Oxacalix[3]arenes p-methyloxacalix[3]arene (L-1), p-isopropyloxacalix[3] arene (L-2), and p-ethoxycarbonyloxacalix[3]arene (L-3) are able to bind the Re-I(CO)(3) moiety with two of their three phenol-O atoms and one of their ether-O atoms. The monoanionic complexes were isolated in the salts (DBUH)[Re(CO)(3)((LH-2)-H-1)]L-.(1)(1) and (NEt4)[Re(CO)(3)( (LH-2)-H-2)](.) L(2.)0.5 MeCN (2) (DBU = 1,8-diazabicyclo[5.4.0]undec-7-ene). Over the course of its reaction with (NEt4)(2)[Re(CO)(3)Br-3] and DBU, p-ethoxycarbonyloxacalix[3]arene decomposes to form [{Re(CO)(3)((LH-2)-H-4)}(2)] (3) {L-4 = 1-(5-ethoxycarbonyl-2-hydroxy-3-hydroxymethyl-benzyl)-2,3,4,6,7,8,9,10-o ctahydro-pyrimido[1,2-a]azepin-1-ium. The expected monoanion [Re(CO)(3)((LH-2)-H-3)](-) (4) was identified by C-13 NMR and mass spectra.