Ketenimine structure complexes

For almost a hundred years, chemists have argued over the identity(ies) of the CgHsN specie(s). Candidate structures for CeHsN have been singlet ( PN) and triplet ( PN) phenylnitrene, benzazirine (BZ) and cyclic ketenimine (K), a menagerie of species described by Schrock and Schuster as wonderfully complex . 

The intermediate Ni(CNBu )3 N2C(CN)2), formed by adding diazodi-cyanomethane to Ni(CNBu )4, rearranges, probably via a carbene insertion, to give the ketenimine complex Ni Bu N=C=C(CN)2 (CNBu )2. An X-ray structural determination of the product has been reported (436). 

Structures of type XVIII or XIX as proposed for the diazodicyanomethane complex (Table 12) may also apply to the complexes of diphenyldiazomethane and 9-diazo-fluorene. The formation of the ketenimine complex (45) from the reaction of (CN)2CN2 and Ni(t-BuNC)4 probably occurs via attack of the complexed dicyano-methylene carbene on the isocyanide ligand113 The observation that these complexes112 113 catalyze the formation of ketenimines from isocyanides and diazo compounds, a reaction which does not proceed under same conditions without the transition metal, may be of preparative value 113 ... 

Few 7r-bonded imine complexes have been prepared and investigated structurally. The only complexes of nonbridging 7r-bonded C=N investigated structurally are a substituted ketenimine complex (XLIV), an iminium complex (XLV), and a complex of the azine [(CF3)2C=N—)2 (XLVI) (see Table I). 

The ketenimine complex is unusual in that angle y for the complex is 11.9(10)° and the average S is 174°. These angles are indicative of a coordinated triple bond, rather than the expected double bond. This seemingly anomalous result can be rationalized on the basis of a large contribution of resonance form B to the structure of the ketenimine. This... 

A related ligand is the ketenimine, Ph2C=C=NPh. This forms the complexes Ph2C=C=NPh(Fe(CO)3)2 and jr-C5HsCoPh2C=C=NPh. The structure proposed for the cobalt complex is shown in 3.38 [95]. 

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