Synthesis, spectroscopic, and X-ray crystallographic analysis of manganese compounds of di-2-pyridyl ketone thiophene-2-carboxylic acid hydrazone (dpktch): The reaction of Mn(CO) 5Br with dpktch

• Published in: Journal of molecular structure Vol. 967; no. 1; pp. 174 - 182
• Main Authors: Bakir, Mohammed, Green, Orville, Wilmot-Singh, Marvadeen
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-04-2010
• Subjects: Di-2-pyridyl ketone thiophene-2-carboxylic hydrazone; Manganese; Spectroscopy; Synthesis; X-ray crystallography; Di-2-pyridyl ketone thiophene-2-carboxylic hydrazone; X-ray crystallography; Spectroscopy; Synthesis; Manganese
• ISSN: 0022-2860; 1872-8014
• DOI: 10.1016/j.molstruc.2010.01.005

The ultrasonic radiation of a mixture of [Mn(CO)
5Br], di-2-pyridyl ketone thiophene-2-carboxylic acid hydrazone (dpktch) and diethyl ether in air gave
fac-[Mn(CO)
3(η
2-N,N-dpktch)Br]. Under refluxing conditions [MnBr
2(η
3-N,N,O-dpktch)] and [Mn(η
3-N,N,O-dpktch-H)
2] were isolated from a mixture of Mn(CO)
5Br, dpktch, and CH
3CN. The infrared spectra of the isolated compounds divulge the facial coordination of the carbonyl (C
O) groups in
fac-[Mn(CO)
3(η
2-N,N-dpktch)Br], the absence of the carbonyl (C
O) groups in [MnBr
2(η
3-N,N,O-dpktch)] and [Mn(η
3-N,N,O-dpktch-H)
2], and the coordination of dpktch/dpktch-H. The electronic absorption spectra of the isolated compounds show two intra-ligand charge transfer (ILCT) transitions that are sensitive to changes in their surroundings. The interconversion between
fac-[Mn(CO)
3(η
2-N,N-dpktch)Br] and its conjugate base
fac-[Mn(CO)
3(η
2-N,N-dpktch-H)Br] in protophilic solvents was demonstrated using stoichiometric amounts of an acid or a base. Acids or bases in concentrations as low as 1.00
×
10
−6
M can be detected and determined using protophilic solutions of
fac-[Mn(CO)
3(η
2-N,N-dpktch)Br]. X-ray crystallographic analysis done on crystals of [MnBr
2(η
3-N,N,O-dpktch)] and [Mn(η
3-N,N,O-dpktch-H)
2] confirmed their identity and show tetragonal (square pyramidal) coordination about manganese in [MnBr
2(η
3-N,N,O-dpktch)] and octahedral coordination about manganese in [Mn(η
3-N,N,O-dpktch-H)
2]. The extended structures of [MnBr
2(η
3-N,N,O-dpktch)] and [Mn(η
3-N,N,O-dpktch-H)
2] revealed digitated units of [MnBr
2(η
3-N,N,O-dpktch)], and anti-parallel stacks of [Mn(η
3-N,N,O-dpktch-H)
2] locked via a network of hydrogen bonds. Analysis of solvent accessible areas in the solid state of [MnBr
2(η
3-N,N,O-dpktch)] and [Mn(η
3-N,N,O-dpktch-H)
2] show the unit cell of the former to be void free while the latter to contain several voids.