Structural Systematics of 2/4-Nitrophenoxide Complexes of Closed-Shell Metal Ions. V 2-Nitrophenoxides of Group 2

Abstract

Room-temperature single-crystal X-ray studies are recorded for 2-nitrophenoxide salts of Group 2 metals, variously hydrated M(2-np)₂.xH₂O, M = Mg, Ca, Sr; the structure of the barium analogue has been previously recorded. Mg(2-np)₂.2H₂O is monoclinic, P2₁/a, a 7·377(1), b 7·518(1), c 12·877(3) Å, β 106·58(2)°, Z = 2; conventional R on |F| 0·13 for N_o 508 independent ‘observed’ (I > 3σ(I)) reflections. Ca(2-np)₂.H₂O is monoclinic, C2, a 25·92(1), b 7·176(3), c 3·660(4) Å, β 93·66(5)°, Z = 2, R 0·061 for N_o 541. M(2-np)₂.4H₂O, M = Ca, Sr, are isomorphous, monoclinic, C2/c, a ≈ 31·3, b ≈ 8·1, c ≈ 12·8 Å, β 103°, Z = 8; R was 0·056, 0·055 forN_o 1988, 1744 respectively. The magnesium salt is a discrete molecular array disposed about a crystallographic inversion centre with chelating phenoxide ligands: trans-[Mg(2-np)₂(OH₂)₂]. The calcium monohydrate salt is a novel one-dimensional polymer with a ... Ca(µ-O)₂Ca(µ-O)₂Ca ... spine, the ligand pairs chelating the calcium with phenoxide-O additionally bridging. The seven-coordinate calcium atoms lie on the crystallographic 2 axis with the water molecule, also on that axis, making up a seven-coordinate environment. The tetrahydrate is also a one-dimensional polymer with a similar spine, the bridging oxygen atoms derivative of water molecules. A chelating ligand and two further water molecules make up an eight-coordinate metal environment, with the free anions interleaving stacks of coordinated anions up c.