Synthesis and structure of samarium benzyl complex supported by bridged bis(guanidinate) ligand and its reactivity toward nitriles and phenyl isocyanate

Reaction of SmCl3 with one equivalent of LLi2 (L = iPr(Me3Si)NC(NiPr)N(CH2)3NC(NiPr)N(SiMe3)iPr) in THF afforded monochloride complex LSmCl(THF)2 (1) or LSmCl(DME) (2) upon crystallization from THF or DME. Treatment of 1 with KCH2C6H5 yielded monobenzyl complex LSm(η1-CH2C6H5)(DME) (3). The reactivity of 3 has been further studied with MeCN, 4-MeOC6H4CN and PhNCO. Complex 3 reacts with MeCN to produce [LSm(μ-(N,N′)-N(H)C(Me)C(H)CN)(THF)]2 (4) via metalation of the methyl group of MeCN and followed by insertion of another MeCN into the new Sm–C bond and 1,3-H shift. Insertion into Sm–benzyl of 3 occurs with 4-MeOC6H4CN to form a dimeric complex [LSm{μ-NH(C6H5(p-OMe))CCC6H5}2SmL] (5) with a new group NH(C6H5(p-OMe))CCC6H5 in a η3-1-aza-allyl coordination mode via 1,3-H shift. Complex 3 reacts with PhNCO to yield a double insertion dinuclear complex [L′Sm{μ-OC(CH2Ph)N(Ph)}2SmL′] (6) (L′ = iPr(Me3Si)NC(N iPr)N(CH2)3(SiMe3)C(NiPr)2(CN(Ph)O)) via insertion reactions of PhNCO both into Sm–benzyl and into Sm–guanidinate of L followed by the rearrangement of the newly formed bridged ligand L′. Complexes 1–6 were fully characterized including X-ray structure analyses.

Graphical abstractMonobenzyl lanthanide complex LSm(η1-CH2C6H5)(DME) supported by bridged bis(guanidinate) ligand L (L = iPr(Me3Si)NC(NiPr)N(CH2)3NC(NiPr)N(SiMe3)iPr)) was first synthesized and proven to be active toward acetonitrile, 4-methoxybenzonitrile and phenyl isocyanate.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Bridged bis(guanidinate) monobenzyl complex was first synthesized. ► The reactivity of the monobenzyl complex with nitriles was demonstrated. ► A double insertion reaction of phenyl isocyanate was first explored.