A two‐step reaction scheme leading to singlet carbene species that can be detected under matrix conditions for the reaction of Zr(³F) with either CH₃F or CH₃CN

Abstract

The results obtained from CASSCF-MRMP2 calculations are used to rationalize the singlet complexes detected under matrix-isolation conditions for the reactions of laser-ablated Zr((3)F) atoms with the CH3F and CH3CN molecules, without invoking intersystem crossings between electronic states with different multiplicities. The reaction Zr((3)F) + CH3 F evolves to the radical products ZrF· + ·CH3. This radical asymptote is degenerate to that emerging from the singlet channel of the reactants Zr((1)D) + CH3 F because they both exhibit the same electronic configuration in the metal fragment. Hence, the caged radicals obtained under cryogenic-matrix conditions can recombine through triplet and singlet paths. The recombination of the radical species along the low-multiplicity channel produces the inserted structures H3C-Zr-F and H2C=ZrHF experimentally detected. For the Zr((3)F) + CH3 CN reaction, a similar two-step reaction scheme involving the radical fragments ZrNC· + ·CH3 explains the presence of the singlet complexes H C-Zr-NC and H2 C=Zr(H)NC revealed in the IR-matrix spectra upon UV irradiation.

Selectivity of C–H Activation and Competition between C–H and C–F Bond Activation at Fluorocarbons

“…117 CASSCF-MRMP2 calculations were carried out to determine the mechanism of formation of (CH 3 )MF in the case of M = Zr. 118 With later metals of the Periodic Table, is energetically facile and exoergic. 120 Migration of H from the methyl group to Pt has a very low energy barrier and the subsequent reverse F migration from the metal to the ligand has an accessible transition state and is energetically favorable.…”

Rationalizing the Low‐Spin Products Observed for the Reactions M+CH3CN (M=V, Nb,Ta) Through a Non‐Spin Flip Scheme.

“…The proposed two‐reaction scheme implicitly takes into account, at least partially, the effect of the confinement medium. It was also been used successfully to explain for the singlet complexes determined under matrix conditions for the reactions of Zr( 3 F) with CH 3 F and CH 3 CN ,. The results obtained from these studies suggest that other confined interactions involving transition metal atoms could be described in terms of two sequential reactions involving radical species, instead of spin‐flip models arising from unlikely interactions between electronic states of different spin multiplicity.…”

Low‐Energy Pathways Found for the NH3 Activation and H2 Elimination by the Werner‐Type Complexes M(NH3)4+ (M=Fe, Ru and Os).

“…A similar two-step radical reaction scheme has been used in previous contributions to explain for the observed products in other reactions. [33][34][35][36][37][38] Although mass-spectrometry determinations on these reactions have inspired the present study, this investigation is mainly focused on the analysis of the factors that could be relevant in determining the role of the metal-ligand interactions on the NH 3 activation by the ammine complexes yielded by sequential addition of NH 3 ligands to the metallic center. However, even when our reaction models do not consider the experimental conditions of the spectroscopic determinations, there is a good agreement between the results presented herein and those obtained by mass spectrometry for the investigated interactions.…”

“…A similar two-step reaction scheme has been used to rationalize the shift in the spin multiplicity between the reactants and the observed products for other interactions. [33][34][35][36][37][38] In Figure 4 are shown the potential energy plots for these recombination reactions. As it is seen in Figure 5, the product Ru(NH 3 ) 3 (H)NH 2 + evolving from the doublet pathway is more stable than that corresponding to the quadruplet one by 38.7 kcal/mol (for both multiplicity-channels a NH 3 ligand is expelled out when the NH 2 group is been attached to the metallic center).…”