Controlling the Structure of Manganese(II) Phosphates by the Choice and Ratio of Organophosphate and Auxiliary Ligands

Abstract

Tetranuclear manganese(II) phosphates [Mn(dipp)(bpy)(4)center dot 4H(2)O (1) and [Mn(4)(dmpp)(2)(dmppH)(4)(bpy)(4) (H(2)O)(2)]center dot H(2)O (2) have been prepared from Mn(OAc)(2)center dot 4H(2)O and 2,6-diisopropylphenyl phosphate (dippH(2)) or 2,6-dimethylphenyl phosphate (dmppH(2)) in the presence of 2,2'-bipyridine (bpy). In contrast, the reaction between [Mn(bpy)(2)(OAc)(ClO(4))center dot H(2)O and dippH(2) affords [Mn(bpy)(2) (dippH)(2)center dot 2ClO(4)center dot 2CH(3)OH (3). The reactions of Mn(OAC)(2)center dot 4H(2)O, dippH(2), and pyridine (py) or 3,5-dimethylpyrazole (dmpz) in CH(3)CN under reflux afford hexanuclear complexes [Mn(6) (dipp)(6)(py)(8)]center dot 2CH(3)CN (4) and [Mn(6)(dipp)(6)(dmpz)(6)(AcOH)(2)]center dot 2H(2)O (5), respectively. Although compounds I and 2 are tetrameric, the former is a closed cubane-like structure resembling the D4R secondary building unit of zeolites, whereas the latter exists in a staircase structure with fused Mn(2)O(4)P(2) rings. The core structure of 3 contains a Mn(2)O(4)P(2) eight-membered ring that resembles the S4R building block of zeolites. Single-crystal X-ray diffraction studies reveal that compounds 4 and 5 have a similar core structure and differ from each other by the neutral ligands coordinated to manganese ions. All six phosphate ligands exist in a doubly deprotonated [(RO)PO(3)(2-)] form and exhibit two types of binding modes [5.222] and [3.111]. An interesting feature of compounds 1-5 is that although they are oligonuclear complexes, there is an absence of oxido bridges. The magnetic properties of compounds 1-5 have been investigated in the temperature range 5-298 K, and it was found that all the compounds obey the Curie law.