Synthesis and properties of arylpalladium(II) azido complexes PdAr(N 3)(PR 3) 2. Nucleophilic reactions of the azido ligand with CO and with isocyanides to afford Pd(II) isocyanate, C-tetrazolate and carbodiimide complexes

Abstract

The tmeda ligand in the complexes, PdAr(N 3)(tmeda) is easily replaced by addition of tertiary phosphine or chelated phosphine to give the corresponding palladium(II) azido complexes with the phosphines ligand, PdAr(N 3)L 2 ( 1: Ar=Ph, L=PMe 3; 2: Ar=Ph, L=PEt 3; 3: Ar=tolyl, L=PMe 3; 4: Ar=naphthyl, L=PMe 3; 5: L 2=dppe). Complex 3 was characterized by X-ray crystallography. Complexes 1– 2 react with CO (1 atm) to afford Pd(II) isocyanates, PdPh(NCO)L 2 ( 6, L=PMe 3; 7: L=PEt 3), in 98 and 76% yields, respectively. In contrast, the reaction of trans-PdMe(N 3)(PMe 3) 2 with CO gives acetylpalladium isocyanate, trans-Pd(COMe)(NCO)(PMe 3) 2 ( 8) in 96% yield, which is characterized by X-ray crystallography. Reactions of 1 with an equal amount of tert-butyl and cyclohexyl isocyanides cause 1,3-dipolar addition of the isocyanides to the azido ligand, to give the complexes, trans-PdPh[CN 4(R)](PMe 3) 2 (R=C(CH 3) 3, 9; C 6H 11, 10) with a five-membered heterocyclic ring ( C-coordinated tetrazolato group). However, similar reactions of 1 and 3 with 2,6-dimethylphenyl isocyanide result in the unusual formation of Pd(II) complexes containing carbodiimido ligand, trans-( p-Y-C 6H 4)Pd(NCN-2,6-Me 2C 6H 3)(PMe 3) 2 (Y=H, 11; Y=Me, 12) in 51 and 94% yields, respectively. Reactions of 1 with protonating agents such as benzenthiol and phenylacetylene are also described.