Two divalent metal acetophosphonates, Pb 6 (O 3 PCH 2 CO 2 ) 4 and Mn 3 (O 3 PCH 2 CO 2 ) 2 , have been synthesised hydrothermally. They crystallise in the triclinic system, space group P1 9, a=11.0064(1), b=12.3604(1), c=8.9783(1) Å , a=98.632(1), b=90.474(1), c=75.629(1)°, Z=2, for M=Pb, and a=10.0146(5), b=6.3942(4), c=8.4796(6) Å , a=101.452(4), b=106.254 (2) , c=96.431(4)°, Z=2, for M=Mn. The structures were solved ab initio using direct methods from synchrotron powder diffraction data

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... .4 Å ) for M=Pb and from laboratory X-ray data for M=Mn. The crystal structure of the Pb compound is very complex with 38 non-hydrogen atoms in general positions (114 refined positional parameters), it had been refined by Rietveld method using soft constraints, and converged to R WP =6.8% and R F =1.6%. The structure for M=Mn has a moderate complexity with 19 nonhydrogen atoms (57 refined positional parameters) which was also refined with soft constraints to R WP =8.3%, R F =3.9%. Both compounds show a framework built of alternate metal oxide inorganic layers, pillared by the organic groups. The metal environments in these materials are very distorted. Manganese atoms present three different distorted oxygen environments: four-, five-and six-coordinate. Thermal and IR data are also reported and discussed. tetrahedral and one octahedral sites for the zinc atoms. As