Alkyne complexe binuclear

Alkyne complexes [N3N]Ta( 72-HC=CH) and [N3N]Ta( 72-C6H4) were prepared via treatment of (15) with 2 eq H2C=CHMgBr and LiPh, respectively (Scheme 15)., 39 In contrast, under the same conditions with H2C=CHMgBr, [N3N ]TaCl2 afforded an approximately equimolar mixture of [N3N ]Ta(HC=CH) and binuclear [N3N ]Ta=CHCH2CH2CH= Ta[N3N ].40... 

In Table 2 appear complexes of transition metals with acetylenic compounds. A study was made of the structure and interconversion of acetylene complexes with binuclear transition metals, where acetylene lies parallel or perpendicular to the metal-metal bond" . Carbonyl alkyne complexes with binuclear iron give good separations in reverse-phase HPLC 4... 

The application of the nucleophilic or electrophilic induced carbonyl carbyne coupling reaction has been perfectly demonstrated by E. O. Fischer [13,14], R. R. Schrock [15], J. L. Templeton [16,17], F. G. A. Stone [18], Angelici [19,20], A. Mayr [21,22], R. J. G. L. Geoffroy [23] and S. J. Lippard [24], preparing a variety of interesting ketenyl, alkyne and binuclear complexes involving r 2-ketenyl species as possible intermediates. 

When more than one metal is present in an organometallic complex rather different electrochemical behaviour is possible. For example, metal-metal bonds can function as electron sinks so that extended redox series, linked by sequential one-electron transfer steps, may become available. In addition, the paramagnetic members of such series may show unusual properties associated with mix valency. Here we describe not only the reactions of binuclear species which undergo two or more sequential electron-transfer reactions but also a study of the bonding in alkyne-bridged binuclear species. 

The first complexes of a-keto ylides and group 5 early transition metals have only recently been obtained by reaction of Nb(III) derivatives [[NbCl3(dme) (R C=CR")] with 25 (R = thiazolyl) (Scheme 16). The chelation of the ylide occurs through an N,0-coordination to the metal center and in presence of MeLi a deprotonation of a phenyl ring takes place with the loss of alkyne, leading to the formation of a new orfho-metallated binuclear compound 32. The two ylides involved in the complexation behave as tridentate anionic ligands and are mutually in a trans disposition in order to minimize the steric hindrance [71,72]. Another binuclear niobium complex 33 has been obtained from 25 (R = Me, Ph) with this time an 0-coordinated a-keto ylide [68]. 

The binuclear complex [I I(binap)Ir(/x-OMe)2(p-Cl)Irl I(binap)]Cl catalyzes the hydrogenation transfer from methanol to alkynes via the five co-ordinate intermediate lrHCl(OMe)(binap)].226... 

The species responsible for alkyne polymerization, which is kinetically more facile than eyelotrimerization since only a small fraction of the added alkyne is converted to benzenes, is not yet known. Carbene-metal complexes, both mononuclear (54) and binuclear (y2-CR2) complexes (55,56), have been shown to act as alkyne polymerization initiators and several years ago it was shown that terminal alkynes and alcohols can react to give alkoxycarbene ligands (57) As yet, we have no evidence... 

The cationic binuclear complex [(Mes3PAu)2Cl]BF4 has been found to catalyse the reaction of 2-methyl- or 2-pentyl-furan (78) with phenylacetylene, pent-l-yne, or hept-l-yne (79) to afford the products of a twofold hydroarylation of the alkyne (80).120... 

The ability of the binuclear complex [Cp RuCl(p2-SR)2RuCl(Cp )] to generate cationic allenylidene complexes by activation of terminal prop-2-ynols in the presence of NH4BF4 as a chloride abstractor opens the way to a variety of catalytic transformations of propargylic alcohols involving nucleophilic addition at the Cy atom of the ruthenium allenylidene intermediate (Scheme 19). This leads to the formation of a functional ruthenium vinylidene species which tau-tomerizes into an -coordinated alkyne that is removed from the ruthenium centre in the presence of the substrate. 

Reaction of Fe3(CO)12 with 3-pentyn-l-ol gives the hydrido cluster 4, formed by coupling of an allenylidene unit with a coordinated carbonyl ligand and methoxy group. In contrast, reaction with the isomeric alkyne 2-methyl-3-butyn-2-ol affords a binuclear iron complex.18 Treatment of Fe3(p3-S)2(CO)9 with Me3NO affords the vinylferrocene complex 5, whereas the similar reaction with Fe3(p3-Te)2(CO)9 gives no cluster products.19... 

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