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 var ious synthetic procedures for the covalent linking of Mn carboxylate a ggregates into aggregates-of-aggregates and polymers-of-aggregates. Tr eatment of (NBun4) [Mn4O2(OAc)7(pic)2] (1) (picH = picolinic acid) wit h Me3SiCl leads to selective abstraction of the unique Jahn-Teller lab ilized AcO- and the dimerization of the resulting fragment to yield Mn 8O4(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 a n octanuclear complex analogous to 3 being prevented by steric repulsi ons. In addition, treatment of 3 with excess PhCOOH leads to clean con version to 5. The structure of 3 consists of two [Mn4O2(OAc)6(pic)2] f ragments held together by two interfragment Mn-O linkages involving pi c oxygen atoms formerly uncoordinated in 1. The structure of 5 is simi lar to 4; the seventh BzO- group is replaced by two MeCN groups. Cryst al data for 3 at -157-degrees-C: monoclinic, P2(1)/n, a = 11.276(5) an gstrom, 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-deg rees-C: monoclinic, C2/c, a = 22.312(4) angstrom, b = 21.725(3) angstr om, c = 12.657(2) angstrom, 90.81(1)degrees, Z = 4, V = 6134.69 angstr om3, R (R(w)) = 7.35% (6.86%) using 2964 unique data with F > 2.33sigm a(F).