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Y, Lu, and Gd Complexes of NCO/NCS Pincer Ligands: Synthesis, Characterization, and Catalysis in the cis‐ 1,4‐Selective Polymerization of Isoprene
Author(s) -
Zhang Jingshun,
Hao Zhiqiang,
Gao Wei,
Xin Lan,
Zhang Lei,
Mu Ying
Publication year - 2013
Publication title -
chemistry – an asian journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.18
H-Index - 106
eISSN - 1861-471X
pISSN - 1861-4728
DOI - 10.1002/asia.201300581
Subject(s) - pincer movement , chemistry , pincer ligand , pentagonal bipyramidal molecular geometry , trigonal bipyramidal molecular geometry , metal , crystallography , catalysis , dimer , polymerization , medicinal chemistry , crystal structure , organic chemistry , polymer
Abstract A series of NCO/NCS pincer precursors, 3‐(Ar 2 OCH 2 )‐2‐Br‐(Ar 1 NCH)C 6 H 3 (( Ar1 NCO Ar2 )Br, 3a , 3b , 3c , 3d ) and 3‐(2,6‐Me 2 C 6 H 3 SCH 2 )‐2‐Br‐(Ar 1 NCH)C 6 H 3 (( Ar1 NCS Me )Br, 4a and 4b ) were synthesized and characterized. The reactions of [ Ar1 NCO Ar2 ]Br/ [ Ar1 NCS Me ]Br with n BuLi and the subsequent addition of the rare‐earth‐metal chlorides afforded their corresponding rare‐earth‐metal–pincer complexes, that is, [( Ar1 NCO Ar2 )YCl 2 (thf) 2 ] ( 5a , 5b , 5c , 5d ), [( Ar1 NCO Ar2 )LuCl 2 (thf) 2 ] ( 6a , 6d ), [( Ar1 NCO Ar2 )GdCl 2 (thf) 2 ] ( 7 ), [{( Ar1 NCS Me )Y( μ ‐Cl)} 2 {( μ ‐Cl)Li(thf) 2 ( μ ‐Cl)} 2 ] ( 8 , 9 ), and [{( Ar1 NCS Me )Gd( μ ‐Cl)} 2 {( μ ‐Cl)Li(thf) 2 ( μ ‐Cl)} 2 ] ( 10 , 11 ). These diamagnetic complexes were characterized by 1 H and 13 C NMR spectroscopy and the molecular structures of compounds 5a , 6a , 7 , and 10 were well‐established by X‐ray diffraction analysis. In compounds 5a , 6a , and 7 , all of the metal centers adopted distorted pentagonal bipyramidal geometries with the NCO donors and two oxygen atoms from the coordinated THF molecules in equatorial positions and the two chlorine atoms in apical positions. Complex 10 is a dimer in which the two equal moieties are linked by two chlorine atoms and two ClLiCl bridges. In each part, the gadolinium atom adopts a distorted pentagonal bipyramidal geometry. Activated with alkylaluminum and borate, the gadolinium and yttrium complexes showed various activities towards the polymerization of isoprene, thereby affording highly cis ‐1,4‐selective polyisoprene, whilst the NCOlutetium complexes were inert under the same conditions.