(η5-C5Me5)2U(=P-2,4,6-tBu3C6H2)(OPMe3) Revisited—Its Intrinsic Reactivity toward Small Organic Molecules

Abstract

The Lewis base stabilized uranium phosphinidene (η5-C5Me5)2U(═P-2,4,6-tBu3C6H2)(OPMe3) (2), which was derived from (η5-C5Me5)2U(Cl)Me (1) and 2,4,6-(Me3C)3C6H2PHK in toluene in the presence of Me3PO, was originally reported in 1996, but since then its reactivity toward small organic molecules has not been extensively explored. This contribution closes this gap, and divergent reactivity patterns are established in the reaction of complex 2 toward (small) organic substrates. For example, complex 2 may release the phosphinidene moiety (2,4,6-tBu3C6H2P:) and therefore may act as a source of a (η5-C5Me5)2UII fragment in the presence of Ph2S2, Ph2Se2, bipy, ketazine (Ph2C═N)2, and conjugated alkynes RC≡CC≡CR, forming the disulfido compound (η5-C5Me5)2U(SPh)2 (5), diselenido compound (η5-C5Me5)2U(SePh)2 (6), bipy compound (η5-C5Me5)2U(bipy) (8), diiminato compound (η5-C5Me5)2U(N═CPh2)2 (9) and the metallacyclopentatrienes (η5-C5Me5)2U[η4-C4(R)2] (R = Ph (10), Me3Si (11)), respectively. Furthermore, compound 2 may also straightforwardly react with terminal alkynes and a variety of heterounsaturated (organic) molecules such as CS2, isothiocyanates, imines, diazenes, carbodiimides, nitriles, isonitriles, and organic azides. For instance, on treatment with phenylacetylene (PhC≡CH) the dialkynyl uranium complex (η5-C5Me5)2U(C2Ph)2(OPMe3) (12) is formed, whereas CS2 and PhNCS furnish the carbodithioates (η5-C5Me5)2U[SC(═P-2,4,6-tBu3C6H2)S](OPMe3) (13) and (η5-C5Me5)2U[SC(═NPh)S](OPMe3) (14), respectively. In the reaction of the secondary aldimine PhCH═NPh or the diazene PhN═NPh and 2 the uranium(IV) imido complex (η5-C5Me5)2U(═NPh)(OPMe3) (15) is isolated, which is in contrast to its reactivity with the primary ketimine 9-(C12H8)C═NH and the carbodiimides (RN═)2C, yielding the diiminato uranium(VI) complex (η5-C5Me5)2U[N═C(C12H8)]2 (16) and the four-membered uranaheterocycles (η5-C5Me5)2U[N(R)C(═P-2,4,6-tBu3C6H2)N(R)] (R = C6H11 (17), iPr (18)), respectively. Furthermore, treatment of 2 with nitriles RCN affords the imido uranium(IV) complexes (η5-C5Me5)2U[═NC(═P-2,4,6-tBu3C6H2)R](OPMe3) (R = C6H11 (19), Me3C (20)), whereas isonitriles RNC furnish the metallaaziridines (η5-C5Me5)2U[C(═P-2,4,6-tBu3C6H2)N(R)](OPMe3) (R = C6H11 (21), 2,6-Me2Ph (22)). However, in the reaction with organic azides RCN3, complex 2 yields the imido uranium(IV) complexes (η5-C5Me5)2U(═NR)(OPMe3) (R = Ph3C (23), p-tolyl (24)) as a result of 3,3-Me2-5,7-tBu2C8H5P (7) formation and N2 release. The new compounds 12–24 were characterized by various spectroscopic techniques, including single-crystal X-ray diffraction analyses. Furthermore, with complex 2 in hand a comparison between the reactivity of uranium phosphinidenes differing in the steric bulk of its cyclopentadienyl ligands and the effects of a Lewis base (OPMe3) adduct was undertaken.