Tungsten complexes imines

The reaction of alkynyllithium compounds with alkoxycarbene tungsten complexes leads to anionic propargyl tungsten complexes (Figure 2.33 see also Figure 3.9). These intermediates are stable at low temperatures and react upon Lewis acid catalysis with aldehydes or A -sulfonyl imines to yield five-membered heterocycles [280]. Oxidative methoxycarbonylation [375] of the intermediate vinyl tungsten complex, followed by elimination of methanol leads to pyrroles or furanes (Figure 2.33 Entry 6, Table 2.22). 

Compound 79 reacts with 0(CH2)4 and NCMe in the presence of CFsSOsMe, like the iron complex 11 and the molybdenum and tungsten complexes 45 and 46, to give zwitterionic compounds [2-NO-2-PEt3-7-L-c/ow-2,l-CoCBioHio] [L = 0(CH2)4 (83), NCMe (84)]. Interestingly, the acetonitrile reaction gave in addition to 84 small amounts of the imine complex [7- N(Me) = C(H)Me -2-NO-2-PEt3-c/oio-2,l-CoCBioHio] (85), a product related to the iron and nickel compounds 34 and 78, respectively. The latter pair were the only products when 11 and 75, respectively, were... 

Treatment of the tungsten complex [W(=C=C=CPh2)(CO)5[ with benzylidene-isopropylimine gives rise to the formation of the azetidinylidene derivative 41 through a formal [2 + 2] cycloaddition between the Co =Cp moiety and the iminic... 

The chemistry of pyrrol-1-ylbenzylidene pentacarbonyl chromium, molybdenum and tungsten complexes was investigated. Reaction with electrophilic alkenes gives l-(phenylcyclo-propyl)pyrroles Under photolytic decarbonylation conditions 2 + 2 cycloaddition products were obtained with nucleophilic alkenes, cyclic dienes and imines. <950M2522>... 

Tungsten(O) pentacarbonyl-methylene chloride complex and alkynes form vinylidene complexes by photo-irradiation, which react with an imine or a dialkylcarbodimide to afford /3-lactams after decomplexation of the metal.233... 

The heat of formation of [MolCOlg] has been determined as -960 + 12 kJ mol by measuring its heat of decomposition. The Mossbauer parameters for the 100 keV transition of in [W(CO)g] and some tungsten(vi) complexes have been measured and discussed in terms of known bonding and structure. Secondary ions [M (CO) ] (M = Mo, m = I or 2 M = W, m = 1—4 n = 0—14) formed by ion-molecule reactions have been observed in the mass spectra of the hexacarbonyls. A mixt u re of [Cr(CO) ] and [MolCO) ] vapours affords [CrMo(CO) ] ( = 5—7). [MofCOl ] and [WICO) ] catalyse the condensation of isocyanates with aldehydes to give imines in high yields. ... 

It is worthwhile to comment on the catalytic species. As opposed to oxometal species, which convert amines to imines, hydroperoxymetal complexes (MOOH) convert amines to nitrones. Thus the oxidation of amines is a convenient way of distinguishing the active species. The reactivity of oxometal versus peroxometal species is illustrated in Fig. 22. In practice, tungsten is the catalyst of choice to convert amines to nitrones [130]. 

An unstable adduct between triphenylphosphine and a photochemically-generated dimethylgermylene has been characterised spectrophotometrically.The first 2,3-dihydro-l,3,2-X -benzodiazaphospholes (73) have been formed in the reactions of triphenylphosphine with g-benzoquinone di-imines stabilised by coordination.A complex of phenylnitrene with a tungsten pentacarbonyl acceptor has been trapped using triphenylphosphine. A kinetic study of the reactions of diazoalkanes with triphenylphosphine, leading to the phosphazenes (74), indicates a biphilic mechanism, the dominant interaction in the transition state involving the diazoalkane as a net electron donor,... 

When the Schiff base tungsten(0) compound mcr-[W(CO)(L)] (L = Ph2PC6H4CHNC6H4PPh2 Scheme 17) was exposed to HC1 gas, it converted to m-[WnCl2(CO)2(L )] (L = Ph2PC6H4CH2NHC6H4PPh2) as the final product. The 7r-iminium intermediate, i.e., the protonated complex mer-[W(CO)3(LH)]BF4, and the final product were both characterized structurally. In this reaction, the metal center has undergone a two-electron oxidation (W° to W11) and the original imine bond has been reduced to a secondary amine, as indicated by X-ray analysis and spectroscopic measurements.197... 

Encouraged by our results on stoichiometric and catalytic metathesis reactions of carbodiimides and imines with Fischer type carbene tungsten(O) complexes (9) we started 1984 with metathesis like reactions of the Schrock type carbyne tungsten (VI) complex Cl3(dme)WCtBu with heteroallenes (isocyanates, carbodiimides, isothiocyanates) and with heteroalkenes (imines and nitroso compounds). 

A problem is that the Pauson-Khand reaction uses two equivalents of cobalt. More efficient versions, many of them catalytic, using other metals have been developed. These include carbonyl complexes of titanium, molybdenum, tungsten (Scheme 7.15), rhodium and ruthenium (Scheme 7.16). Rhodium, iridium and iron (Scheme 7.17) have also been used with two alkynes to give cyclopentadienones, often as complexes 7.59. A version of the Pauson-Khand reaction employing a nickel catalyst and an isonitrile in place of CO has been developed. The product is an imine, which can be hydrolysed to a cyclopentenone. 

---