(SrN)(SrIn)[CN] and Sr(SrN)[In][CN]: Two Fully Deprotonated Guanidinates Accessible from Pressureless Sodium Flux Synthesis.

Two novel compounds featuring the fully deprotonated guanidinate ion, CN, representing the true nitridocarbonate ion as the nitrogen analogue of the (oxido)carbonate ion CO, were obtained from essentially pressureless sodium flux synthesis. CN ions in (SrN)(SrIn)[CN] and Sr(SrN)[In][CN] are embedded in frameworks of strontium nitride next to the indide In- and In-units. The CN ion in both compounds is coordinated by three-capped trigonal prisms of Sr. (SrN)(SrIn)[CN] shows fully trigonal planar symmetry, but slightly distorted to nonplanar symmetry is seen in Sr(SrN)[In][CN] due to noncentrosymmetric coordination. C-N distances in the CN ion arrive at longer than typical C-O distances in the CO ion, fully consistent with expectations. Density functional theory (DFT) calculations also suggest pseudomolecular features of CN-, In-, and In-entities. The CN-entity is formed via an electron-rich multicenter bonding mechanism, as evidenced by multicenter COBI, whereas multicenter COBI suggested that In- and In-entities are formed through an electron-deficient manner.