Palladacycle Chemistry on the Edge of Naphthalene and Triphenylene: Alkyne Cycloadditions and Autocatalytic Coupling

Abstract

The four-membered palladacycle Pd(PEt3)2(1,8-naphthalenediyl) (3) and the five-membered palladacycle Pd(PEt3)2(1,12-triphenylenediyl) (4) were prepared from Pd(PEt3)2Cl2 and the appropriate dilithio reagent. Both palladacycles are thermally unstable, decomposing autocatalytically at 100 °C to palladium black, Pd(PEt3)3, and perylene (for 3) or dinaphtho[def,pqr]tetraphenylene (for 4). In the presence of PhCCPh, the decomposition is slowed and the cycloaddition products 1,2-diphenylacenapthylene (for 3) and 4,5-diphenylbenzo[e]pyrene (for 4) are formed, along with the decomposition products. Kinetic data again indicate autocatalytic behavior. The decomposition and cycloaddition reactions are faster in the presence of dioxygen but are arrested by the addition of PEt3 or mercury, consistent with colloidal palladium (detected by TEM) catalysis. Further reactions of the previously reported platinum analogue of 3 are also reported. The thermally stable platinacycle Pt(PEt3)2(1,8-naphthalenediyl) (1) decomposes ...