Structural complexity and metal coordination flexibility in two acetophosphonates

Two divalent metal acetophosphonates, Pb-6(O3PCH2CO2)(4) End Mn-3(O3PCH2CO2)(2), have beep synthesised hydrothermally. They crystallise in the triclinic system, space group P (1) over bar, a = 11.0064(1), b-12.3604(1), c=8.9783(1) Angstrom, alpha=98.632(1), beta=90.474(1), gamma=75.629(1)degrees, Z=2, for M = Pb, and a =10.0146(5), b = 6.3942(4), c=8.4796(6) Angstrom, alpha=101.452(4), beta=106.254(2), gamma=96.431 (4)degrees, Z=2, for M=Mn. The structures were solved ab initio using direct methods from synchrotron powder diffraction data (lambda approximate to 0.4 Angstrom) 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), if 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 bu lt 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.