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Synthetic investigations toward metal nitrosyl complexes

University of British Columbia

Reaction of Cp*W(NO)(CH₂SiMe₃)Cl with AgBF4 in MeCN leads to isolation of [Cp*W(NO)(CH₂SiMe₃)(NCMe)₂]BF₄, 2.1. The reactivity of this complex is explored, in particular, the reaction of 2.1 with H₂0 which results in stepwise hydrolysis of the nitrosyl ligand. Labelling studies with D₂0 and H₂¹⁸O are performed which give some insight into the mechanism of the transformation of 2.1 to Cp*W0₂(CH₂SiMe₃) and the fate of the NO ligand. The synthesis and characterisation of a range of carboxylate-containing nitrosyl complexes of the general class Cp*W(NO)(0₂CR')X [X = CH₂SiMe₃ , CI] and attempts to form cationic complexes from them are also described. The Li salt of [Cp*Mo(NO)(CH₂SiMe₃)(=CHSiMe₃)]⁻ 3.1 may be synthesised by treatment of Cp*Mo(TSfO)(CH2SiMe3)2 with a variety of Li reagents. The reaction pathway varies greatly between each reagent and in some cases intermediate complexes may be isolated. Treatment of Cp*Mo(NO)(CH₂SiMe₃)₂ with LiN(SiMe₃)₂ in THF leads directly to the alkylidene complex 3.1. A kinetic study of this reaction is presented. Treatment of Cp*Mo(NO)(CH₂SiMe₃)₂ with LiN(C₃H₇)₂ results in deprotonation of the Cp* ligand and formation of [(n⁵,n¹- C₅Me₄CH₂)Mo(NO)(CH₂SiMe₃)₂][Li(THF)₃], 3.2 which converts to 3.1 when left in solution. Reaction of Cp*Mo(NO)(CH₂SiMe₃)₂ with LiPPh₂ in THF results in a one-electron reduction and production of {[Cp*Mo(NO)(CH₂SiMe₃)2][Li(THF)]}₂ 3.3. If not isolated, this complex is converted to 3.1 by the Ph₂P-PPh₂ coproduct by hydrogen-atom abstraction. 3.1 may also be formed by warming [Cp*Mo(NO)(CH₂SiMe₃)₂(Me)][Li(THF)₃], which is formed from the reaction of Cp*Mo(NO)(CH₂SiMe₃)₂ with MeLi. MeLi may also be reacted directly with Cp*Mo(NO)Cl₂ to yield [Cp*Mo(NO)(Me)₃][Li(THF)₃], Treatment of Cp*M(NO)(X)Cl complexes [M = Mo, W; X, = CH₂SiMe₃ , CH₂CMe₃ , NHCMe₃ , OCMe₃ , CI]) with lithium phosphides can result in one of three different types of reactions. Reaction of Cp*M(NO)(X)Cl with LiPPh₂ results in metathesis and leads to formation of the respective phosphido-containing complexes. When metathesis of the chloride ligands in the Cp*M(NO)Cl₂ complexes of Mo and W is attempted with either LiPPh₂ or LiPPhH, the only isolable products formed are those resulting from the reduction of the organometallic reactant. Finally, the reaction of Cp*W(NO)(NHCMe₃)(Cl) with LiPPhH induces a ligand-scrambling reaction to afford Cp*W(NO)(NHCMe₃)₂ . A similar example of ligand scrambling occurs during the reaction of Cp*Mo(NO)(CH₂SiMe₃)Cl with LiPPhH producing {[Cp*Mo(NO)(CH₂SiMe₃)₂][Li(THF)]}₂.

Thesis/Dissertation

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2009-03-17

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http://hdl.handle.net/2429/6167

Chemistry

University of British Columbia

UBCV

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