Vapor-phase rearrangement of (7r-C5H5)Co|>-(3)-l,2-B9C2Hii] (la), (T-C5H5) Co[7r-(3)-l,2-(CH:i)2-1,2-B9C2H9] (2a), and ( -5 5) [ -(3)-µ-1,2-( 2)3-1,2-9 2 9] (3a) at 400-700°y ielded isomeric complexes lb-g, 2b-g, 3d, 3h, and 3i. These compounds incorporate all nine isomeric dicarbollyl ligands and are formed by the migration of the cage carbon atoms over the polyhedral surface. All isomers were separated by thick-layer chromatography and their structures determined on the basis of their chromatographic, electrochemical, and spectral (uv-visible, , and 1LB nmr) properties.Polyhedral rearrangement of boranes, carboranes, and halocarboranes has been known for some time.1 Interest in the rearrangement of metal complexes of the dicarbollyl ligand is of more recent origin. The first thermal rearrangement of dicarbollyl derivatives, viz. those ofNiIV, were reported in 1970 by Warren and Hawthorne. 2 More recently, rearrangement of 3-MCH2-CH3-l,2-B9C2Hn (M = Al, Ga)3 and 3-Ge-l,2-B9-C2Hh4 5has been studied. In the rearrangement of these metallocarboranes, the 1,2-dicarbollyl moiety rearranges to the isomeric 1,7-and 1,6-dicarbollyl structures. Complexes with other isomeric dicarbollyl ligands were not observed. Since, at the present, only three (1,2, 1,7, and 1,12) of the possible nine dicarbollide ions can be obtained by the basic degradation of the parent Bi0C2Hi2 carboranes6 and there are no known synthetic pathways leading to the remaining dicarbollides, it was of interest to study the rearrangement of metallocarboranes to isomeric complexes incorporating the novel dicarbollyl ions. We now wish to report the detailed results of the thermal rearrangement of three monodicarbollyl complexes of cobalt: (tt-C5H5)Co(7r-(3)-l,2-R2-l,2-B9C2H9), R = H (la), R = CHa (2a), and R2 = (CH2)3 (3a)6•7 (Figure 1).
ResultsThe starting materials la, 2a, and 3a were synthesized from the corresponding trimethylammonium 1,2dicarbaundecaborate( -1) ions6a•8 according to a modi-(1) For recent reviews see (a) E.
