| abstract |
The diosmium diamide carbonyl complexes Os2(CO)6(RCONH)2(R = CH3, Ph) and the
acetamide polymer, [Os2(CO)4(CH3CONH)2]n were synthesized and investigated for their kinetic
and thermodynamic properties.
The Os2(CO)6(RCONH)2(R = CH3, Ph) monomers exist as two isomers in which the
amides coordinate in a head-to-tail and head-to-head configuration. The interconversion of the
isomers of Os2(CO)6(CH3CONH)2 was investigated by 1H NMR over a range of temperatures to
determine the thermodynamic parameters; ΔS + 6.14 J and ΔH — 1.65 J. The lack of exchange of
the coordinated amide with a free carboxylic acid in solution proved the mechanism was
intramolecular and the polymerization was more favorable than an exchange with the
coordinated amide.
The proposed acetamide polymer structure, [Os2(CO)4(CH3CONH)2]n, is bonded together
by a weak osmium oxygen bond. In the presence of carbon monoxide, the polymer converted
back to the monomer species as confirmed by IR. The analogous benzamide complex did not
polymerize. Additionally, prolonged heating of the Os2(CO)6(COOCH3)2 complex lead to a
polymer formation, which decomposed to the monomer species over time.
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