Anions, bidentate

Figure 1.27 Structure of the anionic, bidentate nitrogen ligands [hpp] and [tbo] ...

X-ray diffraction analysis show that these receptors can bind neutral and anionic bidentate guests species, e.g. 1,4-diazabicyclo[2.2.2]octane, isonicotin-ate, or terephthalate to form 1 1 intramolecular inclusion complexes.415... 

In contrast, the mono-anionic bidentate ligand bis(diphenyl-thiophosphoryl)amide Na(dtp)... 

A. Complete dissociation of an anionic bidentate ligand followed by reaction of the free ligand and subsequent recombination to form a substituted chelate ring. 

Anionic bidentate [P2] ligated derivatives chromium(II) complexes, 5, 365... 

In 2002, Hoveyda et al. reported the synthesis of a novel chiral anionic bidentate carbene ligand combining an NHC unit with a phenolato donor and its use in asymmetric olefin metathesis [73]. The five-step synthesis of the... 

A range of other anionic bidentate ligand compounds also has been described (Table 15), including several [Mn(N—N)2]° tetrahedra, but these are generally very sensitive to air and the studies so far have been of limited scope. We have real reservations about the dipyrromethane compound there is little in the report, except stoichiometry, to distinguish it from the tris-Mn111 species. 

Although several compounds of ligands (114) and (115) in their monoanion form have been described,304 they are not fully characterized as Mn species, and the reported dark colours suggest the oxidation may have occurred during the preparations. Compounds of the other potentially anionic bidentates (116)-(119) are somewhat better characterized, although (116) appears to have been detected so far in only neutral unidentate function.305 One compound of ligand (117) has been shown to be a rranj-[Mn(0,0)2(H20)2] octahedral species,306 and the ligands (118) and (119) form rather insoluble Mn(L—H)2 species, which are probably polymeric with [MnOs] octahedra.307,308... 

The bispyridine-substituted carbyne complexes 182 react with several anionic bidentate donor ligands to afford the anionic / -ketenyl complexes 183 [Eq. (149)] (149,167). The bis(pyrrole carboxaldiminato) complexes were further transformed into alkoxyacetylene complexes by methylation at the ketenyl oxygen atom. Addition of trimethylphosphine to the anionic carborane-substituted carbyne complex 184 at — 30°C gives the ketenyl complex 185 [Eq. (150)] (135). The hydroxy and methoxyacetylene complexes were obtained by further addition of HBF4 and methyl triflate. 

Complexes with Anionic Bidentate Nitrogen Ligands... 

Complexes of Anionic Bidentate Sulfur, Selenium, or Tellurium Ligands... 

Complexes of a related anionic bidentate di-carboxamido-cyclopentadienyl ligand, ZrCl3[CsI I3(COM IBur)2](TI IF) and ZrCyCsI I3(CONIIBut)2]2 (91) have also been described. This ligand chelates to Zr via the carbonyl O-atoms in a manner similar to diketonates. Structural data were consistent with 7r-delocalization of electron density in the ligand.466... 

There have been reports on four types of macrocyclic organotin(IV) assemblies formed from neutral or anionic bidentate organic connectors (i) mononuclear R4 Sn(IV) + macrocycles (ii) di- and oligonu-clear R4 Sn(IV) + macrocycles (iii) dinuclear cryptands and (iv) macrocycles and cryptands formed from oligonuclear secondary building blocks. 

Surprisingly little work has been reported on tris(amino acid) complexes of Rh". Reaction of RhClj-SHjO with sodium bicarbonate causes precipitation of Rh203, which forms [Rh(D-ala)j] if heated immediately with D-alanine. Fractional crystallization allows separation of mer(-) and mer +) isomers, as well as some impure fac isomer. Reaction of the Li salt of DL-methionine (Li MeSCH2CH2CH(NH2)COO ) with anhydrous RhClj in refluxing ethanol leads to the precipitation of [Rh(DL-methionine)3], in which the methionines act as anionic bidentates, bonded through the O and N atoms. The solid state reaction of RhClj with glycine is reported to lead to [Rh(gly)j], characterized thermogravimetrically and by IR, UV and H NMR spectroscopy. Several [Rh(en)2 (amino acid)] " complexes have been prepared and resolved (Section 48.6,2.2.ii). ... 

Nitrate Reductase.—Reduction of nitrate by molybdenum(v) complexes of the type [M0OCI3L] and [MoOClL 2l where L and L are neutral or anionic bidentate ligands, proceeds by rate-determining loss of Cl in DMF at 25 °C ... 

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