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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 15, Number 11
BKCSDE 15(11)
November 20, 1994 

Selective Dimerization and Cyclotrimerization of Phenylacetylene with Rhodium and Iridium Complexes
Chong Shik Chin*, Gyongshik Won, Joongho Song
Oligomerization of phenylacetylene is catalyzed by Rh(ClO4)(CO)(PPh3)2 (Rh-1), [Rh(CO)(PPh3)3]ClO4 (Rh-2), [Rh(COD)L2]ClO4 (L2=(PPh3)2, Rh-3; (PPh3)(PhCN), Rh-4; (PhCN)2, Rh-5), [Rh(C3H5)(Cl)(CO)(SbPh3)2]ClO4 (Rh-6), [Ir(COD)L2]ClO4 (L2=(PPh3)2, Ir-1; (PPh3)(PhCN), Ir-2; (PhCN)2, Ir-3; (AsPh3)(PhCN), Ir-4; Ph2PCH2CH2PPh2, Ir-5; COD, Ir-6 and 2,2'-dipyridyl, Ir-7), Ir(ClO4)(CO)(PPh3)2, Ir-8, [Ir(PhCN)(CO)(PPh3)2]ClO4, Ir-9 to produce dimerization products, 1,3-diphenylbut-1-yn-3-ene, 1, (E)-1,4-diphenylbut-1-yn-3-ene, 2 and (Z)-1,4-diphenylbut-1-yn-3-ene, 3, and cyclotrimerization products, 1,3,5-triphenylbenzene, 4 and 1,2,4-triphenylbenzene, 5. Product distribution of the oligomers varies depending on various factors such as the nature of catalysts, reaction temperature, counter anions and excess ligand present in the reaction mixtures. Increasing reaction temperature in general increases the yield of the cyclotrimerization products. Exclusive production of dimer 1 and trimer 4 can be obtained with Ir-1 at 0 ℃ and with Ir-2 in the presence of excess PhCN (or CH3CN) at 50 ℃, respectively. Dimer 2 (up to 81%) and trimer 5 (up to 98%) are selectively produced with Rh-1 at 50 and 100 ℃ respectively. Production of 3 is selectively increased up to 85% by using PF6- salt of [Ir(COD)(PPh3)2]+ at 25 ℃. Addition of CH3I to Rh-1 produces CH3PPh3+I- and increases the rate of oligomerization(disappearance of phenylacetylene). Among the metal compounds investigated in this study, Ir-1 catalyzes most rapidly the oligomerization where the catalytically active species seems to contain lr(PPh3)2 moiety. The stoichiometric reaction of phenylacetylene wth Ir-9 at 25 ℃ quantitatively produces hydridophenyl-ethynyl iridium(Ⅲ) complex, [lr(H)(C≡CPh)(PhCN)(CO)(PPh3)2]ClO4 (Ir-11), which seems to be an intermediate for the oligomerization.
961 - 966
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