Chatt and Davidson 843 154. The Tautornerism of Arene and Ditertiary Phosphine Complexes of Ruthenium(O), and the Preparation of New Types of Hydrido- complexes of Ruthenium(rr) .* By J. CHATT and J. M. DAVIDSON.The reduction of truns-[RuCl,(PP) ,] (PP = Me,PCH,CH,-PMe,) by " arene " negative ions (arene = benzene, naphthalene, anthracene, and phenanthrene) has given a new series of hydrido (aryl) -complexes typified by cis-[RuH(2-Cl0H,) (PP),] (Ia). Members have been characterised from their physical properties, particularly infrared and n.m.r. spectra, and their chemical reactions. Although (Ia) is a hydridic reducing agent and reduces bromoethane to ethane, it is in tautomeric equilibrium with a finite concentration of [Ru(C,,H,) (PP),] (Ib) which probably contains ruthenium(0) and is so reactive that its reactions predominate in those of the complex.Pyrolysis of (I) gives naphthalene and [Ru(PP),] (11) which has similarly dual properties. Its physical properties are consistent with the formulation

A survey has been made to identify those metal ions that will displace hydrogen ions from benzene with formation of arylmetal complexes. Certain stable complexes were isolated while the formation of thermally unstable complexes was detected by the appearance of biphenyl. An isotopic tracer method was used to seek hydrolytically unstable complexes. Gold(rll), mercury(ll), and thallium(lll) react with benzene in aqueous acid solution while gold(lll). rnercury(ii), palladium(ll), platinum(ll), and thallium(tll) react in acetic acid solution. Reactivity is associated with ' class b ' character. A more detailed study of the reaction of diacetatopalladium with benzene and toluene in 0.5N-perchloric acid in acetic acid was made. It appears to be an electrophilic substitution that yields arylpalladium complexes. These decompose by a concerted mechanism to give biaryls and either palladium metal or a univalent palladium complex depending on temperature. An explosive purple complex, [Pd(C,H,) (H,O)CIO,], has been isolated. The ultraviolet absorption of this compound at 380 and 550 mp has been used to determine its rate of appearance in solution during the reaction of benzene with diacetatopalladium in perchloric acid-acetic acid at 50". The kinetic data are consistent with a second-order reaction between benzene and monomeric palladium(ll) (k2 = 4.6 x 1 0-4 I. mole-lsec.-l) followed by fast decomposition. For deuteriobenzene, a large primary isotope effect (kH/kD = 5.0) was found.THE potentialities of organometallic reactions for reactions would be found. We now report a study of the industrial catalytic syntheses are important. There direct formation of metal-carbon bonds and especially have been efforts to elucidate the chemistry of an element palladium-carbon bonds in aromatic systems ; later such as nickel or palladium in the hope that useful A. Aguilo in ' Advances in ~~~~~~~ Chemistry,' ed.

The stoichiometry and rate of the reaction of H2S (0.05-0.80% in N2) with high surface area ZnO have been studied at 273-318 K. Absorption of H2S by ZnO is not accompanied by evolution of the stoichiometric amount of H2O which has a catalytic action via chemisorption as surface hydroxide. Shallow bed reactors have been used to limit the conversion, providing rate data at nearly uniform gas composition. Three reaction regimes have been identified being, in order of decreasing rate, gaseous diffusion-reaction of H2S, formation, desorption, and diffusion of H2O, and solid state diffusion. The fast rates appear to depend upon the crystallite size and morphology, as influenced by the thermal and environmental history of the sample and doping of the ZnO by divalent ions or Na+. The rate in the slowest regime is independent of H2S partial pressure and zinc oxide conversion and is promoted by water vapor. The mechanism appears to involve proton transfer from adsorbed H2S to chemisorbed OH.

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The preparation and far-infrared spectra (190-460 cm.-l) of anhydrous complex chlorides (and some complex bromides) of 30 metallic elements are described. Metal-chlorine stretching frequencies were found in the range 228-377 cm.-l and are discussed in terms of the bonding within the complexes. The use of thionyl chloride as solvent in the preparation of complex chlorides is described.