TETRA(AMINO)METHANES - IMPLICATIONS OF THEIR STRUCTURE AND REACTIVITYPATTERN FOR HYPOTHETICAL CARBON NITRIDE FRAMEWORKS

Because of their possible role as model compounds for the structural u nits of carbon nitride C3N4, the preparation, structural chemistry, an d some representative reactions of tetra(amino)methanes have been (re) investigated. In the crystal, C(NMe2)(4) (1) has a molecular geometry close to D-2d symmetry as proposed by theoretical calculations using s tate-of-the-art density functional methods. The coordination of the ce ntral carbon atom is distorted tetrahedral and the configuration of th e nitrogen atoms is strongly pyramidal, as opposed to almost planar in the tetra(amino)silanes. Tetra(pyrrolidinyl)methane has a similar cor e structure, with all heterocyclic substituents in an envelop conforma tion flexible in solution. Tetra (piperidinyl)methane is more rigid in solution, owing to a more congested structure, with much higher inver sion barbers for the six-membered rings. Hydrolysis of 1 leads to Me2N H and hexamethylguanidinium hydroxide, and treatment of 1 with HAuCl4( aq) affords crystalline [C(NMe2)(3)](+) AuCl4-, the structure of which has also been determined. Compound 1 is a strong nucleophile and can be used as an aminating agent, converting e.g. halosilanes into dimeth yl-aminosilanes, with the guanidinium cation as the leaving group. The experimental results are discussed in the light of recent predictions regarding bulk carbon nitrides.