Synthesis and Characterization of Novel Oxo-Centered Phosphanylzincates of Potassium and Cesium with a Central Zn₆O₂P₄ Double-Heterocubane Cage

The hydrolysis reaction of K2(MeZn)2(PSitBu3)2 in THF/toluene solution yields the [(MeZn)4Zn2(μ3-PSitBu3)4(μ4-O)2]4- anions independent of the applied stoichiometry. If the applied molar ratio resembles the composition of the anion, [(thf)K]2[(η6-toluene)K]2[(MeZn)4Zn2(μ3-PSitBu3)4(μ4-O)2] (1) crystallizes from a mixture of THF and toluene. In the case with less water, a phosphanediylzincate moiety is bonded to this anion, and [Zn(PSitBu3)2K4(thf)6]2[(MeZn)4Zn2(μ3-PSitBu3)4(μ4-O)2] (2) crystallizes. However, again the major product is 1. The same anion is also observed with larger and softer cations, and [(thf)3Cs2]2[(MeZn)4Zn2(μ3-PSitBu3)4(μ4-O)2] (3) is obtained if the cesium zincate is used in this reaction. In all of these compounds, the anion is a slightly distorted Zn6O2P4 double-heterocubane cage with a central Zn2O2 ring having Zn−O bond lengths of approximately 207 pm.