Mono-ligand lanthanide complexes utilizing the bulky tris(trimethylsilyl)cyclopentadienyl ligand are reported. Achiral mono-anilido complexes, in which the iodide and anilido groups are trans -disposed, are readily converted to chiral analogues, where the iodide and anilido groups are oriented in a cis fashion, by the addition of a chelating bidentate ligand such as 2,2 ′ -bipyridine. Use of the bulky cyclopentadienyl ligand [η 5 -C 5 H 2 (SiMe 3 ) 3 -1,2,4] − (Cp‴) allows for the isolation of monomeric, mono-ring lanthanide species. As previously reported, (Cp‴)K reacts with LaI 3 (THF) 4 (THF=tetrahydrofuran) in THF/pyridine to form the mono-ring complex (Cp‴)LaI 2 (py) 3 ( 1 ) (py=pyridine); a minor product of this reaction is the bis-ring species (Cp‴) 2 LaI(py) ( 2 ). The solid state structure of 2 reveals a monomeric compound containing a pseudo-tetrahedral metal center exhibiting no unusual intramolecular contacts. Addition of one equiv of KNHAr (Ar=2,6- i Pr 2 C 6 H 3 ) to complex 1 in THF generates the mono-anilido compound (Cp‴)LaI(NHAr)(THF) 2 ( 3 ), which may be converted to the more stable pyridine adduct (Cp‴)LaI(NHAr)(py) 2 ( 4 ) by the addition of pyridine to 3 . An X-ray crystal structure of 3 indicated a trigonal bipyramidal metal center with the anilido group oriented trans to the iodide atom (N1–La1–I1=123.1(3)°). A structural study on the bis-pyridine adduct 4 revealed a similar C s -symmetric structure with a slightly increased N anilido –La–I angle of 132.1(2)°. Addition of KNHAr to the di-iodo bipyridine adduct (Cp‴)LaI 2 (bipy)(py) ( 5 ), in which the two iodide atoms are cis -disposed, yields the mono-anilido complex (Cp‴)LaI(NHAr)(bipy)(py) ( 6 ) (bipy=2,2 ′ -bipyridine); this compound may also be prepared by the addition of bipy to (Cp‴)LaI(NHAr)(py) 2 ( 4 ). An X-ray diffraction study shows that the lanthanum center in 6 is octahedrally coordinated by a Cp‴ ring, an iodide, an anilido group, a pyridine molecule and two nitrogens of a bipy molecule. In this case, the anilido moiety and the iodide ligand are arranged in a cis fashion (N anilido –La–I=111.2(2)°), resulting in a complex with C 1 symmetry. Both (Cp‴)LaI(NHAr)(py) 2 ( 4 ) and (Cp‴)LaI(NHAr)(bipy)(py) ( 6 ) are inactive as catalysts for the hydroamination/cyclization of 2-amino-hex-5-ene.