Pseudohalide HCN aggregate ions: [N3(HCN)3]-, [OCN(HCN)3]-, [SCN(HCN)2]- and [P(CN·HCN)2]- .

In the presence of μ-nitridobis(triphenylphosphonium) cation, [PPN]+, it was possible to stabilize and isolate [PPN]+-salts bearing the highly labile hydrogen cyanide aggregate anions of pseudohalides X (X = N3, OCN and SCN). From a concentrated solution of the [PPN]X salts in HCN, crystals of [PPN][X(HCN)3] (X = N3, OCN) or [PPN][SCN(HCN)2] could be obtained, when the crystallization was carried out fast and at low temperatures. The reaction of liquid HCN with the PCO- salt led to formation of dicyanophosphide, which crystallized as HCN disolvate [P(CN·HCN)2]-. All synthesized salts with hydrogen-bridged pseudohalide solvate anions are thermally unstable. Immediate loss of HCN was observed in the crystals outside the HCN solution. Oligomerization begins at ambient temperature, even in HCN solution. All discussed species were characterized by means of Raman spectroscopy, single crystal X-ray analysis and quantum-chemical calculations.