Benzyl complexes chemistry

A fourth focus of catalytic chemistry in our laboratory has been iridium-catalyzed asymmetric allylic substitution. Dr. Toshimichi Ohmura had been studying additions to rhodium and iridium allyl and benzyl complexes in hopes of developing... 

Benzyl complexes metal hydroxides chemistry, 358 a-monooxime, 272 Benzylideneimine Schiff bases metal complexes, 721 Beryllium, alkylalkoxy synthesis, 340 ... 

Transition metal-benzyl complexes also react readily with nucleophiles, but the origin of this enhanced reactivity results from effects other than the typical rapid rate of nucleophilic attack at an electrophilic benzyUc carbon. As shown in Equation 11.17, benzyl groups can be bound in an fashion, much like an aUyl group. As presented later in this chapter, cationic iq -allyl complexes react with a variety of nucleophiles. iq -Benzyl groups are common in the chemistry of palladium(II), - and these ti -benzyl and phen-ethyl complexes react with a variety of nucleophiles. For example, these complexes react with malonate anions, and they have been shown to react with amines " during some recently developed hydroamination processes. These reactions occur with predominant inversion of configuration. ... 

An important development over the last two years has been the confirmation that cationic Group IV metal alkyl complexes are the catalytically active species in olefin polymerizations with homogeneous Ziegler-Natta catalysts. A number of complexes of the type [Cp2MR(L)] (M = Ti, Zr, Hf) have now been prepared, particularly when stabilized by donor ligands such as L = THF. The chemistry of zirconium complexes of this type has been reviewed. Some cationic benzyl complexes with stereorigid ligands (29)... 

R B Woodward was one of the leading organic chemists of the middle part of the twenti eth century Known pnmanly for his achievements in the synthesis of complex natural products he was awarded the Nobel Pnze in chemistry in 1965 He entered Massachusetts Institute of Tech nology as a 16 year old freshman in 1933 and four years later was awarded the Ph D While a student there he earned out a synthesis of estrone a female sex hormone The early stages of Woodward s estrone synthesis required the conversion of m methoxybenzaldehyde to m methoxy benzyl cyanide which was accomplished in three steps... 

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. 

The syntheses and spectroscopic and electrochemical characterization of the rhodium and iridium porphyrin complexes (Por)IVI(R) and (Por)M(R)(L) have been summarized in three review articles.The classical syntheses involve Rh(Por)X with RLi or RMgBr, and [Rh(Por) with RX. In addition, reactions of the rhodium and iridium dimers have led to a wide variety of rhodium a-bonded complexes. For example, Rh(OEP)]2 reacts with benzyl bromide to give benzyl rhodium complexes, and with monosubstituted alkenes and alkynes to give a-alkyl and fT-vinyl products, respectively. More recent synthetic methods are summarized below. Although the development of iridium porphyrin chemistry has lagged behind that of rhodium, there have been few surprises and reactions of [IrfPorih and lr(Por)H parallel those of the rhodium congeners quite closely.Selected structural data for rr-bonded rhodium and iridium porphyrin complexes are collected in Table VI, and several examples are shown in Fig. 7. ... 

A Au mdssbauer study of reaction products of trimeric l-benzyl-2-gold(I)-imidazole leading to Au carbene or Au imidazoline complexes and trinuclear Au " imidazolyl derivatives. X-Ray crystal structure of [ (p-l-benzylimidazolato-N, C )Au 3l2j. Journal of Organometallic Chemistry, 470, 275-283. 

Hydride transfer reactions from [Cp2MoH2] were discussed above in studies by Ito et al. [38], where this molybdenum dihydride was used in conjunction with acids for stoichiometric ionic hydrogenations of ketones. Tyler and coworkers have extensively developed the chemistry of related molybdenocene complexes in aqueous solution [52-54]. The dimeric bis-hydroxide bridged dication dissolves in water to produce the monomeric complex shown in Eq. (32) [53]. In D20 solution at 80 °C, this bimetallic complex catalyzes the H/D exchange of the a-protons of alcohols such as benzyl alcohol and ethanol [52, 54]. 

Abstract The purpose of this chapter is to present a survey of the organometallic chemistry and catalysis of rhodium and iridium related to the oxidation of organic substrates that has been developed over the last 5 years, placing special emphasis on reactions or processes involving environmentally friendly oxidants. Iridium-based catalysts appear to be promising candidates for the oxidation of alcohols to aldehydes/ketones as products or as intermediates for heterocyclic compounds or domino reactions. Rhodium complexes seem to be more appropriate for the oxygenation of alkenes. In addition to catalytic allylic and benzylic oxidation of alkenes, recent advances in vinylic oxygenations have been focused on stoichiometric reactions. This review offers an overview of these reactions... 

The coordination chemistry of optically pure, chiral phosphetanes has been studied with special attention to the preparation and characterization of complexes since they are suitable for asymmetric catalytic reactions. The optically active P-menthylphosphetanes showed similar reactivities with usual trivalent phosphines to afford stable palladium(n) and ruthenium complexes, under usual reaction conditions. Similarly, the Pd-allyl complex 28 <1997JOM(529)465> has been prepared from [(allyl)PdCl]2 and was characterized by X-ray crystallography. Reaction of the P(R),C(3 )-2-benzyl-3,3,4,4-tetramethyl-l-menthylphosphetane 64 with Ru3(C0)12/HC02H proceeds normally to give the formato bridged dimer 65 (Figure 11) <1998S1539>. 

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