Three-Dimensional Metal Piperazinyldiphosphonate Phases with Ellipsoidal Cavities Defined by 44-Membered Rings: Crystal Structures of [M{O3PCH2NH(C2H4)2NHCH2PO3}] · H2O,M= Mn and Co

Abstract

The hydrothermal reaction of a mixture of (Et4N)2MnCl4,N,N′-piperazinebis(methylenephosphonic acid), Et4NCl · H2O, and H2O in the mole ratio 1:1:5:300, adjusted to pH 5 with 40% aqueous (Bu4N)OH, at 160°C for 63 h yielded [Mn{O3PCH2NH(C2H4)2NHCH2PO3}] · H2O (1) in 60% as off-white platelets. The analogous reaction using (Et4N)2CoCl4produced [Co{O3PCH2NH(C2H4)2NHCH2PO3}] · H2O (2). The isomorphous materials 1 and 2 display three-dimensional network structures, based on binuclear units of corner-sharing metal and phosphorus tetrahedra, forming eight membered {–Co–O–P–O–}2rings. The diphosphonate groups serve to tether the binuclear units into large ellipsoidal 44-membered rings. As the piperazinyl nitrogen atoms are protonated, the organic moiety of the disphosphonate group serves as both tether and charge compensating site. Compound 1 exhibits Curie–Weiss paramagnetism with weak antiferromagnetism between Mn centers. In contrast, the susceptibility of 2 exhibits a broad maximum at low temperatures consistent with short range antiferromagnetic coupling. Crystal data: 1, C6H16MnN2O7P2, triclinicP1,a= 8.393(2)Å,b= 9.043(2)Å,c= 9.125(2)Å, α = 62.88(3)°, β = 86.36(3)°, γ = 78.96(3)°,V= 604.8(3)Å3;R= 0.056 for 1663 reflections. 2, C6H16CoN2O7P2, triclinicP1,a= 8.340(2)Å,b= 8.917(2)Å,c= 9.018(2)Å, α = 64.11(3)°, β = 86.24(3)°, γ = 78.87(3)°,V= 591.9(2)Å3;R= 0.083 for 1917 reflections.