Lawrence Berkeley National Laboratory

The uranium metallocenes, [eta5-1,3-(Me3E)2C5H3]2UMe2 (E = C, Si), react with NH3 to give the dimers {[eta5-1,3-(Me3E)2C5H3]2U}2(mu-NH)2 (E = C (1), Si (2)) but with p-toluidine to give the monomeric diamides, [eta5-1,3-(Me3E)2C5H3]2U(NH-p-tolyl)2 (E = C (3), Si (4)). The diamides [eta5-1,3-(Me3E)2C5H3]2U(NH-p-tolyl)2 (E = C (3), Si (4)) do not eliminate p- toluidine but sublime intact at 140oC in vacuum. The uranium metallocene, [eta5-1,2,4-(Me3C)3C5H2]2UMe2, reacts with RNH2 to yield [eta5-1,2,4-(Me3C)3C5H2]2U(NHR)2 (R = Me (8), PhCH2 (9), p-tolyl (10)), which are isolated as crystalline solids. In benzene solution these diamides are in equilibrium with [eta5-1,2,4-(Me3C)3C5H2]2U=NR, which may be isolated pure when R is Me (11) or p-tolyl (12), and the primary amine. The monomeric imide, [eta5-1,2,4-(Me3C)3C5H2]2U=NMe (11), reacts with R'=CR' to yield the cycloaddition products [eta5-1,2,4-(Me3C)3C5H2]2U[N(Me)C(R')=C(R')] (R' = Me (15), Ph (16)), which react with excess MeNH2 to regenerate the diamide [eta5-1,2,4-(Me3C)3C5H2]2U(NHMe)2 (8) and MeN=C(R')CH(R'). The methylimide, [eta5-1,2,4-(Me3C)3C5H2]2U=NMe (11), does not react with Me3SiX reagents; a model is proposed that rationalizes this reactivity pattern.