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A series of Ni(I1) complexes with methyl-, ethyl-, and sym-dimethyl-, sym-diethyl-, and sym-di-n-butylthioureas and halide, perchlorate, and thiocyanate anions have been prepared and characterized. Spectral and magnetic studies show that compounds NiL4X2 (L = N,N'-dimethyl and N,N'-diethylthiourea, X = halide) are tetragonally distorted octahedral species with a singlet ground state and a thermally populated triplet excited state. The remaining compounds are octahedral. Infrared evidence shows sulfur bonding of the disubstituted ligands to the metal, but suggests nitrogen coordination of the methylthiourea con~pounds.

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The synthesis of vinyl isocyanide provides a new, relatively small molecule useful for testing theories of bonding and conjugation. N-Formylethanolamine treated with benzenesulfonyl chloride in pyridine yielded 2-isocyanoethyl benzenesulfonate, which was converted to vinyl isocyanide by alcoholic potassium hydroxide. The 60-MHz nmr spectrum of vinyl isocyanide has been fully interpreted, and the vinyl protons show considerably more diamagnetic shielding than those in acrylonitrile, in accord with predicted conjugative effects and in opposition to inductive effects. Vinyl isocyanide undergoes 1,3-dipolar addition of diphenyldiazomethane to the vinyl group but at only Viso the rate that acrylonitrile does at 25°. Other reactions of vinyl isocyanide include the formation of complexes with transition metals and the condensation with benzaldehyde and piperidine to yield N-vinyl-a-(l-piperidino)phenylacetamide.We undertook the synthesis of vinyl isocyanide (CH2=CHN=C, 1) because its close structural relationship to acrylonitrile (CH2=CHC=N, 2) is of theoretical interest. These isoelectronic isomers differ only in the location of one nuclear charge, but grossly different -electron distributions in the vinyl groups are expected as a result of conjugation. The cyano group, but not the isocyano group, withdraws -electron density from the terminal vinyl carbon.However, if inductive effects dominate the electron distribution, the vinyl group in vinyl isocyanide will be the more electron deficient. This outcome seems implicitly predicted by the theoretical viewpoint expressed by Dewar2 and refined by Dewar and Gleicher,3 who have pointed out that the ground-state properties of classical conjugated hydrocarbons are additive functions of bond properties, and therefore there is no evidence that "resonance" in the chemical sense is important in such systems. This view has been challenged on the basis of recent advanced quantum mechanical calculations.4•5 It is difficult to find a system in which Dewar's views actually predict different experimental results from conventional theory. Most types of experiments do not measure ground-state properties, and changes in hybridization or other nonconjugative effects can be invoked to explain those which do.2 However, vinyl isocyanide and acrylonitrile use exactly the same set of bonding orbitals. We therefore hoped that some useful comparisons could be made without intrusion of the usual ambiguities. ResultsSynthesis. The synthesis of vinyl isocyanide from ethanolamine is based on the general isonitrile synthesis of Hertler and Corey6 and is straightforward and convenient. Treatment of N-formylethanolamine in (1) (a) Preliminary communication: D.

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