Coordination Chemistry of the PdmBOX Pincer Ligand: Reactivity at the Metal and the Ligand. Issue 47 (29th November 2017)

• Record Type: Journal Article
• Authors: Wenz, Jan; Vasilenko, Vladislav; Kochan, Alexander; Wadepohl, Hubert; Gade, Lutz H.
• Is Part Of: European journal of inorganic chemistry. Issue 47(2017)
• Page Start: 5545
• Page End: 5556
• Publication Date: 2017-11-29
• Subjects: Asymmetric catalysis -- Iron -- Cobalt -- Manganese -- Nickel -- Palladium -- Rhodium -- Homogeneous catalysis -- Hydride ligands -- Hydrosilylation -- N ligands -- Reduction; Chemistry, Inorganic -- Periodicals; Organometallic chemistry -- Periodicals; Bioinorganic chemistry -- Periodicals; Solid state chemistry -- Periodicals; 546
• DOI: 10.1002/ejic.201701195
• Languages: English
• ISSNs: 1434-1948

Abstract

Abstract : The coordination chemistry of PdmBOX [2, 5‐bis(2‐oxazolinyldimethylmethyl)pyrrole] pincer ligands, in which a dimethylmethylidene linker has been introduced to preclude rearrangements in the backbone, has been studied with 3d and 4d late transition metals. The in situ lithiated PdmBOX ligand was treated with MnCl2, FeCl2 and CoCl2 to give [ i Pr (PdmBOX)MCl] (M = Mn:2 ; Fe:3 ; Co:4 ) which were found to adopt a distorted tetrahedral coordination geometry in the crystal. Addition of 2, 6‐dimethylphenylisocyanide to3 gave the diamagnetic tris(isocyanide) derivative [ i Pr (PdmBOX)Fe(CNxyl)3 ]Cl (5 ) with the chloride as the counteranion. Complexes2 –4 were found to be precatalysts for the enantioselective hydrosilylation and hydroboration of acetophenone. The synthesis of PdmBOX‐palladium(II) complexes was achieved by deprotonation of the protioligand with potassium bis(trimethylsilyl)amide (KHMDS) and subsequent reaction with [(cod)PdCl2 ] giving [ i Pr (PdmBOX)PdCl] (6 ) or by stirring ( S )‐ i Pr (PdmBOX)H with palladium acetate yielding the palladium acetato complex7 . Treatment of the latter with phenylsilane at 60 °C also led to the slow formation of the metal hydride complex which was the key species in the catalytic hydrosilylation of styrene oxide, albeit with low activity. The coordination of ( S )‐ iPr (PdmBOX)H to rhodium(I) was accomplished by reaction with (acetylacetonato)dicarbonylrhodium(I) to give the corresponding PdmBOX‐Rh complex8 which reacted with methyl iodide to give the octahedrally coordinated rhodium(III) complex [ i Pr (PdmBOX)Rh(CH3 )I(CO)]9 . Reaction of8 with one equivalent of CsBr3 led to the full conversion to the dibromorhodium(III) complex [ i Pr (PdmBOX)Rh(CO)Br2 ]10 . Upon reaction of10 with N ‐bromosuccinimide (NBS), the pyrrole backbone in10 was brominated to give complex11 . In a similar way, a selective conversion of [ i Pr (PdmBOX)NiCl] to the backbone‐chlorinated [ i Pr ( Cl PdmBOX)NiCl] (12 ) was achieved by the treatment with N ‐chlorosuccinimide. Abstract : The coordination chemistry of the newly developed PdmBOX ligand with first and second row transition metals is presented. Since an isomerization of the ligand backbone is prevented, the pyrrole building block is also retained in the corresponding metal complexes.