Cyclopalladated azido complexes containing C,N-donor (HC∼N = 2-(2′-thienyl)pyridine, azobenzene, 3,3′-dimethyl azobenzene, N,N′-dimethylbenzylamine, 2-phenylpyridine) ligands: reactivity towards organic unsaturated compounds and catalytic properties

Abstract

Cyclopalladated azido dimers having various C,N-donor ligands, [Pd(mu-N3)(C,N-Ln)]2 (L1H = 2-(2'-thienyl)pyridine; L2H = azobenzene; L3H = 3,3'-dimethylazobenzene; L4H = N,N'-dimethylbenzylamine; L5H = 2-phenylpyridine), underwent cleavage with tertiary (or chelating) phosphines to form the cyclopalladated [Pd(N3)(PR3)(C,N-L)], the sigma-bonded [Pd(N3)(PR3)2(C-L)], or the dinuclear-cyclopalladated [PdN3(PR3)(C,N-L)]2(mu-P approximately P) complexes. In particular, treating [Pd(mu-N3)(C,N-L)]2 with the basic chelating phosphine (depe or dmpe) produced the homoleptic bis(chelating) complex [Pd(C,N-Ln)2] (n = 1-3). Complex [Pd(N3)(PR3)(C,N-L4)] or [Pd(N3)(PR3)2(C-L4)] reacted with aryl isocyanides to selectively give the imidoyl [Pd(N3)(-C=N-Ar)(PR3)(N-L4)] or the imidoyl carbodiimido complex [Pd(N=C=N-Ar)(-C=N-Ar)(PR3)(N-L4)], which was formed by the CN-Ar insertion into the orthometallated Pd-C bond on the phenyl moiety or the interaction into the Pd-N3 bond of the supporting ligand. In addition, reactions of [Pd(N3)(PR3)2(C-Ln)] (n = 1, 2, 4) with R-NCS {R = i-Pr, C6H4-NCS, (CH3)3Si} gave the S-coordinated tetrazole-thiolato Pd(II) complexes. Finally, the catalytic activity of the cyclopalladated azido complexes was evaluated.

A Highly Efficient Palladium‐Catalyzed Decarboxylative ortho‐Acylation of Azobenzenes with α‐Oxocarboxylic Acids: Direct Access to Acylated Azo Compounds

“…PdA et al have carried out detailed research on Pd-catalyzed CÀ H activation and a reaction mechanism involving a Pd II /Pd IV process was proposed and confirmed. [16] Inspired by Sanfords excellent work, a complex of Pd IV with azobenzene was prepared in situ [16,17] and was then reacted with 2-oxo-2phenylacetic acid (2 a) in DCE at room temperature for 36 h, after which time 3 a was isolated with a yield of 47 % (see the control experiments in Supporting Information for details). Based on the above results, a reaction mechanism involving a Pd II /Pd IV process for this system was proposed and is shown in Scheme 2.…”

Synthesis and Structure of Multinuclear Pd(II) Complexes Bridged by Phosphide or Azide Ligands

“…We had reported that Pd­(II)–chloride complexes could undergo facile conversion to the corresponding Pd­(II)–azide complexes by reaction with NaN 3 in an H 2 O/CH 2 Cl 2 two-phase system. , When this method was applied to the chloride-bridged Pd­(II) dinuclear complex [PdCl­(μ-Cl)­(PEt 3 )] 2 ( 3a ), the corresponding azide-bridged Pd­(II) dinuclear complex [Pd­(N 3 )­(μ-N 3 )­(PEt 3 )] 2 ( 4 ) was formed in 47% isolated yield. On the other hand, the reaction of the chloride-bridged Pd­(II) dinuclear complex [PdCl­(μ-Cl)­(PPhMe 2 )] 2 ( 3b ) with NaN 3 in H 2 O/CH 2 Cl 2 did not afford the analogue of 4 but afforded an azide-bridged Pd­(II) tetranuclear complex [Pd­(N 3 )­(μ-N 3 )­(PPhMe 2 )] 4 ( 5 ) in 50% yield.…”

“…The synthesis of phosphide-bridged Pd­(II) complexes was reported first in 1962, and they have been studied extensively since then . However, applications of phosphide-bridged Pd­(II) complexes are sparse, likely because of the challenges in their synthesis due to the handling and sourcing problems associated with hydrophosphines. , The azide-bridged Pd­(II) complexes have also been known since 1968 with a variety of supporting ligands, which include phosphines, π-allyl ligands, imines, and pyridine . However, all of them form a Pd 2 N 2 four-membered ring with azide ligands via the side-on approach, and no other coordination modes are known.…”

“…2,3 The azide-bridged Pd(II) complexes have also been known since 1968 with a variety of supporting ligands, which include phosphines, 4 π-allyl ligands, 5 imines, 6 and pyridine. 7 However, all of them form a Pd 2 N 2 fourmembered ring with azide ligands via the side-on approach, and no other coordination modes are known.…”

Covalently cyclopalladium(II) complex/reduced-graphene oxide as the effective catalyst for the Suzuki–Miyaura reaction at room temperature

“…The heterogeneous catalysts are used in the present project. When the reaction was tested at room temperature, the nonpolar solvent toluene gave an excellent yield [42]. The solvents such as THF, 1,4-dioxane, EtOH, H 2 O, and THF/H 2 O=2:1 also afforded low yields of the coupling product.…”