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Bridging alkylidene

Terminal alkylidene complexes generated in this manner can react further with the organometallic substrate when steric interactions are not unfavorable, forming dinuclear species. Herrmann has used this methodology extensively in the preparation of bridging alkylidene complexes (84). [Pg.156]

Thermolysis of the complexes R2M[N(SiMe3)2]2 (M = Zr, Hf) was found to proceed with double activation of the y-CH bonds leading to a dimeric complex containing a bridging alkylidene function (equation 98).252... [Pg.184]

Hahn, James E., Transition Metal Complexes Containing Bridging Alkylidene... [Pg.525]

R CN (Table 2) [86]. The molecular structure of the 2,2-dimethylpropanonitrile derivative contains unsymmetrically bridging alkylidene amide ligands. Reaction of the yttrium and erbium hydride species with isonitrile results in the formation of a formidoyl moiety (Table 2) [87], Surprisingly the Ln-N interaction is in the range of the nitrile product A similar molecular structure was found in the oximato complex [Cp2Gd(/i-t/2-ONCMe2)]2 (Gd-Nav 2.42(1) A) [88]. [Pg.50]

Diazoalkanes are important sources of reactive CR2 fragments in alkylidene chemistry. Bridging alkylidenes are extensively reviewed (116-118). A number of diazoalkanes add across the metal-metal triple bond associated with 2. The reactions are, however, highly complex (as shown by the formation of 30 above), with reaction products heavily dependent on the R substituents of R2CN2 as well as the substituents on the cyclopentadienyl ring. While many interesting products arise in these reactions, the consequence is a minimum ability to predict reaction products. [Pg.125]

Most of these reactions are reversible under either thermal or photochemical conditions. Interestingly, the bridging alkylidene complex (32) is redox active. [Pg.306]

Electrochemical reduction or oxidation causes the elimination of the bridging alkylidene moiety (128, 129). [Pg.307]

The bridging alkylidene ligand in 12 has been found to be a reactive species towards several small molecules. The addition of dihydrogen (45 psi, 50°) to 12a resulted in cleavage of the alkyl -idene from the metals diphenylmethane (confirmed by XH NMR spectroscopy and GC/MS) and 1 were obtained in high yield (eq. 34). [Pg.243]

COMPOUNDS WITH BRIDGING ALKYLIDENE AND ALKYLIDYNE LIGANDS. [Pg.300]

R H, R" = CH CH2 R = H, R = C02Et) to give bridging alkylidene complexes (51). The latter undergo dynamic behaviour in solution. Herrmann et al(31) have prepared a number of related dirhodium complexes with bridging alkylidene groups by reacting either... [Pg.310]

The results described in this paper suggest that further studies in this area would be very profitable. The heteronuclear metal —metal bonded species will have a rich chemistry at the metal centres, particularly in those cases where bridging alkylidene or alkylidyne ligands are present. [Pg.312]

Griitzmacher, Jansjorg, see De Bruin, Bas Gultneh, Yilma, see Karlin, Kenneth D. Hahn, James E., Transition Metal Complexes Containing Bridging Alkylidene Ligands 31 205... [Pg.575]

The generation and interconversion of hydrocarbon fragments on metal surfaces is an important aspect of transition metal catalysis. In an effort to model and understand these transformations, much attention has been focused on the synthesis and reactivity of organic species coordinated at polynuclear transition metal centers. Organodiruthenium complexes have provided a particularly rich area of study. The availability of a variety of organometallic derivatives of the bis(T) -cyclopentadienyl)diruthenium carbonyl system has allowed extensive examination of the reactivity of bridging alkylidene, alkylidyne, and ethenylidene ligands. [Pg.179]

Formation of the dimer with the bridging carbonyl occurs in 67% yield, and formation of dimer with a bridging alkylidene occurs in 86% yield for R=H, Me . The addition of dry hydrogen halides (HCl or HBr) yields the following complex ... [Pg.81]

Olefin additions to bridging alkylidenes yield dimetallacyclopentanes . These reactions also provide a mechanism for olefin metathesis, a topic not discussed here. Although addition of an olefin to a metal carbone, a 2n + In addition, would be symmetry forbidden in organic chemistry, ab initio calculations " of the conversion of a metal carbene-alkene to a metallocyclobutane show it to be a barrierless reaction. Metal d orbitals relax the symmetry restrictions for the In + 2n addition. The mechanism of reaction (p) has not been widely considered for the olefin polymerization, but it may be relevant to olefin dimerization and oligomerization—reaction (s), for example ... [Pg.659]

One problem with this approach is the ever-present, rapid, competing side reaction of -elimination (Section 8-1-2). As we shall see, a-elimination is indeed used to produce alkylidenes, but the circumstances of this reaction are unique. Other approaches that we will discuss include decomposition of bridged alkylidenes and direct attack of a free carbene precursor on a metal. [Pg.410]

Equation 10.15 provides another example of the use of A1 compounds to form bridging alkylidenes, providing stabilization for the very reactive Group 4 carbene complexes. Later in Chapter 10 (Section 10-3-2), we shall encounter some of the synthetically useful chemistry of Tebbe s reagent. [Pg.415]

Both complexes result from the insertion of butyne into one of the tungsten-carbon bonds of the bridging alkylidene ligand. However, in XVII the two double bonds are... [Pg.103]

Bridging alkylidene complexes similarly react with alkynes to afford isolatable derivatives arising from the formal insertion into one metal-carbon bond. So, UV irradiation of M2(CO)2(/t-CO)( U-CHCH3)(>j -Cp), in the presence of acetylene results in the fomation of a new carbene and a three-carbon bridging system, XXII ... [Pg.104]


See other pages where Bridging alkylidene is mentioned: [Pg.1033]    [Pg.371]    [Pg.371]    [Pg.168]    [Pg.43]    [Pg.126]    [Pg.145]    [Pg.208]    [Pg.236]    [Pg.300]    [Pg.1143]    [Pg.2962]    [Pg.3778]    [Pg.290]    [Pg.236]    [Pg.487]    [Pg.247]    [Pg.170]    [Pg.413]    [Pg.413]    [Pg.1148]    [Pg.2961]   
See also in sourсe #XX -- [ Pg.2 , Pg.4 , Pg.5 , Pg.9 , Pg.14 ]

See also in sourсe #XX -- [ Pg.2 , Pg.4 , Pg.5 , Pg.9 ]




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Alkylidene complexes Bridged

Bridging alkylidene and alkylidyne

Bridging alkylidene complex

Bridging ligands Alkylidene

Ligand compounds with bridging alkylidene

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