Abstract
1
H-n.m.r. spectroscopy has been used to demonstrate that nucleophilic attack by pyridine on the C&z.dbd6;C bond in
cis
-dichloro(
π
-ethene)(pyridine)platinum(
II
) readily leads to the formation of the σ-bonded complex,
cis
-dichloro(pyridine)(2-pyridinioethanide)platinum(
II
), which is much more stable than the corresponding
trans
isomer.