10.1021/ic070174i.s009 Rashmi Bagai Rashmi Bagai Khalil A. Abboud Khalil A. Abboud George Christou George Christou A New N,N,O Chelate for Transition Metal Chemistry:  Fe<sub>5</sub> and Fe<sub>6</sub> Clusters from the Use of 6-Hydroxymethyl-2,2‘-bipyridine (hmbpH) American Chemical Society 2007 ZFS Fe 5 O 2 5 ground state OH Fe 6 Clusters hmbpH O 2 CR Fe 6 O 2 H 2 O O atoms DC AC Fe atom 2007-07-09 00:00:00 Journal contribution https://acs.figshare.com/articles/journal_contribution/A_New_N_N_O_Chelate_for_Transition_Metal_Chemistry_Fe_sub_5_sub_and_Fe_sub_6_sub_Clusters_from_the_Use_of_6_Hydroxymethyl_2_2_bipyridine_hmbpH_/2997604 The initial use of the anion of 6-hydroxymethyl-2,2‘-bipyridine (hmbpH) as a chelate in coordination chemistry is described. The syntheses, crystal structures, and magnetochemical characterization are reported of four new iron(III) clusters [Fe<sub>5</sub>O<sub>2</sub>(OH)(O<sub>2</sub>CMe)<sub>5</sub>(hmbp)<sub>3</sub>](ClO<sub>4</sub>)<sub>2</sub> (<b>1</b>) and [Fe<sub>6</sub>O<sub>2</sub>(OH)<sub>2</sub>(O<sub>2</sub>CR)<sub>6</sub>(hmbp)<sub>4</sub>](NO<sub>3</sub>)<sub>2</sub> (R = Ph (<b>2</b>), Me (<b>3</b>), Bu<sup>t</sup> (<b>4</b>); hmbpH = 6-hydroxymethyl-2,2‘-bipyridine). The reaction of Fe(ClO<sub>4</sub>)<sub>3</sub>, hmbpH, and sodium acetate in a 1:1:∼4 ratio in EtOH gave <b>1</b>, and the reaction between [Fe<sub>3</sub>O(O<sub>2</sub>CR)<sub>6</sub>(H<sub>2</sub>O)<sub>3</sub>](NO<sub>3</sub>) (R = Ph, Me, Bu<sup>t</sup>) and hmbpH in a 1:1 ratio in MeCN gave <b>2</b>−<b>4</b>, respectively. The core of <b>1</b> consists of a [Fe<sub>4</sub>(μ<sub>3</sub>-O)<sub>2</sub>]<sup>8+</sup> butterfly unit to which is attached a fifth Fe atom by bridging O atoms. The core of <b>2</b>−<b>4</b> also consists of a [Fe<sub>4</sub>(μ<sub>3</sub>-O)<sub>2</sub>]<sup>8+</sup> butterfly unit to which are attached an Fe atom on either side by bridging O atoms. Variable-temperature (<i>T</i>) and -field (<i>H</i>) solid-state DC and AC magnetization (<i>M</i>) studies were carried out on complexes <b>1</b>−<b>4</b> in the 5.0−300 K range. Fitting of the data revealed that <b>1</b> has an <i>S</i> = 5/2 ground state spin whereas <b>2</b>−<b>4</b> possess an <i>S</i> = 5 ground state. Fitting of the <i>M</i>/<i>N</i>μ<sub>B</sub> vs <i>H</i>/<i>T</i> data by matrix diagonalization and including only axial zero-field splitting (ZFS) gave values of the axial ZFS parameter |<i>D</i>| of 0.75, 0.36, 0.46, and 0.36 cm<sup>-1</sup> for <b>1</b>−<b>4,</b> respectively.