Organosulphur–transition-metal chemistry. Part 2. Reactions of isothiocyanates with metal carbonyl anions: crystal and molecular structure of di-µ-N-methylimino(methylthio)methanethiolato-bis(tricarbonylmanganese)

Abstract

Treatment of Na[Mn(CO)₅] with RNCS (R = Me or Ph) provides dithiocarbamato-complexes [Mn(CO)₄-{S₂CN(H)R}] and [Mn(CO)₃(CNR){S₂CN(H)R}] as a result of sulphur incorporation, the former complex being readily converted into the latter with RNC. Addition of Mel subsequent to MeNCS diverts the reaction to yield the title complex [Mn₂(CO)₆{µ-SC(SMe)(NMe)}₂] predominantly, with small amounts of [Mn(CO)₄(S₂CSMe)] and [Mn(CO)₄{S₂CN(H)Me}]. Reaction of [N(PPh₃)₂][Mn(CO)₅] with MeNCS produces the same monomanganese complexes as the sodium salt, but also a trimer (MeNCS)₃ when Mel is added. This trimer is formed in the reaction of [N(PPh₃)₂][Mo(CO)₃(η-C₅H₅)] with MeNCS, co-products being [Mo(CO)₂(S₂CSMe)(η-C₅H₅)] and [Mo(CO)₂{S₂CN(H)Me}(η-C₅H₅)], while Na[Mo(CO)₃(η-C₅H₅)] yields only the trithiocarbonate. The sodium salt of [Re(CO)₅]^– treated with MeNCS and then Mel behaves similarly to manganese, affording low yields of [Re(CO)₄{S₂CN(H)Me}], [Re(CO)₃(NCMe){S₂CN(H)Me}], and [Rel(CO)₄(CNMe)]. A scheme is proposed to account for the various products of the [Mn(CO)₅]^––MeNCS–Mel system, features of which are applicable to other anions. Crystals of [Mn₂(CO)₆{µ-SC(SMe)(NMe)}₂] are monoclinic, space group P2₁/n with Z= 4 in a unit cell of dimensions a= 9.845(2), b= 13.791(4), c= 14.972(5)Å, and β= 98.23(4)°. Atoms have been located by a combination of direct methods (Mn) and successive difference-Fourier syntheses (S, O, N, C, and H) from diffractometer data, and refined to R 0.029 for 3 239 independent reflections. There are two octahedrally co-ordinated manganese atoms joined by sulphur bridges; the four-atom ring so produced carries, on opposite edges, two further four-membered [graphic omitted]Me rings in a cis orientation to one another. Each of the three rings is planar and the molecule as a whole has C₂ symmetry (not required crystallographically). Within the bridge system, Mn–S is 2.41–2.43 Å and the Mn ⋯ Mn distance (3.23 Å) is non-bonding.