Diene bimetallic complexes

The method has been extended to bimetallic complexes (equation 87) and to butadiene type compounds (equation 88).309 These dienes may be used in complex formation producing complexes analogous to butadiene, as shown by equation (89). The structure of (59b) and the diene [Cp(CO)2 Mo=P(R)CH=P(R)] (59c) have been proved by X-ray crystallography. A similar series of dienyl complexes have been synthesized by Huttner et a/.281 (see Section 14.5.1.3.i). 

The M[ZnR4] and M[A1R4]2 ate complexes (M = Ca, Sr, Ba) polymerize vinyl and conjugated diene monomers including styrene, methylmethacrylate, acrylonitrile, vinyl-ketones, isoprene and butadiene . The bimetallic complexes produce polymers of differing microstructure to that formed by simple alkaline-earth metal initiators, so that the presence of Zn or A1 influences the stereochemistry of propagation. Thus, polybutadiene obtained in benzene from a Ba-Zn initiator contains more than 90% 1,4-bonds (trans-1,4 75-81 %) ... 

Bimetallic Complexes A novel type of bridging buta-1,3-diene coordination in the dimeric species [Cp2 H-(l,2-ti-2-Zr) 4-Ti-l-Al)-C4H6)(p-Cl)AlQ2] was rcpcHted272. 

Bimetallic complexes of Sm were used for the living bis-initiated polymerization of MMA and -caprolac-tone, giving polymers with discrete functionalities at the center of the backbone ( link-functionalized ) [109]. When the bis-allyl complex [Cp2Sm(/x-i -CH2-CH-CH-)]2 [110], depending on the mode of attack during initiation, the link functionality resulting from this process should comprise either two pendant vinyl groups or a backbone 1,3-diene unit. 

The fact that organosamarium allyl complexes of the type Cp 2Sm(CH2CH=CHR) can arise from the treatment of Cp 2Sm or [Cp 2Sm(/r-H)]2 with a variety of olefin and diene substrates makes samarium chemistry more intriguing. The reaction modes are illustrated in Scheme 18. These allylsamarium complexes 55 react with C02 to afford the carboxylate products 56, which participate in monometallic/bimetallic interconversions (Equation (10)). Carbon disulfide and 0=C=S also insert into carbon-samarium bonds, which form only monometallic species.29... 

The thermal reaction of 1,3-dienes with Co2(CO)8 gives the corresponding bimetallic dimers [(diene)Co(CO)2]2 132 as orange red solids in good yields (Scheme 27)28,133. Oxidation of the dimeric complexes 132 with ferricinium tetrafluoroborate or triphenyl-carbenium tetrafluoroborate gives the monomeric (diene)Co(CO)3+ cations 133 in modest... 

Compared to the extensive use of phenolate ligands and the isolation and structural characterization of a broad variety of differently alkylated hetero-bimetallic Ln(III)/Al complexes, only two examples of anilides AIR3 adduct formation and [anilide] [alkyl] exchange are reported in the literature. There exist no reports on the use of simple anilide ligands in diene polymerization. 

Upon the addition of CO or H2 in the presence of appropriate stabilizers, the controlled chemical decomposition of zerovalent transition metal complexes yields isolable products in multigram amounts [49]. The growth of metallic Ru particles from Ru(COT) (COD) (COT = cyclooctatetraene, COD = cycloocta-1,5-diene) with low-pressure dihydrogen was first reported by Ciardelli et al. [49a]. This material was, however, not well characterized, and the colloidal aspect of the ill-defined material seems to have been neglected in this work. Bradley and Chaudret [49b-l] have demonstrated the use of low-valent transition metal olefin complexes as a very clean source for the preparation of nanostructured mono- and bimetallic colloids. 

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