Solution Conformational Features of the Unsymmetrical Metalla Crown Ether cis-Mo(CO)4{2-(2,2′-O2C12H 8)PO(CH2CH2O)2-2-C 20H12-2′-OP(2,2′-O2C 12H8)} from 2D NMR Spectroscopy and Molecular Modeling

Academic Article

Abstract

  • A new unsymmetrical metalla crown ether, cis-Mo(CO) {2-(2,2′-O C H )PO(CH CH 0) -2-C H -2′-O (2,2′-O C H )}, has been designed for solution conformation studies. The complex was prepared by the reaction of the α,ω-bis(phosphorus donor) polyether ligand 2-(2,2′-O C H )PO(CH CH 0) -2-C H -2′-OP(2,2′-O C H ) with Mo(CO) (nbd). Separate H NMR resonances were observed for six of the eight methylene protons of the metalla crown ether, indicating that the motion of the metalla crown ether ring was restricted. The H, C, and P NMR chemical shifts of the metalla crown ether were completely assigned using a combination of C DEPT, H- H COSY, C{ H} HETCOR, P{ H} HETCOR, H-{ C} HMBC, and H- H NOESY NMR experiments. The solution conformation was analyzed using H- H vicinal coupling constants and H- H NOESY NMR experiments. The vicinal H- H coupling constants for the ethylene protons indicated that both ethylenes were gauche. The H- H NOESY NMR experiments showed a number of close contacts between aromatic protons. Good qualitative agreement was observed between the H-H distances obtained from molecular modeling studies and the intensities of the direct H- H NOEs of the aromatic protons. The structure of the metalla crown ether from the molecular modeling studies also explained the unusual shieldings and deshieldings of certain aromatic protons in the molecule. 4 2 12 8 2 2 2 20 12 2 2 12 8 2 12 8 2 2 2 20 12 2 12 8 4 1 1 13 31 13 1 1 13 1 31 1 1 13 1 1 1 1 1 1 1 1 1 1 1 1
  • Published In

  • Organometallics  Journal
  • Digital Object Identifier (doi)

    Author List

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

  • 1232
  • End Page

  • 1238
  • Volume

  • 19
  • Issue

  • 7