~ Pergamon 0277-5387(95)00572-2 Polyhedron Vol. 15, No. 13, pp. 2299-2302, 1996 Copyright © 1996 Elsevier Science Ltd Printed in Great Britain. All rights reserved 027%5387/96 $15.00+0.00 COMMUNICATION CHLOROPALLADATION OF PROPARGYL THIOETHERS: A FACILE SYNTHESIS OF CYCLOPALLADATED COMPOUNDS JAIRTON DUPONT,* NARA R. BASSO and MARIO R. MENEGHETTI Grupo de Catfilise--Instituto de Qulmica--UFRGS, Av. Bento Gongalves, 9500-91501-970, Porto Alegre, RS, Brazil (Received 10 October 1995 ; accepted 1 December 1995) Abstract--The reaction of the propargyl thioethers Ph--C~C--CH(RI)SR (R = Me, Pr i, Ph and R1 = H, Me) with Li2PdC14 in methanol at room temperature produced in very good yields (70-90%) five-membered palladocycles [Pd(C(Ph)=C(C1)CH(R1)SR)(#-C1)]2. Under the same reaction conditions the homopropargylthioether Ph--C~C--(CH2)2SPh yielded unexpectedly the complex {Pd[S(Ph)(CHz)3C-----O(Ph)](C1)(/~-C1)}2 resulting from the hydrolysis of the C~C bond. It is well known that group 8 and 10 metal com- plexes catalyse many remarkable oligomerization reactions of acetylenes. 1 For example, palladium chloride complexes catalyse the trimerization of diphenylacetylene and mono-tert-butylacetylene, producing selectively hexaphenylbenzene and 1,3,5- tri-tert-butylbenzene, respectively/The mechanism of these palladium chloride-catalysed oligomer- izations of acetylenes is characterized by a series of acetylene insertion steps. 3'4 It is assumed that in the first step an acetylene complex of PdC12 is formed that rapidly rearranges to a chlorovinyl derivative by insertion of the C~---C bond into the Pd--C1 bond. This is followed by successive insertion of acetylenes into the Pd--C vinyl bond. 2~ However, the presence of potential coordinating groups attached to the alkyne apparently inhibit these mul- tiple insertion reactions and allow the isolation of chloropalladated complexes. 5 In this respect, we have recently shown that in the case of Pt chloride complexes, the chlorination reaction is strongly dependent on the nature of the coordinating group attached to the C~C bond. 6 In this work, we pre- sent the chemical behaviour of a series of homo- and * Author to whomcorrespondenceshould be addressed. propargyl thioethers towards palladium chloride compounds. RESULTS AND DISCUSSION The homo- and propargyl thioethers 1-3 were easily prepared in 70-95% yield by substitution of the corresponding mesylated hydroxyl groups of the homo- and propargyl alcohols with NaSR. 7The phenyl derivatives 4--6 were prepared from 1-3 and phenyliodide in the presence of catalytic amounts of PdC12(PPh3)z/CuI (Scheme 1).8 The reaction of the terminal alkynes 1-3 with Li2PdC14 in methanol or with PdC12(PhCN)2 in dichloromethane, under various reaction con- ditions, afforded a complex mixture of products, probably resulting from the oligomerization of these alkynes. However, the addition of equimolar amounts of the alkyne 4 to a methanolic solution of Li2PdC14 resulted almost instantaneously in the air stable compound 7 as a yellow solid in 85% yield (Scheme 2). The presence of an AB spin sys- tem centred at 3.98 ppm for the methylene protons in the 1H NMR spectrum and the C=C bond res- onances at 148.0 and 120.4 ppm in the 13C NMR spectrum of compound 7 are good evidence for the formation of the five-membered palladocyclic ring. Under the same reaction conditions used above 2299