Structure and properties of beryllium phosphinate polymers

Abstract

The characterisation of beryllium phosphinates of stoicheiometry Be(Buⁿ₂PO₂)₂, Be(Ph₂PO₂)₂, and of some mixed-ligand species Be[(Buⁿ₂PO₂)_{2 – 2x}(Ph₂PO₂)_2x] is reported. The compounds richer in alkyl groups give stable solutions in hydrocarbon and halogenated solvents. Solution properties indicate that these compounds are linear polymers which undergo a reversible degradation influenced by the nature of the solvent, concentration, and temperature. The mixed-ligand species can be crystallised and are formulated as random copolymers. Isomorphous replacement of the two kinds of phosphinate groups within the crystal lattice of the related homopolymers is observed. The X-ray diffraction fibre photographs indicate that the homopolymer [Be(Buⁿ₂PO₂)₂]_n and the copolymers {Be[(Beⁿ₂PO₂)_{2 – 2x}(Ph₂PO₂)_2x]}_n(x= 0·20 or 0·33) have a backbone structure with alternate single and triple bridging phosphinate groups between tetrahedral metal atoms. The same chain-type structure is proposed for the homopolymer [Be(Ph₂PO₂)₂]_n and the copolymers richer in diphenylphosphinate groups.