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)(μPhTe)3 (R = MeO2C, EtO2C), and [η5-RC5H4(CO)2Mo]2(μ-PhTe)2 (R = MeO2C, EtO2C)

While reaction of triply bonded dimers [eta(5)-RC5H4(CO)(2)Mo](2) (R = MeCO, MeO2C) with Ph-2-Te-2 in xylene at 110 degrees C and subsequent treatment with Cp2TiCl2 at reflux gives novel tetrakis-bridged complexes (eta(5)-RC5H4Mo)(2)(mu-PhTe)(4) (1, R = MeCO; 3, R = MeO2C) and (eta(5)-RC5H4Mo)(2)(mu-Cl)(mu-PhTe)(3) (2a,b, R = MeCO; 4a,b, R = MeO2C), the dimers [eta(5)-RC5H4(CO)(2)Mo](2) (R = MeO2C, EtO2C) reacted with Ph2Te2 and Cp2ZrCl2 or Cp2ZrBr2 under similar conditions to afford novel tetrakis-bridged complexes (eta(5)-RC5H4Mo)(2)(mu-PhTe)(4) (3, R = MeO2C; 5, R = EtO2C), (eta(5)-RC5H4Mo)(2)(mu-Cl)(mu-PhTe)(3) (4a,b, R = MeO2C; 6a,b, R = EtO2C), and (eta(5)-RC5H4Mo)(2)(mu-Br)(mu-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 [eta(5)-RC5H4(CO)(2)Mo](2) (R = MeO2C, EtO2C) with Ph2Te2 in xylene at 110 degrees C produces bis-bridged complexes [eta(5)-RC5H4(CO)(2)Mo](2)(mu-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, H-1, and Te-125 NMR spectroscopies, and 4b and 9 by single-crystal X-ray diffraction techniques.