Trithiocarbonate and dithiocarbonate complexes of η-cyclopentadienyl cobalt(III): X-ray crystal structure of [Co(η-C5H5)(CNBut)(CS3)]

Abstract

Complexes [Co(η-C₅H₅)L(CS₃)] have been prepared (a) by the thermal reaction of CS₂ with [Co-(η-C₅H₅)(CO)L], or [Co(η-C₅H₅)(CO)₂] and L (L = tertiary phosphine or organoisocyanide only), or (b) from [Co(η-C₅H₅)(L)I₂] and Na₂[CS₃] in dichloromethane solution (L = tertiary phosphine, phosphite, arsine, or organoisocyanide). A variant of (b), the reaction of Na[S₂COR](R = Me or Et) with [Co(η-C₅H₅)(L)I₂], has been used to prepare the dithiocarbonate complexes [Co(η-C₅H₅)(L)-(CS₂O)]. The i.r. and ¹H n.m.r. spectra of the complexes have been measured and are assigned. They are consistent with molecular structures in which the CS₂Y^2– ions (Y = O or S) chelate to cobalt via the two S atoms; this has been confirmed unambiguously for [Co(η-C₅H₅)(CNBu^t)(CS₃)] by an X-ray diffraction study which shows that the co-ordination about Co is of the well known pseudooctahedral, ‘piano-stool’ type. The structure was solved by the heavy-atom method and refined by least squares to R= 0.074 for 1 593 non-zero unique reflections. Crystals of the compound are monoclinic, space group P2₁/c, with a= 9.085(4), b= 12.386(5), c= 12.997(5)Å, and β= 107.7(1)° for Z= 4. The unco-ordinated S_u atoms of the CS₃ ligands are very basic and with electrophiles, E, form adducts containing S_u→ E bonds; Mel gives [Co(η-C₅H₅)(PBuⁿ₃)(S₂CS_uMe)]I and [Co(η-C₅H₅)I(S₂CS_uMe)], mercury(II) halides form [Co(η-C₅H₅)(PBuⁿ₃)(S₂CS_u·nHgX₂)](X= Cl, n= 2; X= Br or I, n= 1), and I₂ gives [Co(η-C₅H₅)(PPrⁿ₃)(S₂CS_uI)]I. The ν(C–S_u) vibrations of these adducts have lower frequencies, and their ν(C–S_c) vibrations (S_c is the co-ordinated S atom) have higher frequencies, than do their trithiocarbonate precursors. The dithiocarbonate complexes also form adducts with electrophiles but the unco-ordinated O atom, O_u, is only weakly basic. Consequently Mel fails but MeSO₃F is successful in forming the xanthate cation [Co(η-C₅H₅)(PMe₂Ph)(S₂CO_uMe)]⁺, and although [Co(η-C₅H₅)(PMe₂Ph)-(S₂CO_u·2HgX₂)] are obtained, their i.r. spectra give no clear guide as to their structure. With iodine, [Co(η-C₅H₅)(PMe₂Ph)I₂] is formed. The bonding between the cobalt atoms and the CS₂Y^2– ligands is discussed on the basis of the i.r. spectra of the complexes where Y = S, O, SMe⁺, or OMe⁺.