The five-coordinate, sixteen-electron manganese(I) complex [N(PPh3)2][Mn(CO)3(S,S-C6H 4)] 1 was prepared from reaction of [N(PPh3)2][Mn(CO)3(NH,S-C6H 4)] and 1,2-benzenedithiol via the hexacoordinate intermediate fac-[Mn(CO)3(S-C6H4SH)(NH2,S-C 6H4)]-. Alternatively, oxidative addition of 1,2-benzenedithiol to [Mn(CO)5]-, followed by a Lewis acid-base reaction, with evolution of H2 gas (identified by gas chromatography), led to formation of the coordinatively-unsaturated complex 1. In contrast, reaction of bis(2-pyridyl) disulfide and [N(PPh3)2][Mn(CO)5] afforded hexacoordinate fac-[N(PPh3)2][Mn(CO)3(S-C5H 4-N)(S-C5H4N)] 2, with one anionic [S-C5H4N]- ligand bound to MnI in a monodentate (S-bonded) manner and the other [S-C5H4-N]- ligand bound in a bidentate manner (S,N-bonded). Complexes 1 and 2 have been characterized in solution by infrared spectroscopy and in the solid state by X-ray crystallography. The strong π-donating ability of the bidentate [S,S-C6H4]2- ligand stabilizes the unsaturated complex 1 which has short MnI-S bond lengths of 2.230(1) Å (average) as a result. The existence of one π and two σ bonds between the [Mn(CO)3]+ and [S,S-C6H4]2- fragments, based on qualitative frontier molecular orbital analysis, also indicates that the lone-pair electrons are delocalized around the sulfur-manganese-sulfur system stabilizing the five-coordinate complex 1. The IR carbonyl stretching frequencies and the MnI-S bond distances of complexes 1 and [N(PPh3)2][Mn(CO)3(NH,S-C6H 4)] suggest that the relative π-donating ability of the bidentate ligands is [NH,S-C6H4]2- > [S,S-C6H4]2-. The Mulliken atomic charges derived from Hartree-Fock calculations roughly quantify the charge distribution in the complex [Mn(CO)3(NH,S-C6H4)]- (δ(N) = -1.14; δ(S) = -0.43; δ(Mn) = 1.14), and supports the premise that the reactions of [Mn(CO)3(NH,S-C6H4)]- with electrophiles (1,2-benzenedithiol, thiophene-2-thiol, 1,2-ethanedithiol) occur at the more electron-rich amide site, yielding charge-controlled, collision complexes.
|Number of pages||6|
|Journal||Journal of the Chemical Society - Dalton Transactions|
|Publication status||Published - 1999 Jul 21|
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