New access to homodinuclear half-sandwich vinylidenemanganese complexes

The d⁶ low-spin Mn¹ half-sandwich dinuclear complexes of the type [{Mn(MeC₅H₄)(R₂PCH ₂CH₂PR₂)=C=C(SnMe₃)}₂{X}] (X = {μ-1,4-C₆H₄}, R = Me, 2a; X = {μ-1,4-C ₆H₄}, R = Et, 2b; X = {μ-1,3-C₆H ₄}, R = Me, 3a; X = {μ-1,3-C₆H₄}, R = Et, 3b; X = {μ-4,4-C₆H₄-C₆H₄}, R = Me, 4a; X = {μ-4,4-C₆H₄-C₆H₄), R = Et, 4b; X = {μ-1,4-C₄H₂S}, R = Me, 5a, X = {μ-1,4-C₄H₂S}, R = Et, 5b) were obtained by the treatment of [Mn(C₅H₄Me) (η⁶- cycloheptatriene)] with 0.5 equiv. of the corresponding acetylene Me ₃Sn-C≡C-X-C≡C-SnMe₃ (X = {μ-1,4-C ₆H₄), {μ-1,3-C₆H₄}, {μ-4,4-C₆H₄-C₆H₄}, {μ-1,4-C₄H₂S}) and R₂PCH₂CH ₂PR₂ (R = Me, Et) at 50 °C for 12 h to yield the corresponding dinuclear complexes in very good yields. These dinuclear tin-substituted vinylidene complexes were further treated with an excess of MeOH to give the corresponding dinuclear parent vinylidene complexes of the type [{Mn(MeC₅H₄)(R₂PCH₂CH ₂PR₂)=C=C(H)}₂{X}] (X = (μ-1,4-C ₆H₄), R = Me, 6a; X = {μ-1,4-C₆H ₄), R = Et, 6b; X = {μ-1,3-C₆H₄}, R = Me, 7a; X = {μ-1,3-C₆H₄}, R = Et, 7b; X = {μ-4,4-C ₆H₄-C₆H₄), R = Me, 8a; X = {μ-4,4-C₆H₄-C₆H₄), R = Et, 8b). All dinuclear compounds were characterised by NMR and IR spectroscopy and elemental analysis. X-ray diffraction studies were performed on complexes 2b, 3a, 4a and 6a.