The effects of light lanthanoid elements (La, Ce, Nd) on (Ar)CF-Ln coordination and C-F activation in N,N-dialkyl-N′-2,3,5,6-tetrafluorophenylethane-1,2-diaminate complexes

A new class of homoleptic organoamido rare earth complexes [Ln(L-Me or L-Et)(3)] (Ln = La, Ce, Nd; L-Me/Et = p-HC6F4N(CH2)(2)NMe2/Et-2) exhibiting (Ar)CF-Ln interactions has been isolated from redox-transmetallation/protolysis (RTP) reactions between the free metals, Hg(C6F5)(2) and (LH)-H-Me/Et in tetrahydrofuran, together with low yields of [Ln(L-Me)(2)F](3) (Ln = La, Ce) or [Nd(L-Et)(2)F](2) species, resulting from C-F activation reactions. The structures of the homoleptic complexes have eight-coordinate Ln metals with two tridentate (N,N',F) amide ligands including (Ar) CF-Ln bonds and either a bidentate (N, F) ligand (Ln = La, Ce, Nd; L-Et) or a bidentate (N,N') ligand (Ln = Nd; L-Me), in an unusual case of linkage variation. All (Ar) CF-Ln bond lengths are shorter than or similar to the corresponding Ln-NMe2/Et-2 bond lengths. In [Ln(L-Me)F-2](3) (Ln = La, Ce) complexes, there is a six-membered ring framework with alternating F and Ln atoms and the metal atoms are eight-coordinate with two tridentate (N,N',F) L-Me ligands, whilst [Nd(L-Et)(2)F](2) is a fluoride-bridged dimer.