Two isomeric lead(II) carboxylate-phosphonates: syntheses, crystal structures and characterizations

Abstract

Two isomeric layered lead(II) carboxylate-phosphonates of N -(phosphonomethyl)- N -methyl glycine ([MeN(CH 2 CO 2 H)(CH 2 PO 3 H 2 )]=H 3 L), namely, monoclinic Pb 3 L 2 ·H 2 O 1 and triclinic Pb 3 L 2 ·H 2 O 2 , have been synthesized and structurally determined. Compound 1 synthesized by hydrothermal reaction at 150°C is monoclinic, space group C 2/ c with a =19.9872(6), b =11.9333(1) and c =15.8399(4) Å, β =110.432(3)°, V =3540.3(1) Å 3 , and Z =8. The structure of compound 1 features a 〈400〉 layer in which the lead(II) ions are bridged by both phosphonate and carboxylate groups. The lattice water molecules are located between the layers, forming hydrogen bonds with the non-coordinated carboxylate oxygen atoms. Compound 2 with a same empirical formula as compound 1 was synthesized by hydrothermal reaction at 170°C. It has a different layer structure from that of compound 1 due to the adoption of a different coordination mode for the ligand. It crystallizes in the triclinic system, space group P 1 ̄ with cell parameters of a =7.1370(6), b =11.522(1), c =11.950(1) Å, α =110.280(2), β =91.625(2), γ =95.614(2)°, V =915.3(1) Å 3 and Z =2. The structure of compound 2 features a 〈020〉 metal carboxylate-phosphonate double layer built from 1D lead(II) carboxylate chains interconnected with 1D lead(II) phosphonate double chains. XRD powder patterns of compounds 1 and 2 indicate that each compound exists as a single phase.