Multiple state emission from rhodium(I) and iridium(I) complexes

The effect of temperature (2–100 K) on the emission spectra and lifetimes of [M(2 = phos)₂]ClO₄ (M = Rh(I), Ir(I): 2 = phos is cis-1,2-bis-(diphenylphosphino)ethylene) is interpreted with a two-level spin-orbit-split emitting manifold. For [Ir(2 = phos)₂]ClO₄, Δ? = 143cm^?1, τ(lower) = 999μs, and τ(higher) = 1.54 μs. For the rhodium species, Δ? = 35 cm^?1, τ(lower) = 5920 μs, and τ(higher) = 20.3 μs.     

Intramolecular rearrangement in diphenylfulvene complexes of iridium(I) and rhodium(I)

Variable temperature NMR spectra of the complexes [M(C₅H₄CPh₂)(C₈H₁₂)]X (C₅H₄CPh₂ = 6,6-diphenylfulvene; C₈H₁₂ = 1,5-cyclooctadiene; M = Ir, X = PF₆; M = Rh, X = ClO₄) provide evidence of intramolecular rearrangement involving rotation of the diphenylfulvene ligand about the metal-fulvene axis. Rearrangement is slow on the NMR time-scale for both complexes at 223 K: spectra recorded at higher temperatures indicate that the barrier to rotation of the diphenylfulvene ligand is lower for the iridium than for the rhodium complex.     

Oxidative addition of dialkylphosphites to complexes of iridium(I) and rhodium(I)

The PH bond of dialkylphosphites (dimethylphosphite, 5,5-dimethyl-1,3-dioxa-2-phosphorinane and 4,4,5,5-tetramethyl-1,3-dioxa-2-phospholane) oxidatively adds to irClL₂(L = PPh₃, AsPh₃) and IrCl(PMe₂Ph)₃ generated in situ to give six-coordinate hydrido(dialkylphosphonato)iridium(III) complexes, e.g. IrHClL₂[{(MeO)₂-PO}₂H] and IrHCl(PMe₂Ph)₃[PO(OMe)₂]. Addition of triphenylphosphine to a solution containing [IrCl(C₈H₁₄)₂]₂ and dimethylphosphite in a 1:2 mol ratio gives a five-coordinate hydrido (dimethylphosphonato)iridium(III) complex IrHCl(PPh₃)₂{PO(OMe)₂}, from which six-coordinate pyridine and acetylacetonato complexes IrHCl(PPh₃)₂(C₅H₅N){PO(OMe)₂} and IrH(PPh₃)₂(acac){PO(OMe)₂} can be obtained. The ligand arrangements in the various complexes are inferred from IR, ¹H and ³¹P NMR data.     

Binuclear copper(I) macrocycles synthesized via the weak-link approach

The weak-link approach has been employed to synthesize a series of bimetallic Cu(I) macrocycles in high yield. Addition of phosphinoalkylether or -thioether ligands to [Cu(MeCN)4]PF6 produces "condensed" intermediates, [mu-(1,4-(PPh2CH2CH2X)2Y)2Cu2][PF6]2 (X = S, O; Y = C6H4, C6F4), containing strong P-Cu bonds and weaker O-Cu or S-Cu bonds. The weak bonds of these intermediates can be cleaved through ligand substitution reactions to generate macrocyclic structures, [mu-(1,4-(PPh2CH2CH2X)2Y)2(Z)nCu2][PF6]2 (X = S, O; Y = C6H4, C6F4; Z = pyridine, acetonitrile, diimines, isocyanide) in nearly quantitative yields. The incorporation of tetrahedral Cu(I) metal centers into these macrocycles provides a pathway to complexes that differ from analogous d8 square planar macrocycles generated via this approach in their increased air stability, small molecule reactivity, and ability to form multiple structural isomers. Solid-state structures, as determined by single-crystal X-ray diffraction studies, are presented for condensed intermediates and an open macrocycle     

Hydrogenation of cyclohexene catalyzed by polymer- bound rhodium(I) and iridium(I) complexes

The catalytic hydrogenation of cyclohexene using Rh^I and Ir^I polymer-bound cationic complexes as catalysts is reported, and the solvent effect in these reductions has been investigated. In most case the reaction is characterized by the presence of a solvent-dependent induction period which has been investigated and is discussed. In several cases ESR-active Rh^II species have been detected at the end of the catalytic reaction. Recycling of the catalysts led to higher catalytic activity.     

Functionalized phosphorus analogues of the beta-diketiminato ligand systems: bis(N-arylphosphinimino)acetonitrile-derived complexes of rhodium and iridium

Staudinger reaction of dppm-CN (5) gave the corresponding bis(N-phenylphosphinimino)acetonitrile system (6). Deprotonation with LDA furnished the corresponding anionic ligand 9. Its reaction with [(CO)(2)RhCl](2) gave the corresponding kappa(2)N,N'-chelate complex 11. X-Ray diffraction revealed a non-planar boat-like conformation of the six-membered chelate ring in the crystal. Treatment of 9 with [(nbd)RhCl](2) gave the six-membered chelate complex 12 which features a different twist-like structure in the solid state, as does 13, which was formed by reacting 9 with [(cod)IrCl](2).     

Carbonyl cationic rhodium(I) and iridium(I) complexes with sulphur donor and triphenylphosphine ligands

Summary The reaction of previously reported Rh^I and Ir^I cationic complexes towards carbon monoxide and triphenylphosphine has been studied. Carbonyl rhodium(I) mixed complexes of the formulae [Rh(CO)L₂(PPh₃)]ClO₄, (L=tetrahydrothiophene(tht), trimethylene sulfide(tms), SMe₂, or SEt₂), [(CO)(PPh₃)Rh{-(L-L)}₂Rh(PPh₃)(CO)](ClO₄)₂ (L-L= 2,2,7,7-tetramethyl-3,6-dithiaoctane (tmdto), (MeS)₂(CH₂)₃ (dth), or 1,4-dithiacyclohexane (dt), [Rh(CO)L(PPh₃)₂]ClO₄ (L= tht, tms, SMe₂, or SEt₂), and carbonyl iridium(I) complexes of the formulae [Ir(CO)₂(COD)(PPh₃)]ClO₄, [Ir(CO)(COD)(PPh₃)₂]ClO₄, [(CO)(COD)(PPh₃) Ir{-(L-L)} Ir(PPh₃)(COD)(CO)](ClO₄)₂ (L-L = tmdto or dt), [(CO)₂ (PPh₃)Ir(-tmdto)Ir(PPh₃)(CO)₂](ClO₄)₂, [(CO)₂(PPh₃) Ir(-dt)₂Ir(PPh₃)(CO)₂](ClO₄)₂, were prepared by different synthetic methods.     

Cationic rhodium(I) and iridium(I,III) complexes of cinnamonitrile and their catalytic activities

Summary Reactions of cinnamonitrile (trans-PhCH=CHCN) with [M(ClO₄)(CO)(PPh₃)₂] (M=Rh or Ir) produce hydrogenation oftrans-PhCH=CHCN to PhCH₂CH₂CN at 100°C under 3 atm of hydrogen.     

Oxidative addition of dimethylphosphite to iridium(I) and rhodium(I) complexes: Stereoselective reduction of 4-t-butylcyclohexanone

Dimethylphosphite, (CH₃O)₂P(O)H, adds oxidatively to iridium(I) and rhodium(I) complexes to give hydrido-iridium(III) or -rhodium(III) dimethylphosphonate complexes. A complex Ir(H)Cl[P(O)(OCH₃)₂][P(OH)(OCH₃)₂]₃ obtained from [IrCl(C₈H₁₄)₂]₂ and dimethylphosphite catalyses the stereo-selective reduction of 4-t-butylcyclohexanone to $\text{97}\text{3}$cis/trans-4-t-butylcyclohexanol, the ratio being identical with that obtained using the Henbest catalyst iridium(IV) chloride, phosphorous acid or one of its esters, and aqueous isopropanol.     

Reversible switching of the sol-gel transition with ultrasound in rhodium(I) and iridium(I) coordination networks

Reversible coordination networks were prepared by combining diphenylphosphinite telechelic polytetrahydrofuran (2) with [RhCl(COD)]2 or [IrCl(COD)]2 in chloroform. Both systems resulted in stable gels at concentrations above 50 and 30 g/L for the rhodium(I) and iridium(I) networks, respectively. The rheological properties of the two coordination networks (100 g/L) were determined with oscillatory shear experiments, which showed that the elastic moduli are constant over a wide frequency range, indicating gel-like behavior; the iridium(I) gel has an elastic modulus distinctly higher (2.8x10(3) Pa) than that of the rhodium(I) gel (1.0x10(3) Pa). Ultrasonication of the rhodium(I) gel caused liquefaction after 3 min; regelation occurred 1 min after sonication was stopped. The iridium(I) gel was also liquefied after 3 min of sonication, but regelation took 1.5 h at room temperature and more than 10 days at -20 degrees C. 31P NMR measurements on model complexes showed that the large differences in gelation times are in agreement with the ligand exchange kinetics of the rhodium(I) and iridium(I) complexes. We propose that sonication of the gels results in ligand exchange, which changes the network topology without changing the coordination chemistry. Upon sonication, the fraction of metal centers in active cross-links decreases and thereby reduces the gel fraction to zero. The system is not at equilibrium, and upon standing the gel fraction increases at a rate that is determined by the exchange kinetics of the metal complex. The observed effects offer opportunities to use ultrasound in the activation of dormant transition metal catalysts.     

The classification of trigonal bipyramidal platinum(II), rhodium(I) and iridium(I) olefin complexes

It is shown that trigonal bipyramidal platinum(II), rhodium(I) and iridium(I) olefin complexes are better classified with the platinum(O) complex [Pt(PPh₃)₂(C₂H₄)] as class T olefin complexes than with the square-planar platinum(II) complexes such as [Pt(C₂H₄)Cl₃]^- which fall in class S. The underlying reasons for this are considered to be electronic rather than steric as was previously suggested.     

Preparation and catalytic activity of cationic rhodium(I) and iridium(I) complexes with phosphine sulphide ligands

The preparation and properties of cationic rhodium and iridium complexes of types [M(diolefin)L₂](ClO₄) and [M(diolefin)L(PPh₃)](ClO₄) [M = Rh, diolefin = 1,5-cyclooctadiene (COD) or 2,5-norbornadiene; M = Ir, diolefin = COD; L = phosphine sulphide] are described. The complexes have been characterized by IR, ¹H NMR and ³¹P NMR spectroscopy. The use of [M(diolefin)L₂](ClO₄) as catalyst precursors in homogeneous hydrogenation of olefins has been studied.     

1,4-Bis(4-nitrosophenyl)piperazine: novel bridging ligand in dinuclear complexes of rhodium(III) and iridium(III)

The synthesis, spectroscopic characterization and crystal structures of the first 1,4-bis(4-nitrosophenyl)piperazine (BNPP) (4) bridged dinuclear complexes of rhodium(III) and iridium(III) are presented. The reaction of the μ(2)-halogenido-bridged dimers [(η(5)-C(5)Me(5))IrX(2)](2) [X = Cl (5a), Br (5b), I (5c)] and [(η(5)- C(5)Me(5))RhCl(2)](2) (6a) with 4 yields the dinuclear complexes [(η(5)-C(5)Me(5))IrX(2)](2)-BNPP (7a-c) and [(η(5)-C(5)Me(5))RhCl(2)](2)-BNPP (8a). All new compounds were characterized by their NMR, IR and mass spectra. The X-ray structure analyses of the obtained half-sandwich complexes revealed a slightly distorted pseudo-octahedral configuration ("three-legged pianostool") for the metal(III) centers. The bridging BNPP ligand is σ-N coordinated by both nitroso groups and shows different conformations of the piperazine ring depending on the solvent used for crystallization. Moreover the crystal structures of 1,4-bis(4-nitrosophenyl)piperazine (4) and its precursor 1,4-diphenylpiperazine (3) are reported.     

Mono and dinuclear cationic rhodium(I) and iridium(I) complexes with sulphur donor and group Vb ligands

Summary Rhodium(I) and iridium(I) mixed complexes of the formulae [M(diolefin)LL]ClO₄, [M(diolefin)L₂L]ClO₄, [(diolefin)LIr(-L)₂IrL(diolefin)](ClO₄)₂, [(diolefin)LM(-L-L)ML'(diolefin)](ClO₄)₂, [(diolefin)Rh{-(L-L)}₂Rh(PPh₃)₂](ClO₄)₂ and [(diolefin)LIr{-(L-L)}₂IrL (diolefin)](C1O₄)₂, (L=monodentate sulphur ligand, L-L=bidentate sulphur ligand, L=group Vb ligand; M=Rh, diolefin=1,5-cyclooctadiene (COD) or 2,5-norbornadiene (NBD); M=Ir, diolefin=COD) are described.Author to whom all correspondence should be directed.     

Complexes of rhodium(I) and iridium(I) with 2,2′-bipyridine and similar ligands as hydrogenation catalysts

Complexes of the type [Rh(Chel)ED]PF₆ (Chel = 2,2-bipyridine; 1,10-phenanthroline; methyl substituted phenanthrolines; ED = 1,5-hexadiene; X^- = PF₆^-; B(Ph)₄) have been synthesized. They are good catalysts for hydrogenation of ketones in an alkaline medium even at atmospheric pressure and room temperature. In the presence of an excess of Chel (Chel : Rh = 2), they also catalyse the selective reduction of C=O groups in the presence of C=C bonds.     

Allylic C-H bond activation and functionalization mediated by tris(oxazolinyl)borato rhodium(I) and iridium(I) compounds

Allylic C-H bond oxidative addition reactions, mediated by tris(oxazolinyl)borato rhodium(I) and iridium(I) species, provide the first step in a hydrocarbon functionalization sequence. The bond activation products To(M)MH(η(3)-C(8)H(13)) (M = Rh (1), Ir (2)), To(M)MH(η(3)-C(3)H(5)) (M = Rh (3), Ir (4)), and To(M)RhH(η(3)-C(3)H(4)Ph) (5) (To(M) = tris(4,4-dimethyl-2-oxazolinyl)phenylborate) are synthesized by reaction of Tl[To(M)] and the corresponding metal olefin chloride dimers. Characterization of these group 9 allyl hydride complexes includes (1)H-(15)N heteronuclear correlation NMR experiments that reveal through-metal magnetization transfer between metal hydride and the trans-coordinated oxazoline nitrogen. Furthermore, the oxazoline (15)N NMR chemical shifts are affected by the trans ligand, with the resonances for the group trans to hydride typically downfield of those trans to η(3)-allyl and tosylamide. These group 9 oxazolinylborate compounds have been studied to develop approaches for allylic functionalization. However, this possibility is generally limited by the tendency of the allyl hydride compounds to undergo olefin reductive elimination. Reductive elimination products are formed upon addition of ligands such as CO and CN(t)Bu. Also, To(M)RhH(η(3)-C(8)H(13)) and acetic acid react to give To(M)RhH(κ(2)-O(2)CMe) (8) and cyclooctene. In contrast, treatment of To(M)RhH(η(3)-C(3)H(5)) with TsN(3) (Ts = SO(2)C(6)H(4)Me) gives the complex To(M)Rh(η(3)-C(3)H(5))NHTs (10). Interestingly, the reaction of To(M)RhH(η(3)-C(8)H(13)) and TsN(3) yields To(M)Rh(NHTs)(H)OH(2) (11) and 1,3-cyclooctadiene viaβ-hydride elimination and Rh-H bond amination. Ligand-induced reductive elimination of To(M)Rh(η(3)-C(3)H(5))NHTs provides HN(CH(2)CH=CH(2))Ts; these steps combine to give a propene C-H activation/functionalization sequence.     

Regiocontrolled synthesis of allylsilanes by means of rhodium(I) or iridium(I) catalyzed isomerization of olefins

Rhodium(I) or iridium(I) catalyzed migration of double-bond has been successfully applied to the regiocontrolled synthesis of allylsilane from olefin silylated at a remote sp carbon.