Metal tetraphosphonate "wires" and their corrosion inhibiting passive films

Herein, we describe the preparation and characterization of five new divalent metal tetraphosphonates, M-HDTMP [M = Mg(2+), Ca(2+), Sr(2+), Ba(2+), and Cu(2+); HDTMP = hexamethylenediaminetetrakis(methylenephosphonate) dianion]. Materials {Sr[(HDTMP)(H(2)O)(6)] x 2 H(2)O}(n) (1), {Ba[(HDTMP)(H(2)O)(6)] x 2 H(2)O}(n) (2), and {Cu[(HDTMP)(H(2)O)(4)] x 6 H(2)O}(n) (3), as well as (en)(HDTMP) x 2 H(2)O (en = ethylenediammonium cation) have been structurally characterized. Structures depend on the coordination requirements of the M(2+) center and waters of crystallization content. The formation and characterization of effective anticorrosion passive films of M-HDTMP (M = Sr(2+) and Ba(2+)) are also reported.