Synthesis of five-coordinate manganese(I) carbonyl complex [(CO) 3 Mn (-S,-Se-C 6 H 3 -4-Me)] − : influences of non-innocent ligand to the structure, reactivity and electrochemical property

Oxidative addition of Br 2 to [Mn(CO) 5 ] − leads to the formation of [(CO) 4 MnBr], followed by the ligand exchange of bromide to [S,Se-C 6 H 3 -4-Me] 2 2− to form complex (CO) 3 Mn ( µ - ŋ 4 -SC 6 H 3 -4-(CH 3 )Se-SeC 6 H 3 -4-(CH 3 )S)Mn(CO) 3 ( 1 ). A new five-coordinate complex [(CO) 3 Mn(-S,-Se-C 6 H 3 -4-CH 3 )] − ( 2 ) can be synthesized through two different routes: (a) oxidative addition of diselenide [HS,Se-C 6 H 3 -4-Me] 2 to the [Mn(CO) 5 ] − followed by deprotonation and ligand dissociation to generate complex 2 ; (b) reduction of diselenide bonds of complex 1 by [BH 4 ] − to produce 2 . Drop-wise addition of HBF 4 ·OEt 2 at 0 °C results in the formation of complex 1 . The X-ray analysis shows that complex 2 has relative short Mn–Se and Mn–S bond distances compare to the published structures of cis -[(CO) 4 Mn(EPh) 2 ] − (E = S and Se; Liaw et al. in J. Chin. Chem. Soc. 43:427–431, 1996 ; Liaw et al. in Inorg. Chem. 35:2530, 1996 ). Interestingly, exposure of the coordinated unsaturated complex 2 under CO (g) atmosphere resulted in complex cis -[(CO) 4 Mn(-S,-Se-C 6 H 3 -4-Me)] − ( 3 ) being formed. After purging the solution of complex 3 with N 2 , it was reconverted completely back to complex 2 ; this observation was characterized by FTIR. The cyclic voltammetry scan of complex 2 shows a quasi-reversible redox couple with E 1/2 = −1.94 V and I pa / I pc = 0.68. Ligand [HS, Se-C 6 H 3 -4-CH 3 ] 2 and complexes 1 and 2 are all characterized by IR, UV–Vis, NMR, EA and X-ray single crystal diffraction.