Unprecedented Metal-Free C(sp3)-C(sp3) Bond Cleavage: Switching from N-Alkyl- to N-Methyl-1,3,5-triaza-7-phosphaadamantane

N-Alkyl-1,3,5-triaza-7-phosphadamantane halides [PTA-R]X (X = I-, Br-) with more than two carbon atoms in the alkyl chain are shown to easily convert, under mild conditions in aqueous medium, into the corresponding N-methyl derivatives, thus representing a novel type of metal-free C(sp(3))-C(sp(3)) bond cleavage that affects inert, unstrained, and unbranched aliphatic groups. This unusual transformation is promoted by Cu ions and is proposed to occur via a postulated ammonium ylide. In the presence of Cu ions, this C-C bond dissociation is also a key point for the formation of a unique 2D Cu(I) coordination polymer with a rare P,N-coordination mode of the PTA cage.