CONTROLLED AGGREGATION AND DEAGGREGATION OF A POLYNUCLEAR OXIDO-BRIDGED MANGANESE COMPLEX - UTILITY TO SYNTHESIS OF THE JAHN-TELLER EFFECT IN HIGH-SPIN MANGANESE(III)

Initial results are described in a new program designed to develop various synthetic procedures for the covalent linking of Mn carboxylate aggregates into aggregates-of-aggregates and polymers-of-aggregates. Treatment of (NBun4) [Mn4O2(OAc)7(pic)2] (1) (picH = picolinic acid) with Me3SiCl leads to selective abstraction of the unique Jahn-Teller labilized AcO- and the dimerization of the resulting fragment to yield Mn8O4(OAc)12(pic)4 (3). A similar reaction employing (NBu(n)4)[Mn4O2(OBz)7(pic)2] (4) yields [Mn4O2(OBz)6(pic)2(MeCN)2] (5), dimerization to an octanuclear complex analogous to 3 being prevented by steric repulsions. In addition, treatment of 3 with excess PhCOOH leads to clean conversion to 5. The structure of 3 consists of two [Mn4O2(OAc)6(pic)2] fragments held together by two interfragment Mn-O linkages involving pic oxygen atoms formerly uncoordinated in 1. The structure of 5 is similar to 4; the seventh BzO- group is replaced by two MeCN groups. Crystal data for 3 at -157-degrees-C: monoclinic, P2(1)/n, a = 11.276(5) angstrom, b = 26.159(11) angstrom, c = 11.671(5) angstrom, beta = 93.11(2)degrees, Z = 2, V = 3437.39 angstrom3, R(R(w)) = 8.71% (8.28%) using 1364 unique data with F > 3.0sigma(F). Crystal data for 5 at -173-degrees-C: monoclinic, C2/c, a = 22.312(4) angstrom, b = 21.725(3) angstrom, c = 12.657(2) angstrom, 90.81(1)degrees, Z = 4, V = 6134.69 angstrom3, R (R(w)) = 7.35% (6.86%) using 2964 unique data with F > 2.33sigma(F).