Basicity of N-(Tetramesityltetraphosphacyclopentylidene)cyclohexylamine: An Unusual Diphospha(III)guanidine Derivative

The nitrogen atom in cyclic hetero-oligophosphane cyclo-P4Mes4C(NCy) (1) can be protonated with HCl or HBF4. The resulting cation was isolated as the BF4–, AlCl4– and GaCl4– salts and characterised by NMR spectroscopy, mass spectrometry and X-ray crystallography. According to quantum mechanical calculations, the basicity of compound 1 is comparable to that of methyl-substituted monophospha(III)guanidine. The pKα value of 1 was also determined experimentally with indicator bases.