2-Imino-2,3-dihydrobenzoxazole-a useful platform for designing rare- and alkaline earth complexes with variable di- and trianionic O,N,N, ligands

• Published in: Dalton transactions : an international journal of inorganic chemistry Vol. 51; no. 5; pp. 1995 - 24
• Main Authors: Basalov, Ivan V, Kissel, Alexander A, Nikolaevskaya, Elena N, Druzhkov, Nikolai O, Cherkasov, Anton V, Long, Jérôme, Larionova, Joulia, Fukin, Georgy K, Trifonov, Alexander A
• Format: Journal Article
• Language: English
• Published: England Royal Society of Chemistry 01.02.2022
• Subjects: Chemical Sciences; Coordination chemistry; Coordination compounds; Electron transfer; Hydrogen bonds; Ligands; Nitrogen; Yttrium
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/d1dt04139h

The reactions of 2-imino-2,3-dihydrobenzoxazole LH with M[N(SiMe 3 ) 2 ] 2 (THF) 2 (M = Yb and Ca) and Y(CH 2 SiMe 3 ) 3 (THF) 2 proceed with the opening of the dihydrobenzoxazole ring and the elimination of HN(SiMe 3 ) 2 or SiMe 4 . Besides, in the case of Yb[N(SiMe 3 ) 2 ] 2 (THF) 2 , an electron transfer from Yb( ii ) to L takes place and Yb( iii ) complex 1 is coordinated by a dianionic phenolate ligand containing a pendant radical-anionic diazabutadiene fragment form. When LH is reacted with Ca[N(SiMe 3 ) 2 ] 2 (THF) 2 , C-H bond activation of a methyl fragment by imino nitrogen occurs and affords a dimeric calcium complex 2 . In 2 , the phenolate ligand is dianionic due to the presence of the amido-imino fragment [R-N&z.dbd;C(CH 3 )-C(&z.dbd;CH 2 )-NR′] − (R = 2,4- t Bu 2 -C 6 H 2 O; R′ = 2,6-iPr 2 C 6 H 3 ). In situ generated ate-complex {Na(Et 2 O) n }{Ca[N(SiMe 3 ) 2 ] 3 } also enables C-H bond activation, however the dianionic phenolate ligand in the resulting complex 3 contains an amido-imino fragment [R-N-C(&z.dbd;CH 2 )-C(CH 3 )&z.dbd;NR′] − featuring the sequence of N-C and N&z.dbd;C bonds opposite to that in 2 . The reaction of Y(CH 2 SiMe 3 ) 3 (THF) 2 with LH affords mono(alkyl) yttrium complex 4 . 4 contains a dianionic amido-imino phenolate ligand resulting from the migration of one alkyl group to the C&z.dbd;N bond [R-N-C(Me)(CH 2 SiMe 3 )-C(Me)&z.dbd;NR′]. 4 undergoes slow intramolecular C-H bond activation of the residual CH 3 group to afford a yttrium complex coordinated by a trianionic diamido-phenolate ligand [R-N-C(Me)(CH 2 SiMe 3 )-C(&z.dbd;CH 2 )NR′]. Yb( iii ), Y( iii ) and Ca( ii ) complexes coordinated by di- and trianionic diiminophenolate ligands.