Synthesis, spectroscopic and X-ray crystallographic properties of manganese compounds of keto- and enol-coordinated di-2-pyridyl ketone benzoyl hydrazone (dpkbh). Reactions of [Mn(CO)<sub>5</sub>Br] with dpkbh
Creators: name: Bakir, Mohammed
name: Conry, Rebecca
Publisher: name: Taylor & Francis
Year: 2016
Subjects: subject: Biochemistry
subject: 29999 Physical Sciences not elsewhere classified
subject: FOS: Physical sciences
subject: FOS: Physical sciences
subject: Molecular Biology
subject: 59999 Environmental Sciences not elsewhere classified
subject: FOS: Earth and related environmental sciences
subject: FOS: Earth and related environmental sciences
subject: 39999 Chemical Sciences not elsewhere classified
subject: FOS: Chemical sciences
subject: FOS: Chemical sciences
subject: Science Policy
subject: Developmental Biology

description: Reactions between [Mn(CO)<sub>5</sub>Br] and dpkbh in low boiling solvents in air gave <i>fac</i>-[Mn<sup>I</sup>(CO)<sub>3</sub>(κ<sup>2</sup>-N<sub>py</sub>,N<sub>im</sub>-dpkbh)Br]·H<sub>2</sub>O, [Mn<sup>II</sup>Br<sub>2</sub>(κ<sup>3</sup>-N<sub>py</sub>,N<sub>im</sub>,O-dpkbh)], and [Mn<sup>II</sup>(κ<sup>3</sup>-N<sub>py</sub>,N<sub>im</sub>,O-dpkbh-H)<sub>2</sub>]·0.5H<sub>2</sub>O (N<sub>im</sub> = imine nitrogen and N<sub>py</sub> = pyridyl nitrogen). Crystallization of <i>fac</i>-[Mn<sup>I</sup>(CO)<sub>3</sub>(κ<sup>2</sup>-N<sub>py</sub>,N<sub>im</sub>-dpkbh)Br]·H<sub>2</sub>O from dmso or CH<sub>3</sub>CN produced dark red crystals of [Mn<sup>II</sup>(κ<sup>3</sup>-N<sub>py</sub>,N<sub>im</sub>,O-dpkbh-H)<sub>2</sub>]·nX (X = dmso, n = 1 and X = H<sub>2</sub>O, n = 0.22). This is in contrast to the reaction of [Re(CO)<sub>5</sub>Cl] with dpkbh in refluxing toluene to form <i>fac</i>-[Re<sup>I</sup>(CO)<sub>3</sub>(κ<sup>2</sup>-,N<sub>py</sub>,N<sub>py</sub>-dpkbh)Cl] which can be crystallized from CH<sub>3</sub>CN, dmso or dmf to form <i>fac</i>-[Re<sup>I</sup>(CO)<sub>3</sub>(κ<sup>2</sup>-,N<sub>py</sub>,N<sub>py</sub>-dpkbh)Cl]·nX (X = CH<sub>3</sub>CN, n = 0 and solvate = dmso or dmf, n = 1). Infrared spectral measurements are consistent with keto coordination of dpkbh to Mn(I) in <i>fac</i>-[Mn<sup>I</sup>(CO)<sub>3</sub>(κ<sup>2</sup>-N<sub>py</sub>,N<sub>im</sub>-dpkbh)Br]·H<sub>2</sub>O and Mn(II) in [Mn<sup>II</sup>Br<sub>2</sub>(κ<sup>3</sup>-N<sub>py</sub>,N<sub>im</sub>,O-dpkbh)] plus enol coordination of the amide-deprotonated dpkbh, to the Mn(II) center in [Mn<sup>II</sup>(κ<sup>3</sup>-N<sub>py</sub>,N<sub>im</sub>,O-dpkbh-H)<sub>2</sub>]·0.5H<sub>2</sub>O. Electronic absorption spectral measurements in non-aqueous solvents indicate sensitivity of <i>fac</i>-[Mn<sup>I</sup>(CO)<sub>3</sub>(κ<sup>2</sup>-N<sub>py</sub>,N<sub>im</sub>-dpkbh)Br]·H<sub>2</sub>O and [Mn<sup>II</sup>(κ<sup>3</sup>-N<sub>py</sub>,N<sub>im</sub>,O-dpkbh-H)<sub>2</sub>]·0.5H<sub>2</sub>O to changes in their outer-shell environments. X-ray crystallographic analyses elucidated the identities of [Mn<sup>II</sup>Br<sub>2</sub>(κ<sup>3</sup>-N<sub>py</sub>,N<sub>im</sub>,O-dpkbh)] and [Mn<sup>II</sup>(κ<sup>3</sup>-N<sub>py</sub>,N<sub>im</sub>,O-dpkbh-H)<sub>2</sub>]·nX and divulged weaker coordination of [dpkbh] to Mn(II) in [Mn<sup>II</sup>Br<sub>2</sub>(κ<sup>3</sup>-N<sub>py</sub>,N<sub>im</sub>,O-dpkbh)] and stronger coordination of [dpkbh-H]<sup>−</sup> to Mn(II) in [Mn<sup>II</sup>(κ<sup>3</sup>-N<sub>py</sub>,N<sub>im</sub>,O-dpkbh-H)<sub>2</sub>]·0.22H<sub>2</sub>O. Low-temperature X-ray structural analyses were employed to account for the disorder in the structure of [Mn<sup>II</sup>(κ<sup>3</sup>-N<sub>py</sub>,N<sub>im</sub>,O-dpkbh-H)<sub>2</sub>] and the short NH bond distance observed in the structure of [Mn<sup>II</sup>Br<sub>2</sub>(κ<sup>3</sup>-N<sub>py</sub>,N<sub>im</sub>,O-dpkbh)]. A <i>PLATON</i> Squeeze treatment was invoked to account for the fractional occupancy of lattice water in the structure of [Mn<sup>II</sup>(κ<sup>3</sup>-N<sub>py</sub>,N<sub>im</sub>,O-dpkbh-H)<sub>2</sub>].