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Role of the metal, ligand, and alkyl/aryl group in the hydrolysis reactions of group 10 organometallic cations [(L)M(R)]+
journal contributionposted on 2023-05-17, 22:39 authored by Woolley, MJ, Khairallah, GN, da Silva, G, Donnelly, PS, Brian YatesBrian Yates, O'Hair, RAJ
The reactions of water with the coordinatively unsaturated group 10 organometallic cations [(L)M(R)]+ (4; where L = 1,10-phenanthroline (phen), neocuproine (neo); M = nickel, palladium, platinum; R = CH3, C6H5, CH2C6H5), formed via decarboxylation of the carboxylate complexes [(L)M(O2CR)]+, were examined in the gas phase using a combination of multistage mass spectrometry experiments and DFT calculations at the M06/SDD6-31+G(d) level of theory. Two main types of primary product ions were observed: the aqua adduct [(L)M(R)(H2O)]+ (5) and the hydroxide [(L)M(OH)]+ (7), formed via a hydrolysis reaction. A secondary product ion, arising from formation of the adduct [(L)M(OH)(H2O)]+, was also observed when L = phen, R = CH3, and M = Pt. The rates of reaction of 4 and the product branching ratios for 5 and 7 were dependent upon the nature of M, L, and R. When L = phen and R = CH3, the hydroxide 7 dominates for Ni, with the adduct 5 as the major product for both Pd and Pt. For R = C6H5 the rate of the reaction is slower, while for R = CH2C6H5 no reaction occurs. Replacing the phen auxiliary ligand with neo dramatically slows down the rate of reaction with water. DFT calculations reveal that an acid−base hydrolysis mechanism is favored over an oxidative addition/reductive elimination mechanism proceeding via the M(IV) intermediate [(L)M(CH3)(H)- (OH)]+. Furthermore, the relative energies calculated for the barriers of these hydrolysis reactions are consistent with the experimentally observed reactivity trends. This mechanism is also supported by RRKM theory/master equation simulations, which demonstrate that formation of the aqua adduct and hydroxide can be explained by competition between unimolecular dissociation and collisional deactivation of the chemically activated reaction adduct within the ion trap. The lack of reactivity of the benzyl systems appears to arise from η3 binding of the benzyl group, which blocks access to the incoming water. Finally, links are made to group 10 three-coordinate organometallic complexes in the condensed phase.
Department/SchoolSchool of Natural Sciences
PublisherAmerican Chemical Society
Place of publication1155 16Th St, Nw, Washington, USA, Dc, 20036
Rights statementCopyright 2013 American Chemical Society