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The pyrolysis kinetics of primary, secondary, and tertiary p-hydroxy ketones have been studied in static seasoned vessels over the pressure range of 21-152 torr and the temperature range of 190"-260°C. These eliminations are homogeneous, unimolecular, and follow a first-order rate law. The rate coefficients are expressed by the following equations: for l-hydroxy-3-butanone, log k l ( s -' ) = (12.18 2 0.39) -(150.0 ? 3.9) k J mol-' (2.303RT)-'; for 4-hydroxy-2-pentanone, log k l ( s -' ) = (11.64 ? 0.28) -(142.1 ? 2.7) k J mol-' (2.303RT)-'; and for 4-hydroxy-4-methyl-2-pentanone, log k 1 k -l ) = (11.36 ? 0.52) -(133.4 -t 4.9) k J mol-' (2.303RT)-'. The acid nature of the hydroxyl hydrogen is not determinant in rate enhancement, but important in assistance during elimination. However, methyl substitution at the hydroxyl carbon causes a small but significant increase in rates and, thus, appears to be the limiting factor in a retroaldol type of mechanism in these decompositions. 0

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Carbonylation of the known cluster [Ru3(CO)6(μ-CO)(μ3-η5:η3:η3−C10H8)] (1) gives the metastable trinuclear derivative [Ru3(CO)8(μ3-η5:η2:η1-C10H8)] (2). On further carbonylation of 1 the stable product [Ru2(CO)5(μ2-η5:η3-C10H8)] (3) is obtained. X-ray diffraction studies and full spectroscopic assignment of 3 show that the azulene ligand is bonded through a π-Cp to one metal and via a π-allyl moiety to the other. Compound 3 reacts reversibly with CO to yield [Ru2(CO)6(μ2-η5:η1-C10H8)] (4), which maintains the π-Cp bond while the heptadienyl ring contributes to the bonding only through one σ-C−Ru interaction.