Celebratory Symposium A – Catalysis and the Periodic Table Mechanistic Studies on Rhodium and Iridium Homogeneous Catalysts

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Intramolecular C-H oxidative addition to iridium(I) triggered by trimethyl phosphite in N,N′-diphosphanesilanediamine complexes

The reaction of [Ir(SiNP)(cod)][PF] ([1][PF]) and of IrCl(SiNP)(cod) (5) (SiNP = SiMe{N(4-CHCH)PPh}) with trimethyl phosphite affords the iridium(iii) derivatives of the formula [IrHCl(SiNP-H){P(OMe)}] (x = 0, 3; x = 1, 6) containing the κC,P,P′-coordinated SiNP-H ligand (SiNP-H = Si(CH)(CH){N(4-CHCH)PPh}). The thermally unstable pentacoordinated cation [Ir(SiNP){P(OMe)}(cod)] (2) has been detected as an intermediate of the reaction and has been fully characterised in solution. Also, the mechanism of the C-H oxidative addition has been elucidated by DFT calculations showing that the square planar iridium(i) complexes of the formula [IrCl(SiNP){P(OMe)}] (x = 0, 4; x = 1, 7) should be firstly obtained from 2 and finally should undergo the C-H oxidative addition to iridium(i) via a concerted intramolecular mechanism. The influence of the counterion of 2 on the outcome of the C-H oxidative addition reaction has also been investigated.Financial support from Spanish “Ministerio de Economía y Competitividad” (CTQ2013–42532–P), “Diputación General de Aragón” (Group E07) and University of Zaragoza (UZCUD2014–CIE–13) is gratefully acknowledged.Peer Reviewe

Intramolecular C-H oxidative addition to iridium(I) in complexes containing a N,N'-diphosphanosilanediamine ligand

The iridium(I) complexes of formula Ir(cod)(SiNP)+ (1+) and IrCl(cod)(SiNP) (2) are easily obtained from the reaction of SiMe2{N(4-C6H4CH3)PPh2}2 (SiNP) with [Ir(cod)(CH3CN)2]+ or [IrCl(cod)]2, respectively. The carbonylation of [1][PF6] affords the cationic pentacoordinated complex [Ir(CO)(cod)(SiNP)]+ (3+), while the treatment 2 with CO gives the cation 3+ as an intermediate, finally affording an equilibrium mixture of IrCl(CO)(SiNP) (4) and the hydride derivative of formula IrHCl(CO)(SiNP–H) (5) resulting from the intramolecular oxidative addition of the C–H bond of the SiCH3 moiety to the iridium(I) center. Furthermore, the prolonged exposure of [3]Cl or 2 to CO resulted in the formation of the iridium(I) pentacoordinated complex Ir(SiNP–H)(CO)2 (6). The unprecedented κ3C,P,P′ coordination mode of the [SiNP–H] ligand observed in 5 and 6 has been fully characterized in solution by NMR spectroscopy. In addition, the single-crystal X-ray structure of 6 is reported.Financial support from Spanish “Ministerio de Economía y Competitividad” (CTQ2010– 15221) and “Diputación General de Aragón” (Group E07) is gratefully acknowledged.Peer Reviewe

Tetranuclear [Rh4(μ-PyS2) 2(diolefin)4] complexes as building blocks for new inorganic architectures: Synthesis of coordination polymers and heteropolynuclear complexes with electrophilic d8 and d10 metal fragments

The reaction of [Rh4(μ-PyS2)2(cod) 4] (PYS2 = 2,6-pyridinedithiolate, cod = 1,5-cyclooctadiene) with CF3SO3Me gave the cationic complex [Rh4(μ-PyS2Me)2(cod) 4][CF3SO3]2 (1) with two 6-(thiomethyl)pyridine-2-thiolate bridging ligands from the attack of Me+ at the terminal sulfur atoms of the starting material. Under identical conditions [Rh4(μ-PyS2)2(tfbb)4] (tfbb = tetrafluorobenzobarrelene) reacted with CF3SO3Me to give the mixed-ligand complex [Rh4(μ-PyS2)(μ-PyS 2Me)(tfbb)4][CF3SO3] (2). The nucleophilicity of the bridging ligands in the complexes [Rh4(μ -PyS2)2(diolefin)4] was exploited to prepare heteropolynuclear species. Reactions with [Au(PPh3)(Me 2CO)][ClO4] gave the hexanuclear complexes [(PPh 3)2Au2Rh4(μ-PyS2) 2(diolefin)4][ClO4]2 (diolefin = cod (3), tfbb (4)). The structure of 4, solved by X-ray diffraction methods, showed the coordination of the [Au(PPh3)]+ fragments to the peripheral sulfur atoms in [Rh4(μ-PyS2) 2(diolefin)4 along with their interaction with the neighbor rhodium atoms. Neutral coordination polymers of formula [CIMRh 4(μ-PyS2)2(diolefin)4] n (M = Cu (5, 6), Au (7)) result from the self-assembly of alternating [Rh4(μ-PyS2)2(diolefin) 4] ([Rh4]) blocks and MCI linkers. The formation of the infinite polymetallic chains was found to be chiroselective for M = Cu; one particular chain contains exclusively homochiral [Rh4] complexes. Cationic heterometallic coordination polymers of formula [MRh 4(μ-PyS2)2(diolefin)4] n (M = Ag (8, 9), Cu (10, 11)) and [Rh5(μ-PyS 2)2(diolefin)5]n[BF 4]n (12, 13) result from the reactions of [Rh 4] with [Cu(CH3CN)4]BF4, AgBF 4, and [Rh(diolefin)(Me2CO)2]BF4, respectively. The heterometallic coordination polymers exhibit a weak electric conductivity in the solid state in the range (1.2-2.8) × 10-7 S cm-1.The financial support from Ministerio de Ciencia y Tecnología (MCyT(DGI)/FEDER, Projects BQU2002-00074 and BQU2000-1170) is gratefully acknowledged.Peer Reviewe

gem-selective cross-dimerization and cross-trimerization of alkynes with silylacetylenes promoted by a Rhodium-Pyridine-N-heterocyclic carbene catalyst

The gem-selective cross-dimerization and -trimerization of silylacetylenes with alkynes through C[BOND]H activation using a rhodium(I)–pyridine–N-heterocyclic carbene catalyst have been developed. This reaction is applied to various aliphatic or aromatic terminal alkynes, internal alkynes, and gem-1,3-disubsituted enynes to afford the corresponding enynes and dienynes with high regio- and stereoselectivities and in good isolated yields (up to 91 %).Financial support from the Spanish Ministerio de Economía y Competitividad (MEC/FEDER) of Spain Project (CTQ2010-15221), the Diputación General de Aragón (E07), the KFUPMUNIZAR agreement, and CONSOLIDER INGENIO-2010, under the Project MULTICAT (CSD2009-00050) are gratefully acknowledged. L. R.-P. thanks CONACyT (Mexico, 186898 and 204033) for a postdoctoral fellowship.Peer Reviewe

Early (Ti, Zr)-late (Rh, Ir) heteronuclear complexes with bridging sulphido ligands

[EN]: We report in this account on the controlled synthesis of novel d0-d8 early-late heteropolynuclear diolefin and carbonyl clusters. The synthetic approach was based on additive-deprotonation reactions involving the titanium and zirconium bis-hydrosulphido complexes of formula [Cp2Ti(SH)2] and [Cptt 2Zr(SH)2] and appropriate rhodium and iridium diolefin and carbonyl compounds. The significant differences between the resulting early-late complexes and their structures coming from the titanium or zirconium metalloligand precursors are highlighted. The catalytic activity of some representative titanium-rhodium and zirconium-rhodium compounds towards alkene hydroformylation was explored. Interestingly, the heterotetranuclear 'CpTi(μ3-S)3Rh3' structure was maintained as such under mild conditions.[FR]: Nous rapportons dans cet article la préparation contrôlée de nouveaux clusters hétéropolynucléaires early-late d0–d8 portant les ligands oléfine et carbonyle. La réaction de déprotonation–addition a été la méthode de synthèse utilisée et implique la condensation de complexes bis-hydrogénosulfure du titane et du zirconium, de formule [Cp2Ti(SH)2] et [Cptt2Zr(SH)2], sur les composés adéquats du rhodium et de l’iridium portant les ligands oléfine et carbonyle. Les différences significatives de structure entre les complexes early-late ainsi préparés, dues à la nature du métalloligand précurseur du titane ou du zirconium employé, sont mises en évidence. L’activité catalytique de quelques composés représentatifs titane–rhodium et zirconium–rhodium dans l’hydroformylation d’alcènes a été mesurée. Il convient de noter que la structure hétérotétranucléaire « CpTi(μ3-S)3Rh3 » est maintenue comme telle sous des conditions douces de réaction.Peer Reviewe

Heterolytic H2 activation on a carbene-ligated rhodathiaborane promoted by isonido-nido cage opening

A new mechanism of H2 activation is reported to occur on a carbene-ligated rhodathiaborane that features metal-thiaborane bifunctional synergistic effects. The key is the creation of vacant coordination sites by an isonido-nido structural transformation leading to the heterolytic H-H bond splitting. © 2013 The Royal Society of Chemistry.We gratefully acknowledge the Spanish Ministry of Science and Innovation (CTQ2009-10132, CSD2009-00050, and CSD2006-0015, CTQ2012-35665) for financial support. B.C. thanks the ‘‘Diputación General de Aragón’’ for a pre-doctoral scholarship.Peer Reviewe

An insight into transfer hydrogenation reactions catalysed by iridium(III) bis-N-heterocyclic carbenes

A variety of [M(L)2(L′)2{κC,C′-bis(NHC)}]BF4 complexes (M = Rh or Ir; L = CH3CN or wingtip group; L′ = I– or CF3COO–; NHC=N-heterocyclic carbene) have been tested as pre-catalysts for the transfer hydrogenation of ketones and imines. The conversions and TOF's obtained are closely related to the nature of the ligand system and metal centre, more strongly coordinating wingtip groups yielding more active and recyclable catalysts. Theoretical calculations at the DFT level support a classic stepwise metal-hydride pathway against the concerted Meerwein–Ponndorf–Verley (MPV) mechanism. The calculated catalytic cycle involves a series of ligand rearrangements due to the high trans effect of the carbene and hydrido ligands, which are more stable when situated in mutual cis positions. The reaction profiles obtained for the complexes featuring an iodide or a trifluoroacetate in one of the apical positions agree well with the relative activity observed for both catalysts.The authors would like to acknowledge the support by the Ministry of Higher Education, Saudi Arabia, in establishment of the Centre of Research Excellence in Petroleum Refining & Petrochemicals at KFUPM (KACST-funded project ART-32-68). The support under the KFUPM–University of Zaragoza research agreement is also highly appreciated. This work was further supported by the Spanish Ministry of Economy and Competitiveness (MINECO/FEDER) (CONSOLIDER INGENIO CSD2009-0050, CTQ2011-27593 and CTQ2012-35665 projects) and the Diputación General de Aragón (DGA/FSE-E07).Peer Reviewe