Monomeric, dimeric, and trimeric calcium compounds containing substituted pyrrolyl and ketiminate ligands: Synthesis and structural characterization

Shih Mao Ho, Ching Sheng Hsiao, Amitabha Datta, Chen Hsiung Hung, Ling Chueh Chang, Ting Yu Lee, Jui Hsien Huang

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Abstract

A series of monomeric, dimeric, and trimeric calcium compounds containing substituted pyrrolyl or ketiminate ligands were synthesized, and characterized by NMR spectroscopy and single crystal X-ray diffractometry. The reaction of Ca[N(SiMe3)2]2(THF)2 with 1 equiv of [C4H3NH(2-CH2NEt2)] in toluene generates the dimeric complex, [Ca{N(SiMe3)}[μ-η1: η5-{C4H3N(2-CH2NEt 2)}]]2 (1) in which two substituted pyrrolyl ligands bind two Ca centers in a η1 and η5 fashion. The reaction between Ca[N(SiMe3)2]2(THF) 2 and 2 equiv of [C4H3NH(2-CH2NEt2)] in THF yields a monomeric calcium compound Ca[C4H 3N(2-CH2NEt2)]2(THF)2 (2) that exhibits a facial octahedral geometry on the central Ca atom. Similarly, the reactions of Ca[N(SiMe3)2]2(THF) 2 with 1 and 2 equiv of OCMeCHCMeNHAr (Ar = 2,6-diisopropylphenyl) generate [Ca(OCMeCHCMeNAr){N(SiMe3)2}]2 (3) and [Ca(μ-OCMeCHCMeNAr)-(OCMeCHCMeNAr)]2 (4), respectively. In 3, the Ca atom possesses a distorted tetrahedral geometry where as in 4, a square plane is developed by the two calcium atoms with the bridging participation of two oxygen atoms from two ketiminate ligands. The in situ reaction of OCMeCHCMeNHAr, Ca[N(SiMe3)2]2(THF)2, and isopropyl alcohol results in a trimeric calcium alkoxide compound Ca 3(μ-OCMeCHCMeNAr)2(OCMeCHCMeNAr)(μ3-O- iPr)22-O-iPr) (5). Compounds 1, 2, and 5 showed good catalytic activity in the ring-opening polymerization of ε-caprolactone and L-lactide.

Original languageEnglish
Pages (from-to)8004-8011
Number of pages8
JournalInorganic Chemistry
Volume48
Issue number16
DOIs
Publication statusPublished - 2009 Aug 17

All Science Journal Classification (ASJC) codes

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry

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