title: Breaking chemistry's strongest bond: can three-coordinate [M{N(R)Ar}3] complexes cleave carbon monoxide?
abstract: The reaction pathway for the interaction of CO with three-coordinate TaIII, WIII and ReIII complexes (modelled on the experimental [M{N(tBu)Ar}3] system) has been explored by using density functional methods. Calculations show that CO binds without a barrier to [Re(NH2)3], forming the encounter complex [OC--Re(NH2)3], which is stabilized by approximately 280 kJ mol-1 relative to the reactants. The binding of [Ta(NH2)3] to the oxygen terminus of CO is inhibited by a barrier of only 20 kJ mol-1 and is followed by spontaneous cleavage of the C--O bond to form the products [C--Re(NH2)3] and [O--Ta(NH2)3]. The salient features of the potential energy surface are more favourable to CO cleavage than the analogous N2 cleavage by [Mo(NH2)3], which is less exothermic (335 vs. 467 kJ mol-1) and is impeded by a significant barrier (66 kJ mol-1). The ReIII/TaIII/CO system therefore appears to be an excellent candidate for cleaving the exceptionally strong C--O bond under mild laboratory conditions. The related WIII/TaIII dimer, which significantly weakens but does not cleave the CO bond, may be a suitable alternative when the chemistry is to be performed on activated CO rather than on the strongly bound oxide and carbide cleavage products.
authors: Department of Chemistry, Australian National University, Canberra, ACT 0200, Australia.
authors: Gemma
authors: G
authors: Christian
authors: Robert
authors: R
authors: Stranger
authors: Simon
authors: S
authors: Petrie
authors: Brian F
authors: BF
authors: Yates
authors: Christopher C
authors: CC
authors: Cummins