O- and N-Donor Ligands

Handlovic and F. Hanic, Proc. 2nd Semin. Crystallochem. Coord. Metallorganic Compounds, 1973, 32 Chem. Abs., 1974, 80, 101 135). 

Ti(OPr )4 reacts with the Schiff bases acetylacetone, 2-hydroxylalkyIimines, and N-[(3-hydroxy-2-naphthyl)methylene]-2-hydroxylalkylimines (H L) in a 1 1 or 1 2 molar ratio to give [TiL(OPr )2] and [TiLj], respectively. Similarly, TKOR) (R = Et or Bu ) react with Af-salicylidene-2-hydroxyethyl-amine (H2L ) to form [TiL (OR)2] or [TiLa]. Treatment of [TiLHOEt)2] with MeOH gives [TiL OMelj] and both these alkoxides appear to have the dimeric structure (16), whereas [TiL (OBu )] and TiLj are monomeric.  

Triazene 1-oxides (17) in methanol react with TiCl4 to give dinuclear complexes which are suggested to have the oxygen-bridged structure (18) on the basis of i.r. and n.m.r. studies.  

Zacharias and A. Chakravorty, Inorg. Nuclear Chem. Letters, 1972, 8, 65. 

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The utility of the concept may be illustrated by comparing the chemistries in the III oxidation state of cobalt, rhodium and iridium. Co3+ is classified as a relatively hard acid, and the very large number of Co(III) complexes mostly involve N- and O-donor ligands. Attempts to prepare Co(III) complexes with P- or 5-donor ligands often lead to reduction to... 

Mixed N- and O-Donor Ligands. Spectrophotometric titration methods have been used to establish the existence and stoicheiometry of V111 complexes with alanine, a-aminobutyric acid, lysine, and glycylglycine pH measurements showed that the amino-acid ligand is co-ordinated in the anion form.385... 

Zhou, Y, Hong, M., and Wu, X. (2006) Lanthanide-transition metal coordination polymers based on multiple N and O-donor ligands. Chemical Communications, (2), 135-143. 

N- )onor and Mixed N- and O-Donor Ligands. The i.r. spectra of the adducts VOCI2-OMe,L (L = MeCN, 2,6-lutidine, a-pic, or 2,6-dimethylpyrazine) and VOCl20Me,2L (L = py or 2,6-dimethylpyrazine) could not be obtained because of the low thermal stability. With an excess of pyridine, reduction to VOCl2,py occurred. This type of reaction is common among the halides and their derivatives of the early transition metals. It prevented the isolation of pure products from reactions between VOCI3 or... 

In light of these resources, we hesitate to present an in-depth treatment of Ln coordination chemistry here, and instead simply call attention to a few characteristics of particular importance to polymeric materials, specifically, the predominance of N- and O- donor ligands in the first coordination sphere of Ln ions. Carboxylate functional groups as organic linkers have been used extensively in CP construction and chelating N-donor ligands have been shown to influence polymerization (and ultimately, topology), as well as luminescent properties. 

Complexes containing N- and O-donor ligands are very common, and coordination numbers of 4, 5 and 6 predominate. We have already mentioned the aqua species [Cu(H20)6] + and [Cu(H20)4] +. When NH3 is added to... 

The ability of some Cr(III) complexes to activate ATP dependent kinases (496, 497) may seem surprising, as stable Cr -ATP complexes (such as XIV in Chart 2 one of the many possible stereoisomers is shown) (629) are well known to act as kinase inhibitors. Chromium(III) in these complexes is a kinetically inert replacement of a natural ATP binding ion, Mg(II) (629-631). However, a Cr(III) complex, [Cr(NH3)5(OH)] +, has recently been shown to promote the in vitro phosphorylation by ATP of the hydroxo groups of Ser and Thr residues in bovine serum albumin at pH 7.4, while several other Cr(III) complexes with N- and O-donor ligands did not possess such activity (632). The proposed phosphorylation mechanism (Scheme 12) (632) involves the formation of a ternary complex of Cr(III), ATP, and the amino acid residue. This mechanism may be related to the kinase-catalyzed phosphorylation of protein Tyr residues. 

Complexes containing N- and O-donor ligands are very common, and coordination numbers of 4, 5 and 6 predominate. We have already mentioned the aqua species [Cu(OH2)6] + and [Cu(OH2)4] +. When NH3 is added to aqueous Cu, only four aqua ligands in [Cu(OH2)6l are replaced (see Section 20.12), but salts of [Cu(NH3)g] can be made in liquid NH3. [Cu(en)3] is formed in very concentrated aqueous solutions of 1,2-ethanediamine. Deep blue aqueous [Cu(NH3)4](OH)2 (formed when Cu(OH)2 is dissolved in aqueous NH3) has the remarkable property of dissolving cellulose, and if the resulting solution... 

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