, Volume 30, Issue 11, pp 705-716

Identification of a new family of diphosphate compounds, AI2BII3(P2O7)2: Structures of Ag2Co3(P2O7)2, Ag2Mn3(P2O7)2, and Na2Cd3(P2O7)2

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Abstract

Syntheses and single-crystal X-ray structural results are reported for three new mixed diphosphates of the family AI 2BII 3(P2O7)2; Ag2Co3(P2O7)2 (I), Ag2Mn3(P2O7)2 (II), and Na2Cd3(P2O7)2 (III). All crystallize in the triclinic system, space group P1 bar: (I) a = 5.351(4), b = 6.375(4), c = 16.532(4) Å, α = 80.83(6) β = 81.45(4), γ = 72.87(5)°, V = 528.9(6) Å3, Z = 2, D calc = 4.649 mg/m3, R/Rw = 0.0428/0.0548 for 3949 obs. reflns; (II) a = 5.432(7), b = 6.619(6), c = 16.51(3) Å, α = 80.78(8) β = 82.43(9), γ = 72.82(7)°, V = 557.7(13) Å3, Z = 2, D calc = 4.338 mg/m3, R/Rw = 0.0679/0.1303 for 2100 obs. reflns and (III) a = 5.67(3), b = 7.08(4), c = 7.90(4) Å, α = 77.0(2), β = 82.5(2), γ = 67.8(2)°, V = 286(3) Å3, Z = 2, D calc = 4.249 mg/m3, R/Rw = 0.0307/0.0342 for 1945 obs. reflns. (I) and (II) are isostructural but (III) is of a different type. All three structures are characterized by layers of P2O7 groups alternating with layers of mixed metal atoms. Differences are seen in the conglomerate bonding patterns of B atoms and in the irregular geometry of Ag in (I) and (II) compared to the octahedral bonding seen for Na in (III). The differences in structure may be understood in terms of the ratios of the ionic radii of A and B atoms.