Benzene as 176 ligand

Hermann A, Silva LS, Peixoto CRM, Oliveira ABD, Bordinhao J, Homer M (2008) Electrochemical properties of Cu4[PhN3C6H4N3(H)Ph]4(p-0)2, a tetranuclear Copper(II) complex with l-phenyltriazenido-2-phenyltriazene-benzene as ligand. Eclet Quim 33(3) 43 6... 

Highly active, selective, and recyclable palladium catalyst systems for the hydroesterification of styrene (at room temperature and 6 bar CO pressure) and vinyl acetate (at 40-60 °C and 6-10 bar CO pressure) were found by using l,2-bis(di-tert-butylphosphinomethyl)benzene as ligand and polymeric sulfonic adds of limited SO3H loadings as promoter [148]. 

In view of the excellent donor properties of tertiary arsines, it is of interest to inquire whether these cyc/o-polyarsanes can also act as ligands. Indeed, (MeAs)s can displace CO from metal carbonyls to form complexes in which it behaves as a uni-, bi- or triden-tate ligand. For example, direct reaction of (MeAs)5 with M(CO)6 in benzene at 170° (M = Cr, Mo, W) yielded red crystalline compounds [M(CO)3( -As5Me5)] for which the structure... 

Cycloaddition of aUcynes catalysed by transition metals is one of the most efficient and valuable ways to prepare benzene and pyridine systems [12], Among the possible catalytic systems able to catalyse this reaction, cobalt and iron complexes containing NHCs as ligands have shown high catalytic activity in the intramolecular cyclotrimerisation of triynes 36 (Scheme 5.10) [13]. The reaction was catalysed with low loading of a combination of zinc powder and CoC or FeClj with two or three equivalents of IPr carbene, respectively. 

It soon became apparent, however, that even the TMS activation mechanisms, both for dtbpm and dcpm as ligands at platinum, are more complicated than originally assumed. First it was noticed that 24 and 19 are in equilibrium with each other in solution. Compound 19, if dissolved in THF or benzene, creates an equilibrium concentration of 24 at a concentration level of around 5%. The same equilibrium is reached when pure 24 rearranges to 19. The energy difference between 24 and 19 therefore must be in the range of only 1-2 kcal/mol, favoring 19, and in fact this is found in EH MO calculations [23]. 

Ionic liquids have also been applied in transfer hydrogenation. Ohta et al. [110] examined the transfer hydrogenation of acetophenone derivatives with a formic acid-triethylamine azeotropic mixture in the ionic liquids [BMIM][PF6] and [BMIM][BF4]. These authors compared the TsDPEN-coordinated Ru(II) complexes (9, Fig. 41.11) with the ionic catalyst synthesized with the task-specific ionic liquid (10, Fig. 41.11) as ligand in the presence of [RuCl2(benzene)]2. The enantioselectivities of the catalyst immobilized by the task-specific ionic liquid 10 in [BMIM][PF6] were comparable with those of the TsDPEN-coordinated Ru(II) catalyst 9, and the loss of activities occurred one cycle later than with catalyst 9. 

The comparison of hydrogen consumption in the rhodium-catalyzed enantiomeric hydrogenation of a yS-dehydroamino acid using Et-Duphos (Et-Du-PHOS = l,2-bis(2,5-diethyl-phospholanyl)benzene)) as the chiral ligand shows the huge differences in rate, depending on the manner in which the catalyst was prepared (Fig. 44.1) [10b,c]. 

Several mixed 7r-benzene-jr-cyclopentadienyl complexes have been investigated in UPS in order to compare the properties of these groups as ligands. The ds system Cr(cp)(bz) was investigated by Evans etal (57) together with the d6 complexes Cr(bz)2, Cr(tol)2, and Mn(cp)(bz). The spectmm of Cr(cp)(bz) shows in the region... 

Automated parallel experiments were carried out to rapidly screen and optimize the reaction conditions for ATRP of methyl methacrylate (MMA) [34]. A set of 108 different reactions was designed for this purpose. Different initiators and different metal salts have been used, namely ethyl-2-bromo-tTo-butyrate (EBIB), methyl bromo propionate (MBP), (1-bromo ethyl) benzene (BEB), and p-toluene sulfonyl chloride (TsCl), and CuBr, CuCl, CuSCN, FeBr2, and FeCl2, respectively. 2,2 -Bipyridine and its derivatives were used as ligands. The overall reaction scheme and the structure of the used reagents are shown in Scheme 2. 

Carbonylchlorocopper(I) (A) is a valuable precursor for the synthesis of organometallic and coordination compounds of copper(I). Previous methods11 utilizing water, tetrahydrofuran, methanol, or benzene as solvent may yield lower-purity products because copper(I) chloride is not soluble in these solvents without excess halide ligand. The synthetic method described here also provides a convenient way of growing large crystals of X-ray quality of carbonylchlorocopper(I). 

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