Synthesis and Reactivity of Remarkably Stable and Nucleophilic Hydroxide-Bridged Dimetallic Nickel NHC Complexes

Bertini, Simone; Albrecht, Martin (2020). Synthesis and Reactivity of Remarkably Stable and Nucleophilic Hydroxide-Bridged Dimetallic Nickel NHC Complexes. Organometallics, 39(18), pp. 3413-3424. American Chemical Society 10.1021/acs.organomet.0c00495

[img] Text
om-2020-00495d_ms_revised.pdf - Accepted Version
Restricted to registered users only until 17 September 2021.
Available under License Publisher holds Copyright.

Download (1MB) | Request a copy
[img] Text
acs.organomet.0c00495.pdf - Published Version
Restricted to registered users only
Available under License Publisher holds Copyright.

Download (2MB) | Request a copy

The novel class of dicationic homodimetallic nickel(II) NHC complexes [(NHC)2Ni(μ-OH)2Ni(NHC)2]2+ was synthesized starting from nickel acetate as the metal precursor. Symmetrically substituted N-alkyl (methyl, isopropyl, and isobutyl) imidazolylidene (imi) as well as N1-methyl-, N1-phenyl-, N1-mesityl-, and N1-butyl-substituted triazolylidene (trz) ligands were coordinated to the metal center through NaH-mediated metalation. Reaction of these bimetallic complexes with CH3+ as an electrophile (MeOTf) induced alkylation of the bridging hydroxide ligands and afforded the new alkoxy-bridged complexes [(NHC)2Ni(μ-OMe)2Ni(NHC)2]2+. In contrast, reactions of [(imi)2Ni(μ-OH)2Ni(imi)2]2+ with H+ as electrophile (mild acids with pKa > 6) led to cleavage of the dimeric structure and formation of mononuclear complexes [Ni(X)2(imi)2]. Conversely, no reaction occurred for the triazolylidene analogues [(trz)2Ni(μ-OH)2Ni(trz)2]2+, indicating different robustness of the dimetallic core to acidic media. Only exposure to stronger acids (pKa < 5) induced dimer cleavage for the trz complexes and gave either the corresponding triazolium salt or, in the presence of a coordinating anion, the monomeric species [Ni(X)2(trz)2] with X = I, OAc or (X)2 = CO3. All complexes were inert toward Lewis and Brønsted bases such as NEt3 and NaOMe. These results reveal a remarkable robustness of the acidic Ni centers and the OH protons toward bases and is in contrast with the distinct reactivity of the Lewis basic oxygen donor sites, which are more reactive than the carbene toward electrophiles.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Department of Chemistry, Biochemistry and Pharmaceutical Sciences (DCBP)

UniBE Contributor:

Bertini, Simone and Albrecht, Martin

Subjects:

500 Science > 540 Chemistry

ISSN:

0276-7333

Publisher:

American Chemical Society

Funders:

[18] European Research Council ; [180] Marie Skłodowska-Curie Actions Innovative Training Networks ; [42] Schweizerischer Nationalfonds

Projects:

[1134] Exploiting Synergistic Properties of Mesoionic Carbene Complexes: Teaching Rusty Metals Challenging Catalysis
[1343] Non-Noble Metal Catalysis - NoNoMeCat
[1283] Designer ligands for oxidative bond activation catalysis

Language:

English

Submitter:

Eik Szee Goh Aschauer

Date Deposited:

03 Feb 2021 12:19

Last Modified:

03 Feb 2021 12:19

Publisher DOI:

10.1021/acs.organomet.0c00495

BORIS DOI:

10.48350/151065

URI:

https://boris.unibe.ch/id/eprint/151065

Actions (login required)

Edit item Edit item
Provide Feedback