In Situ Synthesis of Trisubstituted Methanol Ligands and Their Potential as One‐Pot Generators of Cubane‐like Metal Complexes

Two different one pot routes to a variety of metal cubane compounds are reported; one route is based on an in situ benzilic acid type rearrangement and the other involves in situ nucleophilic attack at a ketone. Diketosuccinic acid in basic solution in the presence of certain divalent metal ions undergoes a benzilic acid type rearrangement to generate the carbon oxyanion, C(CO 2 − ) 3 O − , which serves as a cubane‐forming bridging ligand in a series of octanuclear complexes of composition [M 8 {C(CO 2 ) 3 O} 4 ](H 2 O) 12 (M=Mg, Mn, Fe, Co, Ni, Zn). At the heart of each of these highly symmetrical aggregates is an M 4 O 4 cubane core, each oxygen component of which is provided by the alkoxo centre of a C(CO 2 − ) 3 O − ligand. Reaction of 2,2′‐pyridil, (2‐C 5 H 4 N)COCO(2‐C 5 H 4 N), and calcium nitrate in basic alcoholic solution, which proceeds by a similar benzilic acid type rearrangement, gives the cubane compounds, [Ca 4 L 4 (NO 3 ) 4 ] in which L=(2‐C 5 H 4 N) 2 C(COOR)O − (R=Me or Et). Nucleophilic attack by bisulfite ion at the carbonyl carbon atom of 2,2′‐dipyridyl ketone in the presence of certain divalent metals generates the electrically neutral complexes, [{(C 5 H 4 N) 2 SO 3 C(OH)} 2 M] (M=Mn, Fe, Co, Ni, Zn and Cd). Cubane‐like complexes [M 4 {(C 5 H 4 N) 2 SO 3 C(O)} 4 ] (M=Zn, Mn) can be obtained directly from 2,2′‐dipyridyl ketone in one‐pot reaction systems (sealed tube, 120 °C) if a base as weak as acetate ion is present to deprotonate the OH group of the initial [(C 5 H 4 N) 2 SO 3 C(OH)] − bisulfite addition compound; the [(C 5 H 4 N) 2 SO 3 C(O)] 2− ligand in this case plays the same cubane‐forming role as the ligands C(COO − ) 3 O − and (2‐C 5 H 4 N) 2 C(COOR)O − above. When excess sodium sulfite is used in similar one‐pot reaction mixtures, the monoanionic complexes, [M 3 Na{(C 5 H 4 N) 2 SO 3 C(O)} 4 ] − (M=Zn, Mn, Co) with an M 3 NaO 4 cubane core, are formed directly from 2,2′‐dipyridyl ketone.