Coordination of N2 and Other Small Molecules to the Phosphorus Centre of RPW(CO)5: A Theoretical Study on the Janus Facets of the Stabilization/Activation Problem

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Coordination of N2 and Other Small Molecules to the Phosphorus Centre of RPW(CO)5: A Theoretical Study on the Janus Facets of the Stabilization/Activation Problem

Arturo Espinosa Ferao, Rainer Streubel

Bonding of neutral terminal phosphinidene tungsten(0) complexes stabilized by ligands bound to phosphorus (ligand-to-P) have been studied using a large testbed of predominantly N-ligands. Most complexes (1 a–r,v–z and 2 l) exhibit a pyramidal P centre with a formal single ligand-to-P bond order. Three ligand-to-P complexes (1 s–u) exhibit planar sp2-hybridization of P and P,N bonds featuring double bond character. All derivatives with C-ligands (1 v,x–z) exhibit a ligand-to-P bond strength intermediate between the P−N single and double bonded species. Remarkably, dinuclear complexes containing CN− (1 p,w), N3− (1 r) and N2 (1–3 t) as bridging ligands between two phosphorus centres show intertwined terminal W(CO)5 fragments. In particular, the case of N2 bridging ligand (1–3 t) represents a noteworthy example of activation, displaying a weakened N,N bond and two sets of very strong P,N double bonds, the latter resembling the activation-picture of dinitrogen by transition metal complexes. Bond dissociation energies (BDEs) of ligand-to-P bonds do not show any correlation with a range of bond strength descriptors, but display some meaningful, roughly linear variation with the ligand softness. Based on Haaland's definition of dative bonding, a reasonable linear correlation of BDE with dativity (d1) and the dative covalence energy (DCE1) was found. A moderate correlation was also obtained with the vertical ionization potential of the ligand (I(L)) as well as with the ligands HOMO energy. Steady on: The stabilization of phosphinidene P-W(CO)5 complexes by various ligand-to-P interactions is described. Dinuclear complexes of bridging ligands, such as dinitrogen, represent a noteworthy example of activation, resembling the picture of dinitrogen activation by transition-metal complexes.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1002/chem.201700524