Early/Late Heterobimetallic Tantalum/Rhodium Species Assembled Through a Novel Bifunctional NHC‐OH Ligand

The straightforward synthesis of a new unsymmetrical hydroxy‐tethered N‐heterocyclic carbene (NHC) ligand, HL, is presented. The free ligand exhibits an unusual OH–carbene hydrogen‐bonding interaction. This OH–carbene motif was used to yield 1) the first tantalum complex displaying both a Fischer‐ a...

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Published in:Chemistry : a European journal 2018-03, Vol.24 (17), p.4361-4370
Main Authors: Srivastava, Ravi, Moneuse, Raphaël, Petit, Julien, Pavard, Paul‐Alexis, Dardun, Vincent, Rivat, Madleen, Schiltz, Pauline, Solari, Marius, Jeanneau, Erwann, Veyre, Laurent, Thieuleux, Chloé, Quadrelli, Elsje Alessandra, Camp, Clément
Format: Article
Language:English
Subjects:
Alkylidene
carbenes
Chelates
Chemical bonds
Chemical Sciences
Chemistry
heterometallic complexes
Ligands
nitrogen heterocycles
organometallic chemistry
Rhodium
Tantalum
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Summary:The straightforward synthesis of a new unsymmetrical hydroxy‐tethered N‐heterocyclic carbene (NHC) ligand, HL, is presented. The free ligand exhibits an unusual OH–carbene hydrogen‐bonding interaction. This OH–carbene motif was used to yield 1) the first tantalum complex displaying both a Fischer‐ and Schrock‐type carbene ligand and 2) a unique NHC‐based early/late heterobimetallic complex. More specifically, the protonolysis chemistry between the ligand's hydroxy group and imido‐alkyl or alkylidene‐alkyl tantalum precursor complexes yielded the rare monometallic tantalum–NHC complexes [Ta(XtBu)(L)(CH2tBu)2] (X=N, CH), in which the alkoxy‐carbene ligand acts as a chelate. In contrast, HL only binds to rhodium through the NHC unit in [Rh(HL)(cod)Cl] (cod=cycloocta‐1,5‐diene), the hydroxy pendant arm remaining unbound. This bifunctional ligand scaffold successfully promoted the assembly of rhodium/tantalum heterobimetallic complexes upon either 1) the insertion of [Rh(cod)Cl]2 into the Ta–NHC bond in [Ta(NtBu)(L)(CH2tBu)2] or 2) protonolysis between the free hydroxy group in [Rh(HL)(cod)Cl] and one alkyl group in [Ta(NtBu)(CH2tBu)3]. A two‐way ligand: The simple synthesis of a new alcohol‐tethered mesityl‐carbene ligand that has been successfully used to stabilise rare monometallic imido‐alkyl and alkylidene‐alkyl Ta–NHC complexes is presented. Furthermore, we employed this bifunctional ligand platform to prepare unique early/late tantalum/rhodium heterobimetallic assemblies.
ISSN:0947-6539
1521-3765
DOI:10.1002/chem.201705507