PALLADIUM-COPPER-CATALYZED COUPLING OF TRICARBONYLCHROMIUM-COMPLEXED PHENYLACETYLENE WITH IODOARENES - A FACILE ACCESS TO ALKYNYL-BRIDGED CR(CO)(3)-COMPLEXED BENZENES

The palladium-copper-catalyzed coupling of the tricarbonylchromium-com plexed chlorobenzene 1 with (trimethylsilyl)acetylene gives tricarb et a(6)-[(trimethylsilyl)thynyl]benzene}chromium(0) (2) in high yield. Af ter desilylation of 2 tricarbonyl[eta(6)-(ethynylbenzene)]chromium (3) is obtained quantitatively. Using the palladium-copper-catalyzed meth odology, we can readily introduce Cr(CO)(3)-complexed phenylethynyl un its by a multifold coupling of 3 with iodobenzene, 1,2-, 1,3-, 1,4-di- and 1,3,5-tiiodobenzene (4a-e) or 1 to give polynuclear Cr(CO)(3)-com plexed (phenylethynyl)benzenes 5a-e and doubly Cr(CO)(3)-complexed tol ane 6 in good to moderate yield. The crystal structure analyses of mu( 3){eta nediyl)]tris(benzene)}tris[tricarbonylchromium(0)] (5e) and mu- {eta(6):eta thynediylbis(benzene)]}bis[tricarbonylchromium(0)] (6) rev eal that the tricarbonylchromium tripods in the same molecule are arra nged in antiparallel syn-eclipsed conformations. The Eglington couplin g of 3 affords a doubly Cr(CO)(3)-complexed diphenylbutadiyne 7 in exc ellent yield.