The Transition Metal Chemistry of Azo Compounds

Bruce, Michael I.; Goodall, Brian

doi:10.1002/0470023414.ch9

Cited by 14 publications

(3 citation statements)

References 159 publications

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“…An azobenzene, which is expected to work as a chromophore and a structural changing unit, is well utilized for the photoswitching of various functions and properties . An azobenzene framework has been used as a bidentate ligand in some transition metal complexes . In the ( E )-form of a 2-silyl substituted azobenzene, the nitrogen atom is expected to coordinate to the silicon atom and form a five-membered ring, which should suitably stabilize the pentacoordination state of the silicon.…”

Section: Introductionmentioning

confidence: 99%

Reversible Photoswitching of the Coordination Numbers of Silicon in Organosilicon Compounds Bearing a 2-(Phenylazo)phenyl Group

et al. 2006

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Several organosilicon compounds bearing a 2-(phenylazo)phenyl group were synthesized from the corresponding chlorosilanes and 2-lithioazobenzene prepared by halogen-lithium transmetalation of 2-iodoazobenzene. Their structures were determined by (1)H, (13)C, (19)F, and (29)Si NMR spectra, UV-vis spectra, and X-ray crystallographic analyses. In the UV-vis spectra, silyl groups caused red shifts of both the n-pi and pi-pi transitions of the azo group compared with the transitions of the unsubstituted azobenzene. The E-isomers of the fluorosilanes showed an intramolecular interaction between a nitrogen atom of the azo group and the silicon atom, leading their intermediate structures between a distorted trigonal bipyramidal structure and a tetrahedral structure around the silicon atoms, which were revealed by the X-ray crystallographic analyses and the NMR spectra. On the other hand, silanes without fluorine atoms showed tetrahedral structures in the absence of such an interaction. The photoirradiation of the E-isomers of the fluorosilanes afforded reversibly the corresponding Z-isomers in good yields. The silicon atoms of the Z-isomers were found to be tetracoordinate in the absence of Si-N interactions by the (29)Si NMR spectra. The coordination numbers of the silicon atom of the fluorosilanes were reversibly switched between four and five by photoirradiation. These properties were compared to those of a tetrafluoro[2-(phenylazo)phenyl]silicate.

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Section: Introductionmentioning

confidence: 99%

Reversible Photoswitching of the Coordination Numbers of Silicon in Organosilicon Compounds Bearing a 2-(Phenylazo)phenyl Group

et al. 2006

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“…We recently reported versatile synthetic methods for azobenzenes with a silyl, germyl, or stannyl group at the 2-position, respectively . A 2-(phenylazo)phenyl group is considered to act as a potential coordination site judging from the structural resemblance with the van Koten ligand, 2-(Me 2 NCH 2 )C 6 H 4 group and from many examples of transition metal complexes which show intramolecular coordination of an azo group . Therefore, photo- and thermal isomerization of an azo unit which has been widely utilized for the switch of properties promoted by its geometrical change of the compound are expected to be effective for the control of the coordination number of the central atom .…”

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confidence: 99%

Reversible Photocontrol of the Coordination Number of Silicon in a Tetrafluorosilicate Bearing a 2-(Phenylazo)phenyl Group

2001

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Experimental SectionGeneral Procedure. All melting points are uncorrected. Solvents were purified before use by reported methods. All reactions were carried out under argon atmosphere unless otherwise noted. The 1 H NMR (500 MHz), 13 C NMR (125 MHz), 29 Si NMR (99 MHz) spectra were measured with a JEOL A500 spectrometer using tetramethylsilane (TMS) as internal standard. The 19 F NMR (254 MHz) spectra were taken with a JEOL EXcalibur270 spectrometer using Fleon ® as external standard. Elemental analyses were performed by the

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“…As summarized in Table , the yields of pyridines 11 and ammonia were very high irrespective of the ancillary ligands on the tungsten center. The selective formation of 11 through the N−N bond cleavage is in sharp contrast to the reaction of the (1-pyrrolyl)imido complex [WBr 2 (NNC 4 H 4 )(CO)(PMe 2 Ph) 2 ] with KOH in alcohols, where the W−N bond is selectively cleaved 4b …”

Section: Resultsmentioning

confidence: 97%

Synthesis and Structures of Tungsten (1-Pyridinio)imido Complexes and Their Facile N−N Bond Cleavage¹

et al. 1999

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+ (X ) Cl, Br; L ) CO, C 2 H 4 , PMe 2 Ph) were synthesized by the reaction of the salts of pyrylium cations with the hydrazido complexes [WX 2 (NNH 2 )(L)(PMe 2 Ph) 2 ], which were derived from the dinitrogen complex cis-[W(N 2 ) 2 (PMe 2 Ph) 4 ]. The complexes obtained were characterized by spectroscopic measurements as well as crystallographic studies of cis,mer-[WBr 2 (][ClO 4 ], which revealed that the N-N bond distances of these (1-pyridinio)imido complexes are shorter than those of the trialkyl-or unsubstituted hydrazidium complexes so far reported. The (1-pyridinio)imido complexes with a π-acidic ligand (CO or C 2 H 4 ) underwent smooth N-N bond cleavage on reaction with cobaltocene under ambient conditions to liberate the pyridines in moderate to high yields. In some reactions that were conducted in the presence of HNEt 3 -Cl, the corresponding imido (NH) complexes were recovered as the metal products. The (1-pyridinio)imido complexes also reacted with KOH in MeOH to give the pyridines and ammonia in high yields. These reactions provide the first examples of N-N bond cleavage of well-defined hydrazidium complexes and accomplish the synthesis of pyridines from molecular nitrogen under mild conditions. IntroductionGreat efforts have been directed toward the activation and chemical transformation of dinitrogen assisted by transition metal complexes with the intention not only of understanding the biological dinitrogen reduction mechanisms but also of developing a new nitrogen fixation process under mild conditions. 2,3 Incorporation of dinitrogen directly into organic substrates by using transition metal dinitrogen complexes is one of the most fascinating goals in the chemistry of nitrogen fixation. In this context, we have continuously been investigating the conversion of ligating dinitrogen into organonitrogen ligands.Previously, we have shown that facile transformations of coordinated dinitrogen in molybdenum or tungsten complexes of the type [M(N 2 ) 2 (PR 3 ) 4 ] (M ) Mo, W; PR 3 ) tertiary phosphine) into various diazoalkane ligands 4 (N 2 CR 1 R 2 ) are realized by the two-step process: 5 the protonation of the dinitrogen complexes leading to the hydrazido(2-) complexes

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The Transition Metal Chemistry of Azo Compounds

Cited by 14 publications

References 159 publications

Reversible Photoswitching of the Coordination Numbers of Silicon in Organosilicon Compounds Bearing a 2-(Phenylazo)phenyl Group

Reversible Photoswitching of the Coordination Numbers of Silicon in Organosilicon Compounds Bearing a 2-(Phenylazo)phenyl Group

Reversible Photocontrol of the Coordination Number of Silicon in a Tetrafluorosilicate Bearing a 2-(Phenylazo)phenyl Group

Synthesis and Structures of Tungsten (1-Pyridinio)imido Complexes and Their Facile N−N Bond Cleavage¹

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The Transition Metal Chemistry of Azo Compounds

Cited by 14 publications

References 159 publications

Reversible Photoswitching of the Coordination Numbers of Silicon in Organosilicon Compounds Bearing a 2-(Phenylazo)phenyl Group

Reversible Photoswitching of the Coordination Numbers of Silicon in Organosilicon Compounds Bearing a 2-(Phenylazo)phenyl Group

Reversible Photocontrol of the Coordination Number of Silicon in a Tetrafluorosilicate Bearing a 2-(Phenylazo)phenyl Group

Synthesis and Structures of Tungsten (1-Pyridinio)imido Complexes and Their Facile N−N Bond Cleavage1

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Synthesis and Structures of Tungsten (1-Pyridinio)imido Complexes and Their Facile N−N Bond Cleavage¹