Chemistry of tetrairidium carbonyl clusters. Part 1. Synthesis, chemical characterization, and nuclear magnetic resonance study of mono- and di-substituted phosphine derivatives. X-Ray crystal structure determination of the diaxial isomer of [Ir4(CO)7(µ-CO)3(Me2PCH2CH2PMe2)]

Ros, Renzo; Scrivanti, Alberto; Albano, Vincenzo G.; Braga, Dario; Garlaschelli, Luigi

doi:10.1039/dt9860002411

Cited by 59 publications

(20 citation statements)

References 4 publications

(5 reference statements)

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“…Because it has been shown experimentally [40] that no more than four carbonyls can be substituted by phosphines, only the Ir 4 PH 3 (CO) 11 , Ir 4 (PH 3 ) 2 (CO) 10 , Ir 4 (PH 3 ) 3 (CO) 9 , and Ir 4 (PH 3 ) 4 (CO) 8 clusters are considered here. Besides the lowest energy isomers characterized by experiment, other isomers with substitution at various positions were also investigated, including both C 3v and T d structures and terminal and bridging position substitution and dissociation.…”

Section: Ir 4 (Ph 3 ) Y (Co) Z Structures Relative Energies and Dismentioning

confidence: 99%

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Structures, relative energies, and ligand dissociation energies of iridium carbonyl phosphine clusters

Zhang

Katz

Gates

et al. 2015

Computational and Theoretical Chemistry

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a b s t r a c tThere is significant interest in the catalytic properties of substituted iridium carbonyl clusters but little thermodynamic information available characterizing them. The low-energy isomers of Ir x (PH 3 ) y (CO) z (x = 1, 2, 4) were investigated with density functional theory and correlated molecular orbital theory at the coupled cluster CCSD(T) level. The relative energies and ligand dissociation energies were calculated. Differences in relative energies are consequences of both electronic and steric effects of the phosphines and carbonyls. The calculations predict three fundamental structural types for Ir 2 (PH 3 ) y (CO) z : C 2v , C 2 , and D 3d . Ten exchange-correlation functionals were used for the ligand dissociation energy calculations in addition to CCSD(T) for the smaller clusters. The xB97X-D functional gave the most consistent ligand dissociation energies as compared with the CCSD(T) benchmark calculations, and, so it was used to predict the dissociation energies for larger clusters when CCSD(T) calculations were infeasible. The dissociation energies characteristic of Ir 4 (PH 3 ) y (CO) z were in the range of $30 to $60 kcal/mol. Dissociation of a bridging ligand often involved a hydrogen atom transfer from a phosphine to a coordinatively unsaturated iridium atom and a phosphine converting from a bridging site to an equatorial site. The products of such reactions are predicted to have lower relative energies than other isomers.Phosphines act as r-electron donors, and there is a trend of an increase in carbonyl ligand dissociation energies as more phosphines are substituted in the small clusters.

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Section: Ir 4 (Ph 3 ) Y (Co) Z Structures Relative Energies and Dismentioning

confidence: 99%

“…1) ligand L is small; isomer b becomes preferred as the bulk of L increases [40]. Electronic effects may also be significant in this chemistry, reflecting the electron withdrawing or donating tendencies of the groups bonded to the phosphorus [38].…”

Section: Introductionmentioning

confidence: 99%

Structures, relative energies, and ligand dissociation energies of iridium carbonyl phosphine clusters

Zhang

Katz

Gates

et al. 2015

Computational and Theoretical Chemistry

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“…In the I3C-NMR spectrum of a I3C-enriched sample of 1 in CD,CI,/CHFCl [7], and the general observation that, in the I3C-and 3'P-NMR spectra of Ir, cluster compounds, the 6's of the ligands decrease in the positional sequence bridging > radial > axial x apical [9]. The four CO's c and e are undistinguishable, but this is of no importance for the following discussion.…”

Section: Nmr Study Ofmentioning

confidence: 90%

Intramolecular Dynamics of Tetranuclear Carbonyliridium Cluster Compounds. Part II. Disubstituted complexes with one chelating ligand. Crystal structure of [Ir₄(CO)₇(μ‐CO)₃(1,5‐cyclooctadiene)]

Strawczynski

Ros

Roulet

et al. 1988

Helvetica Chimica Acta

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The two complexes [Ir~(CO)lo(diarsine)] (1) and [Ir4(CO)Io( 1,5-cyclooctadiene)] (2) bear a bidentate ligand chelating one metal atom of the basal face of the Ir, tetrahedron. However, they differ in fluxional behaviour as observed by 2D-exchange' and variable-temperature I3C-NMR. The CO-site exchange with lowest activation energy proceeds via an unbridged intermediate in 2, whereas that in 1 occurs via a concerted edge-bridging of C O s to an alternative face of the metal core. This difference is apparently related to different ground-state geometries: the basal C O s are symmetrically bridging in 2, whereas two CO's are semi-bridging in 1. The molecular structure of 2 was determined by single crystal X-ray diffractometry. The crystals are orthorhombic, space group Pbcu, a = 11.651(4), b = 13.1 18(3), L' = 28.64(1) A. The idealized molecular symmetry is C,. The diolefin chelates a basal Ir-atom replacing an axial and a radial CO group on the tetrahedral metal-atom framework. ). The PEt, and Br-complexes have the same ground-state geometry with one axial L ligand, and behave similarly (the mechanism of CO exchange proposed in the first study on the PEt, complex has recently been reassessed [2], and is identical with that found for the Brcomplex). The latter two complexes have different ground-state geometries and present different fluxional processes.

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“…The "P-NMR spectrum of a freshly prepared sample of 1R in CD2C12 at 273 K consists of a doublet at 6 +10.6 ppm ('J(P,Rh) = 119.3 Hz) relative to external 85% H,PO,. The chemical-shift difference of the coordinated and free ligand (AS = +5.3 ppm) suggests that the Rh-bonded PPh, ligand is located in axial position from a comparison with the corresponding A6 values of [lr,(CO),,PPh,] [6] and of the axial isomer of [Ir,(CO),,PEt,] [la]. The "C-NMR spectrum of a sample of 1R enriched in "CO (ca.…”

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confidence: 98%

Variable‐Temperature and ‐Pressure ³¹P‐NMR Study of the Intramolecular PPh₃ Migration in the Cluster Compound [Ir₂Rh₂(CO)₁₁PPh₃]

Laurenczy

Bondietti

Merbach

et al. 1994

Helvetica Chimica Acta

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The reaction of [Ir2Rhz(CO)lz] with 1 mol-equiv. of PPh; yields [Ir,Rh,(CO),,PPh,] (1) as a mixture of two isomers with the phosphine ligand axially bound either to one basal Rh-atom in the kinetically preferred isomer 1R or to one basal Ir-atom in the thermodynamically preferred isomer 11. Both isomers are fluxional on the "C-NMR time scale at low temperature due to CO scrambling. Around room temperature, a new type of fluxional process starts to operate which is responsible for the isomerisation 1R F=? 11, i.r. the intramolecular migration of the reputedly inert PPh, ligand from one metal centre to another. The activation volumes ofconversions 1R + 11 and 11 + 1R are both positive, indicating that the migration of PPh, is dissociative in character. This article reports the first application of variable pressure 3'P-NMR to mechanistic studies. We report here on a new type of intramolecular rearrangement, distinct from CO scrambling, which was identified by a variable-temperature and variable-pressure "P-NMR study of the cluster compound [Ir2Rh,(CO),,PPh,] (1).

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Chemistry of tetrairidium carbonyl clusters. Part 1. Synthesis, chemical characterization, and nuclear magnetic resonance study of mono- and di-substituted phosphine derivatives. X-Ray crystal structure determination of the diaxial isomer of [Ir₄(CO)₇(µ-CO)₃(Me₂PCH₂CH₂PMe₂)]

Cited by 59 publications

References 4 publications

Structures, relative energies, and ligand dissociation energies of iridium carbonyl phosphine clusters

Structures, relative energies, and ligand dissociation energies of iridium carbonyl phosphine clusters

Intramolecular Dynamics of Tetranuclear Carbonyliridium Cluster Compounds. Part II. Disubstituted complexes with one chelating ligand. Crystal structure of [Ir₄(CO)₇(μ‐CO)₃(1,5‐cyclooctadiene)]

Variable‐Temperature and ‐Pressure ³¹P‐NMR Study of the Intramolecular PPh₃ Migration in the Cluster Compound [Ir₂Rh₂(CO)₁₁PPh₃]

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Chemistry of tetrairidium carbonyl clusters. Part 1. Synthesis, chemical characterization, and nuclear magnetic resonance study of mono- and di-substituted phosphine derivatives. X-Ray crystal structure determination of the diaxial isomer of [Ir4(CO)7(µ-CO)3(Me2PCH2CH2PMe2)]

Cited by 59 publications

References 4 publications

Structures, relative energies, and ligand dissociation energies of iridium carbonyl phosphine clusters

Structures, relative energies, and ligand dissociation energies of iridium carbonyl phosphine clusters

Intramolecular Dynamics of Tetranuclear Carbonyliridium Cluster Compounds. Part II. Disubstituted complexes with one chelating ligand. Crystal structure of [Ir4(CO)7(μ‐CO)3(1,5‐cyclooctadiene)]

Variable‐Temperature and ‐Pressure 31P‐NMR Study of the Intramolecular PPh3 Migration in the Cluster Compound [Ir2Rh2(CO)11PPh3]

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Chemistry of tetrairidium carbonyl clusters. Part 1. Synthesis, chemical characterization, and nuclear magnetic resonance study of mono- and di-substituted phosphine derivatives. X-Ray crystal structure determination of the diaxial isomer of [Ir₄(CO)₇(µ-CO)₃(Me₂PCH₂CH₂PMe₂)]

Intramolecular Dynamics of Tetranuclear Carbonyliridium Cluster Compounds. Part II. Disubstituted complexes with one chelating ligand. Crystal structure of [Ir₄(CO)₇(μ‐CO)₃(1,5‐cyclooctadiene)]

Variable‐Temperature and ‐Pressure ³¹P‐NMR Study of the Intramolecular PPh₃ Migration in the Cluster Compound [Ir₂Rh₂(CO)₁₁PPh₃]