Rhenium complexes imines

Bruce and co-workers demonstrated mesomorphism in benzylideneaniline complexes bound to octahedral Mn(l) and Re(l), providing that the imine ligand was sufficiently anisotropic these complexes were the first simple octahedral complexes to show N and lamellar phases. They were formed by the or/.4o-metallation reaction of the imine with [MMe(GO)s] (M = Mn, Re). The parent ligands showed smectic and nematic phases at temperatures up to 300 °C, whereas on complexation to Mn(l), only a nematic phase was seen for 11 (11 M = Mn, = 5, 7) and 12 (12 M = Mn X = Y = H n = m = 8) which cleared below 190 °C with decomposition. The related Re(l) complexes yielded materials with very similar transition temperatures and enhanced thermal stability, so that decomposition was not observed at the clearing point.Therefore, in the following part of this study, only rhenium complexes were studied. 

The effect of the nature of the terminal group and the position of the imine link has also been investigated. Thus, when hexyl chains are substituted at each end of a rhenium complex with the same motif as 12, a nematic phase was observed (Cr 129N 167 1). Moreover, when one of the two hexyl chains were replaced by one (Figure 28) or two perfluorinated chains, the mesophase was changed to SmA phase, and occurred at higher temperatures, with decomposition taking place in the mesophase. ... 

Landwehr A, Dudle B, Fox T, Blacque O, Berke H (2012) Bifunctional rhenium complexes for the catalytic transfer-hydrogenation reactions of ketones and imines. Chem Eur J 18 5701-5714... 

Bifunctional rhenium complexes related to the Shvo catalyst have been used in TH reactions, including tests on three non-prochiral imines, with TOFs up to 79 h obtained for imines. In common with the Shvo catalysts, DFT calculations have indicated the operation of an outer-sphere mechanism for the reaction [118]. 

Bifunctional rhenium complexes [Re(H)(N0)(PR3)(C5H40H)] (R = Cy, j-Pr) have effected the transfer hydrogenation of ketones and imines DFT calculations suggest a secondary-coordination-sphere mechanism for the former. ... 

Primary amines at a primary carbon can be dehydrogenated to nitriles. The reaction has been carried out with a variety of reagents, among others, IF5,"9 lead tetraacetate, 20 nickel peroxide,121 NaOCl in micelles,122 S g-NiSO, 2-1 and CuCl-02-pyridine.124 Several methods have been reported for the dehydrogenation of secondary amines to imines.125 Among them126 are treatment with(l) iodosylbenzene PhIO alone or in the presence of a ruthenium complex, 27 (2) Me2SO and oxalyl chloride, 2" and (3) f-BuOOH and a rhenium catalyst. 29... 

The cycloaddition of imines to the metal-carbon triple bond in the cationic rhenium carbyne complex 263 was reported by Geoffroy and... 

Ligand-metal bifunctional catalysis provides an efficient method for the hydrogenation of various unsaturated organic compounds. Shvo-type [83-85] Ru-H/OH and Noyori-type [3-7] Ru-H/NH catalysts have demonstrated bifimctionality with excellent chemo- and enantioselectivities in transfer hydrogenations and hydrogenations of alkenes, aldehydes, ketones, and imines. Based on the isoelectronic analogy of H-Ru-CO and H-Re-NO units, it was anticipated that rhenium nitrosyl-based bifunctional complexes could exhibit catalytic activities comparable to the ruthenium carbonyl ones (Scheme 29) [86]. 

Vinylidene complexes of manganese and rhenium, generated in situ, undergo [2+2] cycloaddition reactions with imines to form 52. ... 

Another facet of surface organometallic chemistry involves modelling of the mechanisms of surface reactions on the basis of the reactivity of molecular models. For example, the reactivity of metal-imine complexes of molybdenum is considered by CHAN, who proposes elementary steps constituting the catalytic cycle of the surface-catalyzed alkene ammoxidation reaction, which is of great industrial importance. HERRMANN provides some very fine examples of molecular models of the rhenium oxide catalysts used commercially in the alkene metathesis reaction. 

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