CpCo(dithiolene) complexes of highly flexible oxddt ligand with two different Z-shaped and U-shaped structures

[CpCo(oxddt)] complex (2, oxddt = o-xylenediyldithioethylene-1,2-dithiolate, Cp = η5-cyclopentadienyl) was obtained from o-xylenediyldithioethylene-1,3-dithiol-2-one (OC(oxddt)) (1). 2 further reacted with diazoalkanes (N2CHR) to form some alkylidene-bridged adducts [CpCo(CHR)(oxddt)] (R = H (3a), SiMe3 (3b)). Adduct 3a further reacted with protic acids (HX) to give some S-methylated adducts [CpCo(X)(oxddt)(S-Me)] (X = Cl (4a), OCOCF3 (4c)), followed by the Co–C bond cleavage in the three-membered cobaltathiirane ring. Two different Z-shaped and U-shaped molecular structures were observed by X-ray diffraction studies. In the former structure (Z), the dithiolene and o-xylylene planes are located at almost parallel position each other, and in the latter structure (U), both planes are not parallel but the o-xylylene moiety is located closer to the dithiolene plane than the Z-shaped one. The Z-shaped structure involves 1 and 2. The U-shaped structure involves 3a, 3b, 4a and 4c. Complex 1 showed a one-dimensional chain through intermolecular π–π interaction in the crystal. Complex 2 had a dimeric interaction between dithioethylenedithiolate moieties (S2C2S2) in the oxddt. The SiMe3 group in 3b was placed at an exo-position with respect to the cobaltadithiolene ring due to a steric hindrance from the U-shaped oxddt ligand. In 4a, the X and Me groups are located at the opposite side of the dithiolene plane (anti-form) but in 4c, both groups are presented at the same side of the dithiolene plane (syn-form). The NMR analysis of 4a in solution indicated existence of both anti- and syn-isomers (7:1).

Graphical abstract[CpCo(oxddt)] (2) was prepared from OC(oxddt) (1). The alkylidene-bridged adducts [CpCo(CHR)(oxddt)] (R = H (3a), SiMe3 (3b)) were derived from 2 and some S-methylated adducts [CpCo(X)(oxddt)(S-Me)] (X = Cl (4a), OCOCF3 (4c)) were obtained from 3a. Two different Z-shaped (for 1 and 2) and U-shaped (for 3 and 4) molecular structures were observed by X-ray diffraction studies.Figure optionsDownload full-size imageDownload as PowerPoint slide