THE FIRST EXAMPLES OF TRIPHENYLPHOSPHINEOXIDE AND TRIPHENYLPHOSPHINESULPHIDE SEVEN-COORDINATE COMPLEXES OF MOLYBDENUM(II) AND TUNGSTEN(II)

Abstract

Seven-coordinate complexes of molybdenum(II) and tungsten(II) have become increasingly important in recent years; in particular the compounds [MX₂(CO)₃L₂] (M = Mo or W; X = Cl or Br; L = PPh₃ or AsPh₃) have been shown to be catalysts for the ring-opening polymerisation of norbornene and norbornadiene.^1,2 It is believed that it is the ease of phosphine or arsine dissociation in these compounds which is the rate determining step in the mechanism. Although many examples of bisphosphine seven-coordinate compounds of the type [MX₂(CO)₃L₂] (M = Mo or W; X = Cl, Br or I; L = PR₃) have been reported,^3–6 hitherto no examples of seven-coordinate complexes containing the phosphorus(v) ligands triphenylphosphineoxide or triphenylphosphinesulphide have been described. We wish to report in this communication the preparation of some new seven-coordinate complexes of molybdenum(II) and tungsten(II) containing triphenylphosphineoxide and triphenylphosphinesulphide as attached ligands.

Key Words:

• Molybdenum(II)
• tungsten(II)
• seven-coordinate
• triphenylphosphine sulphide
• triphenylphosphineoxide