A novel cadmium aminophosphonate: X-ray powder diffraction structure, solid-state IR and NMR spectroscopic determination of the fine structure of the organic moieties

A new divalent cadmium phosphonate, Cd2Cl2(H2O)(4)(H2L), has been synthesized from the ethylenediamine-N,N'-bis(methylenephosphonic acid) (H4L). The obtained microcrystalline compound has been characterized by solid-state IR spectra and C-13, P-31, and Cd-113 CP MAS NMR. The static P-13 NMR spectra have been also recorded to give the delta(11), delta(22), and delta(33) chemical shift parameters for both compounds. The spectral data, collected for Cd2Cl2-(H2O)(4)(H2L), are in an agreement with its X-ray powder diffraction structure solved with the cell dimensions a = 16.6105(10), b = 7.1572(4), and c = 6.8171(4) Angstrom and beta = 98.327(4)degrees. The octahedral coordination sphere of the cadmium atoms consists of two phosphonate oxygen atoms, two water oxygen atoms, and the two chlorine atoms. Cadmium atoms are bridged by the chlorine atoms forming four-membered rings. The phosphorus atoms exhibit a tetrahedral coordination with two oxygen atoms bonded to the cadmium atoms with P-O distances of 1.503(10) and 1.504(10) Angstrom. The third oxygen atom, showing a longer P-O distance (1.546(9) Angstrom), is not bonded to the metal center, nor is it bonded to a proton. The combined IR and NMR proton-phosphorus cross-polarization kinetic data together with the X-ray data confirm that the cadmium phosphonate has the zwitterionic structure (NH2+CH2P(O2Cd2)O-) similar to the initial aminophosphonic acid H4L.