Gallophosphonates Containing Alkali Metal Ions. 2.1 Synthesis and Structure of Gallophosphonates Incorporating Na+ and K+ Ions

The reactions between t-BuP(O)(OH)(2) and equimolar quantities of MGaMe(4) (M = Na, K) yield ionic and alkali metal containing molecular gallophosphonates [Na(4)((2)-OH(2))(2)(THF)(2)][(Me(2)GaO(3)PBu-t)(2)](2).2THF (2) and [K(THF)(6)][K(5)(THF)(2){(Me(2)GaO(3)PBu-t)(2)}(3)] (3), respectively. Compounds 2 and 3are soluble in common organic solvents and have been characterized by means of analytical and spectroscopic techniques, as well as by single-crystal X-ray diffraction studies. These compounds represent the rare examples of molecular ionic phosphonate cages which contain coordinated Na(+) or K(+) ions. Compound 2 is constructed from two eight-membered Ga(2)O(4)P(2) gallium phosphonate rings which sandwich a central Na(4)(H(2)O)(2) unit. In the case of 3, three eight-membered Ga(2)O(4)P(2) gallium phosphonate units envelope an aggregated K(5) core which exists in the form of a trigonal-bipyramidal polyhedron. The Na(+) and K(+) ions in 2 and 3 are also coordinated by the endocyclic oxygen atoms of the eight-membered gallophosphonate crowns, apart from the regular exocyclic P-O coordination. Unlike the lithium gallophosphonate [Li(4)(THF)(4)][{(MeGaO(3)PBu-t)(3)((3)-O(2))}(2)] (1), compounds 2 and 3 do not undergo any clean cage conversion reaction in the presence of 15-crown-5 and 18-crown-6, respectively.