Charge donation to and dearomatization of benzene attending complexation: DFT estimates of binding energies of TpMXO(L) with benzene, for Tp = hydridotris(pyrazolyl) borate, MXO = MoNO, ReCO, and WNO, and L = ammonia, N‐methylimidazole, pyridine, phosphine, methyl isocyanide, and carbon monoxide

Abstract

By density functional methods we characterize the bonding and charge distribution in complexes of benzene with dearomatizing agents tpReCO(L), tpMoNO(L), and tpWNO(L), where tp = hydrido Tris (pyrazolyl)borate), for a range of ligands L. Our LSDA and B3LYP density functional calculations use the Spartan LACVP+ basis and pseudopotential on Re, Mo, and W and 6-31G* on light atoms. The binding energy is strongly dependent on the nature of the ligand L, being greatest for L = ammonia and N-methylimidazole and weakest for CH3NC and CO. We find a correlation between strength of binding and electron transfer from the dearomatizing agents toward benzene. For the most strongly bound systems we find substantial (up to 500 millielectrons) charge transfer towards benzene, while for the most weakly bound systems charge is withdrawn from benzene. Structural details illustrate the ability of Re, Mo, and W species to dearomatize complexed benzene, which is extensive for all but the most weakly bound species with L = MeNC and CO. Re and W dearomatizing agents, which are computed and observed to form stable complexes with benzene, may be economic alternatives to osmium dearomatizing agents.

Divergent Electronic Structures of Isoelectronic Metalloclusters: Tungsten(II) Halides and Rhenium(III) Chalcogenide Halides

“…The quality of the predicted geometries compares favorably with recent optimizations of tungsten complexes. [122][123][124][125][126][127][128] Calculated tungsten-halogen bond lengths vary as expected from periodic trends in ionic radii. [129] Calculated WÀW distances change according to the face-bridging halogens.…”

The role of electrochemistry in the development of π-basic dearomatization agents

“…Binding energy and charge-transfer calculations show just how stringent the conditions are for stable g 2 -arene binding. 44 Using LSDA and B3LYP basis sets, density functional calculations were performed on a series of complexes of the form [MTp(XO)(L)(g 2benzene)], (where M(XO) is Mo(NO), W(NO) and Re(CO) and L = NH 3 , methylimidazole (MeIm), pyr, PH 3 , MeNC (CNR) and CO). The general trend for each series shows the expected increase in binding energy as a function of electron-density transferred to the arene (Fig.…”

Development of 2nd Row Molybdenum Dearomatization Agents

“…63,66,68,72 The coordination of the aromatic ligand is achieved in a manner similar to that of the 2 nd generation rhenium system (Method A, Scheme 6), by reduction in the presence of the desired ligand (Scheme 8). 7,66,68 In some cases these η 2 -aromatic complexes are also available via a onepot reaction from TpMo(NO)(X)2, when L is amendable to the highly reducing reaction conditions required (Method C, Scheme 8).…”

“…66 However, despite the range of TpMo I (NO)(L)(X) complexes synthesized, and their more reducing nature than the {TpRe(MeIm)(CO)} fragment (Table 3); the molybdenum based dearomatization agent was found to have a limited coordination scope (naphthalene, furan, and thiophene). 7,66,68,72 This result is likely due to the less effective backbonding ability of the 2 nd row molybdenum center compared to the 3 rd row osmium and rhenium forerunners. coordination offered by the tungsten system is access to a variety of aromatic ligands with biologically interesting cores.…”