Pentakis(methoxycarbonyl)cyclopentadiene chemistry. Part 2. Some derivatives containing the alkaline-earth metals (Mg, Ca, Sr, or Ba) or Group 2 metals (Zn or Cd). Crystal and molecular structure of Ba[C5(CO2Me)5]2

Abstract

White, air-stable, and water-soluble compounds M[C₅(CO₂Me)₅]₂(M = Mg, Ca, Sr, Ba, Zn, and Cd) are obtained from HC₅(CO₂Me)₅ and the metal carbonates or acetates, or from MCl₂ and Tl[C₅(CO₂Me)₅]; the i.r., ¹H n.m.r., and mass spectra are reported and briefly discussed. The structure of the barium derivative has been determined at 295 K by single-crystal X-ray diffraction methods, and refined to a residual of 0.036 for 8 173 ‘ observed ’ reflections. Crystals are triclinic, space group P, with a= 14.499(4), b= 12.940(4), c= 10.745(2)Å, α= 100.54(2), β= 100.02(2), γ= 114.23(2)°, and Z= 2. The barium atom is eight-co-ordinate with an environment made up of three pairs of chelating carboxyl-carbonyl oxygen atoms and two others [Ba–O 2.655(3)–2.932(3)Å]; as in the alkali-metal derivatives, there is a tendency for adjacent carboxyl-carbonyl groups to behave as chelate functions.