Hydrated ruthenium trichloride reacts with cyclohexa-l,3-diene and cyclo-octa-l,5-diene, in the presence of metallic zinc, to give the ruthenium(0) compounds 1 -6-q-benzene(l4-q-cyclohexa-l,3-diene)ruthenium, (1 ), and (1 -2 : 5-6-~-cyclo-octa-l ,5-dinee) (1 -6-q-cyclo-octa-l,3,5-triene)ruthenium,(2), respectively. The analogous reaction with cyclo-octa-l,3-diene, cyclohepta-l,3-diene, and cyclopentadiene leads to the isolation of the corresponding dienyl complexes bis( 1 -5-q-cyclo-octadienyl)ruthenium,(3), bis( 1 -5-q-cycloheptadienyl) -ruthenium, (4), and ruthenocene, (5). Complex (3) is best prepared by heating (2) in hydrocarbon solvents at ca. 100 "C.CYCLO-OLEFIN complexes of metals in the iron triad have received a good deal of attention in recent years as potential catalysts,' as models for oxidative-addition reactions,2 as a means of studying electrophilic and/or nucleophilic attack on co-ordinated organic molecule^,^ and, most recently, as examples of highly fluxional comp o u n d~.~ In general, however, the availability of convenient synthetic routes to such species, particularly to cyclo-olefin-ruthenium (0) or cyclodienyl-rut henium ( I I) compounds.By treatment at room temperature of cyclohexa-l,3-diene with hydrated ruthenium trichloride and zinc, in tetrahydrofuran (thf) or ethanol as solvent, (1-6-qbenzene) (14-q-cyclohexa-lJ3-diene)ruthenium, ( 1), has been obtained with yields of ca. 80%. The corresponding reaction with cyclohexa-1,4-diene, again yielded (1), Some examples are given in Scheme 1. ( 2 ) 0 t-4 h ( i i ) R u C~~*~H 2 0 t Zn Q R " Q 1 5 ). . SCHEME 1 (i) EtOH or t h f , 20 "C; (ti) litOH or thf, reflux those not containing carbon monoxide, has proved to be a particular problem.We report that the direc.t reaction of cyclo-olefins with RuC1,-3H2O, in the presence of metallic zinc, seems to be an extremely versatile and useful reaction for the preparation of cyclo-olefin ruthenium complexes, many of which are inaccessible or obtained with great difficulty by classical methods5 A summary of this work has been given .6
RESULTS A N D DISCUSSIONHydrated ruthenium trichloride reacts with a variety with isomerization of cyclohexa-l,4-diene to the conjugated form (ca. 40%). The compound has been characterized by elemental analysis, spectroscopic propcrties, and coinparison of the i.r. and lH n.m.r. spectra with those of an authentic ~arnple.~b The l3C n.m.r. spectrum is presented in part (a) of the Figure. Signals are observed at 79.5 (Cl), 75.2 (Cz), 53.3 (C3), and 28.1 (C4) p.p.m. Those due to the arene carbons directly bonded to the metal are shifted upfield with respect to the free ligand; similar phenomena have previously been noted for many arene ligands,79* although cases are reported in which a shift to lower field is of cyclodiolefins, in the presence of metallic zinc, t o give observed.9 The upfield shift is 49 p.p.m. relative t o