Trimers metal structure

Thomassen, E., Gielen, G., Schutz, M., Schoehn, G., Abrahams, J. P., Miller, S., and van Raaij, M. J. (2003). The structure of the receptor-binding domain of the bacteriophage T4 short tail fibre reveals a knitted trimeric metal-binding fold. J. Mol. Biol. 331, 361-373. 

Enzyme-mimicking systems that contain metal cations have also been designed. A very elegant supramolecular assembly was designed by Sanders et al.I l (see Fig. 7.11). They constructed trimeric porphyrin structures where Zn " " porphyrin moieties function as templates for the organization of substrates into a conformationaUy optimal configuration that undergoes an efficient acyl-transfer reaction or that lead to Diels Alder products. 

Much work has been done on the structure of the metal alkoxides (49). The simple alkaU alkoxides have an ionic lattice and a layer stmcture, but alkaline earth alkoxides show more covalent character. The aluminum alkoxides have been thoroughly studied and there is no doubt as to their covalent nature the lower alkoxides are associated, even in solution and in the vapor phase. The degree of association depends on the bulkiness of the alkoxy group and can range from 2 to 4, eg, the freshly distilled isopropylate is trimeric (4) ... 

Dimeric zinc complexes of tertiary phosphines, [Zn(PR3)I2]2, are also formed from zinc powder and R3PI2, (R = Me, Et, n-Pr, ra-Bu). The crystal structure of the ethyl derivative demonstrates the dimeric nature of the complexes.295 Metallation of diphenylphosphine with ZnEt2 results in a trimeric species with a Zn3P3 core and bridging diphenyl phosphide ligands. Two protic (HPPh2)... 

Trinuclear zinc carboxylate structures of the form MZn2(MeCH=CHC02)6(quinoline)2 have been structurally characterized with M = Mn, Co, Ni, Zn, Cd, Mg, Ca, Sr. Structural variation is observed for the group 2 metals. The remaining complexes all show linear trimers with the central metal atom octahedrally coordinated and linked to each zinc by two bidentate and one mono-dentate carboxylate.377 A basic benzoate octanuclear structure with four vanadium(III) and four zinc atoms has been characterized, [VZnO(benzoate)3(TF[F)]4-2TnF.378... 

Other Cg hydrocarbons. The dehydrogenation of normal hexane and 2,3-di methyl butane also proceeds but not as voraciously on small platinum clusters. Figure 8 is a plot of the hydrogen content in the first adduct as a function of the size of the platinum metal cluster. The metal atom reacts via dihydrogen elimination to produce PtC6Hi2 products. The platinum trimer is now the smallest cluster that will produce a C H near one. The similarity of size dependent dehydrogenation of the normal hexane and the branched molecule suggest that these systems may not readily aromatize these alkanes. Further structural studies are needed to identify the reaction products. 

Zhou and Pfaltz (149) note that complex 215 mirrors the behavior of van Koten s complex 210. The catalyst is trimeric in solution and solid state and displays an intricate nonlinear effect (78, 146) in the conjugate addition reaction, Fig. 19 (149). It seems likely that these ligand-metal complexes are structurally related. 

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