Chelate coordination

In these structures, the cupf assumes its typical chelating coordination pattern and is nearly symmetrically bound to the [Me2Sn(IV)] center. In complex (4) a pentagonal bypiramidal (PBP) geometry containing C2SnOs moiety was found by XRD method. The Bu2Sn(IV)-cup complex proved to be... 

In order to formally insert CH2, the growing alkyl chain must attain a situation of metal-to-carbon bonding that favors CH2 insertion over coupling of two CHR groups (R=H, alkyl).29 A (C, H)-chelating coordination mode characterized by agostic M-H-C interaction30 would meet this requirement. 

Owing to their conformational flexibility, bridging and/or chelating coordination modes are typical for polychalcogenide ligands. As a result, very few... 

Inhibitors for 2-OG dependent iron oxygenases thus have a huge pharmaceutical potential as future drugs. In particular inhibitors for prolyl 4-hydroxylase could help to control collagen production (34,36). Such an inhibitor should mimic the k 0, 0 chelate coordination of 2-OGs but should not react with O2. A -Oxalylglycine (Fig. 3) is such an inhibitor for prolyl 4-hydroxylase (IC50 = 3 pM) (34,36). 

When the chiral a,jS-enone enoate 98 was treated with magnesiocuprates in the presence of 1.5-2 equivalents of diethylaluminium chloride, the anti addition product 99 was obtained in moderate yield and with good diastereoselectivity (Scheme 6.21) [43, 44]. A reasonable explanation might assume a chelating coordination of the aluminium reagent [45]. Thus, if the enone 98 were to adopt an s-trans conformation, as indicated for complex 100, subsequent front side attack of the nucleophile would furnish the major diastereomer anti-99. 

The results of some initial experiments indicated that the catalytic activity of 1 is strongly temperature-dependent. For instance, at 100 °C, the rates are relatively low but there is an appreciable turnover [turnover frequency (TOE) = 20.5 h" j. Increasing the reaction temperature to 200 °C increases the TOE to 720 h hence, the thermal robustness of the iridium catalyst is pivotal for optimal catalyst performance. The tridentate pincer-type ligands provide a particularly stable platform for metal confinement through covalent Ir—C bonding combined with the terden-tate chelating coordination. 

Iminio-phosphonio dications have been obtained by N- and F-methylation of (imidazolylphenyl)diphenylphosphine. These dications are suitable precursors for C,C-chelating ligands. Deprotonation of the N-heterocycle leads to an NHC carbene which can be coordinated to a suitable metal center like Pd The subsequent deprotonation of the phosphonio moiety gave the complex with a bidentate chelating coordinated NHC-ylide ligand [207, 208]. 

The technique of vertical dipping for construction of multilayer LB films containing metal ions is depicted in Figure 3.5.2. Centrosymmetric bilayers, with metal ions sandwiched between the polar head groups in the film, are deposited onto vertically mounted substrates passed down and then up through the metal/surfactant monolayer at the air/water interface. The structure of the film is represented by the bis chelate coordination of the carboxylate function of the fatty acid around a divalent metal ion. This type of structure has been determined for a number of metal ions including Cd, Co, Mn, Pb and Zn (24 and ref. within). The structure of CoSt (25), inferred from infrared (IR) and XRD studies, is depicted in Figure 3.5.3a (25). Centrosymmetric films, where the area of the film transferred to the substrate... 

The complex of Me2Zn with (5, 5 )-ebpe, 107, has been applied successfully as catalyst in the enantioselective reduction of ketones by polymethylhydrosiloxane and combines excellent product yields with high ee values . Its structure comprises the iV,iV-chelate coordination of the ebpe ligand to the MeiZn unit (Figure 51). It is remarkable that in this case the two secondary amine functionalities are coordinated to zinc and leave the Zn—C bonds unaffected. Indeed, usually secondary amines undergo a fast deprotonation reaction with dialkylzinc compounds. 

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