X-ray crystallography.

(h) A new platinum silacyclopropane was synthesized by a direct reaction of a Pt0 complex with a silene. Its structure and the structure of its unusual complex with benzene were determined by X-ray crystallography.