Fifteen centered zirconium chloride cluster phases with five different interstitial atoms (Z = H, Be, B, C, Fe) were successfully derivatized in solution by replacing the six terminal or intercluster bridging chlorine ligands of the starting (Zr[subscript]6Cl[subscript]12Z)Cl[subscript]6 type clusters with a variety of neutral (RNH[subscript]2, R[subscript]3P) or charged (Cl[superscript]-, Br[superscript]-) ligands. Acetonitrile was the only solvent used successfully for derivatization reactions;Reactions of solid KZr[subscript]6Cl[subscript]15C, Rb[subscript]5Zr[subscript]6Cl[subscript]18B, K[subscript]3Zr[subscript]6Cl[subscript]15Be, Na[subscript]4Zr[subscript]6Cl[subscript]16Be and KZr[subscript]6Cl[subscript]15Fe with X[superscript]- (X = Cl,Br) led to the isolation and X-ray crystallographic analyses of a series of eleven compounds containing ((Zr[subscript]6Cl[subscript]12Z)Cl[subscript]3X[subscript]3][superscript]4- clusters (Z = Be, B, C, for X = Cl; Z = Fe for X = Cl, Br), many with Et[subscript]4Y[superscript]+ (Y = N,P) or Ph[subscript]4P[superscript]+ cations. Oxidation of some of the normal 14-electron clusters centered by main group elements to the 13- and 12-electron clusters by the solvent was observed. While 13- and 14-electron clusters are known for solid state precursors, the 12-electron (Zr[subscript]6Cl[subscript]18Be)[superscript]4- cluster has been obtained exclusively by the non-aqueous solution route. The bond distances within the 13- and 12-electron clusters reflect the loss of one and two electrons from the metal-metal bonding HOMO (t[subscript] 2g[superscript]6) with an average increase in Zr-Zr bond lengths of 0.05A and 0.10A, respectively, relative to the distances in the solid state phases;Cyclovoltammograms of a (Zr[subscript]6Cl[subscript]18B)[superscript] n- solution in acetonitrile indicate the presence of not only 14-, 13-, and 12-electron clusters, which have already been isolated with different interstitial atoms, but also of a possible 15-electron cluster;Primary amines and Et[subscript]3P were used for the successful derivatization of K[subscript]3Zr[subscript]6Cl[subscript]15Be, Na[subscript]4Zr[subscript]6Cl[subscript]16Be and Li[subscript]6Zr[subscript]6Cl[subscript]18H in acetonitrile and subsequent isolation and X-ray crystallographic analysis of (Zr[subscript]6Cl[subscript]12Z)(RNH[subscript]2)[subscript]6·CH[subscript]3CN (Z = Be, R = Et, i-Pr; Z = H, R = Et) and (Zr[subscript]6Cl[subscript]12Be)(Et[subscript]3P)[subscript]6. The average bond lengths within these clusters show that the change from Cl[superscript]- exo ligands in the original phases to the neutral organic bases in the derivatives essentially does not affect the bond distances within the (Zr[subscript]6Cl[subscript]12Z) cluster core. ftn*This research was supported by the National Science Foundation - Solid State Chemistry - Grants DMR - 8318616 and - 8902954.