The reactions o f ter/-butylcalix[4]arene (1) and the phosphorus-substituted rm -butylcalix- [4]arene (2), respectively, with terf-butylbis[N-(N',N',N",N"-tetramethyl)guanidinyl]phosphine (3) led to the first calix[4]arene-anions with the protonated phosphonium cations 4 and 5. No protonation o f the imino nitrogen atom was observed. In the case of compound 4, a singlecrystal X-ray structure analysis has been conducted. In compound 5, phosphorus atoms in the oxidation states +III and +V are present in one molecule