Novel reactivity of silver isocyanide complexes and palladium bis(acyclic diaminocarbenes) as catalyst for the Nazarov cyclization

Abstract

Scope and Method of Study: Inorganic Chemistry

Findings and Conclusions:

N-heterocyclic carbenes (NHCs) have been widely used in catalysis since the discovery of the first stable carbene by Arduengo in 1991. Acyclic diaminocarbenes (ADCs) have been studied very little, even though they have similar electronic stabilization as the NHCs. The first research goal was to synthesize silver(I) acyclic carbenes by the nucleophilic attack of dimethyl amine on isocyanide bound silver precursors. However, on treating silver(I) tris isocyanide with dimethyl amine, an unexpected silver(I) bis(amidine) complex was formed instead of the silver(I) tris carbene. The second research goal was to synthesize palladium bis(ADC) complexes via a general route by the nucleophilic attack of a chiral diamine on palladium bound isocyanide precursors. With a goal to study the donor ability of these palladium bis(carbene) complexes trans influence studies were carried out using methyl isocyanide as a probe by comparing the stretching frequencies using infrared spectroscopy. Dicationic bis(acetonitrile) adducts were synthesized and used as precatalysts in the electrocyclic Nazarov cyclization. The cyclization reactions were monitored by gas chromatography with catalyst loadings of 5 mol% to 0.5 mol %.