Gas‐phase formation of Grignard‐type organolanthanide (III) ions RLnCl3−: The influences of lanthanide center and hydrocarbyl group

Compared with organomagnesium compounds (Grignard reagents), the Grignard-type organolanthanides (III) exhibit several utilizable differences in reactivity. However, the fundamental understanding of Grignard-type organolanthanides (III) is still in its infancy. Decarboxylation of metal carboxylate ions is an effective method to obtain organometallic ions that are well suited for gas-phase investigation using electrospray ionization (ESI) mass spectrometry in combination with density functional theory (DFT) calculations.The (RCO2 )LnCl3- (R = CH3 , Ln = La-Lu except Pm; Ln = La, R = CH3 CH2 , CH2 CH, HCC, C6 H5 , and C6 H11 ) precursor ions were produced in the gas phase via ESI of LnCl3 and RCO2 H or RCO2 Na mixtures in methanol. Collision-induced dissociation (CID) was employed to examine whether the Grignard-type organolanthanide (III) ions RLnCl3- can be obtained via decarboxylation of lanthanide chloride carboxylate ions (RCO2 )LnCl3- . DFT calculations can be used to determine the influences of lanthanide center and hydrocarbyl group on the formation of RLnCl3- .When R = CH3 , CID of (CH3 CO2 )LnCl3- (Ln = La-Lu except Pm) yielded decarboxylation products (CH3 )LnCl3- and reduction products LnCl3 ·- with a variation in the relative intensity ratio of (CH3 )LnCl3- /LnCl3 ·- . The trend is as follows: (CH3 )EuCl3- /EuCl3 ·- < (CH3 )YbCl3- /YbCl3 ·- ≈ (CH3 )SmCl3- /SmCl3 ·- < other (CH3 )LnCl3- /LnCl3 ·- , which complies with the trend of Ln (III)/Ln (II) reduction potentials in general. When Ln = La and hydrocarbyl groups were varied as CH3 CH2 , CH2 CH, HCC, C6 H5 , and C6 H11 , the fragmentation behaviors of these (RCO2 )LaCl3- precursor ions were diverse. Except for (C6 H11 CO2 )LaCl3- , the four remaining (RCO2 )LaCl3- (R = CH3 CH2 , CH2 CH, HCC, and C6 H5 ) ions all underwent decarboxylation to yield RLaCl3- . (CH2 CH)LaCl3- and especially (CH3 CH2 )LaCl3- are prone to undergo β-hydride transfer to form LaHCl3- , whereas (HCC)LaCl3- and (C6 H5 )LaCl3- are not. A minor reduction product, LaCl3 ·- , was formed via C6 H5 radical loss of (C6 H5 )LaCl3- . The relative intensities of RLaCl3- compared to (RCO2 )LaCl3- decrease as follows: HCC > CH2 CH > C6 H5 > CH3 > CH3 CH2 >> C6 H11 (not visible).A series of Grignard-type organolanthanide (III) ions RLnCl3- (R = CH3 , Ln = La-Lu except Pm; Ln = La, R = CH3 CH2 , CH2 CH, HCC, and C6 H5 ) were produced from (RCO2 )LnCl3- via CO2 loss, whereas (C6 H11 )LaCl3- did not. The experimental and theoretical results suggest that the reduction potentials of Ln (III)/Ln (II) couples as well as the bulkiness and hybridization of hydrocarbyl groups play important roles in promoting or limiting the formation of RLnCl3- via decarboxylation of (RCO2 )LnCl3- .