TY - JOUR
T1 - Pincer chromium(II) and chromium(III) complexes supported by bis(imino)aryl ncn ligands
T2 - Synthesis and catalysis on isoprene polymerization
AU - Liu, Zhizhou
AU - Gao, Wei
AU - Liu, Xiaoming
AU - Luo, Xuyang
AU - Cui, Dongmei
AU - Mu, Ying
PY - 2011/2/28
Y1 - 2011/2/28
N2 - Reactions of 2,6-(ArN-CH)2C6H3Li with CrCl2(THF)2 afford two trinuclear bis(imino)aryl NCN pincer Cr(II) complexes {[2,6-(ArN-CH)2C6H 3]Cr(μ-Cl)2}2Cr [Ar = 2,6-Me 2C6H3 (1a), 2,6-Et2C 6H3 (1b)], and a mononuclear bis(imino)aryl NCN pincer Cr(II) complex [2,6-(ArN-CH)2C6H3]Cr(μ-Cl) 2Li(THF)2 [Ar = 2,6-iPr2C 6H3 (1c)], respectively. Similar reactions of 2,6-(ArN-CH)2C6H3Li with CrCl 3(THF)3 produce only mononuclear bis(imino)aryl NCN pincer Cr(III) complexes [2,6-(ArN-CH)2C6H3]CrCl 2(THF) [Ar = 2,6-Me2C6H3 (2a), 2,6-Et2C6H3 (2b), 2,6-iPr 2C6H3 (2c)]. X-ray crystallographic analysis reveals that the terminal Cr(II) atoms in 1a and 1b and the Cr(II) atom in 1c possess a distorted trigonal bipyramidal coordination environment with the Cipso atom of the pincer ligand and two chloride atoms in the equator and the two imine nitrogen atoms in the apical positions, while the Cr(III) complexes 2a, 2b, and 2c all adopt a distorted octahedral geometry around the chromium metal. Upon activation with trialkylaluminum and [Ph3C] +[B(C6F5)4]-, the Cr(III) complexes show high catalytic activity for isoprene polymerization and afford polyisoprene with predominately trans-1,4 units, whereas the Cr(II) complexes are inert under the same conditions.
AB - Reactions of 2,6-(ArN-CH)2C6H3Li with CrCl2(THF)2 afford two trinuclear bis(imino)aryl NCN pincer Cr(II) complexes {[2,6-(ArN-CH)2C6H 3]Cr(μ-Cl)2}2Cr [Ar = 2,6-Me 2C6H3 (1a), 2,6-Et2C 6H3 (1b)], and a mononuclear bis(imino)aryl NCN pincer Cr(II) complex [2,6-(ArN-CH)2C6H3]Cr(μ-Cl) 2Li(THF)2 [Ar = 2,6-iPr2C 6H3 (1c)], respectively. Similar reactions of 2,6-(ArN-CH)2C6H3Li with CrCl 3(THF)3 produce only mononuclear bis(imino)aryl NCN pincer Cr(III) complexes [2,6-(ArN-CH)2C6H3]CrCl 2(THF) [Ar = 2,6-Me2C6H3 (2a), 2,6-Et2C6H3 (2b), 2,6-iPr 2C6H3 (2c)]. X-ray crystallographic analysis reveals that the terminal Cr(II) atoms in 1a and 1b and the Cr(II) atom in 1c possess a distorted trigonal bipyramidal coordination environment with the Cipso atom of the pincer ligand and two chloride atoms in the equator and the two imine nitrogen atoms in the apical positions, while the Cr(III) complexes 2a, 2b, and 2c all adopt a distorted octahedral geometry around the chromium metal. Upon activation with trialkylaluminum and [Ph3C] +[B(C6F5)4]-, the Cr(III) complexes show high catalytic activity for isoprene polymerization and afford polyisoprene with predominately trans-1,4 units, whereas the Cr(II) complexes are inert under the same conditions.
UR - http://www.scopus.com/inward/record.url?scp=79951862273&partnerID=8YFLogxK
U2 - 10.1021/om1009236
DO - 10.1021/om1009236
M3 - Article
AN - SCOPUS:79951862273
SN - 0276-7333
VL - 30
SP - 752
EP - 759
JO - Organometallics
JF - Organometallics
IS - 4
ER -