The first evidence of insertion of isocyanide into a metal-sulfur bond: Catalytic and stoichiometric behavior of isocyanide and thiolate ligands on palladium and platinum

The first evidence of insertion of isocyanide into M-S bond has been demonstrated. Tetrakis(triphenylphosphine)palladium [Pd(PPh3)(4)] catalyzes the reaction of a disulfide (ArS)(2) (1) with an isocyanide ArNC (2) (Ar = 4-MeC6H4) to produce the adducts (ArS)(C=NAr)(m)(SAr). The reactions of 1:m adducts with 2 are also catalyzed by the Pd complex to afford 1:k adducts (k not equal m). The mechanistic study reveals that the complex Pd(SAr)(2)(CNAr)(PPh3) (8) is a resting state for giving 1:1 adduct and converted into 1:1 adduct 3 (m = 1) in the presence of another 1 equiv of 1. The stoichiometric reaction of 3 with Pd(PPh3)(4) provides 8, but the stoichiometric oxidative addition of 1:m adducts (m = 2, 3, 4) to Pd(PPh3)(4) did not give any definitive Pd(II) species. These facts reveal that both the insertion of isocyanide(s) into Pd-S bond and the reductive elimination of 1:m adduct are reversible. The study on reactivities of isocyanide and thiolate ligands on platinum, including the X-ray crystallographic analysis of the imidoyl platinum trans-Pt[(C=NAr)(2)SAr](SAr)(PPh3)(2) (21) obtained by the oxidative addition of the C-S bond of 1:2 adduct 4 (m = 2) to Pt(PPh3)(4) has also been reported.