Poly transition metal salts

This catalytic sequence is known as Kharasch addition or atom transfer radical addition (ATRA) [4]. Various polyhalogenated compounds such as CCI4 and CCI3CO2R are used as the organic halides, and transition metal salts or complexes are used as the catalyst [3]. Intramolecular version of the Kharasch addition reaction (atom transfer radical cyclization, ATRC) has opened novel synthetic protocols to the synthesis of carbocyde or heterocyles catalyzed by transition metals [5-7], and this has become a very important field in free radical cydization in organic synthesis. Transition metal-catalyzed Kharasch reactions sometimes afford telomers or poly-... 

Many polymer-salt complexes based on PEO can be obtained as crystalline or amorphous phases depending on the composition, temperature and method of preparation. The crystalline polymer-salt complexes invariably exhibit inferior conductivity to the amorphous complexes above their glass transition temperatures, where segments of the polymer are in rapid motion. This indicates the importance of polymer segmental motion in ion transport. The high conductivity of the amorphous phase is vividly seen in the temperature-dependent conductivity of poly(ethylene oxide) complexes of metal salts. Fig. 5.3, for which a metastable amorphous phase can be prepared and compared with the corresponding crystalline material (Stainer, Hardy, Whitmore and Shriver, 1984). For systems where the amorphous and crystalline polymer-salt coexist, NMR also indicates that ion transport occurs predominantly in the amorphous phase. An early observation by Armand and later confirmed by others was that the... 

The rates, selectivities, and stabilities of transition-metal-substituted poly-oxometalates in olefin epoxidation are compared with those of metallopor-phyrins, Schiff base complexes, and triflate salts, as follows (320b) ... 

Like many late transition metals, nickel has featured, albeit briefly, in the pursuit of poly(pyrazolyl)borate-metal-carbollide complexes. Thus, [c/oso-3-(r 2-Ph2Bp)-3,l,2-NiC2B9H11] (90 ) has been obtained as the tet-ramethylammonium salt,39 via the reaction of [Me4N][Ph2Bp] with the neutral bisphosphine nickel dicarbollide [doso-3,3-(PhEt2P)2-3,l,2-... 

The development of CTOwn ether functionalised imidazolinm salts starts from the consideration that it is possible to link one polyether chain with two imidazolinm nnits at the end points. Since a transition metal can coordinate two imidazoUnm salts in trans fashion [131,162,208], two of these (poly)ether fnnctionaUsed bis-carbenes can form a macrocychc crown ether type hgand system with two transition metal carbene linkages. In favonrable cases, a pincer type C,0,C ms-coordination to the same transition metal is conceivable, bnt may not be very likely when the great affinity of late transition metals to NHC ligands and the aversion of these same late transition metals to ether donor Ugands is taken into account. However, hanilabile stabilisation of transition metal complexes in catalytic processes can certainly be hoped for. 

In 1988 Lalor reported the synthesis and spectroscopic characterization of some new poly(benzo-triazolyl)borate salts (Scheme 8).180 The regiospecifity of the synthesis of I I B( Btz)4 differs from that of pyrazole/BH4 reaction in that B—N bond formation takes place in a manner that maximizes steric crowding at boron (i.e., at the triazole N(l) atoms). In 1989 Shiu describes some new metal carbonyls of HB(Btz)3.181 The synthesis and spectroscopic characterization of some first-row transition metal complexes was reported by Cecchi,182 whereas Hill described some new Rh183 and Ru184 carbonyl and isonitrile complexes. The formation of isonitrile derivatives was proposed to proceed through an associative mechanism involving an intermediate complex... 

Hydrogenation of Compounds with C=C Bonds Hirai and Toshima have published several papers on the synthesis of transition metal nanopartides by alcoholic reduction of metal salts in the presence of a polymer such as polyvinyl alcohol (PVA), poly(methyl vinyl ether) (PMVE) or polyvinylpyrrolidone (PVP) in methanol (or ethanol) /water mixtures or in pure alcohols. This simple and reproducible process has been applied for the preparation of rhodium nanopartides from rhodium (III) trichloride [15]. The particles size of metallic fee rhodium is distributed in a narrow range, 3-7nm and the average diameter is 4nm. The PVP-stabilized Rh nanoparticies are more stable. These nanomaterials are effident catalysts for olefin and diene hydrogenation in rruld conditions (30 C PH2=lbar) as shown in Table 11.1. 

Further, silica-supported poly-y-aminopropylsilane transition metal complexes derived from Ni(II), Cu(II) and Co(II) salts were probed in arylation reactions of acrylic acid (16), methyl acrylate (1) and styrene (2) using iodobenzene derivatives. The most efficient catalysis was again observed with the nickel-based recyclable catalyst [23,25]. 

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