With Rhodium Metallocycles

Rhodium metallocycles reacted with freshly prepared amorphous tellurium in refluxing absolute xylene to give tellurophene derivatives .  

10-Dioxo-l,3-diphenyl-4ff,10/7-[l]benzothieno[5,6-6][2]benzotellurophene Several g of powdered tellurium are dissolved in aqua regia, the solution is heated until all nitrogen oxides have been expelled, and is then diluted with water. A solution of sodium hydrogen sulfite is added to precipitate amorphous tellurium. The tellurium is filtered off, washed with water until the washings arc neutral, and then several times with ethanol. 50 ml of xylene are placed in a nitrogen-flushed, 250 ml flask fitted with a reflux condenser. 638 mg (5 mmol) of the moist, amorphous tellurium and 502 mg (0.5 mmol) of the rhodium metallocycle are added. The mixture is refluxed under nitrogen for 8 h while a spatula tip of tellurium is added every 2 h. The mixture is then filtered, and the filter is placed on a silica gel column which is eluted with 9/1 benzene/petroleum ether. The second yellow band is collected, the solvent is evaporated, and the residue is crystallized from benzene/ethanol yield 100 mg (38%) m.p. 248°. 

The metallocycles react only with freshly prepared amorphous tellurium. Metallocycles with aliphatic substituents in place of the phenyl or 4-methylphenyl groups did not yield tellurophenes.  

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Bicyclobutane derivatives react with rhodium complexes to give products which convincingly implicate metallocycles and metal-carbene species (72). 

An alternative pattern for functionalization of quinoline-)V-oxides is observed with rhodium and iridium catalysis. The A -oxide functionality can direct the metal insertion to the 2-or the 8-position of the quinoline, and stable five-membered metallocycles can form after C-H insertion at the latter. As... 

In contrast to the reaction of an i72-CS2-rhodium complex with dimethyl acetylenedicarboxylate which gives rise to a metallocycle,186 the iron complexes 103 are converted by activated acetylenes into air-sensitive carbene complexes 104. Decomposition of the latter in air provides an unusual synthetic route to substituted tetrathiofulvene derivatives (Scheme 121).187... 

Me, R = R = R = H R = R = Me, R = R =H) (90JA2432, 9IJA559, 92JAI5I). The dienic group and the sulfur atom are planar but the rhodium atom is above the plane. A localized dienic structure is observed in the six-membered metallocycle. Complex 215 (X = H) formed in the corresponding photochemical reaction with thiophene appears unstable and gradually rearranges to 241... 

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