Synthesis, reactions and X-ray crystal structures of metallacrown ethers with unsymmetrical bis(phosphinite) and bis(phosphite) ligands derived from 2-hydroxy-2′-(1,4-bisoxo-6-hexanol)-1,1′-biphenyl

Academic Article

Abstract

  • Chlorodiphenylphosphine and 2,2′-biphenylylenephosphorochloridite react with 2-hydroxy-2′-(1,4-bisoxo-6-hexanol)-1,1′-biphenyl to yield the new α,ω-bis(phosphorus-donor)-polyether ligands, 2-Ph2PO(CH2CH2O)2-C 12H8-2′-OPPh2 (1) and 2-(2,2′-O2C12H8)P(CH2CH 2O)2-C12H 8-2′-P(2,2′-O2C12H8) (2). These ligands react with Mo(CO)4(nbd) to form the monomeric metaflacrown ethers, cis-Mo(CO)4{2-Ph2PO(CH2CH2O) 2-C12H8-2′-OPPh2} (cis-3) and cis-Mo(CO)4{2-(2,2′-O2C12H 8)P(CH2-CH2O)2-C12H 8-2′-P(2,2′-O2C12H8)} (cis-4), in good yields. The X-ray crystal structures of cis-3 and cis-4 are significantly different, especially in the conformation of the metal center and the adjacent ethylene group. The very different 13C-NMR coordination chemical shifts of this ethylene group in cis-3 and cis-4 suggest that the solution conformations of these metallacrown ethers are also quite different. Both metallacrown ethers undergo cis-trans isomerization in the presence of HgCl2. Although the cis-trans equilibrium constants for the isomerization reactions are nearly identical, the isomerization of cis-3 is more rapid. Phenyl lithium reacts with cis-3 to form the corresponding benzoyl complexes but does not react with either trans-3 or cis-4. Both the slower rate of cis-trans isomerization of cis-4 and its lack of reaction with PhLi are consistent with weaker interactions between the hard metal cations and the carbonyl oxygens in both trans-3 and cis-4. © 1999 Elsevier Science S.A. All rights reserved.
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    Author List

  • Hariharasarma M; Lake CH; Watkins CL; Gray GM
  • Start Page

  • 328
  • End Page

  • 338
  • Volume

  • 580
  • Issue

  • 2