Reaction mechanisms of metal–metal-bonded carbonyls. Part 14. Reactions of 1,1,1,2,2,2,3,3,3-nonacarbonyl-1,2,3-tris(triphenylphos-phine)-triangulo-triruthenium

Abstract

Some reactions of the complex [{Ru(CO)3(PPh3)}3], in decalin between 40 and 150 °C, have been studied and found to proceed by three kinetically distinct paths leading to a variety of products. Reactions with tributylphosphine, carbon mono-oxide, and low concentrations of triphenylphosphine under an atmosphere of argon occur by path A which involves reversible loss of PPh3 at some stage. The limiting rate at [PPh3]= 0 is governed by the parameters klim.A(100 °C)= 2 × 10–1 s–1, ΔH‡= 122.8 ± 2.1 kJ mol–1. and ΔS‡= 68.6 ± 6.2 J K–1 mol–1. Reaction with PPh3, under an atmosphere of argon and at values of [PPh3] sufficient to completely suppress path A, occurs by path B which involves reversible loss of CO at some stage. The limiting rate at [CO]= 0 is governed by the parameters klim.B(100 °C)= 1.0 × 10–5 s–1, ΔH‡= 137.8 ± 4.4 kJ mol–1, and ΔS‡= 27.2 ± 10.9 J K–1 mol–1. Reaction with PPh3 in the presence of sufficient PPh3 and CO to completely inhibit reaction by paths A and B proceeds by C for which klim.c(at 100° C)= 5.7 × 10–7 s–1, ΔH‡= 147.9 ±3.9 kJ mol–1. and ΔS‡= 29.6 ± 9.2 J K–1 mol–1. The three paths may simply involve the three distinct primary processes: reversible PPh3 dissociation (A), reversible CO dissociation (B), and fission into mono- and hi-nuclear fragments (C). It is possible, however, that these three processes are preceded by a common initial step involving reversible fission of a single Ru–Ru bond.