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Synthesis, Structure, and Ring‐Opening Polymerization Catalysis of Zinc Complexes Containing Amido Phosphinimine Ligands
Author(s) -
Liang LanChang,
Tsai TzungLing,
Li ChunWei,
Hsu YuLin,
Lee TingYu
Publication year - 2011
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.201001362
Subject(s) - chemistry , deprotonation , toluene , zinc , medicinal chemistry , polymerization , adduct , alkyl , catalysis , stereochemistry , nuclear magnetic resonance spectroscopy , solvent , organic chemistry , ion , polymer
A series of amido phosphinimine ligands of the type [(NAr 1 )‐ o ‐(Ph 2 P=NAr 2 )C 6 H 4 ] – ( 2a : Ar 1 = 2,6‐C 6 H 3 i Pr 2 , Ar 2 = 2,6‐C 6 H 3 i Pr 2 ; 2b : Ar 1 = 2,6‐C 6 H 3 i Pr 2 , Ar 2 = 2,4,6‐C 6 H 2 Me 3 ; 2c : Ar 1 = 2,6‐C 6 H 3 Me 2 , Ar 2 = 2,4,6‐C 6 H 2 Me 3 ), which are electronic variations of monoanionic β‐diketiminates, have been employed to examine the coordination chemistry of zinc. Alkane elimination reactions of ZnR 2 (R = Me, Et) with H[ 2a – c ] in toluene or ethereal solutions at –35 °C afforded cleanly the corresponding organozinc complexes [ 2a – c ]ZnMe ( 3a – c ) and [ 2a – c ]ZnEt ( 4a – c ). Deprotonation of H[ 2a – c ] with n BuLi at –35 °C generated [ 2a – c ]Li ( 5a – c ), which may be isolated as either solvent‐free complexes or solvated adducts depending on the reaction solvents employed (toluene, OEt2, or THF). Metathetical reactions of 5a· OEt 2 with Zn(OAc) 2 in THF at –35 °C produced [ 2a ]Zn(OAc) ( 6a ). These amido phosphinimine derivatives all display solution C s symmetry on the NMR timescale. The mononuclear nature of the three‐coordinate alkyls 3 – 4 and four‐coordinate acetate 6a was confirmed by single‐crystal X‐ray diffraction analyses. Interestingly, the alkyl complexes 3a – c and 4a – c are all active initiators for the catalytic ring‐opening polymerization of ϵ‐caprolactone, whereas the acetate 6a is comparatively inactive.