摘要:
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)(2)Cl-2 and the appropriate dilithio reagent. Both palladacycles are thermally unstable, decomposing autocatalytically at 100 degrees 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 at 120 degrees C in the presence of colloidal platinum, yielding perylene, platinum black, and platinum(0) phosphine complexes. Complex 1 also decomposes in wet toluene, and the colloidal platinum catalyzed cycloaddition reaction of 1 with PhCCPh is promoted by water. Interestingly, colloidal platinum also appears to catalyze the decomposition and alkyne cycloaddition reactions of palladacycle 3. Finally, heating alkyne complex Pt(PEt3)(2)(eta(2)-PhCCPh) with O-2 and PhCCPh gives Pt(eta(2)-PhCCPh)(2) in good yield.