Half-sandwich organometallic complexes with stereogenic metal centres: Synthesis and characterization of diastereomeric [(ηn-ring)M(Aa)X] (Aa = α-amino carboxylate) compounds

Carmona, Daniel; Lamata, M. Pilar; Viguri, Fernando; José, Emilio San; Mendoza, Antonio Gómez; Lahoz, Fernando J.; Garcı́a-Orduña, Pilar; Atencio, Reinaldo; Oro, Luis A.

doi:10.1016/j.jorganchem.2012.07.022

Cited by 27 publications

(35 citation statements)

References 72 publications

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“…[22,23,[36][37][38][39][40] All complexes adopt the three-legged piano-stool (half-sandwich) configuration, as expected. As is the case with Cp ⁄ Ir amino acid complexes previously reported, the iridium atom becomes a pseudo-tetrahedral chiral center upon coordination of the amino acid, resulting in diastereomers that differ at configuration of the metal when using an enantiomerically pure amino acid.…”

Section: Synthesis Of Amino Acid Complexessupporting

confidence: 76%

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Extending the range of pentasubstituted cyclopentadienyl compounds: The synthesis of a series of tetramethyl(alkyl or aryl)cyclopentadienes (Cp ∗ R ), their iridium complexes and their catalytic activity for asymmetric transfer hydrogenation

Morris¹,

McGeagh²,

Peña³

et al. 2014

Polyhedron

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Section: Synthesis Of Amino Acid Complexessupporting

confidence: 76%

“…No great pains were taken to screen other crystals for ones that would contain the other diastereomer. Fully alkylated amino acids such as N-methyl-L-proline produce exclusively one diastereomer in solution, as reported by Carmona et al [36].…”

Section: Crystal Structuressupporting

confidence: 57%

Extending the range of pentasubstituted cyclopentadienyl compounds: The synthesis of a series of tetramethyl(alkyl or aryl)cyclopentadienes (Cp ∗ R ), their iridium complexes and their catalytic activity for asymmetric transfer hydrogenation

Morris¹,

McGeagh²,

Peña³

et al. 2014

Polyhedron

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“…As a result of the coordination of the pyrrolidino- [60]fullerene carboxylate moiety, two additional stereogenic centers are formed at the pyrrolidine nitrogen atom and at the iridium atom. As inferred from NOE experiments and in analogy with other related systems, [9] the NÀH bond remains in a cis disposition with respect to the C2-H pyrrolidine bond; probably to avoid an unfavorable trans disposition between the two fused five-membered rings. Despite the fact two different configurations can be adopted by the iridium center, a single product is formed.…”

mentioning

confidence: 74%

“…The functionalization and stereochemistry of the chiral fullerene ligand determines the final configuration of the metal center. Interestingly, the chiral metal center does not undergo any epimerization process, as indicated by variable-temperature NMR analysis as well as by DFT theoretical calculations.The syntheses of the chiral metal-fullerene hybrids were inspired by the preparation of half-sandwich complexes with aminocarboxylate ligands, [9] and take advantage of the full control previously achieved in stereodivergent synthesis of pyrrolidino [60]fullerenes. [8a,d,e] Thus, the addition of a tBu-aiminoester, endowed with a labile ester moiety for further hydrolysis and complexation, was directed enantioselectively toward each one of the four possible stereoisomeric pyrrolidino [60]fullerenes by selecting the appropriate chiral metal catalyst.…”

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confidence: 99%

Stereodivergent‐at‐Metal Synthesis of [60]Fullerene Hybrids

et al. 2017

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Chiral fullerene-metal hybrids with complete control over the four stereogenic centers, including the absolute configuration of the metal atom, have been synthesized for the first time. The stereochemistry of the four chiral centers formed during [60]fullerene functionalization is the result of both the chiral catalysts employed and the diastereoselective addition of the metal complexes used (iridium, rhodium, or ruthenium). DFT calculations underpin the observed configurational stability at the metal center, which does not undergo an epimerization process.Preparation of fullerenes in multigram amounts by Krätschmer et al. in 1990 [1] permitted the study of the reactivity of the new carbon allotropes with transition-metal complexes, which subsequently arose as one of the main fields in fullerene science. [2] To date, interest in fullerene-transitionmetal complexes has been renewed in the search for new applications and synergies arising from the complementary properties of transition metals and fullerenes. [3] Transition metal involvement in organic transformations drives the investigation of new complexes with catalytic activity. In particular, preparative methods for chiral metal complexesspecifically chiral-at-metal complexes-are highly sought after in current organometallic chemistry because of their relevance in enantioselective metal-mediated processes. [4] Despite the wealth of metal-fullerene hybrids reported to date, only a few are optically active. [2,5] To the best of our knowledge, only a single case presents a stereogenic metal center, [6] while in all examples the chiral information stems from the stoichiometric use of chiral ligands. [7] In this regard, the use of asymmetric organo-and metal-catalysis in fullerene chemistry has provided an easy access to optically active derivatives by precise stereocontrol of the newly formed asymmetric carbon atoms. [8] Conversely, control of the metalcentered chirality is not a trivial issue because of the configurational lability of the metals, which often undergo rapid ligand exchange. [4] Herein, we report the first enantioselective synthesis of fullerene hybrids endowed with a stable stereogenic metal center whose configuration can be defined at will by the proper choice of chiral catalyst. In these reactions, iridium, rhodium, and ruthenium pyrrolidino [3,4:1,2][60]fullerene half-sandwich complexes with four new stereocenters are formed; namely the two C2 and C5 chiral carbon atoms at the pyrrolidine ring, the asymmetric nitrogen atom, and the transition-metal center (Scheme 1). The functionalization and stereochemistry of the chiral fullerene ligand determines the final configuration of the metal center. Interestingly, the chiral metal center does not undergo any epimerization process, as indicated by variable-temperature NMR analysis as well as by DFT theoretical calculations.The syntheses of the chiral metal-fullerene hybrids were inspired by the preparation of half-sandwich complexes with aminocarboxylate ligands, [9] and take advantage ...

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“…In this subject many papers on coordination compounds and organometallic ones have been published also during the past few years. 21 In addition to the above-mentioned goals, many other ones have initiated synthesis of various rhodium, 22,23 iridium, 22,23 ruthenium, 22,24 palladium 25 complexes of amino acids or derivatives. 9 A series of prepared and characterized Pt(II) and Pd(II) complexes of amino acid derivatives, 10 or analogues 11 have been tested as potential anticancer agents, but lower activities compared to that of cisplatin were detected.…”

Section: Introductionmentioning

confidence: 99%