Authentication of aminomethyl(hydrogen)phosphonate coordination to a main group metal: synthesis and crystal structure of [Mg(O 3PCH 2NH 3) 2(H 2O) 2]·2H 2O

Abstract

A magnesium complex of aminomethyl(hydrogen)phosphonate ([O 3PCH 2NH 3] −; AMPH −), the monoanion of aminomethylphosphonic acid (AMPH 2) has been prepared from the free acid and Mg(OH) 2 in water. According to an X-ray structure analysis it has to be formulated as [Mg(AMPH) 2(H 2O) 2]·2H 2O containing magnesium ions which are octahedrally coordinated by four phosphonate oxygen atoms of four different AMPH − anions and two water molecules trans to each other. Two additional water molecules are interstitial without coordination to Mg 2+ but take part in an extended network of hydrogen bonds. [Mg(AMPH) 2(H 2O) 2]·2H 2O is one of the rare cases in which phosphonate coordination by an α,ω-aminoalkylphosphonate to a main group metal has been authenticated in the solid state by an X-ray structure determination (C 2H 18MgN 2O 10P 2, monoclinic, space group P2 1/c, a = 9.682(4), b = 6.846(2), c = 9.797(4) A ̊ , β = 115.59(2)°, V = 585.7(4) A ̊ 3, Z = 2, wR(F 2) = 0.079 for 115 refined parameters and 1337 F 2).