Organolanthanide-based coordination and insertion reactivity of the anion formed by deprotonation of epsilon-caprolactam

Methods to incorporate the strong ligation capacity of epsilon -caprolactam into monoanionic ligands suitable for electropositive metals such as yttri um are described. epsilon -Caprolactam, HN(CH2)(5)C=O, is deprotonated by ( C5H4Me)(2)Y[N(SiMe3)(2)] to form the dimeric complex [(C5H4Me)(2)Y(mu -NC6H 10O)](2), 1. Each caprolactamate anion, (NC6H10O)(-), forms one Y-N bond an d coordinates to both yttrium centers via a bridging oxygen such that yttri um has a formal coordination number of nine. epsilon -Caprolactam is also d eprotonated by (C5Me5)(2)Y(C3H5)(THF), to form the monomeric, pentamethylcy clopentadienyl analogue (C5Me5)(2)Y(NC6H10O), 2, in which the caprolactamat e anion chelates the formally eight-coordinate yttrium. CO2 inserts into th e Ln-N bond in 2 to form [(C5Me5)(2)Y(mu -O2CNC6H10O)](2), 3. The tridentat e monoanionic (O2CNC6H10O)(-) ligand forms an eight-membered YOCOYOO ring v ia carboxylate oxygen atoms and also coordinates to each yttrium center via the oxygen originating from epsilon -caprolactam. Phenyl isocyanate insert s into the Y-N bond of 2 to form (C5Me5)(2)Y[(mu (2)-OC- (NPh)NC6H10O)], 4, which contains a planar YOCNCO ring and eight-coordinate yttrium. tert-But yl isocyanide does not undergo insertion chemistry with 2, but instead form s the adduct (C5Me5)(2)Y(NC6H10O)(CNCMe3), 5.