The stereochemisry of molecules containing the C = C =b N group: the crystal structure of N-methyl-2:2-dimethylsulphonylvinylidineamine

A three-dimensional structure analysis of a compound containing the group =C=C=N-R is described. All four atoms in this chain are shown, rather surprisingly, to be linear. The bond number of the central carbon atom in the multiply-linked chain is shown to be very high, being joined on the one side to a nitrogen atom by what appears, from the length of 1.154 A, to be a triple bond, and on the other side to a carbon atom by what seems, from the length of 1.342 A, to be a double bond. The occurrence of this 'pentavalent' carbon atom suggests'that, in condensed systems of this type, bond length is not a satisfactory criterion of bond order.