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 at 120 °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(η2-PhCCPh) with O2 and PhCCPh gives Pt(η2-PhCCPh)2 in good yield.

Reductive Eliminations from Diarylpalladium(II) Complexes: A Combined Experimental and Computational Investigation

“…Perhaps other effects may also contribute to the elimination in para ‐xylene. For example, wall effects, autocatalysis by colloidal Pd 0 , or the participation of other molecules could play a role. The formation of the isomeric elimination products 4 b and 4 c (cf.…”

Phenanthriporphyrin: An Antiaromatic Aceneporphyrinoid as a Ligand for a Hypervalent Organophosphorus(V) Moiety

“…Previously an incorporation of ap hosphorus(V) center into the {CNN} coordination core of carbaporphyrinoid has been reported for N-fused dihydrotelluraporphyrin. [27][28][29] Them ethoxide ligands at the phosphorus(V) center are readily exchangeable for hydroxides during chromatography on basic alumina or if traces of water are present in asolvent as documented by 1 HNMR spectroscopy ( Figure S25). [24,25] Nevertheless,t he binding component where the C(4) and C(5) carbon atoms of phenanthrene (where the numbers refer to "free" phenanthrene) are simultaneously bound has been recognized in silylated phenanthrenes [26] and metalated triphenylene derivatives.…”

Chasing C,C‐Palladacycles

“…For instance, the palladacycle 27 was isolated from the reaction of [PdCl 2 (PEt 3 ) 2 ] with the TMEDA (Me 2 NCH 2 CH 2 NMe 2 ) adducts of 1,8-dilithionaphthalenediyl (Scheme 19). [26] Double transmetalation reactions are not limited the use of organolithium reagents, as shown by Vicente et al [27] They reported the synthesis of several four-membered palladacycles by reaction of dimeric bis-ylide silver(I) complexes with [PdCl 2 (NCPh) 2 ] (Scheme 20). Depending on the molar ratio Ag/ Pd used, mononuclear (28 a and 28 b) or dinuclear metallacycles (29 a and 29 b) were obtained.…”