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

Reactions between [Mn(CO)(5)Br] and dpkbh in low boiling solvents in air gave fac-[Mn-I(CO)(3)((2)-N-py,N-im-dpkbh)Br]H2O, [(MnBr2)-Br-II((3)-N-py,N-im,O-dpkbh)], and [Mn-II((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)((2)-N-py,N-im-dpkbh)Br]H2O from dmso or CH3CN produced dark red crystals of [Mn-II((3)-N-py,N-im,O-dpkbh-H)(2)]nX (X=dmso, n=1 and X=H2O, 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)((2)-,N-py,N-py-dpkbh)Cl] which can be crystallized from CH3CN, dmso or dmf to form fac-[Re-I(CO)(3)((2)-,N-py,N-py-dpkbh)Cl]nX (X=CH3CN, 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)((2)-N-py,N-im-dpkbh)Br]H2O and Mn(II) in [(MnBr2)-Br-II((3)-N-py,N-im,O-dpkbh)] plus enol coordination of the amide-deprotonated dpkbh, to the Mn(II) center in [Mn-II((3)-N-py,N-im,O-dpkbh-H)(2)]0.5H(2)O. Electronic absorption spectral measurements in non-aqueous solvents indicate sensitivity of fac-[Mn-I(CO)(3)((2)-N-py,N-im-dpkbh)Br]H2O and [Mn-II((3)-N-py,N-im,O-dpkbh-H)(2)]0.5H(2)O to changes in their outer-shell environments. X-ray crystallographic analyses elucidated the identities of [(MnBr2)-Br-II((3)-N-py,N-im,O-dpkbh)] and [Mn-II((3)-N-py,N-im,O-dpkbh-H)(2)]nX and divulged weaker coordination of [dpkbh] to Mn(II) in [(MnBr2)-Br-II((3)-N-py,N-im,O-dpkbh)] and stronger coordination of [dpkbh-H](-) to Mn(II) in [Mn-II((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((3)-N-py,N-im,O-dpkbh-H)(2)] and the short NH bond distance observed in the structure of [(MnBr2)-Br-II((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((3)-N-py,N-im,O-dpkbh-H)(2)].