Complexes with Hydrazides
Complexes of composition MnLnX2 with hydrazides of monocarboxylic acids, RC(O)NHNH2 (= L) are prepared in alcoholic and aqueous alcoholic solution. The IR and Raman spectra of the compounds were interpreted mostly in terms of bidentate ligation of the, hy
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Complexes with Hydrazides
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Complexes with Hydrazides
General. Complexes of composition MnL nX2 with hydrazides of monocarboxylic acids, RC(O)NHNH 2 (= L) are prepared in alcoholic and aqueous alcoholic solution. The IR and Raman spectra of the compounds were interpreted mostly in terms of bidentate ligation of the hydrazide ligands to Mn through the carbonyl oxygen atom and the nitrogen atom of the terminal NH 2 group, forming a five-membered metallocycle. This was confirmed by X-ray studies, as reported for the isothiocyanato complexes with aceto- (pp. 169/70) and benzohydrazide (pp. 175/6), and for the chloro complex with 2-pyridinecarbohydrazide (pp. 186/7). The magnetic moments of the MnL nX2 compounds are indicative of high-spin octahedral manganese(lI) complexes, which are often polymeric. A complex with isonicotinohydrazide, [Mn(N03)2C6H7N30(H20)) (pp. 190/1), contains sevencoordinate manganese(lI) in a slightlY distorted pentagonal bipyramidal environment. In this case the organic ligand is bonded to Mn through the carbonyl oxygen, the nitrogen of the NH 2 group, and the pyridine ring nitrogen. The H20 molecule and one of the N03' groups are bonded to Mn through one oxygen whereas the other N03' group is coordinated as a bidentate ligand through two oxygens. Another complex with isonicotinohydrazide, the cation [Mn 2(C 6H7NPhCI(HPhP+, contains two independent manganese atoms each in octahedral environment. Two of the organic ligands are bridging tridentate; they are coordinated to one Mn atom through the terminal amine nitrogen and carbonyl oxygen and to a second metal atom through the pyridine nitrogen. The third ligand is bidentate and coordinated only through the carbohydrazide nitrogen and oxygen. Hydrazides of the type RC(O)-NH-NH-C(O)R, e.g., diformyl-, diacetyl-, or dibenzoylhydrazine (= H2L), form Mn(H 2LhX 2' n H20 complexes (type 1) in neutral or weakly acid solutions. The ligand molecules are coordinated by the carbonyl oxygens and the nitrogens of the NH 2 groups. In weakly alkaline solutions (pH-8 to 10) MnL·nH 20 complexes (type II), containing the doubly deprotonated tautomeric form of the ligands RC(O-)=N-N=C(O-)R, which are tetradentate bridging, are formed. Coordination to Mn through both carbonyl oxygens and both nitrogens of the NH 2 groups was shown for the complex with malonodihydrazide, Mn(C3HsN402)CI2' 2 H20; see p.201. X-ray studies revealed the existence of two modifications. The chief difference between the a- and the (3-forms of the chloro complex is caused by the way in which the Mn atoms are linked by the ligand molecules to give chains in the a-form and networks in the (3-form. The complexes with hydrazides are of interest because of their biological activity.
25.1 25.1.1
With Hydrazides of Monocarboxylic Acids With Formohydrazide HC(O)NHNH 2 (= CH 4NP)
Mn(CH4N20)nX2' Complexes with n = 3 for X = N0 3, CI, or S04/2 and n = 2 for X = CI, S04/2, and NCS were prepared by reaction of the manganese(lI) salt with the appropriate amount of formohydrazide in ethanol or aq
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