{(BuSn)(12)O-14(OH)(6)}(O2PPh2)(2) has been prepared from {(BuSn)(12)O-14(OH)(6)}(OH)(2) and diphenylphosphinic acid. Its full characterization by solution 1D (H-1, C-13, Sn-119 and P-31) and 2D gradient-assisted (H-1-Sn-119 HMQC, H-1-C-13 HMQC, H-1 ROESY, and P-31-H-1 HOESY) NMR is reported and shows that in CD2Cl2 or CD2Cl2/DMSO-d(6) (1/1) the charge compensating diphenylphosphinate anions remain close to the "cage-poles" of the macrocations. A model for the geometry of the interaction is proposed. Sn-119 and P-31 MAS MMR characterization of the title compound is also reported.