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Behavior of Ru–bda Water‐Oxidation Catalysts in Low Oxidation States
Author(s) -
Matheu Roc,
Ghaderian Abolfazl,
Francàs Laia,
Chernev Petko,
Ertem Mehmed Z.,
BenetBuchholz Jordi,
Batista Victor S.,
Haumann Michael,
GimbertSuriñach Carolina,
Sala Xavier,
Llobet Antoni
Publication year - 2018
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201801236
Subject(s) - chemistry , aniline , ligand (biochemistry) , protonation , medicinal chemistry , cationic polymerization , aqueous solution , moiety , catalysis , coordination sphere , solvent , aryl , carboxylate , amine gas treating , ruthenium , molecule , stereochemistry , polymer chemistry , organic chemistry , ion , biochemistry , alkyl , receptor
The Ru complex [Ru II (bda‐κ‐N 2 O 2 )(N‐NH 2 ) 2 ] ( 1 ; bda 2− =2,2′‐bipyridine‐6,6′‐dicarboxylate, N‐NH 2 =4‐(pyridin‐4‐yl)aniline) was used as a synthetic intermediate to prepare new Ru II and Ru III bda complexes that contain NO + , MeCN, or H 2 O ligands. In acidic solution complex 1 reacts with an excess of NO + (generated in situ from sodium nitrite) to form a new Ru complex in which the aryl amine ligand N−NH 2 is transformed into a diazonium salt [N‐N 2 + =4‐(pyridin‐4‐yl)benzenediazonium)] together with the formation of a new Ru(NO) moiety in the equatorial zone, to generate [Ru II (bda‐κ‐N 2 O)(NO)(N‐N 2 ) 2 ] 3+ ( 2 3+ ). Here the bda 2− ligand binds in a κ‐N 2 O tridentate manner with a dangling carboxylate group. Similarly, complex 1 can also react with a coordinating solvent, such as MeCN, at room temperature to give [Ru II (bda‐κ‐N 2 O)(MeCN)(N‐NH 2 ) 2 ] ( 3 ). In acidic aqueous solutions, a related reaction occurs in which solvent water coordinates to the Ru center to form {[Ru II {bda‐κ‐(NO) 3 }(H 2 O)(N‐NH 3 ) 2 ](H 2 O) n } 2+ ( 4 2+ ) and is strongly hydrogen‐bonded with additional water molecules in the second coordination sphere. Furthermore, under acidic conditions the aniline ligands are also protonated to form the corresponding anilinium cationic ligands N‐NH 3 + . Additionally, the one‐electron oxidized complex {[Ru III {bda‐κ‐(NO) 3.5 }(H 2 O)(N‐NH 3 ) 2 ](H 2 O) n } 3+ ( 5 3+ ) was characterized, in which the fractional value in the κ notation indicates the presence of an additional contact to the pseudo‐octahedral geometry of the Ru center. The coordination modes of the complexes were studied in the solid state and in solution through single‐crystal XRD, X‐ray absorption spectroscopy, variable‐temperature NMR spectroscopy, and DFT calculations. While κ‐N 2 O is the main coordination mode for 2 3+ and 3 , an equilibrium that involves isomers with κ‐N 2 O and κ‐NO 2 coordination modes and neighboring hydrogen‐bonded water molecules is observed for 4 2+ and 5 3+ .