Molybdenum complexes alkyne

Secondary amines can be added to certain nonactivated alkenes if palladium(II) complexes are used as catalysts The complexation lowers the electron density of the double bond, facilitating nucleophilic attack. Markovnikov orientation is observed and the addition is anti An intramolecular addition to an alkyne unit in the presence of a palladium compound, generated a tetrahydropyridine, and a related addition to an allene is known.Amines add to allenes in the presence of a catalytic amount of CuBr " or palladium compounds.Molybdenum complexes have also been used in the addition of aniline to alkenes. Reduction of nitro compounds in the presence of rhodium catalysts, in the presence of alkenes, CO and H2, leads to an amine unit adding to the alkene moiety. An intramolecular addition of an amine unit to an alkene to form a pyrrolidine was reported using a lanthanide reagent. 

The symmetrical dienyne 58a was converted to a fused bicyclo [4.3.0] ring in 95% yield [17] (Eq. 27). With substrate 58c containing an unsymmetrical diene tether, two different products, 59c and 59c, were obtained in a ratio of 1 to 1 (Eq. 28). The reaction course in the formation of the different bicyclic rings is shown in Scheme 8. This dienyne metathesis is also catalyzed by tungsten or molybdenum complex 62 or 63 (Fig. 1), and a dienyne bearing terminal alkyne 58b could be cyclized to give 59b in 97% yield. 

Imido-nitrido complexes, with mono-Cp Ti(IV), 4, 425-426 Imido-supporting ligands, in molybdenum complexes alkenes, 5, 535 alkynes, 5, 548... 

Electrocyclization of E is expected to give cyclohexadienone complex F a related molybdenum complex 6 (Scheme 4), in which two carbonyl ligands have been replaced by alkyne ligands, has been isolated from the reaction of a vinyl molybdenum carbene complex with 3-... 

Several mixed bisalkyne molybdenum complexes have been prepared [Eq. (32)] (87). Alkyne exchange is known to occur in the Mo(CO)-(RC=CR)(S2CNMe2)2 reagents (90), and this complicates isolation of pure mixed bisalkyne products. 

In the same way that terminal oxo or nitrene units create a pyramidal distortion in M(0)L5 131) and M(NR)L5 132) complexes, alkynes also tend to pull the metal out of the plane of the four adjacent ligands. In W(CO)(HC=COAlCl3)L3Cl the two PMe3 ligands cis to the alkyne form an L—W—L angle of 161° 130), and in the molybdenum structure the... 

PhS, p-tolS) initially yields the bis(nitrile) complexes [MI2(CO) (NCMe)2(i72-RC2R )]. which dimerize to yield the iodo-bridged complexes [ M(/t-I)I(CO)(NCMe)(T)2-RC2R ) 2].245 The reactions of the diphenylacet-ylene molybdenum complex with donor ligands and alkynes are shown in Scheme 6. 

This is a general reaction for alkynes (acetylene, phenylacetylene, diphenylacetylene, cyclodecyne, etc.) that occurs at RT, producing 75% yields of products. The two cobalt atoms and two carbons form a tetrahedron. Analogous iron complexes are prepared in low yield by reaction of diphenylacetylene with Fe3(CO)i2 . Similar molybdenum complexes are prepared by addition of alkynes to molybdenum multiple bonds ... 

Hydrostannylation. Regioselective hydrostannylation of several types of alkynes (to yield mainly a-stannyl derivatives) is catalyzed by a molybdenum complex. 

A number of authors have reported successful alkyne metathesis reactions catalysed by either tungsten " molybdenum" complexes. 

The carbene complexes M(CO)5 =C(OMe)C6H4feCPh (M = Cr, W) undergo photodecarbonylation and alkyne coordination to form complex 56. The corresponding molybdenum complex undergoes the same reaction in the dark. The chromium species rearranges thermally to form an organic chrysene derivative. s... 

Schrock and Fischer type carbyne tungsten or molybdenum complexes are very interesting catalysts for alkene metathesis or alkyne polymerisation reactions. Within the first reaction steps they form carbene complexes and on these carbene complexes further metathesis or polymerisation occur. 

The cycloruthenated complex 13 reacts with disubstituted alkynes to afford the novel Ti -aiene Ru(0) complexes 49 which were isolated, characterized by X-ray methods, and oxidatively demetallated by treatment with Cu(II) salts to afford metal-free(7i0"isoquinolium salts 43 (with PF as counterion). Kinetic studies have revealed that the reaction proceeds via insertion of the alkyne into the Ru-C bond and that for this process the rate-limiting step is very similar to that found for the analogous palladium compound. Irradiation or thermal treatment of the cycloruthenated complex 50 with diphenylacetylene yields diphenylindole 51 as product. A similar reaction is observed with the corresponding iron or molybdenum complexes. ... 

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