Cyclooctatetraene complexes properties

Cycloheptatrienyl and cyclotatetraene complexes, like other sandwich compounds, and complexes [M(C H )L ] containing polyelectron ligands are thermally stable. Often, these compounds melt at higher temperatures without decomposition. Complexes with ligands which do not contain bulky substituents connected to the ring carbon atoms are usually very sensitive to oxidation and hydrolysis. The compounds of the type M(C0T)2 (M = U, Pa, Ce, etc.) are easily oxidized but are more resistant to water. Table 8.1 gives properties of some cycloheptatrienyl and cyclooctatetraene metal compounds. 

It was found that if bis(duroquinone)-nickel is thermally decomposed in the presence of cyclooctatetraene, cyclooctatetraene-duroquinone-nickel, (XXII), is obtained (56). A more convenient synthesis was found shortly thereafter in a one-step reaction of duroquinone with nickel carbonyl in the presence of the polyolefin. Using the same procedure, analogous complexes with various other olefins were made, the properties of which are listed in... 

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 ... 

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