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)₅Br] with dpkbh

Abstract

To cite this article: Mohammed Bakir & Rebecca Conry (2016): Synthesis, spectroscopic and Xray crystallographic properties of manganese compounds of keto-and enol-coordinated di-2-pyridyl ketone benzoyl hydrazone (dpkbh). Reactions of [Mn(CO) 5 Br] with dpkbh, Journal of Coordination Chemistry, ABSTRACT Reactions between [Mn(CO) 5 Br] and dpkbh in low boiling solvents in air gave fac-[Mn I (CO) 3 (κ 2 -N py ,N im -dpkbh)Br]·H 2 O, [Mn II Br 2 (κ 3 -N py ,N im ,O-dpkbh)], and [Mn II (κ 3 -N py ,N im ,O-dpkbh-H) 2 ]·0.5H 2 O (N im = imine nitrogen and N py = pyridyl nitrogen). Crystallization of fac-[Mn I (CO) 3 (κ 2 -N py ,N im -dpkbh) Br]·H 2 O from dmso or CH 3 CN produced dark red crystals of [Mn II (κ 3 -N py ,N im ,Odpkbh-H) 2 ]·nX (X = dmso, n = 1 and X = H 2 O, n = 0.22). This is in contrast to the reaction of [Re(CO) 5 Cl] with dpkbh in refluxing toluene to form fac-[Re I (CO) 3 (κ 2 -,N py ,N py -dpkbh)Cl] which can be crystallized from CH 3 CN, dmso or dmf to form fac-[Re I (CO) 3 (κ 2 -,N py ,N py -dpkbh)Cl]·nX (X = CH 3 CN, n = 0 and solvate = dmso or dmf, n = 1). Infrared spectral measurements are consistent with keto coordination of dpkbh to Mn(I) in fac-[Mn I (CO) 3 (κ 2 -N py ,N im -dpkbh) Br]·H 2 O and Mn(II) in [Mn II Br 2 (κ 3 -N py ,N im ,O-dpkbh)] plus enol coordination of the amide-deprotonated dpkbh, to the Mn(II) center in [Mn II (κ 3 -N py ,N im ,Odpkbh-H) 2 ]·0.5H 2 O. Electronic absorption spectral measurements in nonaqueous solvents indicate sensitivity of fac-[Mn I (CO) 3 (κ 2 -N py ,N im -dpkbh) Br]·H 2 O and [Mn II (κ 3 -N py ,N im ,O-dpkbh-H) 2 ]·0.5H 2 O to changes in their outershell environments. X-ray crystallographic analyses elucidated the identities of [Mn II Br 2 (κ 3 -N py ,N im ,O-dpkbh)] and [Mn II (κ 3 -N py ,N im ,O-dpkbh-H) 2 ]·nX and divulged weaker coordination of [dpkbh] to Mn(II) in [Mn II Br 2 (κ 3 -N py ,N im ,Odpkbh)] and stronger coordination of [dpkbh-H] − to Mn(II) in [Mn II (κ 3 -N py ,N im ,O-dpkbh-H) 2 ]·0.22H 2 O. Low-temperature X-ray structural analyses were employed to account for the disorder in the structure of [Mn II (κ 3 -N py ,N im ,O-dpkbh-H) 2 ] and the short NH bond distance observed in the structure of [Mn II Br 2 (κ 3 -N py ,N im ,O-dpkbh)]. A PLATON SQUEEZE treatment was invoked to account for the fractional occupancy of lattice water in the structure of [Mn II (κ 3 -N py ,N im ,O-dpkbh-H) 2 ]. ARTICLE HISTORY

Observation of Proton Transfer Coupled Spin Transition and Trapping of Photoinduced Metastable Proton Transfer State in an Fe(II) Complex

“…Hydrazone derivatives have been used to develop various functional molecules in which proton dynamics such as proton relay are observed. − In addition, Fe­(II) complexes with NNO-type hydrazone ligand exhibit spin transition. − We designed an Fe­(II) complex with a ligand of N ′-(di­(pyridin-2-yl)­methylene)-benzohydrazide (HL) derivative, where the HL possesses a hydrazone group and a pyridine ring (Figure (a)). The HL can form an intramolecular hydrogen bond between the N site in the pyridine ring (Py-N) and the N site in the hydrazone moiety (Hyd-N) even while forming a metal complex (Figure (a)). − The Py-N and Hyd-N–H in hydrazone can act as proton acceptor and proton donor sites, respectively. Furthermore, the ligand field of HL on an Fe­(II) ion is within the spin-transition region.…”