19F NMR studies on positional variations of trifluoromethyl groups in CF3-substituted aromatic group 15 trivalent chlorides

• Interesting variations in 19F NMR shifts for o-CF3 groups in RECl2 and R2ECl (E = P, As, Sb or Bi) have been correlated with the compound structures, the electronegativity of E and short E–F contacts.

Several Group 15 trivalent chlorides with CF3-substituted aromatic groups R present, including at least one ortho-CF3 substituent, RnECl3-n (n = 1 or 2; E = P, As, Sb or Bi) have been studied by 19F solution-state NMR spectroscopy. In compounds with both ortho- and para-CF3 groups, the chemical shifts of the para-CF3 fluorines are very similar, irrespective of the central element E. Much more variation is found in the shifts of the ortho-CF3 fluorines, which may be correlated with the nature of the aromatic group, the electronegativity of E and the occurrence of short E–F contacts, as demonstrated by previous crystallographic studies of some of these compounds.

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