Preparation of a uranium metallacyclocumulene and its reactivity towards unsaturated organic molecules.

The uranium metallacyclocumulene, [η5-1,3-(Me3C)2C5H3]2U(η4-C4Ph2) (2) was isolated by the reduction of [η5-1,3-(Me3C)2C5H3]2UCl2 (1) with potassium graphite (KC8) in the presence of 1,4-diphenylbutadiyne (PhC[triple bond, length as m-dash]C-C[triple bond, length as m-dash]CPh) in good yield. Furthermore it was fully characterized including the determination of its molecular structure; and the reactivity of 2 towards various small unsaturated organic molecules was explored. For example, while complex 2 shows no reactivity with alkynes and 2,2'-bipyridine (bipy), it reacts as a nucleophile when exposed to carbodiimides, diazabutadienes, isothiocyanates, ketones, and pyridine derivatives, leading to five-, seven- or nine-membered heterometallacycles. In contrast, treatment of complex 2 with CS2 results in C[double bond, length as m-dash]S bond cleavage and forms the binuclear complex [η5-1,3-(Me3C)2C5H3]2U[μ-η4:η3-PhC[double bond, length as m-dash]C[double bond, length as m-dash]C(S)C(Ph)[double bond, length as m-dash]CS]U[η5-1,3-(Me3C)2C5H3]2 (10). Density functional theory (DFT) studies complement the experimental study.