Amines tungsten complexes

The amine substituent in the corresponding tungsten complex reduces AE to 21.3 kcal/mol, while the effect on AE is negligible. 

Compelling evidence for this mechanism was obtained when a freshly prepared batch of the tungsten complex W2(NEt2)4Me2 failed to react with C02 over a period of 24 hours, but upon addition of a trace of free amine, reaction commenced immediately and was complete within minutes (148). 

The anti addition of amines to the double bond of cationic (alkene)(cyclopentadienyl)di-carbonyliron complexes and to the analogous molybdenum and tungsten complexes has been reported31 33. The adducts underwent carbonyl insertion-cyclization to give chelate complexes, which were then oxidized to /8-lactams. For example, from the Fp complexes of ( )- and (Z)-2-butene the corresponding /8-lactams were obtained diastereoselectively in 10-15% yield by the direct oxidation of the benzylamine adducts with chlorine at low temperature33. The stereochemistry was determined by H-NMR spectroscopy. 

Rhodium, " titanium,and tungsten " complexes have also been used for this reaction. The reaction can be promoted photochemically and the rate is enhanced by the presence of primary amines.Coordinating ligands also accelerate the reaction,polymer-supported promoters have been developed " and there are many possible variations in reaction conditions.The Pauson-Khand reaction has been done under heterogeneous reaction conditions, and with... 

The orientation of the olefin in a -ir complex (Zeise s salt) is known [86] to be mainly defined by steric factors. In the study of tungsten complexes with n-donor two-center ligands, ketimines, and amines, we concluded that the electronic rather than steric factor exerts the crucial effect on the ligand orientation in the complex. 

Diastereoselective and enantioselective [3C+2S] carbocyclisations have been recently developed by Barluenga et al. by the reaction of tungsten alkenylcarbene complexes and enamines derived from chiral amines. Interestingly, the regio-chemistry of the final products is different for enamines derived from aldehydes and those derived from ketones. The use of chiral non-racemic enamines allows the asymmetric synthesis of substituted cyclopentenone derivatives [77] (Scheme 30). 

A variety of catalytically active five-coordinate tungsten oxo and imido alkylidene complexes also have been prepared that contain some donor amine or pyridine linked either to the imido ligand or to a phenyl ligand bound to the metal (A, Scheme 2) [101-105]. Such species show metathesis activity (e.g., ROMP of norbornene),but there does not appear to be any proof that the integrity of the initiator is maintained. 

Amines have also been exchanged by NHC, e.g., TMEDA can be replaced by two NHCs in [(tmeda)2VCl2], and pyridine by one NHC in complexes of chromium, molybdenum, and tungsten. ... 

In a three-component reaction, a cationic platinum isocyanide complex [(Ph3P)2Pt(CNR)Cl][BF4] is reacted with a /3-bromoamine and butyl lithium to give an imidazoldin-2-ylidene complex.This transformation can be a two-component reaction if the isocyanide ligand contains already the necessary amine functionality. This was shown for chromium, molybdenum, tungsten, and rhenium carbonyls. 

The most active d metal peroxo complexes toward nucleophilic substrates, like amines, phosphines, thioethers, double bonds etc., are molybdenum, tungsten and rhenium derivatives vanadium and titanium catalysis is also important, in particular when... 

Hydrazido(2-) and hydrazido(l-) complexes have also been shown to condense with aldehydes and ketones to give diazoalkane complexes containing the W=N—N=CRiR2 unit.387,388 Treatment of these complexes with LiAlFL, gives secondary amines and ammonia, whereas treatment with acid produces hydrazine, keto azines and N2-free tungsten compounds. Amines can also be produced from organohydrazido(2—) complexes.389,390... 

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