Coordination Scheme

By using these parameters, the single coordinate scheme becomes, in practice, a two-coordinate one, the coordinate along which the 8 parameter... 

The n orbitals on the two CO molecules interact with the same lobe of a vacant 3p orbital on a metal atom in the model for the acute angle coordination, and with different lobes for the obtuse angle coordination (Scheme 29b). Cychc orbital interaction occurs between the occupied 3s orbital and the vacant 3p orbitals on M and the n orbitals, n, and n, of the CO molecules (Scheme 29c). The phase is continuous for the same lobe interaction and discontinuous for the different lobe interaction (Scheme 29d, cf. Scheme 4). The acute-angle coordination is favored. 

The conversion of a [3Fe-4S] into a [4Fe-4S] center was achieved by restoring the second residue of the consensus motif in E. coli fu-marate reductase (181) and in D. africanus ferredoxin III (161). However, the coordination scheme of the iron-sulfur centers of A. vinelan-... 

Although the second Cys of the three groups of cysteine residues expected to coordinate the [4Fe-4S] centers of E. coli nitrate reductase were systematically mutated to induce their conversion into [3Fe-4S] centers, this conversion was achieved only in the case of the C247D mutation affecting the lowest potential [4Fe-4S] center (E. Valay, B. Guigliarelli, M. Asso, P. Bertrand, and F. Blasco, unpublished results, 1998). This result, which confirms the proposed coordination scheme (174), shows once again that the coordination capacity of the various Cys motifs of a protein can be differently affected by amino acid substitutions. 

The reaction of the stabilized yUde 46 (a-vinyl substituted) with the cycloocta-dienyl Pd(II) allows the synthesis of a novel complex, the (rj -allyl)palladium 47, in which the olefmic double bond participates in the coordination (Scheme 20) [83]. The coordination of the bis-yUde 48 with the same starting Cl2Pd(COD) leads to the formation of another new palladium complex 49 via COD exchange reactions. A C-coordination mode takes place between the carbanionic centers of the bis-ylide and the soft palladium and two stereogenic centers of the same configuration are thus created [83]. In contrast to the example described in Scheme 19, the Cl2M(COD) (M=Pd or Pt), in presence of a slightly different car-... 

TaniaPhos with (9) or (5) Reacting TaniaPhos with (9) in THF at r.t. resulted in amine coordination (Scheme 23.6) ... 

Mixed organo antimony ligands with one or two electronegative groups have been only rarely used in transition metal chemistry. The resulting complexes belong to type 3 or 4 with -Sb coordination (Scheme 2). 

Fig. 18 Coordination scheme of the 3D Fe(L)2[Ag(CN)2]2 (L -bipy (left) and bpe (right)) coordination polymers...

Insertion of COz into a metal-hydride bond normally requires the prior dissociation of an ancillary ligand to generate a coordinatively unsaturated complex, because C02 coordination to the metal usually precedes the formal insertion (Scheme 17.3, lower pathway). Ah initio calculations [59] support this mechanism for the insertion of C02 into the Ru-H bond of RuH2(PH3)4, a model for the catalyst RuH2(PMe3)4. However, it is theoretically possible for C02 insertion to take place without prior C02 coordination (Scheme 17.3, upper pathway) [60, 61]. The... 

A significantly higher barrier (ca 32 kcalmol-1) is observed for iron migration in linear polyene complexes, e.g. 118 - 118 (Scheme 22). This isomerization is believed to proceed via rf -> rj1 coordination (118 - 119) followed by migration of the iron in the r]2 coordination mode (119 -> 119 ) (Scheme 22)122. While racemization of acyclic (diene)Fe(CO)3 does not occur at ambient temperatures, it is observed at elevated temperatures. This process is also proposed to occur via r/2 coordination (Scheme 23) however the rate for racemization (ca 2.3-2.7 x 104 at 119 °C) is approximately half the rate of polyene migration122. 

Pyrroles are lithiated at the 2-position whether or not the A-protecting group has the ability to coordinate (Scheme 131) . 3-Lithiopyrroles are best obtained by halogen-metal exchange on 3-bromo-A-TIPS pyrrole 275 (Scheme 132). ... 

This is so, as shown by Grubbs reports of the reactions of metallacycles of type L Ni(CH2)4 It is reported that the preferred decomposition pathway depends on the degree of coordination (Scheme 2). Here the formation of cyclobutane from... 

Metallothioneins are small proteins of about 60 amino acids (20 of which are conserved cysteine residues) that bind copper, zinc, and cadmium (Melis etal, 1983 Furey etal, 1986). Solution structures have been elucidated by NMR, showing the coordination schemes (Schultze et ai, 1988). 

Buchbinder, J. L., and Reed, G. H. (1990). Electron paramagnetic resonance studies of the coordination schemes and site selectivities for divalent metal ions in complexes of pyruvate kinase. Biochemistry 29, 1799-1806. 

Any homogeneously distorted two-dimensional coordination scheme should be based upon the distance correlation statistics between next neighbors at least. In the case of a two-dimensional lattice construction, this distance correlation principle has been used by Hosemann and coworkers [13] to generate micro-paracrystals of finite size with the help of a computer. The construction procedure (known as spiral-paracrystal ) terminates if a coordination point cannot be assigned to a lattice point. 

There is now considerable evidence that indicates that metal ion-activated enzymes and metalloenzymes catalyze reactions via ternary complexes consisting of a 1 1 1 ratio of enzyme metal ion substrate. Three coordination schemes are possible ... 

C. Syntheses via Initial Donor Atom Coordination (Scheme lb). 299... 

Figure 4.8. Coordinate scheme for axially symmetric case.

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