Cationic Heterocycles as Ligands: Synthesis and Reactivity with Anionic Nucleophiles of Cationic Triruthenium Clusters Containing C‐Metalated <i>N</i>‐Methylquinoxalinium or <i>N</i>‐Methylpyrazinium Ligands

Cabeza, Javier A.; Rı́o, Ignacio del; Goite, María C.; Pérez‐Carreño, Enrique; Pruneda, Vanessa

doi:10.1002/chem.200901079

Cited by 34 publications

(62 citation statements)

References 67 publications

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“…Clearly, the molecule results from a nucleophilic addition of a hydride to the ligand C 4 carbon atom of 2 + . This should place a double bond in the ligand C 5 C 6 edge (C2C1 in Figure 5) that subsequently displaces one CO from the Ru(CO) 4 fragment to give the final product after an easy rearrangement of the resulting ligand over the Ru 3 triangle 6. The ligand ring is roughly planar, forming a dihedral angle of 59.7(1)° with the Ru 3 plane.…”

Section: Resultsmentioning

confidence: 99%

Synthesis and Reactivity of Cationic Triruthenium Clusters Derived from 2‐Methyl‐ and 4‐Methylpyrimidines: From Conventional Cyclometalated Ligands to Novel Types of N‐Heterocyclic Carbenes

Cabeza

García‐Álvarez

Pérez‐Carreño

et al. 2013

Chemistry A European J

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The methylation of the uncoordinated nitrogen atom of the cyclometalated triruthenium cluster complexes [Ru(3)(μ-H)(μ-κ(2)N(1),C(6)-2-Mepyr)(CO)(10)] (1; 2-MepyrH = 2-methylpyrimidine) and [Ru(3)(μ-H)(μ-κ(2)N(1),C(6)-4-Mepyr)(CO)(10)] (9; 4-MepyrH = 4-methylpyrimidine) gives two similar cationic complexes, [Ru(3)(μ-H)(μ-κ(2)N(1),C(6)-2,3-Me(2)pyr)(CO)(10)](+) (2(+)) and [Ru(3)(μ-H)(μ-κ(2)N(1),C(6)-3,4-Me(2) pyr)(CO)(10)](+) (9(+)), respectively, whose heterocyclic ligands belong to a novel type of N-heterocyclic carbenes (NHCs) that have the C(carbene) atom in 6-position of a pyrimidine framework. The position of the C-methyl group in the ligands of complexes 2(+) (on C(2)) and 9(+) (on C(4)) is of key importance for the outcome of their reactions with K[N(SiMe(3))(2)], K-selectride, and cobaltocene. Although these reagents react with 2(+) to give [Ru(3)(μ-H)(μ-κ(2)N(1),C(6)-2-CH(2)-3-Mepyr)(CO)(10)] (3; deprotonation of the C(2)-Me group), [Ru(3)(μ-H)(μ(3)-κ(3)N(1),C(5),C(6)-4-H-2,3-Me(2)pyr)(CO)(9)] (4; hydride addition at C(4)), and [Ru(6)(μ-H)(2){μ(6)-κ(6) N(1),N(1'),C(5),C(5'),C(6),C(6')-4,4'-bis(2,3-Me(2)pyr)}(CO)(18)] (5; reductive dimerization at C(4)), respectively, similar reactions with 9(+) have only allowed the isolation of [Ru(3)(μ-H)(μ(3)-κ(2)N(1),C(6)-2-H-3,4-Me(2)pyr)(CO)(9)] (11; hydride addition at C(2)). Compounds 3 and 11 also contain novel six-membered ring NHC ligands. Theoretical studies have established that the deprotonation of 2(+) and 9(+) (that have ligand-based LUMOs) are charge-controlled processes and that both the composition of the LUMOs of these cationic complexes and the steric protection of their ligand ring atoms govern the regioselectivity of their nucleophilic addition and reduction reactions.

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Section: Resultsmentioning

confidence: 99%

Synthesis and Reactivity of Cationic Triruthenium Clusters Derived from 2‐Methyl‐ and 4‐Methylpyrimidines: From Conventional Cyclometalated Ligands to Novel Types of N‐Heterocyclic Carbenes

Cabeza

García‐Álvarez

Pérez‐Carreño

et al. 2013

Chemistry A European J

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“…The key difference between both molecules is that their C7 carbon atoms have opposite stereochemistries, while the stereochemistries of their C4 carbon atoms are the same. The coordination of the bridging ligand to the metal atoms of the Ru 3 H-(4-pymMe)(CO) 9 units of 7 and 8 is essentially identical with that found in compound 6 ( Figure 3); however, the different stereochemistry of the C7 carbon atom of each molecule induces a different arrangement of the atoms of the corresponding Ru 3 H(6 0 -pymMe)(CO) 9 unit. While that of 7 is analogous to that found in [Ru 6 (μ-H) 2 {μ 6 -κ 4 N 1 ,N 10 ,C 2 ,C 20 -(3,3 0 -biquinoxMe 2 )}(CO) 18 ] (HquinoxMe = N-methylquinoxaline) (Scheme 6), 18 that of 8 is the same as that found in compound 5 (Figure 2).…”

Section: Synthesis Of the Isomeric Cationic Clustersmentioning

confidence: 85%

Reactivity of Cationic Triruthenium Carbonyl Clusters: From Pyrimidinium Ligands to N-Heterocyclic Carbenes

et al. 2011

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The reaction of [Ru3(CO)12] with pyrimidine (Hpym) leads to the isomeric cyclometalated derivatives [Ru3(μ-H)(μ-κ2 N 1,C 6-pym)(CO)10] (1) and [Ru3(μ-H)(μ-κ2 N 1,C 2-pym)(CO)10] (2), which have been treated with [Me3O][BF4] to give the corresponding N-methylpyrimidinium derivatives [Ru3(μ-H)(μ-κ2 N 1,C 6-pymMe)(CO)10][BF4] (3[BF4]) and [Ru3(μ-H)(μ-κ2 N 1,C 2-pymMe)(CO)10][BF4] (4[BF4]). The reaction of 4[BF4] with K-Selectride renders a separable mixture of two neutral trinuclear products, [Ru3(μ-H){μ-κ2 N 1,C 2-(6-HpymMe)}(CO)9] (5) and [Ru3(μ-H){μ-κ2 N 1,C 2-(4-HpymMe)}(CO)9] (6), which arise from the nucleophilic attack of a hydride at the ligand C6 and C4 carbon atoms of 4 +. This cationic complex can be reduced to the short-lived radical species 4• , which spontaneously dimerizes by forming an intermolecular C−C bond between the ligands of two such radicals. Three hexanuclear derivatives, [Ru6(μ-H)2{μ6-κ4 N 1,N 1′,C 2,C 2′-(4,6′-bipymMe2)}(CO)18] (isomers 7 and 8) and [Ru6(μ-H)2{μ6-κ4 N 1,N 1′,C 2,C 2′-(4,4′-bipymMe2)}(CO)18] (isomer 9), have been isolated by reducing 4[BF4] with cobaltocene. Molecular orbital calculations (at the DFT level) and electrochemical studies have helped rationalize the experimental results. The ligand-based character of the LUMO of 4 + and its atomic orbital composition account for the regiochemistry observed in the reactions of this cationic complex. The N-heterocyclic ligands of 5−9, which have two N atoms in a six-membered ring and a doubly metalated N atom, constitute novel types of N-heterocyclic carbenes.

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“…64 This is because the isolation of NHCs of this type has hitherto been elusive and because there are no general methods to prepare the metal complexes that contain them. 67,68 The synthetic methodology shown in Scheme 30, which involves (a) the preparation of the pyrimidine-derived cluster 67 Compounds 83 and 84, which have been satisfactorily separated by TLC, arise from the nucleophilic attack of a hydride to the ligand C 6 and C 4 carbon atoms, respectively, of 82 + . Pyrimid-2-ylidene derivatives.…”

Section: 24mentioning

confidence: 99%

The N-heterocyclic carbene chemistry of transition-metal carbonyl clusters

Cabeza

García‐Álvarez

2011

Chem. Soc. Rev.

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In the last decade, chemists have dedicated many efforts to investigate the coordination chemistry of N-heterocyclic carbenes (NHCs). Although most of that research activity has been devoted to mononuclear complexes, transition-metal carbonyl clusters have not escaped from these investigations. This critical review, which is focussed on the reactivity of NHCs (or their precursors) with transition-metal carbonyl clusters (mostly are of ruthenium and osmium) and on the transformations underwent by the NHC-containing species initially formed in those reactions, shows that the polynuclear character of these metallic compounds or, more precisely, the close proximity of one or more metal atoms to that which is or can be attached to the NHC ligand, is responsible for reactivity patterns that have no parallel in the NHC chemistry of mononuclear complexes (74 references).

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Cationic Heterocycles as Ligands: Synthesis and Reactivity with Anionic Nucleophiles of Cationic Triruthenium Clusters Containing C‐Metalated N‐Methylquinoxalinium or N‐Methylpyrazinium Ligands

Cited by 34 publications

References 67 publications

Synthesis and Reactivity of Cationic Triruthenium Clusters Derived from 2‐Methyl‐ and 4‐Methylpyrimidines: From Conventional Cyclometalated Ligands to Novel Types of N‐Heterocyclic Carbenes

Synthesis and Reactivity of Cationic Triruthenium Clusters Derived from 2‐Methyl‐ and 4‐Methylpyrimidines: From Conventional Cyclometalated Ligands to Novel Types of N‐Heterocyclic Carbenes

Reactivity of Cationic Triruthenium Carbonyl Clusters: From Pyrimidinium Ligands to N-Heterocyclic Carbenes

The N-heterocyclic carbene chemistry of transition-metal carbonyl clusters

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