Synthesis, characterization and the thermal isomerization mechanism of a series of trans-tetracarbonyl-bis(phosphinite)molybdenum(0) complexes and an evaluation of their potential to form heterobimetallic compounds

Academic Article


  • The reactions of coordinated phosphorus-donor ligands have previously been used to prepare bimetallic trans-[cis-Mo(CO)4(PPh 2NHCH2CH2NCH(o-C6H4)O) 2]M (M = Ni(II), Cu(II)) complexes. Similar bimetallic complexes containing trans-tetracarbonyl-bis(phosphinite)molybdenum(0) centers could be even more interesting because they could serve as molecular gyroscopes. In an attempt to prepare such complexes, the three intermediate compounds trans-Mo(CO)4(PPh2Cl)2 (1), trans-Mo(CO) 4(PPh2NHCH2CH2NH2) 2 (2), and trans-Mo(CO)4(PPh2NHCH 2CH2NCH(o-C6H4)OH)2 (3) were successfully synthesized and fully characterized by multinuclear NMR spectroscopy, elemental analysis and X-ray crystallography. However, the reaction of 3 with Ni(OAc)2(H2O)4 yielded a mixture of crude products with the previously reported trans-[cis-Mo(CO) 4(PPh2NHCH2CH2NCH(o-C6H 4)O)2]Ni being the only product successfully isolated. The cis product was formed due to facile transecis isomerization during the coordination of the Ni(II) to 3. To gain more insight into such isomerizations, the transecis isomerizations of 2 and 3 have been followed by 31P{1H} NMR spectroscopy. The reactions follow reversible first order kinetics and appear to display intramolecular mechanisms due to the lack of carbonyl substitutions of the phosphinamidite ligands when the isomerizations are performed under CO atmospheres. Eyring analyses performed on the two complexes show that they have nearly identical activation energies (2: ΔH = 10 ± 2 kJ mol-1, ΔS = 39±5 J mol -1 K-1; 3: ΔH = 11±2 kJ mol-1, ΔS = 41 ± 7 J mol-1 K-1). © 2013 Elsevier B.V. All rights reserved.
  • Authors

    Published In

    Digital Object Identifier (doi)

    Author List

  • Martin JR; Hastings SD; Freeman JL; Gray GM
  • Start Page

  • 695
  • End Page

  • 702
  • Volume

  • 751