The trivalent lanthanide metallocenes Cp 3Ln (Cp = C 5H 5, Ln = Dy or Yb) react with thiols, HSR (R = CH 2CH 2CH 3 or CH 2CH 2CH 2CH 3) to give the dimeric complexes [Cp 2Ln(μ-SR)] 2 (R = CH 2CH 2CH 3; Ln = Dy ( 1) or Yb ( 2)) (R = CH 2CH 2CH 2CH 3; Ln = Dy ( 3) or Yb ( 4)) in tetrahydrofuran at room temperature. They have been characterized by elemental analysis and mass spectroscopy or 1H NMR spectra, indicating that they are dimers bridged through the sulphide atoms of thiolate ligands. Crystals of 4 are monoclinic, of space group P2 1/a with a = 8.928(3), b = 17.620(7) and c = 9.208(4) A ̊ , β = 103.94(3)°, V = 1405.8(9) A ̊ 3 , Z = 2 and D c = 1.85 g cm 3. The structure was refined by the full-matrix least-squares method to a conventional R factor of 0.039, for 1868 data with I>3 σ( I). The Yb 2S 2 unit is planar, and the geometry about the ytterbium atom is pseudotetrahedral although the geometry is pyramid at sulfur so that the n-butyl groups are anti relative to the Yb 2b 2 ring. The average YC(Cp) and YbS bond distances are 2.59(1) and 2.708(3) Å respectively. It was found that these complexes are thermally unstable and tend to decompose into Cp 3Ln species upon heating.