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

Abstract

Room-temperature single-crystal X-ray structure determinations are recorded for 4-nitrophenolate (4-np^-) salts of Group 2 metal ions, variously hydrated, M(4-np)₂.xH₂O, M = Mg, Ca, Sr, Ba. Mg(4-np)₂.8H₂ O is monoclinic, P2₁/c, a 12·402(3), b 6·673(7), c 11·833(6) Å, β 93·70(3)°, Z = 2; conventional R on |F| was 0·041 for N_o 1995 independent ‘observed’ (I > 3σ(I)) reflections. Ca(4-np)₂.4H₂O is monoclinic, P2₁/c, a 13·109(8), b 3·644(1), c 21·181(8) Å, β 125·55(3)°, Z= 2, R 0·050 for N_o 1371. Sr(4-np)₂.8H₂O is monoclinic, P21/n, a 7·934(1), b 10·658(1), c 23·602(2) Å, β 91·36(1)°, Z = 4, R 0·038 for N_o 2050. Ba(4-np)₂.8H₂O is monoclinic P2₁/c, a 15·990(8), b 6·337(3), c 25·634(8) Å, β 126·1(3)°, Z = 4, R 0·021 for N_o 3115. The magnesium salt is ionic with [Mg(OH₂)₆]²⁺ cations and interleaved anion stacks up b. The calcium salt is a one-dimensional polymer with ... Ca(µ-O)₂Ca(µ-O)₂Ca ... spine, the bridges being phenolic oxygen atoms.trans-Coordinated water molecules make up six-coordination about the calcium, the anion planes stacking at the b spacing. The strontium adduct is also a one-dimensional polymer with a similar spine, but with water molecule oxygen atoms bridging, the nine-coordinate strontium environment being made up by a chelating nitro group and three unidentate water molecules. Coordinated anions stacked up a are interleaved by free anions. The barium salt is simply [Ba(4-np)(OH₂₎₈]⁺ (4-np^-), the ligand anion (semi)chelated through the nitro pair of oxygen atoms, again with interleaving anion/ligand stacking.