Synthesis,stereodynamics, and reactivity of isonitrile derivatives of dodecacarbonyltetrairidium

The reaction of Ir₄₍CO)₁₂ with t-BuNC or MeNC in the presence of trimethylamine oxide in refluxing tetrahydrofuran provides the substituted iridium clusters Ir₄(CO)_12-x(RNC)_x] (χ  14; R  t-Bu, Me). The infrared and ¹³C NMR spectra of these molecules indicate that most of them adopt structures related to Ir₄(CO)₁₂, i.e., they have only terminal carbonyl ligands. The variable temperature ¹³C NMR spectra for Ir₄(CO)₁₁(t-BuNC) establish a carbonyl scrambling process which is the formal inverse of the C_3v→ T_d scrambling mechanism proposed for Rh₄(CO)₁₂. The kinetics of substitution of Ir₄(CO)₁₂ by t-BuNC have been studied. Each substitution step occurs by a ligand-dependent, overall second-order reaction at a rate much greater than for substitution by PPh₃. The observed differences between t-BuNC and PPh₃, can be rationalized on the basis of steric differences between the two ligands.     

Cluster chemistry,isocyanide complexes of ruthenium and hydridoruthenium carbonyls: crystal and molecular structure of Ru3(CO)11(CNBu-t)

Reactions between t-BuNC and Ru₃(CO)₁₂ or H₄Ru₄(CO)₁₂ afford Ru₃(CO)_12?n(CNBu-t)_n (n = 1, 2 or 3) and H₄Ru₄(CO)_12?n(CNBu-t)_n (n = 1, 2 or 4), respectively; an X-ray diffraction study of the molecular structure of Ru₃(CO)₁₁(CNBu-t) shows the isocyanide ligand to occupy an axial position, while from the ¹³C NMR spectrum, all CO groups are equivalent at low temperatures.     

New rhodium(I) supramolecular structures containing pyridyl and bipyridyl ligands

The use of dimeric [RhCl(CO)₂]₂ as acceptor unit in the construction of mono-, bi- and three-dimensional metallosupramolecular structures is reported.The reaction of the dimer with the alkynylgold complex [Au(CCC₅H₄N)(CNC₆H₄O(O)CC₆H₄OC₁₀H₂₁)] resulted in the mononuclear rhodium complex 1, through an unexpected transfer of the isonitrile ligand from the gold to the rhodium centres.The reaction of the linear unit [RhCl(CO)₂]₂(μ-4,4′-bipy) (3) with the diphosphine 1,4-bis(diphenylphosphino)butane (dppb) yielded the simultaneous formation of both metallomacrocycles [RhCl(CO)(dppb)]₂ (4) and {[RhCl(CO)]₂(μ-4,4′-bipy)}₂(μ-dppb)₂ (5). The use of a diphosphine with smaller bite angle, 1,1′-bis-(diphenylphosphino)methane, (dppm) formed the three-dimensional {[RhCl(CO)]₂(μ-4,4′-bipy)}₂(μ-dppm)₄ complex (6) that incorporates four diphosphine units connecting two [RhCl(CO)₂]₂(μ-bipy) linear edges. PM3 semi-empirical method has been used to calculate the optimised geometry of compound 6.     

Complexes dinucleaires pontes des metaux d8: VII. Reactions d'addition oxydante d'halogenures d'alkyle et d'acycle aux complexes μ-halogenes du rhodium(i) [RhX(CO)(PR3)]2. Structure cristalline de [RhCl(CO)(PMe2Ph)(Me)(Br)]2

The halogen bridged binuclear complexes of rhodium(I) [RhCl(CO)(PR₃)]₂ undergo oxidative addition with methyl halides to yield the complexes [RhCl(CO)(PR₃)(Me)(X)]₂ (X = Cl, Br). The crystal and molecular structures of [RhCl(CO)(PMe₂Ph)(Me)(Br)]₂ have been determined from a single crystal by use of X-ray crystallographic methods. The space group is Pca2₁ or Pacm with a 19.501(5), b 10.381(4), c 13.641(5) e? Z = 4. Parameters of 30 nonhydrogen atoms in the space group Pca2₁ were refined by the full-matrix least squares technique to a conventional R factor of 0.073. In a binuclear unit, each rhodium atom is in an octahedral environment being bonded to a carbonyl group, a methyl group and a tertiary phosphine ligand and three halogen atoms for which, due to a disorder phenomenon, the diffusion factors have been determined as the average between those of chlorine and bromine atoms. In solution the cis-migration of the methyl groups occurs, leading to the acetyl complexes. In the case of CH₃I, it is shown that an equilibrium is present in solution: [RhCl(CO)(PR₃(Me)(I)]₂ ? [RhCl(COMe)(PR₃)(I)(solvant)]₂] Carbonylation reactions shift this equilibrium to give the complexes [RhCl(CO)(COMe)(PR₃(I)]₂. Such complexes are readily prepared by direct oxidative addition of acyl halides to the compounds [RhCl(CO)(PR₃)]₂.     

Reaction of alkenyl carbonyl ruthenium(II) complexes with t-butyl isocyanide. Synthesis of η1-acylruthenium(II) complexes by intramolecular CO insertion

Reaction of Ru(CO)Cl(CHCHR)(PPh₃)₂ or Ru(CO)Cl(CHCHR)(PPh₃)₂L (L = py, Me₂Hpz) with 1 equivalent of t-butyl isocyanide gives the alkenyl derivatives Ru(CO)Cl(CHCHR)(PPh₃)₂(t-BuNC). When an excess of isocyanide is used, further reaction results in intramolecular CO insertion to yield η¹-acyl complexes [Ru(COCHCHR) (t-BuNC)₃(PPh₃)₂]Cl. Related complexes were obtained from [Ru(CO)(CHCHR)(MeCN)₂(PPh₃)₂]PF₆ and an excess of isocyanide.     

The reaction between [η5-C5H5M(CO)3]2, η5-C5H5M(CO)3I (M  Mo,W) and isonitriles

The reaction between η⁵-C₅H₅M(CO)₃I (M  Mo, W) and isonitriles, RNC, (RNC  PhCH₂NC, t-BuNC and 2,6-dimethylphenylisocyanide (XyNC)) is catalysed by the dimer [η⁵-C₅H₅M(CO)₃]₂ (M = Mo, W) to yield η⁵-C₅H₅M(CO)_3?n(RNC)_nI (n = 1–3) and [η⁵-C₅H₅Mo(RNC)₄]I. The complexes (η⁵-C₅H₅)₂Mo₂(CO)₆?n(RNC)_n (n = 1, RNC = MeNC, PhCH₂NC, XyNC, t-BuNC; n = 2, RNC = t-BuNC) have been prepared in moderate yield from the direct reaction between [η⁵-C₅H₅Mo(CO)₃]₂ and RNC, and also catalyse the above reaction. A reaction pathway involving a fast non-chain radical mechanism and a slower chain radical mechanism is proposed to account for the catalysed reaction.     

Rhodium(I) and Silver(I) Complexes of 4, 5‐Dicyano‐1, 3‐dimesityl‐ and 4, 5‐Dicyano‐1, 3‐dineopentylimidazol‐2‐ylidene

The new N‐heterocyclic carbene (NHC) precursors 4, ‐dicyano‐1, ‐dimesityl‐ ( 9 ) and 4, 5‐dicyano‐1, 3‐dineopentyl‐2‐(pentafluorophenyl)imidazoline ( 14 ) were synthesized. The structure of 9 could be determined by X‐ray crystallography. With the 2‐pentafluorophenyl‐substituted imidazolines 9 and 14 , the [AgCl(NHC)], [RhCl(COD)(NHC)], and [RhCl(CO)₂(NHC)] complexes [NHC = 4, 5‐dicyano‐1, 3‐dimesitylimidazol‐2‐ylidene ( 3 ) and 4, 5‐dicyano‐1, 3‐dineopentylimidazol‐2‐ylidene ( 4 )] were obtained. Crystal structures of [AgCl( 3 )] ( 15 ), [RhCl(COD)( 3 )] ( 17 ), [RhCl(COD)( 4 )] ( 18 ), and [RhCl(CO)₂( 3 )] ( 19 ) were solved and with the crystal data of 19 , the percent buried volume ( %V_bur) of 31.8(±0.1) % was determined for NHC 3 . Infrared spectra of the imidazolines 9 and 14 and of the complexes 15 – 20 were recorded and the CO stretching frequencies of complexes 19 and 20 were used to determine the Tolman electronic parameters of the newly obtained NHCs 3 (TEP: 2060 cm^–1) and 4 (TEP: 2061 cm^–1), thus proving that 1, 3‐substitution of maleonitrile‐NHCs does not have a significant effect for the high π‐acceptor strength of these carbenes.     

Ferrocenyl-nitrogen donor ligands. Synthesis and characterization of rhodium(I) complexes of ferrocenylpyridine and related ligands

The preparation of a series of complexes of the types [RhCl(CO)₂(L)], [RhCl(cod)(L)] and [Rh(cod)(L)₂]ClO₄, where L is a ligand incorporating a ferrocenyl group and a pyridine ring is described. Complexes were characterized using NMR, IR and electronic spectroscopy. The electrochemical behaviour of the complexes was examined using cyclic voltammetry. The X-ray structures of three of the complexes, [RhCl(CO)₂{NC₅H₄CNC₆H₄(η⁵-C₅H₄)Fe(η⁵-C₅H₅)}], [RhCl(cod)(3-Fcpy)] and [RhCl(cod){3-Fc(C₆H₄)py}], were determined.     

Chelates formed by a constrained bis(diphenylphosphino)xylene; the crystal structures of [FeCl2(anphos)] and [RhCl(CO)(anphos-monoxide)]

The indan derived diphosphine, cis-1,3-(diphenylphosphino)indan (anphos) is synthesised by the addition of Ph₂P(BH₃)Li to cis-1,3-dibromoindan followed by deprotection with diethylamine. Anphos readily forms the bicyclic chelates [RhCl(CO)(anphos)], [PtCl₂(anphos)], [PtCl(Me)(anphos)] and [FeCl₂(anphos)]. The crystal structures of [FeCl₂(anphos)] and the monoxide complex, [RhCl(CO)(anphosO)] have been determined. Reaction of the diphosphine with [Rh(acac)(CO)₂] under moderate hydroformylation conditions catalysed the formation of 1-heptanal and branched aldehydes from 1-hexene in a ratio of 1.5:1.     

μ,μ,-bis(alcoholato)- and μ,μ-bis(phenolato)dirhodium(I) tetracarbonyl complexes

Rh₂(CO)₄(OR)₂ complexes (R = Me, Et, Pr, i-pent, Ph, p-chlorophenyl) were prepared from Rh₂(CO)₄Cl₂ and sodium alcoholates or phenolates. They are converted by phosphines into the monomeric Rh(CO)(PR′₃)₂(OR) derivatives (R′ = Bu, Ph) via Rh₂(CO)₃(PR′₃)(OR)₂ intermediates.     

Alternativ-Liganden. XXII. Rhodium(I)-Komplexe mit Donor/Akzeptor-Liganden des Typs Me2PCH2CH2SiXnMe3−(X = F,Cl, OMe)

Alternative Ligands. XXII. Rhodium(I) complexes with Donor/Acceptor Ligands of the Typs Me₂PCH₂CH₂SiX_nMe_3?n(X = F, Cl, OMe) Donor/acceptor ligand of the type Me₂PCH₂SiX_nMe_3?n react with [Rh(CO)₂Cl]₂ ( 1 ) to give the mononuclear complexes RhCl(CO)(PMe₂CH₂CH₂SiX_nMe_3?n)₂ ( 2-6 , Table 1) with planar geometry of the donor atoms, one exception being Me₂PCH₂CH₂CH₂SiCl₃, yielding the crystalline Rh^III-complex RhCl₂(CO)(PMe₂CH₂CH₂SiCl₂)(PMe₂CH₂CH₂SiCl₃) ( 7 ) by oxidative addition of one of the SiCl bonds to the Rh¹ precursor. Structures with Rh → Si interaction between the basic central atoms and the acceptor group SiX_nMe_3?n could be detected in the isolated products neither spectroscopically nor by X-ray diffraction of the two representatives RhCl(CO)(PMe₂CH₂CH₂SiF₃)₂ ( 2 ) and RhCl(CO)[PMe₂CH₂CH₂siF₃]₂ ( 2 ) and RhCl(CO) [PMe₂CH₂CH₂Si(OMe₃]₂ ( 6 ). The presence of such acid/base adducts in the reaction mixture is indicated for the more acidic acceptor groups SiX_nMe_3?n byv_co values near 1990cm^?1, (see Table 3). The complex RhCl(CO)PMe₃)(PMe₂CH₂CH₂SiF₃ ( 8 ) is obtained by the reaction of RhCl(CO)(PMe₃)₂ ( 9 ) with Me₂PCH₂SiF₃ and has been identified spectroscopically in a mixture with 2 and 9 .     

Heterometallic cyanide-bridged complexes containing RhRuRh triad: NMR data on exchange reactions and ligand effect transmission

Trans-[RuPy₄(CN)₂ cleaves chloro-rhodium bridges in rhodium(I) binuclear complexes, [Rh(CO)₂Cl]₂, [Rh(Cod)Cl]₂, and [(Cod)RhCl₂Rh(CO)₂] yielding heterometallic triad complexes, [(CO)₂ClRh(NC)RuPy₄(CN)RhCl(CO)₂] (I), [(Cod)ClRh(NC)RuPy₄(CN)RhCl(Cod)] (II), and [(Cod)ClRh(NC)RuPy₄(CN)RhCl(CO)₂] (III), respectively. In solutions, III coexists with equilibrium amounts of I and II in the near-binomial proportions. Under action of [Rh(CO)₂Cl]₂, II transforms into I with parallel formation of [Rh(Cod)Cl]₂. Ligand effect transmission along the L-Rh-NC-Ru-CN-Rh-L′ chain is studied by ¹H and ¹³C NMR. Chemical shifts δ¹H and δ¹³C of Ru-bound Py ligands are sensitive to the nature of Rh-bound ligands. Values of δ¹H and δ¹³C of Cod and ¹³C of CO ligands are sensitive to the ligands at the remote end of the L-Rh-NC-Ru-CN-Rh-L′ chain. Reaction of trans-[RuPy₄(CN)₂] with Rh₂(OAc)₄ yields an apparently linear polymer [-Rh(OAc)₄Rh-NCRuPy₄CN-]. Upon action of [Rh(CO)₂Cl]₂, the polymer decomposes yielding I and Rh₂(OAc)₄. X-ray structure data for I are given.     

Efficient Rhodium‐Catalyzed Multicomponent Reaction for the Synthesis of Novel Propargylamines

[{Rh(μ‐Cl)(H)₂(IPr)}₂] (IPr = 1,3‐bis‐(2,6‐diisopropylphenyl)imidazole‐2‐ylidene) was found to be an efficient catalyst for the synthesis of novel propargylamines by a one‐pot three‐component reaction between primary arylamines, aliphatic aldehydes, and triisopropylsilylacetylene. This methodology offers an efficient synthetic pathway for the preparation of secondary propargylamines derived from aliphatic aldehydes. The reactivity of [{Rh(μ‐Cl)(H)₂(IPr)}₂] with amines and aldehydes was studied, leading to the identification of complexes [RhCl(CO)IPr(MesNH₂)] (MesNH₂ = 2,4,6‐trimethylaniline) and [RhCl(CO)₂IPr]. The latter shows a very low catalytic activity while the former brought about reaction rates similar to those obtained with [{Rh(μ‐Cl)(H)₂(IPr)}₂]. Besides, complex [RhCl(CO)IPr(MesNH₂)] reacts with an excess of amine and aldehyde to give [RhCl(CO)IPr{MesN?CHCH₂CH(CH₃)₂}], which was postulated as the active species. A mechanism that clarifies the scarcely studied catalytic cycle of A₃‐coupling reactions is proposed based on reactivity studies and DFT calculations.     

The effect of the conditions of the photocatalytic carbonylation of pentane catalyzed by the Rh2Cl2(CO)4-PMe3 system on the yield of C6-aldehyde

The yield of C₆-aldehyde in the photocatalytic system Rh₂Cl₂(CO)₄-PMe₃ passes through a maximum as the CO pressure and PMe₃ concentration increase. The increase in the yield of aldehydes with increasing CO pressure is related to the increase in the carbonylation rate and to the retardation of the photodecomposition of the aldehydes. The rate of the photocatalytic carbonylation of pentane in this system is 20 times higher than in the presence of RhCl(PMe₃)₂(CO).Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1013–1015, June, 1994.     

Enthalpy changes in oxidative addition reactions of iodine with monomeric and dimeric rhodium(I) complexes

The heat of reaction for addition of iodine to the planar complexes RhCl(CO)dppe, Rh(dppen)₂⁺, Rh(dppe)₂⁺ and to the dimer Rh₂Cl₂(CO)₂(dppm)₂ has been obtained by a calorimetric method. Iodine forms stronger Rh---I bonds with RhCl(CO)dppe than with the bichelate complexes. The presence of metal-metal interaction in the iodine addition compound of Rh₂Cl₂(CO)₂(dppm)₂ makes a significant contribution to the enthalpy change for the oxidative addition. The stereochemistry of the complexes are discussed on the basis of IR and ³¹P NMR spectra.     

Synthesis of (NHC)Rh(cod)Cl and (NHC)RhCl(CO)2 complexes – Translation of the Rh- into the Ir-scale for the electronic properties of NHC ligands

Twenty-three different Rh complexes of the (NHC)RhCl(cod) and (NHC)RhCl(CO)₂ type were synthesized from [RhCl(cod)]₂. The electron donating nature of the NHC ligands was changed in a systematic manner. The redox potentials of the various (NHC)RhCl(cod) and the ν(CO) of the various (NHC)RhCl(CO)₂ were determined. A correlation of the Rh redox potentials and the Rh ν(CO), respectively, with the related data from analogous (NHC)IrCl(cod) and (NHC)IrCl(CO)₂ complexes established two linear relationships. The linear regression (R² = 0.993) of the Rh and the Ir redox potentials results in an equation for the redox potential transformation: E_1/2(Ir) = 1.016 · E_1/2(Rh) ? 0.076 V. The linear regression (R² = 0.97) of the Rh and Ir ν_av(CO) results in an equation for the ν_av(CO) transformation: ν_av(CO)Ir = 0.8695 · ν_av(CO)Rh + 250.7 cm^?1. In this manner the Rh and the Ir-scale for the determination of the electron donating properties of NHC ligands are unified.     

Aqueous biphasic olefin hydroformylation catalyzed by water-soluble rhodium complexes

Catalysis with water-soluble rhodium complexes, RhCl(CO)(TPPMS)₂, [TPPMS = P(C₆H₅)₂(C₆H₄SO₃)] (1), RhCl(CO)(TPPDS)₂, [TPPDS = P(C₆H₅)(C₆H₄SO₃)₂] (2) and RhCl(CO)(TPPTS)₂, [TPPTS = P(C₆H₄SO₃)₃] (3) in hydroformylation of 1-hexene, 2-pentene, 2,3-dimethyl-1-butene, cyclohexene and several mixtures of these olefins have been studied, under moderate reaction conditions (T: 50–150 °C; pCO/pH₂ = 1; total p: 14–68 bar; Substrate/Catalyst: 600/1) in biphasic toluene/water media. The catalytic system shows high activity but low selectivity. The linear and branched oxygenated products obtained are equally useful in naphtha upgrading, as observed in the real El Palito naphtha tried. The catalysts can be recycled several times without significant activity loss.     

Phosphaalkynes as ligands in organometallic chemistry. Syntheses and 31p NMR spectra of platinum(II), palladium(II) and rhodium(I) complexes of dη5-cyclopentadienyltetracarbonyl-μ-(3,3-dimethyl-1-phosphabutyne)dimolybdenum, [Mo2(CO)4(η-c5H5)2tBuCP)]

Syntheses of the complexes trans-[PtCl₂(PR₃)Mo₂(CO)₄(η⁵-C₅H₅)₂(^tBuCP)], (PR₃=PEt₃, PPr₃, PBu₃, PPh₂Me, PPhMe₂) trans-[PdCl₂(PBu₃)Mo₂(CO)₄(η⁵-C₅H₅)₂(^tBuCP)], and trans[RhCl{(PF₂NMe)₂CO}Mo₂(CO)₄(η⁵-C₅H₅)₂(^tBuCP)] are described and their ³¹P NMR spectra presented and discussed.     

A one-pot method to prepare the carbene complex [TpRhCl2(CHNiPr2)] from [TpRh(CO)2], CHCl3, and NHiPr2

The complex [Tp^Me₂,ClRh(CO)₂] reacts with chloroform to give quantitatively the rhodium(III) complex [Tp^Me₂,ClRhCl(CHCl₂)(CO)] resulting from the oxidative addition of a C-Cl bond. Further reaction with diisopropylamine gives the aminocarbene complex [Tp^Me₂,ClRhCl₂(CHNiPr₂)], whose X-ray crystal structure has been solved. Addition of an excess of diisopropylamine to [Tp^Me₂,ClRh(CO)₂] in chloroform provides directly [Tp^Me₂,ClRhCl₂(CHNiPr₂)].     

Olefin complexes of rhodium(I) containing the ligands but-3-enyldiphenylphosphine and diphenylpent-4-enylphosphine

But-3-enyldiphenylphosphine (mbp) and diphenylpent-4-enylphosphine (mpp) react with Rh₂Cl₂(C₂H₄)₄ (molar ratio $\text{2}\text{1}$ to form the four coordinate dimeric complexes Rh₂Cl₂(mbp)₂ and Rh₂Cl₂(mpp)₂ respectively, while but-3-enyldiphenylphosphine reacts with Rh₂Cl₂(C₂H₄)₄ (molar ratio $\text{4}\text{1}$) to form RhCl(mbp)₂, a five coordinate complex in the solid state. The dimers further react with sodium tetraphenylborate to give the π-bonded tetraphenylborate complexes Rh[mbp][C₆H₅)₄B] and Rh[i-mpp][(C₆H₅)₄B] where i-mpp = (C₆H₅)₂P(CH₂CH₂CHCHCH₃). RhCl(CO)(mbp)₂ reacts with sodium tetraphenylborate to form the five coordinate cationic complex [Rh(CO)(mbp)₂][(C₆H₅)₄B]. Both RhCl(CO)(mbp)₂ and RhCl(mbp)₂ react with hydrogen in methanol saturating the olefin to form RhCl[CO][(C₆H₅)₂P(C₄H₉)]₂ and Rh₂Cl₂[(C₆H₅)₂P(C₄H₉)]₂ respectively.