An Isolable Mononuclear Palladium(I) Amido Complex

Abstract

Mononuclear Pd(I) species are putative intermediates in Pd-catalyzed reactions, but our knowledge about them is limited due to difficulties in accessing them. Herein, we report the isolation of a Pd(I) amido complex, [(BINAP)Pd(NHArTrip )] (BINAP = 2,2′- bis(diphenylphosphino)-1,1′-binaphthalene, ArTrip = 2,6-bis(2’,4’,6’-triisopropylphenyl)phenyl), from the reaction of (BINAP)PdCl2 with LiNHArTrip. This Pd(I) amido species has been characterized by X-ray crystallography, electron paramagnetic resonance, and multi-edge Pd Xray absorption spectroscopy. Theoretical study revealed that, while the 3-electron-2-center π interaction between Pd and N in the Pd(I) complex imposes severe Pauli repulsion in its Pd–N bond, pronounced attractive inter-ligand dispersion force aids its stabilization. In accord with its electronic features, reactions of homolytic Pd–N bond cleavage and deprotonation of primary amines are observed on the Pd(I) amido complex.

Isolation and Catalytic Reactivity of Mononuclear Palladium(I) Complexes

“…This shows a remarkable increase in spin density on the palladium ion compared to the other recently reported heteroleptic Pd I -amido complex , in which the SOMO only demonstrated 39.9% Pd character. 32 Importantly, the appreciable contribution of the P atom to the spin density supports the observed superhyperfine coupling constants observed in all three x, y, and z directions, while the DFT-calculated g values and superhyperfine coupling constants for Pd-1 and Pd-2 are closely matching the experimental values (Table 1). Furthermore, the average value (Aiso) of the 31 P superhyperfine coupling constants and the extent of anisotropy for the Ax, Ay, and Az values can be used to calculate the contributions of the P 3s and 3p orbitals to the spin density, respectively, following the method developed by Morton and Preston.…”

“…To the best of our knowledge, only three structurally characterized examples of isolated Pd I complexes have been reported: the cationic [Pd I (P t Bu3)2] + species and the [Pd I (MeCN)(P t Bu3)2] + complex, which were reported independently by Chaplin's and Ozerov's groups, respectively, 30,31 and a recent heteroleptic, formally Pd I complex supported by a redox noninnocent amide ligand. 32 With the goal of isolating and characterizing mononuclear Pd I species and explore their reactivity, we report herein the synthesis and characterization of two unique heteroleptic mononuclear Pd I complexes supported by dithiapyridinophane ligands. Importantly, one of these complexes exhibits catalytic reactivity in the Kumada cross-coupling reaction that is superior to the Pd 0 or Pd II analogs, while the other complex shows an unprecedented Csp 3 -H bond activation proposed to occur at a Pd I center.…”

“…Utilizing these soft donors, we were able isolate two unique heteroleptic mononuclear Pd I complexes with an unambiguous +1 oxidation state at the Pd center. 32 In addition, we have synthesized the Pd II complexes [(N2S2)Pd II (P t Bu3)2] 2+ , Pd-3, and [(N2S2)Pd II (P t Bu3)2] 2+ , Pd-4 (Fig. 1A), which exhibit well-defined, reversible Pd II /Pd I redox waves at -0.47 V for Pd-3 and -0.38 V vs. Fc 0/+ for Pd-4, respectively (Figs.…”

Dispersion stabilizes metal-metal bonds in the 1,8-bis(silylamido)naphthalene ligand environment

“…[20][21][22][23] By comparison, few investigations have systematically and explicitly considered dispersive bond stabilization in complexes featuring bulky amide ligands, despite the prevalence of these ligands in coordination chemistry. [24][25][26][27] Divalent 1,8-bis(silylamido) naphthalenes (Figure 1c) are popular ligands whose steric profiles can be easily tuned by an appropriate choice of inexpensive, diverse, and commercially-available chlorosilanes. This ligand framework also confers additional stability upon complexes due to the chelate effect.…”

Isolation and Catalytic Reactivity of Mononuclear Palladium(I) Complexes

“…To the best of our knowledge, only three structurally characterized examples of isolated Pd I complexes have been reported: the cationic [Pd I (P t Bu3)2] + species and the [Pd I (MeCN)(P t Bu3)2] + complex, which were reported independently by Chaplin's and Ozerov's groups, respectively, [39][40] and a recent heteroleptic, formally Pd I complex supported by a redox noninnocent amide ligand. 41 With the goal of isolating and characterizing mononuclear Pd I species and exploring their reactivity, we report herein the synthesis and characterization of two unique heteroleptic mononuclear Pd I complexes supported by dithiapyridinophane ligands. Importantly, one of these complexes exhibits catalytic reactivity in the Kumada cross-coupling reaction that superior to its Pd 0 or Pd II analogs, while the other complex demonstrates Csp 3 -H bond activation proposed to occur at a Pd I center.…”