Stereocontrol of Metal-Centred Chirality in Rhodium(III) and Ruthenium(II) Complexes with NN'P Ligand.

Rh(III) and Ru(II) complexes, [RhCl(κ-NN'P-L)][SbF] (1) and [RuCl(κ-NN'P-L)] (2), were synthesised using the tetradentate ligand L (L=N,N-bis[(pyridin-2-yl)methyl]-[2-(diphenylphosphino)phenyl]methanamine). In each case only one diastereomer is detected, featuring cis-disposed pyridine groups. The chloride ligand trans to pyridine can be selectively abstracted by AgSbF, with the ruthenium complex (2) reacting more readily at room temperature compared to the rhodium complex (1) which requires elevated temperatures.

Molecular Dihydrogen Activation by (CMe)M/N (M=Rh, Ir) Transition Metal Frustrated Lewis Pairs: Reversible Proton Migration to, and Proton Abstraction from, the CMe Ligand.

The masked transition-metal frustrated Lewis pairs [Cp*M(κN,N',N''-L)][SbF] (Cp*=η-CMe; M=Ir, 1, Rh, 2; HL=pyridinyl-amidine ligand) reversibly activate H under mild conditions rendering the hydrido derivatives [Cp*MH(κN,N'-HL)][SbF] observed as a mixture of the E and Z isomers at the amidine C=N bond (M=Ir, 3Z, 3E; M=Rh, 4Z, 4E). DFT calculations indicate that the formation of the E isomers follows a Grotthuss type mechanism in the presence of water. A mixture of Rh(I) isomers of formula [(Cp*H)Rh(κN,N'-HL)][SbF] (5 a-d) is obtained by reductive elimination of Cp*H from 4.

Dynamic Configuration on a Chiral-at-Rhodium Catalyst Featuring a Flexible Tetradentate Ligand.

The unique dynamic configuration of an enantioselective chiral-at-metal catalyst based on Rh(III) and a non-chiral tetradentate ligand is described and resolved. At room temperature, the catalyst undergoes a dynamic configuration process leading to the formation of two interconvertible metal-stereoisomers, remarkably without racemization. Density functional theory (DFT) calculations indicate that this metal-isomerization proceeds via a concerted transition state, which features a trigonal bipyramidal geometry stabilized by the tetradentate ligand.

Molecular hydrogen and water activation by transition metal frustrated Lewis pairs containing ruthenium or osmium components: catalytic hydrogenation assays.

The transition metal frustrated Lewis pair compounds [(Cym)M(κS,P,N-HL1)][SbF] (Cym = η--MeCHiPr; H2L1 = -(-tolyl)-'-(2-diphenylphosphanoethyl)thiourea; M = Ru (5), Os (6)) have been prepared from the corresponding dimer [{(Cym)MCl}(μ-Cl)] and H2L1 by successive chloride abstraction with NaSbF and AgSbF and NH deprotonation with NaHCO. Complexes 5 and 6 and the previously reported phosphano-guanidino compounds [(Cym)M(κP,N,N'-HL2)][SbF] [H2L2 = ,'-bis(-tolyl)-''-(2-diphenylphosphanoethyl) guanidine; M = Ru (7), Os (8)] and pyridinyl-guanidino compounds [(Cym)M(κN,N',N''-HL3)][SbF] [H2L3 = ,'-bis(-tolyl)-''-(2-pyridinylmethyl) guanidine; M = Ru (9), Os (10)] heterolytically activate H in a reversible manner affording the hydrido complexes [(Cym)MH(H2L)][SbF] (H2L = H2L1; M = Ru (11), Os (12); H2L = H2L2; M = Ru (13), Os (14); H2L = H2L3; M = Ru (15), Os (16)). DFT calculations carried out on the hydrogenation of complex 7 support an FLP mechanism for the process.

Synthesis and catalytic activity of well-defined Co(I) complexes based on NHC-phosphane pincer ligands.

A new methodology for the preparation of Co(I)-NHC (NHC = N-heterocyclic carbene) complexes, namely, [Co(PCP)(CO)][Co(CO)] (1) and [Co(PCP)(CO)]BF (2), has been developed (PCP = 1,3-bis(2-(diphenylphosphanyl)ethyl)-imidazol-2-ylidene). Both complexes can be straightforwardly prepared by direct reaction of their parent imidazolium salts with the Co(0) complex Co(CO). Complex 1 efficiently catalyses the reductive amination of furfural and levulinic acid employing silanes as reducing agents under mild conditions.

Correction: Iridium-(κ-NSi) catalyzed dehydrogenation of formic acid: effect of auxiliary ligands on the catalytic performance.

Correction for 'Iridium-(κ-NSi) catalyzed dehydrogenation of formic acid: effect of auxiliary ligands on the catalytic performance' by Alejandra Gomez-España , , 2023, , 6722-6729, https://doi.org/10.1039/d3dt00744h.

Mixed-Valence Tetrametallic Iridium Chains.

Neutral [X-{Ir }-{Ir }-X] (X=Cl, Br, SCN, I) and dicationic [L-{Ir }-{Ir }-L] (L=MeCN, Me CO) tetrametallic iridium chains made by connecting two dinuclear {Ir } units ({Ir }=[Ir (μ-OPy) (CO) ], OPy=2-pyridonate) by an iridium-iridium bond are described. The complexes exhibit fractional averaged oxidation states of +1.5 and electronic delocalization along the metallic chain.

Correction: Iridium-(κ-NSi) catalyzed dehydrogenation of formic acid: effect of auxiliary ligands on the catalytic performance.

Correction for 'Iridium-(κ-NSi) catalyzed dehydrogenation of formic acid: effect of auxiliary ligands on the catalytic performance' by Alejandra Gomez-España , , 2023, https://doi.org/10.1039/d3dt00744h.

Iridium-(κ-NSi) catalyzed dehydrogenation of formic acid: effect of auxiliary ligands on the catalytic performance.

The iridium(III) complexes [Ir(H)(Cl)(κ-NSi)(κ-bipy)] (2) and [Ir(H)(OTf)(κ-NSi)(κ-bipy)] (3) (NSi = {4-methylpyridine-2-yloxy}ditertbutylsilyl) have been synthesized and characterized including X-ray studies of 3. A comparative study of the catalytic activity of complexes 2, 3, [Ir(H)(OTf)(κ-NSi)(coe)] (4), and [Ir(H)(OTf)(κ-NSi)(PCy)] (5) (0.1 mol%) as catalysts precursors for the solventless formic acid dehydrogenation (FADH) in the presence of EtN (40 mol%) at 353 K has been performed.

Synthesis of chiral-at-metal rhodium complexes from achiral tripodal tetradentate ligands: resolution and application to enantioselective Diels-Alder and 1,3-dipolar cycloadditions.

An improved synthesis of the racemic rhodium compound [RhCl(κ ,,',-L1)] (1) containing an achiral tripodal tetradentate ligand is reported. Their derived solvate complexes [Rh(κ ,,',-L1)(Solv)][SbF] (Solv = NCMe, 2; HO, 3) are resolved into their two enantiomers. Complexes 2 and 3 catalyze the Diels-Alder (DA) reaction between methacrolein and cyclopentadiene and the 1,3-dipolar cycloaddition reaction between methacrolein and the nitrone -benzylidenphenylamine--oxide.

Activation of H-H, HO-H, C(sp)-H, C(sp)-H, and RO-H Bonds by Transition-Metal Frustrated Lewis Pairs Based on M/N (M = Rh, Ir) Couples.

Reaction of the dimers [(Cp*MCl)(μ-Cl)] (Cp* = η-CMe) with PhPCHCHNC(NH(-Tolyl)) () in the presence of NaSbF affords the chlorido complexes [Cp*MCl(κ,-)][SbF] (M = Rh, ; Ir, ). Upon treatment with aqueous NaOH, solutions of and yield the corresponding complexes [Cp*M(κ,,-)][SbF] (M = Rh, ; Ir, ) in which the ligand presents a κ,, coordination mode. Treatment of THF solutions of complexes and with hydrogen gas, at room temperature, results in the formation of the metal hydrido-complexes [Cp*MH(κ,-)][SbF] (M = Rh, ; Ir, ) in which the N(-Tolyl) group has been protonated.

2-Pyridone-stabilized iridium silylene/silyl complexes: structure and QTAIM analysis.

Iridium(iii) complexes of the general formula [Ir(X)(κ2-NSiiPr2)2] (NSiiPr2 = (4-methyl-pyridine-2-yloxy)diisopropylsilyl; X = Cl, 3; CF3SO3, 5; CF3CO2, 6) have been prepared and fully characterized, including X-ray diffraction studies and theoretical calculations. The presence of isopropyl substituents at the silicon atom favours the monomeric structure found in complexes 3 and 5. The short Ir-Si bond distances (2.

Catalytic Enantioselective Alkylation of Indoles with -4-Methylthio-β-Nitrostyrene.

The reaction of the rhodium aqua-complex ( , )-[Cp*Rh{()-Prophos} (OH)][SbF] [Cp* = CMe, Prophos = propane-1,2-diyl-bis(diphenylphosphane)] () with -4-methylthio-β-nitrostyrene (MTNS) gives two linkage isomers ( , )-[Cp*Rh{()-Prophos}(κ -MTNS)] () and ( , )-[Cp*Rh{()-Prophos}(κ -MTNS)] () in which the nitrostyrene binds the metal through one of the oxygen atoms of the nitro group or through the sulfur atom, respectively. Both isomers are in equilibrium in dichloromethane solution, the equilibrium constant being affected by the temperature in such a way that when the temperature increases, the relative concentration of the oxygen-bonded isomer increases. The homologue aqua-complex of iridium, ( , )-[Cp*Ir{()-Prophos}(OH)][SbF] (), also reacts with MTNS; but only the sulfur-coordinated isomer ( , )-[Cp*Ir{()-Prophos}(κ -MTNS)] () is detected in the solution by NMR spectroscopy.

Half-sandwich complexes of osmium containing guanidine-derived ligands.

Pyridinyl- and phosphano-guanidino complexes of formula [(η6-p-cymene)OsCl(H2L)][SbF6] (cymene = MeC6H4iPr; H2L = N,N'-bis(p-Tolyl)-N''-(2-pyridinylmethyl)guanidine, H2L1 (1) and N,N'-bis(p-Tolyl)-N''-(2-diphenylphosphanoethyl)guanidine, H2L2 (2)) have been prepared from the dimer [{(η6-p-cymene)OsCl}2(μ-Cl)2] and H2L in the presence of NaSbF6. Treatment of complex 2 with HCl renders the phosphano-guanidinium complex [(η6-p-cymene)OsCl2(H3L2)][SbF6] (3). Compounds 1 and 2 react with AgSbF6 rendering the cationic aqua complexes [(η6-p-cymene)Os(H2L)(OH2)][SbF6]2 (H2L = H2L1 (4), H2L2 (5)).

Rhodium(I)-NHC Complexes Bearing Bidentate Bis-Heteroatomic Acidato Ligands as gem-Selective Catalysts for Alkyne Dimerization.

A series of Rh(κ -BHetA)(η -coe)(IPr) complexes bearing 1,3-bis-hetereoatomic acidato ligands (BHetA) including carboxylato (O,O), thioacetato (O,S), amidato (O,N), thioamidato (N,S), and amidinato (N,N), have been prepared by reaction of the dinuclear precursor [Rh(μ-Cl)(IPr)(η -coe)] with the corresponding anionic BHetA species. The Rh -NHC-BHetA compounds catalyze the dimerization of aryl alkynes, showing excellent selectivity for the head-to-tail enynes. Among them, the acetanilidato-based catalyst has shown an outstanding catalytic performance reaching unprecedented TOF levels of 2500 h with complete selectivity for the gem-isomer.

Unprecedent formation of methylsilylcarbonates from iridium-catalyzed reduction of CO with hydrosilanes.

The iridium complex [Ir(μ-CFSO)(κ-NSi)] (3) (NSi = {4-methylpyridine-2-yloxy}dimethylsilyl) has been prepared by reaction of [Ir(μ-Cl)(κ-NSi)] (1) with two equivalents of AgCFSO. The solid structure of 3 evidenced its dinuclear nature, being a rare example of an iridium species with triflate groups acting as bridges. The 3-catalyzed reduction of CO with HSiMe(OSiMe) affords a mixture of the corresponding silylformate and methoxysilane together with the silylcarbonate CHOCOSiMe(OSiMe) (4a).

Reversible Activation of Water by an Air- and Moisture-Stable Frustrated Rhodium Nitrogen Lewis Pair.

[Cp*Rh(κ N,N',P-L)][SbF ] (Cp*=C Me ), bearing a guanidine-derived phosphano ligand L, behaves as a "dormant" frustrated Lewis pair and activates H and H O in a reversible manner. When D O is employed, a facile H/D exchange at the Cp* ring takes place through sequential C(sp )-H bond activation.

Synthesis and reactivity at the Ir-Tpm platform: from κ-N coordination to κ-N-based organometallic chemistry.

Reaction of [Ir(μ-Cl)(COE)2]2 (COE = cis-cyclooctene) with tris(3,5-dimethylpyrazol-1-yl)methane (MeTpm) affords [IrCl(κ1-N-MeTpm)(COD)] (1) (COD = 1,5-cyclooctadiene). The formation of 1 implies the transfer dehydrogenation of a COE ligand to give COD and COA (cyclooctane). A mechanistic proposal based on DFT calculations that explains this iridium promoted process has been disclosed.

Selective reduction of formamides to O-silylated hemiaminals or methylamines with HSiMePh catalyzed by iridium complexes.

The reaction of (4-methyl-pyridin-2-iloxy)ditertbutylsilane (NSitBu-H, 1) with [IrCl(coe)2]2 affords the iridium(iii) complex [Ir(H)(Cl)(κ2-NSitBu)(coe)] (2), which has been fully characterized including X-ray diffraction studies. The reaction of 2 with AgCF3SO3 leads to the formation of species [Ir(H)(CF3SO3)(κ2-NSitBu)(coe)] (3). The iridium complexes 2 and 3 are effective catalysts for the reduction of formamides with HSiMe2Ph.

Zwitterionic Rhodium and Iridium Complexes Based on a Carboxylate Bridge-Functionalized Bis-N-heterocyclic Carbene Ligand: Synthesis, Structure, Dynamic Behavior, and Reactivity.

A series of water-soluble zwitterionic complexes featuring a carboxylate bridge-functionalized bis-N-heterocyclic carbene ligand of formula [Cp*MCl{(MeIm)CHCOO}] and [M(diene){(MeIm)CHCOO}] (Cp* = 1,2,3,4,5-pentamethylcyclopentadienyl; M = Rh, Ir; MeIm = 3-methylimidazol-2-yliden-1-yl; diene = 1,5-cyclooctadiene (cod), norbornadiene (nbd)) were prepared from the salt [(MeImH)CHCOO]Br and suitable metal precursor. The solid-state structure of both types of complexes shows a boat-shaped six-membered metallacycle derived of the κC,C' coordination mode of the bis-NHC ligand. The uncoordinated carboxylate fragment is found at the bowsprit position in the Cp*M complexes, whereas in the M(diene) complexes it is at the flagpole position of the metallacycle.

Metal as Source of Chirality in Octahedral Complexes with Tripodal Tetradentate Ligands.

The challenging control of the absolute configuration of chiral-at-metal complexes is efficiently achieved using the tripodal tetradentate ligand L. The optical resolution of rac-[RhCl(κC,N,N',P-L)] mediated by (S)-α-phenylglycine provides access to enantiopure complexes of general formula [Rh(κC,N,N',P-L)A(Solv)][SbF] that enantioselectively catalyze the Diels-Alder reaction between methacrolein and HCp with enantiomeric ratio of up to >99/1. The nature of the active species, the origin of the enantioselectivity and mechanistic details are disclosed by means of NMR spectroscopy and DFT studies.

Half-sandwich complexes of Ir(iii), Rh(iii) and Ru(ii) with the MaxPhos ligand: metal centred chirality and cyclometallation.

The reaction of the acetylacetonates [(η-CMe)M(acac)Cl] with (S)-[HMaxPhos][BF] afforded cationic complexes with the formula (S,R)-[(η-CMe)MCl(MaxPhos)][BF] (M = Rh (1), Ir (2)). The reaction of (S)-MaxPhos with [RuCl(μ-Cl)(η-p-MeCHPr)] and NHX afforded (S,R)-[(η-p-MeCHPr)RuCl(MaxPhos)][X] (X = BF (3), PF (3')). The complexes have been completely characterized by analytical and spectroscopic means, including the determination of the crystal structures of 1, 2 and 3'.

Reactivity of the parent amido complexes of iridium with olefins: C-NH bond formation versus C-H activation.

Herein we report on the different chemical reactivity displayed by two mononuclear terminal amido compounds depending on the nature of the coordinated diene. Hence, treatment of amido-bridged iridium complexes [{Ir(μ-NH)(tfbb)}] (1; tfbb = tetrafluorobenzobarrelene) with dppp (dppp = bis(diphenylphosphane)propane) leads to the rupture of the amido bridges forming the mononuclear terminal amido compound [Ir(NH)(dppp)(tfbb)] (3) in the first stage. On changing the reaction conditions, the formation of a C-NH bond between the amido moiety and the coordinated diene is observed and a new dinuclear complex [{Ir(1,2-η-4-κ-CHFN)(dppp)}(μ-dppp)] (4) has been isolated.

The Stepwise Reaction of Rhodium and Iridium Complexes of Formula [MCl (κ C,N,N',P-L)] with Silver Cations: A Case of trans-Influence and Chiral Self-Recognition.

Acetonitrile suspensions of the dichlorido complexes [MCl (κ C,N,N',P-L)] [M=Rh (1), Ir (2)] react with AgSbF in a 1:2 molar ratio affording the bis-acetonitrile complexes [M(κ C,N,N',P-L)(NCMe) ][SbF ] (3 and 4). The reaction takes place in a sequential manner and the intermediates can be isolated varying the M:Ag molar ratio. In a 2:1 molar ratio, it affords the dimetallic monochlorido-bridged compounds [{MCl(κ C,N,N',P-L)} (μ-Cl)][SbF ] (5 and 6).