Lanthanide complexes pyridine oxide

COT ligands, due to their steric and electronic properties, can in principle stabilize the three possible formal lanthanide oxidation states (11, III, IV). The first cyclooctatetraene lanthanide complexes isolated were the Ln(COT) species [Ln = Eu", Yb COT=(C8Hji) Hayes and Thomas 1969], prepared by direct reaction of the metals and cyclooctatetraene in liquid ammonia. Deep red-black crystals of (COT)Yb(py)3-0.5py (Wayda et al. 1987) obtained by treatment of Yb(COT) with excess pyridine have a crystal structure of the shape of a three-legged piano stool for the coordinated ligands. The first monomeric Sm (COT) complex has been obtained with the highly substituted 1,3,6-trimethylsilylCOT ... 

In addition to these systematic studies of lanthanide sulfoxide complexes, with variation in both sulfoxide and anion, other more isolated reports are available. Lanthanide isothiocyanate complexes of the cyclic sulfoxides thioxane oxide (490) and tetramethylene sulfoxide (493) have been synthesized and complexes of the unusual potentially chelating ligand 2-(ethylsulfinyl)pyridine-V-oxide (63) described. Detailed studies of the solvation of lanthanide-shift reagents by Me2SO have also appeared (178,179). 

We have noted that N-bonded thiocyanate complexes dissociate readily in solution. Mixed ligand complexes of lanthanides with thiocyanates and L = ethanol, pyridine, triphenyl phosphorous oxide, phenanthroline, etc. have been synthesized. 

Phenols that have more than one hydroxyl group may be carboxylated with CO2 at atmospheric pressure under basic conditions. The research team of Y.-C. Gao synthesized 3,5-di-fert-butyl-y-resorcylic acid from 4,6-di-fert-butyl resorcinol using the Kolbe-Schmitt reaction under these conditions. The resorcylic acid derivative was needed in order to prepare ternary complexes of lanthanide(lll)-3,5-di-fert-butyl-Y-resorcylate with substituted pyridine-A/-oxide. 

Ternary complexes of lanthanide (lll)-3,5-di-fert-butyl-y-resorcylate with substituted pyridine-A/-oxide... 

Chu, Y., Gao, Y.-C., Shen, F.-J., Liu, X., Wang, Y.-Y., Shi, Q.-Z. Synthesis, crystal structure and characterization of ternary complexes of lanthanide(lll) 3,5-di-tert-butyl- -resorcylate with substituted pyridine-N-oxide. Polyhedron 1999,18, 3723-3727. 

The first metallasilsesquioxanes incorporating lanthanides were described in 1994 by Herrmann et alJ More recently, several Ln silsesquioxanes resulting from reactions of 1 with lanthanide silylamides and aryloxides have been reportedJ Our own efforts in this field resulted in the isolation of a novel Ce(lV) silsesquioxane complex as well as the structural characterization of a bimetallic Yb/Li derivative.Treatment of [Ce N(SiMe3)2 3] or anhydrous CeCls with two equivalents of Cy8Si80n(0H)2 (42) in diethyl ether in the presence of an excess of pyridine exclusively afforded the diamagnetic complex (Cy8Si80]3)2Ce(py)3 (43, Scheme 29.11). Quite surprisingly, in both cases cerium was oxidized to the tetravalent oxidation state. 

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