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Article Dans Une Revue Inorganic Chemistry Année : 2021

Deaggregation of Zinc Dihydride by Lewis Acids Including Carbon Dioxide in the Presence of Nitrogen Donors

Résumé

Thermally sensitive polymeric zinc dihydride [ZnH2] (n) can conveniently be prepared by the reaction of ZnEt2 with [AlH3(NEt3)]. When reacted with CO2 (1 bar) in the presence of chelating N-donor ligands L-n = N,N,N',N'tetramethylethylenediamine (TMEDA), N,N,N',N'-tetramethyl-1,3-propanediamine (TMPDA), N,N,N',N.,N''-pentamethyldiethylenetriamine (PMDTA), and 1,4,7,10tetramethyl-1,4,7,10-tetraazacyclododecane (Me(4)TACD), insertion into the Zn-H bond readily occurred. Depending on the denticity n, formates [(L-n)Zn(OCHO)(2)] were isolated and structurally characterized, either as a molecule (L-n = TMEDA, TMPDA, PMDTA) or a charge-separated ion pair [(L-n)Zn(OCHO)][OCHO] (L-n = Me(4)TACD). The reaction of [ZnH2] n with the mild Lewis acid BPh3 in the presence of chelating N-donor ligands L-n gave a series of hydridotriphenylborates, either as a contact ion pair [(L-2)Zn(H)(HBPh3)] (L-2 = TMEDA, TMPDA) or a separated ion pair [(L-n)Zn(H)][HBPh3] (L-n = PMDTA, Me(4)TACD). In the crystal, the contact ion pair [(TMEDA)Zn(H)(HBPh3)] showed a bent Zn-H-B bridge indicative of a delocalized Zn-H-B interaction. In contrast, a linear Zn-H-B bridge for [(TMPDA)Zn(H)(HBPh3)] was observed, suggesting a contact ion pair. In THF solution, both complexes show an exchange with free BPh3 as well as [HBPh3](-). DFT calculations suggest the presence of [HBPh3](-) anion with a highly polarized B-H bond that interacts with the Lewis acidic zinc hydride cation [(L-2)Zn(H)](+). The hydridotriphenylborates [(L-n)Zn(H)(HBPh3)] underwent CO2 insertion to give (formato)zinc (formoxy)triphenylborate complexes [(L-n)Zn(OCHO)][(OCHO)BPh3] (L-n = TMPDA, PMDTA, Me(4)TACD). For L-n = TMEDA, a dinuclear complex [(L-n)(2)Zn-2(mu-OCHO)(3)][(OCHO)BPh3] was isolated. Hydridotriphenylborates [(L-n)Zn(H)(HBPh3)] catalyzed the hydrosilylation of CO2 (1 bar) by (BuMe2SiH)-Bu-n in THF at 70 degrees C to give formoxysilane and (methoxy)silane.
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Dates et versions

hal-03717263 , version 1 (08-07-2022)

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Citer

Florian Ritter, Louis J. Morris, Karl N. Mccabe, Thomas P. Spaniol, Laurent Maron, et al.. Deaggregation of Zinc Dihydride by Lewis Acids Including Carbon Dioxide in the Presence of Nitrogen Donors. Inorganic Chemistry, 2021, 60 (20), pp.15583-15592. ⟨10.1021/acs.inorgchem.1c02207⟩. ⟨hal-03717263⟩
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