Cyano-Bridged Fe<sup>III</sup><sub>2</sub>Cu<sup>II</sup><sub>3</sub> and Fe<sup>III</sup><sub>4</sub>Ni<sup>II</sup><sub>4</sub> Complexes:  Syntheses, Structures, and Magnetic Properties

Two tricyanometallate precursors, (Bu<sub>4</sub>N)[(Tp<sup>4Bo</sup>)Fe(CN)<sub>3</sub>]·H<sub>2</sub>O·2MeCN (<b>1</b>) and (Bu<sub>4</sub>N)[(pzTp)Fe(CN)<sub>3</sub>] (<b>2</b>) [Bu<sub>4</sub>N<sup>+</sup> = tetrabutylammonium cation; Tp<sup>4Bo</sup> = tris(indazolyl)hydroborate; pzTp = tetrakis(pyrazolyl)borate], with a low-spin Fe<sup>III</sup> center have been synthesized and characterized. The reactions of <b>1</b> or <b>2</b> with [Cu(Me<sub>3</sub>tacn)(H<sub>2</sub>O)<sub>2</sub>](ClO<sub>4</sub>)<sub>2</sub> (Me<sub>3</sub>tacn = <i>N</i>,<i>N</i>‘,<i>N</i>‘ ‘-trimethyl-1,4,7-triazacyclononane) afford two pentanuclear cyano-bridged clusters, [(Tp<sup>4Bo</sup>)<sub>2</sub>(Me<sub>3</sub>tacn)<sub>3</sub>Cu<sub>3</sub>Fe<sub>2</sub>(CN)<sub>6</sub>](ClO<sub>4</sub>)<sub>4</sub>·5H<sub>2</sub>O (<b>3</b>) and [(pzTp)<sub>2</sub>(Me<sub>3</sub>tacn)<sub>3</sub>Cu<sub>3</sub>Fe<sub>2</sub>(CN)<sub>6</sub>](ClO<sub>4</sub>)<sub>4</sub>·4H<sub>2</sub>O (<b>4</b>), respectively. Assembly reactions between <b>2</b> and [Ni(phen)(CH<sub>3</sub>OH)<sub>4</sub>](ClO<sub>4</sub>)<sub>2</sub> (phen = 1,10-phenanthroline) or Zn(OAc)<sub>2</sub>·2H<sub>2</sub>O afford a molecular box [(pzTp)<sub>4</sub>(phen)<sub>4</sub>Ni<sub>4</sub>Fe<sub>4</sub>(CH<sub>3</sub>OH)<sub>4</sub>(CN)<sub>12</sub>](ClO<sub>4</sub>)<sub>4</sub>·4H<sub>2</sub>O (<b>5</b>) and a rectangular cluster [(pzTp)<sub>2</sub>Zn<sub>2</sub>Fe<sub>2</sub>(OAc)<sub>2</sub>(H<sub>2</sub>O)<sub>2</sub>(CN)<sub>6</sub>] (<b>6</b>). Their molecular structures were determined by single-crystal X-ray diffraction. In complexes <b>1</b> and <b>2</b>, the central Fe<sup>III</sup> ions are coordinated by three cyanide carbon atoms and three nitrogen atoms of Tp<sup>4Bo-</sup> or pzTp<sup>-</sup>. Both complexes <b>3</b> and <b>4</b> show a trigonal-bipyramidal geometry, in which [(L)Fe(CN)<sub>3</sub>]<sup>-</sup> units occupy the apical positions and are linked through cyanide to [Cu(Me<sub>3</sub>tacn)]<sup>2+</sup> units situated in the equatorial plane. Complex <b>5</b> possesses a cubic arrangement of eight metal irons linked through edge-spanning cyanide bridges, while complex <b>6</b> shows Zn<sub>2</sub>Fe<sub>2</sub>(CN)<sub>4</sub> rectangular structure, in which Fe<sup>III</sup> and Zn<sup>II</sup> ions are alternately bridged by the cyanide groups. Intramolecular ferromagnetic couplings are observed for complexes <b>3</b>−<b>5</b>, and they have <i>S</i> = <sup>5</sup>/<sub>2</sub>, <sup>5</sup>/<sub>2</sub>, and 6 ground states and appreciable magnetic anisotropies with negative <i>D</i> values equal to −0.49, −2.39, and −0.39 cm<sup>-1</sup>, respectively.