Inorganic Chemistry, Vol.48, No.19, 9325-9335, 2009
Mn-4, Mn-6, and Mn-11 Clusters from the Use of Bulky Diphenyl(pyridine-2-yl)methanol
The synthesis, crystal structure, and magnetochemical characterization are reported of three new Mn clusters [Mn4O2(O2CBut)(5)(dphmp)(3)] (1), [Mn6O4(OMe)(2)(O2CPh)(4)(dphmP)(4)] (2), and [Mn11O7(OMe)(7)(O2CPh)(7)(dphmp)(4)(MeOH)(2)] (3). They were obtained from the use of diphenyl(pyridine-2-yl)methanol (dphmpH), a bulkier version of the 2-(hydroxymethyl)pyridine (hmpH) reagent commonly employed previously in Mn chemistry. The reaction of dphmpH with MnCl2 center dot 4H(2)O and NaO2CBut in MeCN/MeCH (30 mL, 5:1 v/v) led to the isolation of tetranuclear complex 1, whereas the analogous reaction with NaO2CPh gave hexanuclear complex 2. When the 5:1 solvent ratio in the latter reaction was changed to 1:29, the isolated product was now undecanuclear complex 3. Complexes 1-3 all possess rare or unprecedented Mn-x topologies: Complex 1 possesses a [Mn-4(mu(3)-O)(2)](8+) (4Mn(III)) butterfly core, one edge of which is additionally bridged by an alkoxide arm of a dphmp(-) chelate; complex 2 possesses a [Mn-6(mu(4)-O)(2)(mu(3)-O)(2)(mu(3)-OMe)(2)](8+) (6Mn(III)) core with a face-sharing double cubane topology; and complex 3 (Mn-II, 10Mn(III)) possesses a [Mn-4(mu(4)-O)(3)(mu(3)-OMe)](5+) cubane unit, attached on one side to a Mn-II atom by mu(4)-O atom and alkoxide groups, and on the other side to a [Mn-5(mu(4)-O)(mu(3)-O)(3)(mu(3)-OMe)(mu-OR)(3)](3+) unit consisting of three face-sharing defective cubanes linked to an additional Mn-III atom by a mu(3)-O atom. Solid-state dc and ac magnetic susceptibility measurements on 1-3 establish that they possess S = 0, 3, and 5/2 ground states, respectively. ac susceptibility studies on 2 and 3 reveal weak non-zero frequenc-dependent out-of-phase (chi(M)'') signals at temperatures below 3 K, possibly indicative of single-molecule magnets with very small barriers. The combined results demonstrate a ligating difference between bulky dphmp(-) and hmp(-), and the resulting usefulness of the former to provide access to a variety of Mn-x molecular species not known with the latter.