
%0 Journal Article
%A Field, Leslie D. 
%A Ward, Antony J. 
%A Turner, Peter 
%T The Dimerization and Cyclotrimerization of Acetylenes Mediated by Phosphine Complexes of Cobalt(<emph type="6">I</emph>), Rhodium(<emph type="6">I</emph>), and Iridium(<emph type="6">I</emph>).
%J Australian Journal of Chemistry
%D 2000/02/04
%V 52
%N 11
%P 1085-1092
%K 
%R https://doi.org/10.1071/CH99154
%U https://www.publish.csiro.au/paper/CH99154 
%X The catalytic dimerization and cyclotrimerization of phenylacetylene, ethyl propiolate, and dimethyl acetylenedicarboxylate were studied by using the metal complexes &#91;Co(PPh3)3Cl&#93; (1), &#91;Co(PPh3)2(CO)2Cl&#93; (2), &#91;Co(PMe3)3Cl&#93; (3), &#91;Co(PMe3)2(CO)2Cl&#93; (4), &#91;Rh(dppe)(CO)Cl&#93; (5), &#91;Rh(PPh2Me)2(CO)Cl&#93; (6), &#91;Ir(dppe)(CO)Br&#93; (7), and &#91;Ir(PPh2Me)2(CO)Cl&#93; (8). For all complexes studied, with terminal acetylene substrates, there is competition between head-to-head dimerization to form 1,4-disubstituted butenynes and cyclotrimerization to form 1,3,5- or 1,2,4-trisubstituted benzenes. The metallocyclopentadiene &#91;Ir(dppe)(CO)(L)Br&#93; (L= 1,4- diethoxycarbonylbuta-1,3-diene-1,4-diyl) was formed in the reaction of diethyl acetylenedicarboxylate with &#91;Ir(dppe)(CO)Br&#93; (7), and this stable complex is a possible intermediate in the cyclotrimerization of the acetylene. The metallocyclopentadiene was fully characterized by X-ray crystallography. Crystal data for the benzene solvate of (33), C43H42BrIrO5P2 at 21&#176;C: space group P21/c (No. 14), a 8.774(4), b 22.155(3), c 20.242(2) &#197;, &#946; 92.46(2)&#x02DA;, V 3931(1) &#197;3 , Z 4, No 4804, Nvar 469, R(F) 0.0411, Rw(F) 0.0483. 
