Addition compounds between carbones, CL2, and main group Lewis acids: A new glance at old and new compounds

Abstract In this contribution, addition compounds of carbones C L 2 with main group Lewis acids A are reviewed. The newly recognized class of carbones comprises divalent carbon(0) compounds stabilized by two neutral donor molecules L which have peculiar donor properties due to the fact that the central carbon atom has two lone electron pairs of σ and π symmetry, respectively, prone to donate to Lewis acids A . The majority of addition compounds are of the type L 2 C→ A but few examples of A ← L 2 C→ A have also been reported. Furthermore, diprotonated species [H 2 C L 2 ] 2+ are included, in which A represents H + . High first and second proton affinities are typical features of carbones. The spectrum of the basic carbones includes most prominent members such as carbodiphosphoranes, as well as carbodiarsoranes, tetraaminoallenes (TAA's), carbodicarbenes and various mixed carbones. Compounds established by X-ray analyses are highlighted by an asterisk.