Investigations on Novel Tandem Reaction of Three Components, [η⁵-RC₅H₄(CO)₂Mo]₂, Ph₂Te₂, and Cp₂TiCl₂, Cp₂ZrCl₂, or Cp₂ZrBr₂. Synthesis and Structural Characterization of Tetrakis- and Bis-Bridged Dimolybdenum Complexes (η⁵-RC₅H₄Mo)₂(μ-PhTe)₄ (R = MeCO, MeO₂C, EtO₂C), (η⁵-RC₅H₄Mo)₂(μ-Cl)(μ-PhTe)₃ (R = MeCO, MeO₂C, EtO₂C), (η⁵-RC₅H₄Mo)₂(μ-Br)(μ-PhTe)₃ (R = MeO₂C, EtO₂C), and [η⁵-RC₅H₄(CO)₂Mo]₂(μ-PhTe)₂ (R = MeO₂C, EtO₂C)

While reaction of triply bonded dimers [η⁵-RC₅H₄(CO)₂Mo]₂ (R = MeCO, MeO₂C) with Ph₂Te₂ in xylene at 110 °C and subsequent treatment with Cp₂TiCl₂ at reflux gives novel tetrakis-bridged complexes (η⁵-RC₅H₄Mo)₂(μ-PhTe)₄ (1, R = MeCO; 3, R = MeO₂C) and (η⁵-RC₅H₄Mo)₂(μ-Cl)(μ-PhTe)₃ (2a,b, R = MeCO; 4a,b, R = MeO₂C), the dimers [η⁵-RC₅H₄(CO)₂Mo]₂ (R = MeO₂C, EtO₂C) reacted with Ph₂Te₂ and Cp₂ZrCl₂ or Cp₂ZrBr₂ under similar conditions to afford novel tetrakis-bridged complexes (η⁵-RC₅H₄Mo)₂(μ-PhTe)₄ (3, R = MeO₂C; 5, R = EtO₂C), (η⁵-RC₅H₄Mo)₂(μ-Cl)(μ-PhTe)₃ (4a,b, R = MeO₂C; 6a,b, R = EtO₂C), and (η⁵-RC₅H₄Mo)₂(μ-Br)(μ-PhTe)₃ (7a,b, R = MeO₂C; 8a,b, R = EtO₂C). A possible pathway for production of such tetrakis-bridged complexes has been suggested primarily on the basis of the following facts:  (i) Treatment of triply bonded dimers [η⁵-RC₅H₄(CO)₂Mo]₂ (R = MeO₂C, EtO₂C) with Ph₂Te₂ in xylene at 110 °C produces bis-bridged complexes [η⁵-RC₅H₄(CO)₂Mo]₂(μ-PhTe)₂ (9, R = MeO₂C; 10, R = EtO₂C) and (ii) reaction of 9 with Cp₂MCl₂ (M = Ti, Zr) yields tetrakis-bridged complexes 3 and 4a,b. All the new products 1−10 are fully characterized by elemental analysis and IR, ¹H, and ¹²⁵Te NMR spectroscopies, and 4b and 9 by single-crystal X-ray diffraction techniques.