Benzyl ligand

The benzyhc complex has been synthesized at low temperatures and may owe its stabiUty to possible multihapto coordination, Tj —Tj, of the benzyl ligand. The methyl complex is stable even up to room temperature. Six of the methyl groups are hydrogen-bonded to the Li atom to stabilize this highly charged species. This compound is very reactive with and CO. However, there is no concrete stmctural data for the final products of such reactions. 

Heteroleptic complexes of uranium can be stabilized by the presence of the ancillary ligands however, the chemistry is dominated by methyl and benzyl ligands. Examples of these materials include UR4(dmpe) (R = alkyl, benzyl) and U(benzyl)4MgCl2. The former compounds coordinate "soft" chelating phosphine ligands, a rarity for the hard U(IV) atom. 

Catalytic hydrogenation with platinum liberates the hydrocarbon from methylcobalamin (57) and from alkyl-Co-DMG complexes (161), but not from pentacyanides with primary alkyl, vinyl, or benzyl ligands, though the cr-allyl complex yields propylene (109). Sodium sand gives mixtures of hydrocarbons with the alkyl-Co-salen complexes (64). Dithioerythritol will liberate methane from a variety of methyl complexes [cobalamin, DMG, DMG-BF2, G, DPG, CHD, salen, and (DO)(DOH)pn] (156), as will 1,4-butanedithiol from the DMG complex (157), and certain unspecified thiols will reduce DMG complexes with substituted alkyl ligands (e.g., C0-CH2COOH ->CH3C00H) (163, 164). Reaction with thiols can also lead to the formation of thioethers (see Section C,3). 

A further dramatic comparison of the comparative reactivities of chromium alkyls in diverse oxidation states was furnished by another set of benzyl complexes. [7] Shown below, these three compound are isomers, yet they range in oxidation state from Cr to Cr °. Of the three, only the mixed-valent complex Cp G0i-ti n3-Bz)Cr(Bz)Cp, containing a Bivalent chromium bound to an T)3-benzyl and a ni-benzyl ligand, catalyzed the polymerization of ethylene. 

Toluenesulfonyl iodide reacts with benzylcobaloximes to give good yields of the benzyl p-tolyl sulfones, the key step being the homolytic attack of the sulfonyl radical at the a-carbon of the benzyl ligand ... 

Fig. 32. Dendritically enlarged diamines 90-92 and benzylated ligand 93 (DDB analogs) in the enantioselective addition of methanol to ketene using 0.01 equiv. catalyst [114]...

The benzyl ligand of benzylbis(dimethylglyoximato)pyridine cobalt complex has been selectively converted to 3,5-dibenzyl-l,2,4-oxadiazole by a reaction with alkyl nitrite in the presence of light (426). The reaction proceeds by the in situ formation of an oxime and a nitrile oxide (Scheme 1.44). 

More recently a benzylchromium complex has been found to insert C02, though in this case the benzyl ligand is also bound by an o-NMe2 linkage 143a). Thus, Cr(CH2C6H4-o-NMe2)3 inserts one C02 into a Cr—C bond to yield a product formulated with a bidendate carboxylate. 

Homogeneous alkylaluminium-free olefin polymerisation catalysts also comprise non-metallocene cationic group 4 metal complexes such as those with benzyl ligands [162]. A distinct group of alkylaluminium-free homogeneous olefin polymerisation catalysts consists of nickel complexes [181-183],... 

The benzyl ligand CH2Ph may also be considered as a special case of allyl coordination wherein one double bond of the arene becomes associated with the metal centre (Figure 4.1). 

Homoleptic tetrabenzyl complexes are prepared by reaction between ThCLt and benzyllithinm in THF solntion at low temperature (eqnation 53)d It is nnlikely that these complexes are -alkyls, since the X-ray stmctnre of Cp Th(CH2Ph)3 revealed mnltihapto coordination of the benzyl ligand. ... 

Sim and co-workers (97) reported that irradiation of CpFe(CO)2CH2Ph in benzene solution and in the presence of PPha gave the complex Fe(CO)2(PPh3)(cjco-i7 -C5H5CH2Ph) in which the benzyl ligand had migrated via an intramolecular reaction to the Cp ring. However, no yield or mechanistic details were provided. 

Today, we are studying whether iron can coordinate to aromatics and give, among other things, 77-benzyl derivatives. The 77-benzyl ligand is a modification of the 77-allyl one. So far, however, the coordination has been shown to be not too favorable. Actually ArCH2X (X is Cl, or Br) reacts with di-iron nonacarbonyl to produce, as a rule [437), ArCH2CH2Ar or... 

Replacement of the THF ligand of a Cp2Zr(R)(THF)+ species with a two-electron donor ligand opens up an empty orbital on Zr and invariably results in a compensating structural distortion. Spectroscopic data establish that the cationic benzyl complex (C5H5)2Zr(CH2Ph)(THF)" has a normal f/ -benzyl ligand. This species reacts irreversibly with CHjCN to yield the... 

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