The reaction of the aminophosphane C6H4(o-CN)NHPPh2 with elemental potassium in the presence of 18-crown-6 affords the phosphinoamide-containing complex [C6H4(o-CN)N-PPh2(THF)(18-Crown-6)K] which has been fully characterised in solution and the solid state. The potassium cation interacts with the nitrile substituent group and crown, but does not interact with the P-N bond. The anion appears to be considerably more reactive than related anions in which the cation interacts with the P-N unit, as demonstrated by the reaction with O-2/H2O which affords [Ph2P(:O)OK(18-Crown-6)] and C6H4(o-CN)NH2. A co-crystal containing these two products was obtained and the structure has been elucidated by single-crystal X-ray diffraction analysis. (C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003.