A sterically hindered aryl phosphonic acid ArP(O)(OH)(2) (2) (Ar = 2,4,6-isopropylphenyl) was synthesized and structurally characterized. ArP(O)(OH)(2) forms an interesting hydrogen-bonded corrugated sheet-type supramolecular structure in the solid-state. A three-component reaction involving ArP(O)(OH)(2), 3,5-dimethylpyrazole(DMPZH), and Cu(CH3COO)(2)(H2O)-H-. produces the tetranuclear Cu(II) compound [Cu-4(mu(3)-OH)(2){ArPO2(OH)}(2)(CH3CO2)(2)(DMPZH)(4)]-[CH3COO](2)(CH2Cl 2)-C-. (3). A similar three-component reaction involving ArP(O)(OH)2, 3,5-dimethylpyrazole, and Zn(CH3COO)(2)(.)2H(2)O yields the tetranuclear Zn(II) compound [Zn-4{ArPO3}(2){ArPO2(OH)}(2){DMPZH}(4){DMPZ}(2)](.)5MeOH (4). While 3 has been found to have an asymmetric cage structure where two dinuclear copper cores are bridged by bidentate [ArPO2(OH)](-) ligands, 4 possesses an open-book tricyclic structure composed of three fused metal lop h osphonate rings. Magnetic studies on 3 revealed antiferromagnetic behavior.