Molecular and polymeric zinc(ii) phosphonates: isolation of an octanuclear ellipsoidal ensemble

Abstract

The reaction of zinc(II) perchlorate with trichloromethyl phosphonic acid at room temperature afforded, upon crystallization, a two-dimensional layered coordination polymer possessing a dinuclear repeat unit, [{Zn₂(Cl₃CPO₃)₂(H₂O)₃}·1.5H₂O]_n (1). Modification of the above reaction by involving a co-ligand afforded the tetranuclear complex, [{Zn₄(η¹-DMPzH)₆(Cl₃C–PO₃)₂}(μ-OH)₂(ClO₄)₂] (2). The molecular structure of 2 reveals that the tetranuclear core is non-planar and consists of three contiguous inorganic rings which include one 8-membered Zn₂P₂O₄ ring and two six-membered Zn₂PO₃ rings. Replacement of Zn(ClO₄)₂·6H₂O with ZnCl₂ under the same reaction conditions that afforded 2 allowed the formation of the dinuclear complex [{(ZnCl)₂(η²-Pz)₂(Cl₃CPO₃)}(Et₃NH)₂] (3). 3 possesses a bicyclic core containing a seven-membered Zn₂N₂O₂P ring. In 3, the phosphoryl oxygen atom (PO) is involved in a bifurcated hydrogen bonding interaction with the triethylammonium cation. The reaction of ZnCl₂ and 2,3,5,6-(Me)₄C₆HCH₂PO₃H₂ afforded the octanuclear complex [Zn₈(Cl)₆{2,3,5,6-(Me)₄C₆HCH₂PO₃}₆(Et₃N)₂](Et₃NH)₂]·2n-hexane·3H₂O (4). The core of 4 is ellipsoid-shaped with the end–end polar distance (C–C) being ∼20 Å.