Synthesis, Characterization and Aerobic Alcohol Oxidation Catalysis of Palladium(II) Complexes with a Bis(imidazolyl)borate Ligand. Issue 15 (24th April 2016)

• Record Type: Journal Article
• Authors: Ando, Kenta; Nakazawa, Jun; Hikichi, Shiro
• Other Names: Pettinari C. guestEditor.
• Is Part Of: European journal of inorganic chemistry. Issue 15/16(2016)
• Page Start: 2603
• Page End: 2608
• Publication Date: 2016-04-24
• Subjects: Borates -- Palladium -- N ligands -- Oxidation; Chemistry, Inorganic -- Periodicals; Organometallic chemistry -- Periodicals; Bioinorganic chemistry -- Periodicals; Solid state chemistry -- Periodicals; 546
• DOI: 10.1002/ejic.201600206
• Languages: English
• ISSNs: 1434-1948

Abstract

Abstract : Chloro‐ and hydroxo‐palladium(II) complexes with an imidazole‐based scorpionate ligand bis(1‐methylimidazolyl)methylphenylborate, [B(Im N –Me )2 MePh] – (= L Ph ), have been synthesized. Reaction of a lithium salt of L Ph with [PdCl2 (NCPh)2 ] yields a miscellaneous mixture involving a homoleptic complex [Pd(L Ph )2 ]. Replacement of the neutral ligand (benzonitrile) in the starting material with pyridine leads to the desired chloride complex1 . X‐ray crystallographic analysis reveals the formula of1 to be [PdCl(L Ph )(py)] with a square‐planar palladium(II) center supported by the bidentate L Ph ligand. Treatment of1 with NaOH yields non‐pyridine‐containing hydroxo species with L Ph such as [Pd(OH)(L Ph )(H2 O)] and [(PdL Ph )2 (µ‐OH)2 ]. The hydroxo species2 can convert into active species for catalytic secondary alcohol oxidation with O2 in the absence of extra base. The utility of2 as a catalyst precursor and the inertness of chloride complex1 suggest that the basic nature of the co‐ligand (i.e. OH – ) on the palladium center supported by L Ph is essential to the formation of a putative palladium–alkoxide intermediate. Abstract : Chloro‐ and hydroxo‐palladium(II) complexes containing the imidazole‐based scorpionate ligand bis(1‐methylimidazolyl)methylphenylborate, [B(Im N –Me )2 MePh] – (= L Ph ), have been synthesized. The hydroxo species can be converted into an active species that catalyzes secondary alcohol oxidation with O2 in the absence of base; the chlorido complex is inactive.