Synthesis and crystal structure of Sr₂Cu(OH)₄[B(OH)₄]₂

Single crystals of distrontium copper(II) tetra-hydroxide bis-(tetra-hydroxidoborate), Sr₂Cu(OH)₄[B(OH)₄]₂, were obtained by an ammonia evaporation method at room temperature. The compound crystallizes in the triclinic system, space group P1, and is isotypic with the calcium analogue henmilite, Ca₂Cu(OH)₄[B(OH)₄]₂. The {Cu(OH)₄} units form a deformed square lattice in the ac plane, giving rise to a quasi-two-dimensional arrangement of Cu^II ions. An intricate network of O-H⋯O hydrogen bonds of medium strengths with the [B(OH)₄] units as the primary donor groups consolidate the framework structure.