Theoretical Study of the Reaction of Yttrium with Formaldehyde

Reaction pathways of Rh+ (3F and 1D) with CH3OCH3 in the gas phase

RATIONALE

The mass spectrometric studies of transition metal ion-ether reactions are informative in elucidating the principles of metal ion mediated demethanation and dehydrogenation. In order to obtain a deeper understanding of the role of metal ions, it is essential to explore the detailed reaction mechanisms of these reactions, here studied using Rh(+) and dimethyl ether as a model system.

METHODS

The gas-phase demethanation and dehydrogenation pathways of dimethyl ether mediated by Rh(+) ((3)F and (1)D) were investigated by density functional theory in conjunction with the Stuttgart RSC + 6-311 + G(d) basis set. Both singlet and triplet states of reactivity were explored.

RESULTS

The results indicate that both C-O and C-H bond activation of dimethyl ether mediated by Rh(+) could induce the demethanation reaction. The triplet state demethanation reaction prefers to proceed through C-O bond activation, while the singlet state demethanation channel via C-H bond activation is energetically more favorable. The singlet state dehydrogenation of the ionic product (formaldehyde/Rh(+)) occurs by decomposition of rhodium carbonyl dihydride, while the triplet state dehydrogenation is induced by dissociation of the carbonyl(η(2)-dihydrogen) rhodium species.

CONCLUSIONS

Based on the results, it is believed that the demethanation reaction of dimethyl ether mediated by transition metal monocation would preferably occur through the C-O bond activation pathway. Combined with previous studies, a general reaction mechanism of the transition metal monocation with dimethyl ether is proposed.

Theoretical Investigation of the Reaction of Yttrium Cation with Acetone

The reaction mechanism of Y + with CH3COCH3 has been investigated with a DFT method. All the stationary points are determined at the UB3LYP/ECP/6-311++G** level of the theory. Both the ground and the excited state potential energy surfaces are investigated in detail. The present results show that the title reaction starts with the formation of an O-attached complex (IM0) followed by C–O, C–H and C–C activation. The minimum energy reaction path is found to involve the spin inversion in the initial reaction step. The potential energy curve-crossing dramatically affects reaction exothermic. The present results may be helpful in understanding the mechanism of the title reaction and further experimental investigation of the reaction.

Experimental and theoretical studies of the reactions Y (a2D) + H2CO and Y (a2D) + CH3CHO

The reactions of ground state Y (a(2)D) with H(2)CO and CH(3)CHO were studied at a range of collision energies in crossed molecular beams. For reaction with H(2)CO, three product channels were observed: formation of YH(2) + CO, YCO + H(2), and YHCO + H. Reaction with CH(3)CHO led to three analogous product channels involving formation of HYCH(3) + CO, YCH(2)CO + H(2), and YCH(3)CO + H. The calculated CCSD(T) energetics and DFT geometries for key intermediates in both reactions, together with RRKM theory, are used to calculate a priori the branching ratios between various product channels. These calculated values are compared to those obtained experimentally.