
TY  - JOUR
A1  - Harrowfield, JM 
A1  - Skelton, BW 
A1  - White, AH 
T1  - Structural Studies of Alkaline Earth Metal Picrates
JF  - Australian Journal of Chemistry
JO  - Aust. J. Chem.
Y1  - 1995
VL  - 48
IS  - 7
SP  - 1333
EP  - 1347
KW  - 
UR  - https://doi.org/10.1071/CH9951333 
N2  - Room-temperature, single-crystal X-ray structure determinations are recorded for alkaline earth metal  picrates , M( pic )2.nH2O(M = Mg, Sr , Ba ; Hpic = 2,4,6-trinitrophenol, HOC6H2(NO2)3), all crystallized from aqueous solution. Magnesium picrate ,shown to be the nonahydrate,  Mg( pic )2.9H2O, forms monoclinic crystals, space group P21/c, a 15.023(3), b 6.718(4), c 26.516(2) &#506;, &#946; 109.55(1)&#176;, Z = 4 f.u .,conventional R on |F| was 0.049 for No = 4062 'observed' (I > 3&#963;(I)) reflections. The structure, unusually among the main group metal picrates  studied so far, has no coordinative interaction between the metal and the picrate anion; the complex may be formulated as [Mg(OH2)6] ( pic )2.3H2O, with the metal present as the hexaaqua species (Mg-O 2.043(2)-2.077(2)&#506;). The picrate ions are stacked end to end, presumably as a result of charge-transfer interactions, parallel to b, with side-by-side stacks forming a sheet along ab, and successive sheets are interleaved by layers of cations and water molecules. The strontium salt is a pentahydrate , monoclinic, C2/c, a 24.515(6), b 10.142(6), c 17.932(4) &#506;, &#946; 98.76(2)&#176;, Z = 8 f.u .; R was 0.046 for No 2731. The complex is a linear polymer, [(H2O)3Sr(O,O&#8242;- pic )2(&#956;-OH2)](&#8734;|&#8734;).H2O,  with eight-coordinate (SrO8) strontium. The barium salt is a hexahydrate , also a linear polymer [(H2O)5Ba(O,O&#8242;-pic )( O,O&#8242;,&#956;-O&#8243;-pic )]&#8734;|&#8734;).H2O, the ten-coordinate (BaO10) barium environment comprising the five water molecules, a pair of picrates, bidentate /chelating via the phenolic  oxygen and a 2-nitro group oxygen, with one of the picrates  from an adjacent metal atom offering an additional 4-nitro group oxygen, this bridging successive barium atoms. The complex is triclinic, P&#299; , a 15.120(5), b 11.633(3), c 6.766(3) &#506;, &#945; 87.24(3), &#946; 79.16(3), &#947; 84.88(2)&#176;, Z = 2 f.u .; R was 0.027 for No 3904. Repeated attempts to obtain crystals of beryllium picrate suitable for an X-ray structure determination were unsuccessful. 
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