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Oxido‐Hydroxido‐ and Oxido‐Aminato‐Osmium(V) Complexes with a Cyclohexanediamine‐Based Tetradentate Ligand as Active Oxidants for Dihydroxylation and Aminohydroxylation of Alkenes
Author(s) -
Fujimoto Tomohiro,
Sugimoto Hideki,
Kai Kenichiro,
Maeda Kazuki,
Itoh Shinobu
Publication year - 2019
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.201900339
Subject(s) - osmium , chemistry , dihydroxylation , ligand (biochemistry) , medicinal chemistry , catalysis , stereochemistry , ruthenium , organic chemistry , enantioselective synthesis , biochemistry , receptor
Six‐coordinate osmium(III) complexes coordinated by a cyclohexanediamine‐based tetradentate ligand [ trans ‐ N , N′ ‐dimethyl‐ N , N′ ‐bis(2‐pyridylmethyl)‐1,2‐cyclohexanediamine: BPMCN] are synthesized. The remaining two coordination sites are occupied by chloride (Cl – ), triflate (OTf – ), or hydroxide/water (OH – /H 2 O) to complete the octahedral osmium(III) centers; [Os III X 2 (BPMCN)] + (X = Cl – or OTf – ) and [Os III (OH)(H 2 O)(BPMCN)] 2+ . The Os III (OH)(H 2 O) complex catalyzes cis ‐dihydroxylation and cis ‐aminohydroxylation of styrene with hydrogen peroxide (H 2 O 2 ) and chloramine‐T (TsNClNa) to yield the corresponding diol and aminoalcohol, respectively. The oxido‐hydroxido‐osmium(V) complex {[Os V (O)(OH)(BPMCN)] 2+ } is isolated as the active oxidant of the dihydroxylation. The oxidation of the Os III (OH)(H 2 O) complex with chloramine‐T yields oxido‐aminato‐osmium(V) complex, [Os V (O)(NHTs)(BPMCN)] 2+ . Comparison of the crystal structure with those of the oxido‐hydroxido‐osmium(V) complex and related imido‐ and amino‐osmium complexes indicates that the –NHTs group works as a monoanionic aminate ligand and the osmium(V)–NHTs bond has a single bond character [Os–N; 2.058(4) Å]. The oxido‐aminato‐osmium(V) complex is revealed as the active oxidant for the aminohydroxylation by the direct reaction of the complex with styrene. The characterization of the complex allows us to propose the catalytic mechanism of the aminohydroxylation of alkenes.