Accessing Zinc Monohydride Cations through Coordinative Interactions

Abstract

We present isolable examples of formal zinc hydride cations supported by N-heterocyclic carbene (NHC) donors, and investigate the dual electrophilic and nucleophilic (hydridic) character of the encapsulated [ZnH](+) units by computational methods and preliminary hydrosilylation catalysis.

Group 14 inorganic hydrocarbon analogues

“…91 Inorganic dimetallenes (H 2 EEH 2 ) and their structural isomers 90 It will be of great interest to see if such species can promote catalytic transformations.…”

Efficient CO2 Insertion and Reduction Catalyzed by a Terminal Zinc Hydride Complex

“…Reported zinc-based catalysts for the hydrosilylation of CO 2 . [14][15][16][17] Furthermore,a lso in the AT-IR spectrum the ZnÀHstretching vibration is found at 1769 cm À1 as asharp signal. [14] In the solid state,t he hydrido compound is moderately stable at ambient atmosphere whereas in solution it is sensitive towards moisture and decomposes to yet unidentified products.H owever,i nd ichloromethane,a lso in absence of moisture, 2 is only stable below À30 8 8C, while at room temperature it decomposes in the course of 4-6 h, predominantly forming [k 4 -C,N,S,S-Tntm]Zn(Pn) (4,P n = 6-tertbutyl-3-thiopyridazine;S upporting Information, Figures S8-S10, S19).…”

Investigation of N‐Heterocyclic Carbene‐Supported Group 12 Triflates as Pre‐catalysts for Hydrosilylation/Borylation

“…Somewhat to our surprise given our failure at obtaining welldefined Cd-H complexes, we found 2 to be an active precatalyst, with 96 %c onversion of the ketone to the corresponding hydrosilylation product Ph 2 CH-OSi(H)PhMe [4] after 120 min (TOF = 10 h À1 ), as determined by 1 HNMR spectroscopy.U sing al ower catalyst loading of 1mol %r esulted in the formation of only as mall amount of hydrosilylated product (7 %c onversion, Ta ble 1);i na ll cases the visible formation of Cd metalw as noted. Somewhat to our surprise given our failure at obtaining welldefined Cd-H complexes, we found 2 to be an active precatalyst, with 96 %c onversion of the ketone to the corresponding hydrosilylation product Ph 2 CH-OSi(H)PhMe [4] after 120 min (TOF = 10 h À1 ), as determined by 1 HNMR spectroscopy.U sing al ower catalyst loading of 1mol %r esulted in the formation of only as mall amount of hydrosilylated product (7 %c onversion, Ta ble 1);i na ll cases the visible formation of Cd metalw as noted.…”

“…[2] In 2013 Okuda and co-workers reported the N-heterocyclic carbene (NHC)-supported molecular zinc dihydride dimer [IPr·ZnH(m-H)] 2 (IPr = [(HCNDipp) 2 C:]; Dipp = 2,6-iPr 2 C 6 H 3 ). [4,5] Notably[ IPr·ZnH(OTf)·THF] is catalytically activew ith respectt ot he hydrosilylation andh ydroborylation of benzophenone, [4,6] and contrary to Okuda's initial NHC-ZnH 2 adduct, our [ZnH] + species is monomeric and has considerable thermal stability( up to 260 8C) in the solid state. [4] This result prompted our group to design the NHCcomplex [IPr·ZnH(OTf)·THF] which contains af ormal cationic zinc hydride unit [ZnH] + along with aweakly associated triflate (OTf À = O 3 SCF 3 À )c ounterion.…”

“…The thermal stabilityo ft hesem etal hydrides decreases dramatically as one descends the group, with decompositionn oted for ZnH 2 upon heatingt o9 0 8C( slow decomposition at room temperature), while CdH 2 and HgH 2 decompose into their constituent elements at À20 8Cand À125 8C, respectively. [4] This result prompted our group to design the NHCcomplex [IPr·ZnH(OTf)·THF] which contains af ormal cationic zinc hydride unit [ZnH] + along with aweakly associated triflate (OTf À = O 3 SCF 3 À )c ounterion. [3] This zinc dihydride complex exhibits low thermals tabilitya si t slowly decomposes in the solid state at room temperature, and degradationwas noted upon prolongeds toragea t À35 8C.…”