Stable Paramagnetic Half-Sandwich Mo(V) and W(V) Polyhydride Complexes. Structural, Spectroscopic, Electrochemical, Theoretical, and Decomposition Mechanism Studies of [Cp*MH₃(dppe)]⁺ (M = Mo, W)

Abstract

HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Computational study of the spin-forbidden H2oxidative addition to 16-electron Fe(0) complexes

“…42 The nϩ on going from n = 0 to = 1. 50 We can therefore associate the computed trend of Fe-H stretching frequencies in compounds Fe(L) 4 H 2 to a similar tuning of the metal electron density by the nature of the ancillary ligands. For the series of Fe(CO) 2 (PH 3 ) 4 H 2 isomers, the frequencies clearly respond to the influence of the trans ligands and correlate with the Fe-H distances.…”

Formation and Structure of a Sterically Protected Molybdenum Hydride Complex with a 15‐Electron Configuration: [(1,2,4‐C5H2tBu3)Mo(PMe3)2H]+

“…They are implicated in a variety of catalytic cycles and are also intermediates of CÀH oxidative-addition processes. Open-shell, paramagnetic versions have so far not demonstrated broad utility, mainly because of their instability and multitude of decomposition pathways, including deprotonation, [1] disproportionation, [2] dihydrogen reductive elimination (for complexes containing at least two hydride ligands), [3] atom transfer, and so on. [4] Yet, open-shell hydride complexes appear to play a role in enzymatic processes such as hydrogenase and nitrogenase, [5][6][7][8] and their implication in a variety of electrocatalyzed transformations may be envisaged.…”

“…We have recently reported the first unambiguous case of H 2 OIRE for the complex [Cp*Mo(dppe)H 3 ] (dppe = Ph 2 PCH 2 CH 2 PPh 2 ) by characterization of the solvent-stabilized product [Cp*Mo(dppe)(solv)H] + by EPR spectroscopy (solv = thf, CH 2 Cl 2 ) [3] and electrochemistry (solv = MeCN), [17] although the structure of the product could not be confirmed crystallographically. , although theoretical calculations and circumstantial evidence indicates that the oxidized complex adopts a classical structure.…”

“…[17] We have argued that both stronger electron donation and greater steric protection by the ligands stabilize paramagnetic hydride complexes by disfavoring, through different mechanisms, the various decomposition pathways. [4] We have therefore turned our attention to a new Mo system, using the more strongly donating PMe 3 ligand in place of dppe and the more sterically protecting 1,2,4-C 5 3 . Its X-ray crystal structure shows a very similar geometry to that of [Cp*Mo(dppe)H 3 ], [19] with the two PMe 3 ligands symmetrically disposed in adjacent coordination positions (P-Mo-P angle: 93.71(2)8) and far away from the Cp tBu ligand (Figure 1 a).…”

“…[27] Moreover, a spin-forbidden AE 3 = 2 transition may also be accessible, yielding a weak feature at g % 6 for the z component. A rare example for Mo III is given by [Mo-(acac) 3 ], for which a relatively broad spectrum can be observed between liquid-nitrogen and liquid-helium temperatures. [28] 6 .…”