Grupo de Quimica Organometalica

Almozara, Spain

Grupo de Quimica Organometalica

Almozara, Spain

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Vicente J.,Grupo de Quimica Organometalica | Arcas A.,Grupo de Quimica Organometalica | Julia-Hernandez F.,Grupo de Quimica Organometalica | Bautista D.,University of Murcia
Inorganic Chemistry | Year: 2011

Iodine and the pincer complex [Pd(O,N,C-L)I], where L is the monoanionic ligand resulting from deprotonation of the acetyl group of the dimethylmonoketal of 2,6-diacetylpyridine, are in equilibrium at low temperatures with the palladium(IV) complex [Pd(O,N,C-L)I3], which can be isolated at -40 °C and characterized by 1H NMR spectroscopy and X-ray diffraction studies, in spite of its great instability. When the same reaction is carried out at room temperature, a quantitative reductive elimination process occurs, giving L-I, which in the presence of water affords L′-I, resulting from hydrolysis of L-I. © 2011 American Chemical Society.


Vicente J.,Grupo de Quimica Organometalica | Arcas A.,Grupo de Quimica Organometalica | Julia-Hernandez F.,Grupo de Quimica Organometalica | Bautista D.,University of Murcia | Jones P.G.,TU Braunschweig
Organometallics | Year: 2010

PdCl2 reacts with 2,6-diacetylpyridine(dap) (1:1) in refluxing MeOH to give the pincer complex [Pd(O1,N1,C 1-L)Cl](1) and (QH)2[{PdCl2(μ-Cl)}]2 (2), where L is the monoanionic ligand resulting from deprotonation of the acetyl methyl group of the monoketal of dap and QH is C5H 3NH{C-(OMe)Me}2-2,6, the diketal of Hdap+. Reaction of 2 with NEt3 (1:2) in MeOH affords Q = C5H 3N{C(OMe)2Me}2-2,6(3). Complex 1 reacts with 2 equiv of RNC at 0 °C to give trans-[Pd(C1-L)Cl(CNR) 2](R = Xy = 2,6-dimethylphenyl(4a), tBu (4b)) but at room temperature affords [Pd(O2, C2-LR)Cl(CNR)](R = Xy (5a), tBu(5b)). The ligand LR results from the insertion of one isocyanide into the Pd-C bond plus a tautomerization process from η-ketoimine to β-ketoenamine and coordinates in 5 through the carbonyl oxygen atom (O2) and the inserted isocyanide carbon atom (C2). The reaction of 1 with 1 equiv of RNC at 0 °C leads to a mixture of [Pd (N1,C1-L)Cl(CNR)] (R = Xy (6a), tBu (6b); 85-90%), 1, and 4, but at room temperature gives the pincer complex [Pd (O1,N1,C2-LR)Cl] (R = Xy (7a), tBu (7b)), resulting from insertion/tautomerization processes similar to that leading to 5. Complex 7 reacts at 0 °C (1) with 2 equiv of RNC to give trans-[Pd (C2-LR)Cl (CNXy) 2] (R = Xy (8a), tBu (8b)) or (2) with 1 equiv of tBuNC to afford 5b. The reaction of 1 (1) with [Tl(acac)] gives [Pd(N1,C1-L)(acac)] (9); (2) with chelating ligands N ∧N affords [Pd(C1-L)Cl(N∧N)](N ∧N = 2,2'-bipyridine = bpy (10), 4,4'-di-tert-butyl-2,2'- bipyridine = dbbpy (11)); (3) with 1 equiv of PPh3 gives, in the same way as with isocyanides, an equilibrium mixture of [Pd(N1,C 1-L)Cl(PPh3)] (12), 1, and trans-[Pd(C1-L)Cl (PPh3)2](13), which is the only product when 2 equiv of PPh3 is added to the reaction mixture; and(4) with excess PPh 3 affords the monoketal of dap, C5H3N{C(O)Me-2} {C(OMe)2Me-6}(14), and [Pd(PPh3)4]. The crystal structures of complexes 1, 2, 5b, 6a, and 7a have been determined. © 2010 American Chemical Society.

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