Reactivity of (C5Me5)3LaLx Complexes: Synthesis of a Tris(pentamethylcyclopentadienyl) Complex with Two Additional Ligands, (C5Me5)3La(NCCMe3)2

The limits of steric crowding in tris(pentamethylcyclopentadienyl) complexes have been expanded by isolation of the first compound with this ligand set and two additional ligands, (C(5)Me(5))(3)ML(2). This result was obtained in a study of the effect of added ligands on the reactivity of sterically crowded (C(5)Me(5))(3)La, 1. Although neither THF nor Ph(3)PO formed crystallographically characterizable (C(5)Me(5))(3)LaL(x) complexes with 1, these (C(5)Me(5))(3)La/L(x) mixtures displayed enhanced reactivity compared to 1 with substrates such as C(8)H(8) and CO(2). Attempts to use adamantyl azide, AdN(3), to make (C(5)Me(5))(3)LaL(x) complexes led to the first example of azide insertion into a metal cyclopentadienyl linkage to generate (C(5)Me(5))(2)La[eta(2)-(N,N')-(C(5)Me(5))NN'N''Ad](N(3)Ad). Addition of Me(3)CCN to 1 produced the first crystallographically characterized (C(5)Me(5))(3)ML(2) complex, (C(5)Me(5))(3)La(NCCMe(3))(2).