Toluene, reaction metal atoms

The co-condensation at low temperature of a metal vapor (commonly produced by resistance or electron-beam heating of metals) with a vapor of weakly stabilizing organic ligands (such as -pentane, toluene, tetrahydrofu-ran, acetone, or acetonitrile), using commercially available reactors, affords solid matrices, where reactions between the ligand molecules and metal atoms can take place (Scheme 1(A) Figure 1) [5]. 

Co-condensation of transition metal atoms with arenes such as benzene and toluene is well known to yield bis-arene-metal compounds. However, in many cases the yields based on the metal atoms are less than 40%. Evidence that competing reactions such as carbon-hydrogen activation can occur is provided by the isolation of non-metal-containing products such as biaryl derivatives (2JL). ... 

We were hopeful when toluene solutions of the [MCl(COT)2]2 complexes (M = Rh and Ir), in the presence of PCy3 at 25°C under 1 atm C02 (phosphine dimer = 4) absorbed 1 mol C02 per metal atom. The rhodium solution, for example, changed gradually from yellow to red and, in the constant pressure apparatus used, the measured gas uptake analyzed excellently for the pseudo-first-order rate law k[Rh], with k = 9.3 x 10"4s 1. However, such C02 uptake was observed in only five experiments twenty others revealed no reactivity whatsoever The reasons for the irreproducibility have not been traced water content and visible light are not problems. The systems certainly are complicated by the blank dehydrogenation reactions (vide supra). 

Cadmium slurries, formed from codeposition of Cd vapor with a solvent at 77 K followed by warming to RT, are sufficiently reactive toward RI in hexane, toluene, THF, dioxane or diglyme. Reactions do not proceed well with RBr e.g., only a 10% yield of propylcadmiums is obtained on refluxing in diglyme overnight. The presence of KI increases the reactivity of the slurries. Ethyl iodide reacts at — 196°C with a Cd slurry, obtained from simultaneous evaporation of PhMe and Cd in a metal-atom reactor" the yield of nonvolatile EtCdl is 55 %. 

The iron vapor-toluene reaction has evoked interest because of the lability of the proposed bis(arene)iron complex to ligand subsitu-tion and to loss of both toluene molecules to free the metal atom. In the latter case the toluene molecules may be usefully regarded as metal atom carriers which can be used to direct the latent reactivity of the atom in subsequent solution phase chemistry. In this way the metal atom experiment can benefit from the convenience and additional versatility afforded by bench-top chemical manipulations. These results are relevant to a reported preparation of a dehydroxy-lated silica-supported Fischer-Tropsch catalyst from a static reactor codeposition of Fe and toluene.(46) In the liquid phase, iron atoms "bottled" in this way have also been utilized in an exceedingly mild method for making minute catalytically active superparamagnetic clusters on the surface and within the cavities of a dehydrated sodium zeolite Y.(38) Using the rotary reactor, preformed solutions of solvated iron atoms (as the toluene complex) are cannulated below their decomposition temperature out of the flask to a cold slurry of the support in toluene. Diffusion of intact... 

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