TRICARBONYLCHROMIUM COMPLEXES WITH PHENALENE - SYNTHESIS, STRUCTURE, AND THERMAL REARRANGEMENTS

The reaction of phenalene with Cr(CO)(3)Py-3/BF3 . OEt2 afforded a mix ture of two isomeric complexes, tricarbonyl(6a,7-9,9a,9b-eta(6)-phenal ene)chromium (1) and tricarbonyl(3a,6a,9b,4-6-eta(6)-phenalene)chromiu m (2). Deprotonation of the mixture of compounds 1 and 2 followed by t reatment with Mel, (BuI)-I-n, or D2O gave complexes exo-1-R-1 (3-5: R = Me (3), Bu-n (4), or D (5)). The molecular geometry of complex 3 was established by X-ray structural analysis. Heating of complex 5 in tol uene or C6F6 at 90-110 degrees C resulted in redistribution of deuteri um among positions exo-1, endo-1, and 3 in the resulting complexes of types 1 and 2 via sigmatropic shifts of the H-exo and H-endo atoms in the nonaromatic ring as well as via inter-ring migrations of the trica rbonylchromium group. In the case of 3, the methyl label is distribute d among positions exo-1 and 3 to form isomeric complexes with similar structures (exo-1-Me-2 (6), 3-Me-2 (7), and 3-Me-1 (8), respectively) via processes analogous to those observed in the case of isomerization of compound 5 (except for migration of the H-exo atom). The mechanism s of these rearrangements are discussed.