Dimeric structures complexes

Figure 8. Ribbon diagram showing the FPpoI dimer structure complexed with DNA as reported by Stoddard (PDB lA 73). One monomer has residue numbers and shows Asnl 19, His 98, and the magnesium-water cluster(40).

In the reactions of 10.13a with alkali metal terr-butoxides cage expansion occurs to give the sixteen-atom cluster 10.15, in which two molecules of MO Bu (M = Na, K) are inserted into the dimeric structure. The cluster 10.13a also undergoes transmetallation reactions with coinage metals. For example, the reactions with silver(I) or copper(I) halides produces complexes in which three of the ions are replaced by Ag" or Cu" ions and a molecule of lithium halide is incorporated in the cluster. ... 

The solvated sulfenamides [Li2( BuNSC6H4Me-4)2(THF)n] (n = 2,4) have dimeric structures with a central Li2N2 ring. The coordination mode is determined by the extent of solvation of the Li" ions monosolvation allows for rj -N,S coordination whereas disolvation restricts the coordination mode to // -M Variable temperature NMR studies indicated that a dynamic exchange between these two structural types occurs in THF solution (Scheme 10.10). The dihapto coordination mode is observed exclusively in transition-metal complexes and the... 

The structure of the UQ-cyt c reductase, also known as the cytochrome bc complex, has been determined by Johann Deisenhofer and his colleagues. (Deisenhofer was a co-recipient of the Nobel Prize in Chemistry for his work on the structure of a photosynthetic reaction center [see Chapter 22]). The complex is a dimer, with each monomer consisting of 11 protein subunits and 2165 amino acid residues (monomer mass, 248 kD). The dimeric structure is pear-shaped and consists of a large domain that extends 75 A into the mito-... 

The next step in the calculations involves consideration of the allylic alcohol-carbe-noid complexes (Fig. 3.28). The simple alkoxide is represented by RT3. Coordination of this zinc alkoxide with any number of other molecules can be envisioned. The complexation of ZnCl2 to the oxygen of the alkoxide yields RT4. Due to the Lewis acidic nature of the zinc atom, dimerization of the zinc alkoxide cannot be ruled out. Hence, a simplified dimeric structure is represented in RTS. The remaining structures, RT6 and RT7 (Fig. 3.29), represent alternative zinc chloride complexes of RT3 differing from RT4. Analysis of the energetics of the cyclopropanation from each of these encounter complexes should yield information regarding the structure of the methylene transfer transition state. 

Figure 1.75 The structure of the dimeric nitrido complex [Ru2NC18(H20)2]3. ...

The methylisocyanide complex has a dimeric structure with a direct metal-metal bond (2.531 A) and only terminal isocyanides, in a staggered configuration (Figure 3.22). 

Bidentate dithiolate ligands afford complexes like Au(S2CNR2) (R = Et, Pr, Bu) and Au(S2PR2) (R = Pr), which have dimeric structures based on 8-membered rings with linear S—Au—S coordination and short Au-Au distances. These in turn are associated into chains (Figure 4.16) (Au-Au c. 3.0-3.4 A) [99],... 

Whether these results will also have an impact on the theory of metallaallenes is difficult to predict at least for the compounds Cp (CO)2Mn = M = Mn(CO)2Cp, (M = Ge, Sn, Pb) a linear structure is established and also linear p-carbido complexes are known [198], Recently, a germanium compound has been synthesized which is directly comparable with 22. In this case, the starting material for the synthesis is not a monomeric base adduct, but a dimeric germylene complex which is cleaved by Na2Fe(CO)4 in pyridine to form 72 [199],... 

Addition of anhydrous LiX (X = OH, Cl, Br, 1) to Li[Bu"C(NBu%] in THF afforded laddered aggregates in which two neutral lithium amidinates chelate one LiX unit. When the added salt is Lil, the monomeric laddered aggregate is isolated as a bis-THF adduct. In the case of LiOH, LiCl, and LiBr, the ladders dimerize about their external LiX edges. This process is highlighted in Scheme 10 for LiOH. The molecular structure of the resulting dimeric ladder complex is depicted in Figure 2. °... 

Consequently, due to preferred cis-cis orientation a dimeric structure is observed for the indium complex and an unprecedented cis-trans arrangement in the thallium structure leads to a polymeric aggregate. Further N-NMR spectroscopic studies show that the aluminum and gallium complexes are stable contact ion pairs even in solution whereas the indium and thallium compounds are solvent-separated ion pairs in THE solution. 

With sp bond angles calculated to be around 162°, macrocycle 131 would be highly strained and was therefore expected to be quite reactive [79]. The octa-cobalt complex 132, on the other hand, should be readily isolable. Indeed, 132 was prepared easily from 133 in five steps, and was isolated as stable, deep maroon crystals (Scheme 30). All spectroscopic data supported formation of the strain-free dimeric structure. Unfortunately, all attempts to liberate 132 from the cobalt units led only to insoluble materials. Diederich et al. observed similar problems when trying to prepare the cyclocarbons [5c]. Whether the failure to prepare these two classes of macrocycles is due to the extreme reactivity of the distorted polyyne moiety or to the lack of a viable synthetic route is not certain. Thus, isolation and characterization of smaller bent hexatriyne- and octatetrayne-containing systems is an important goal that should help answer these questions. 

X-ray crystallographic analysis of Fe[0Si(0 Bu)3]3THF revealed a distorted tetrahedral geometry (toward a trigonal pyramid) at the Fe center. Related alkyl siloxide complexes of Fe(III) with dimeric structures, [Fe(OSiMe3)3]2 and [Fe(OSiEt3)3]2, have been reported by Schmidbaur and Richter [98]. 

Adventitious water is responsible for the formation of the dimeric hydroxo complex 31 obtained by reaction of AuCb with 1,4-dilithiotetraphenylbutadiene in ether solution [97[. The hydroxo-bridged complex [Au(C6H4N02-2)2( i-0H)[2 (32) was obtained either by reaction of Na[Au(C6H4N02-2)2(0Ph)2] with traces of water in CH2Cl2/n-hexane solution or by treatment of the dichloroaurated complex with NaOH [98[. The crystal structure of 32 2Et20 shows that it is a centrosymmetric... 

The magnesium hydroxide complex [TpAr2]MgOH (Ar = p-C6H4Bul) has been obtained by the reaction of the methyl derivative [TpAr2]MgMe with H20 [Eq. (29)], although it has not been confirmed that the product is monomeric, and a dimeric structure is possible (148). 

Of course, there are two possible dimeric structures of the 1 1 complex 68, as shown in Figure 1.11, namely 69 and 70. Both dimers of 68 should behave in similar fashion in 6Li NMR to the previous experiment. To differentiate those two structures, the nitrogen atom in the chiral modifier 46 was labeled with 15N. Ii-d (-0.42 ppm) would be a doublet if the intermediate is 69. However, Li-c (-1.2 ppm) would be a doublet if it is 70. 

The aqueous solution chemistry of Ir in its higher oxidation states III, IV, and V has been explored by Sykes et al.41,48 Chemical and electrochemical oxidation of Ir(H20)6]3+ gives a brown-green Irv product, which undergoes chemical and electrochemical reduction to a blue and a purple IrIV complex. 170 NMR studies are consistent with double- and single-bridged dimeric structures, with likely formulas [(H20)4Ir(/i-0H)2Ir(H20)4]6+ for the blue complex and [(H20)5Ir(/r-0)Ir(H20)5]6+ for the purple one. 

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