Rhodium(I) complexes with the 2,2′-bipyrimidine ligand

Mono- and dinuclear rhodium(I) complexes of formulae [Rh(L₂)(bipym)]⁺ and [{Rh(L₂)}₂(μ-bipym)]²⁺ [L₂ = diolefin or (CO)₂] have been prepared and their catalytic activity in hydrogen-transfer reactions explored. The heterodinuclear [Cl₂Pd(μ-bipym)Rh(tfb)]ClO₄ complex was obtained by reacting [Rh(tfb)(bipym)]⁺ with [PdCl₂(cod)] or alternatively from [Rh(tfb)(acetone)_x]⁺ with [PdCl₂(bipym)]. Ion-pair complexes of formulae [Rh(diolefin)(bipym)]⁺ [RhCl₂(diolefin)]₋ (diolefin = cod, nbd or tfb) were prepared by adding bipym to acetone suspensions of [RhCl(diolefin)]₂.     

Isolation of [Rh(diolefin)X2]- species and their reactions with P- or N-donor ligands,tin(II) halides and carbon monoxide

Anionic [Rh(diolefin)X₂]⁻ species (X = Cl, Br) have been prepared and their reactions studied. The reactions with monodentate ligands led to neutral tetracoordinated complexes, and with N-donor bidentate ligands (Rh : LL = 2 : 1) gave Rh(X)(diolefin)(LL), [Rh(diolefin)(LL)]⁺[Rh(diolefin)X₂]⁻, or [Rh(diolefin)(LL)]X compounds, depending on the nature of LL or X. Reactions with carbon monoxide involved diolefin displacement. A trichlorostannato complex was obtained from the [Rh(COD)Cl₂]⁻ species. Reactions of [Rh(COD)Br]₂ with bidentate N-donor ligands were also studied.     

Rhodium(I) diolefin complexes with polycyclic π-arene ligands. Synthesis of bimetallic complexes with diphenylmethane as bridging ligand

Summary The preparation and properties of cationic arenerhodium(I) complexes of general formula [Rh(diolefin)(⁶arene)]ClO₄ (diolefin=1,5-cyclooctadiene, tetrafluorobenzobarrelene or trimethyltetrafluorobenzobarrelene; arene = biphenyl or diphenylmethane) are described. These complexes react with the solvated intermediate complex [Rh(diolefin)(Me₂CO)_x]ClO₄ to give homobimetallic [(diolefin)Rh(Ph₂CH₂)Rh(diolefin)](ClO₄)₂ derivatives. New heterobimetallic complexes of the type [(diolefin)Rh(Ph₂CH₂)Cr(CO)₃]ClO₄ have been synthesized by reaction of Cr(CO)₃(⁶-Ph₂CH₂) with the solvated complex [Rh(diolefin)(Me₂CO)_x]ClO₄ or, alternatively by treatment of [Rh(diolefin)(⁶-arene)]ClO₄ with the complex Cr(CO)₃(⁶Me₃B₃N₃Me₃) in chloroform solution.     

Dicarboxylate rhodium complexes with diolefins and carbon monoxide

Dinuclear rhodium complexes of the type [Rh₂(C₂O₄)(diolefin)₂] (diolefin)₂  1,5-cyclooctadiene, 2,5-norbornadiene and tetrafluorobenzobarrelene) with bridging oxalate ligands have been obtained by reaction of [Rh(acac)(diolefin)] with oxalic acid (2: 1 mol ratio). The use of a 1 : 1 molar ratio affords [Rh(HC₂O₄)(COD)], that reacts with [Ir(acac)(COD)] yielding the heterodinuclear [(COD)Rh(C₂O₄)Ir(COD)] complex. Treatment of [Rh₂(C₂O₄)(diolefin)₂] complexes with phenanthroline type ligands leads to ionic complexes of formula [Rh(diolefin) (phen)][Rh(C₂O₄)(diolefin)]. Bubbling of carbon monoxide through solutions of the diolefin complexes leads to the formation of carbonylrhodium species of formula [Rh₂(C₂O₄)(CO)₂L₂] (L = CO, PPh₃t-BuNC) or [Rh(CO)₂(phen)] - [Rh(C₂O₄)(CO)₂]. Other related malonate complexes are also described.     

Rhodium(I) indazole and indazolate complexes

The preparation of cationic indazole (HIdz) rhodium(I) complexes of the types [(diolefin)Rh(HIdz)₂]ClO₄ and [(CO)₂Rh(HIdz)₂]ClO₄ is described. Neutral binuclear rhodium(I) complexes of the type [Y₂Rh(μ-Idz)]₂ (Y₂  COD, TFB, NBD, (CO)₂ or (CO)(PPh₃)) are obtained by treating the corresponding complexes [Y₂RhCl]₂ with indazole and organic or inorganic bases. The cationic mononuclear derivatives react with the solvated species [Y₂Rh(acetone)_x]ClO₄ in the presence of triethylamine to give neutral binuclear complexes of the types [(CO)₂Rh(μ-Idz)₂Rh(diolefin)], [(Ph₃P)(CO)Rh(μ-Idz)₂Rh(diolefin)] and [(diolefin)Rh(μ-Idz)Rh(diolefin′)] (diolefin  COD, TFB or NBD; diolefin′  COD or TFB). Alternative methods for the synthesis of the binuclear complexes are also described.     

Cationic rhodium tetrafluorobenzobarrelene complexes with diolefin or arene ligands,crystal structures of [Rh(TFB)(arene)] ClO4, (arene = C6Me6, C6H3Me3, C6H4Me2)

The preparation and properties of complexes of the general formulae [Rh(TFB)(diolefin)]ClO₄, [Rh(TFB)(arene)]ClO₄ and [Rh(TFB)L₂]ClO₄, (TFB = tetrafluorobenzobarrelene, L = dimethylsulfoxide and tetrahydrothiophen) are described. The crystal structures of the arene complexes (arene = C₆Me₆, C₆H₃Me₃ and C₆H₄Me₂) have been solved by X-ray methods. The three compounds crystallize in quite similar lattices: R3c, a = b = 27.122, 26.233, 25.731 and c = 17.079, 16.388, 16.256 Å, respectively. δR-plots for about 2000 reflections show the agreement in the refinements carried out up to R-values of 5%, 5% and 4% respectively. The Rh atom is coordinated to the double bonds of the TFB and to the arene ring in all three compounds, but the deviation from planarity of the arene and its relative position with respect to the TFB moiety varies.     

Tetrafluorobenzobarreleneiridium complexes with 1,10- phenanthroline,2,2′-bipyridine and diketonate ligands. Crystal structure of [IrI2(TFB)(phen)]ClO4·(CH32CO (TFB = 5,6,7,8- tetrafluoro-1,4-dihydro-1,4-ethenonapthalene,phen = 1,10- phenanthroline)

The preparations os some new β-diketonate iridium(I) complexes of formula [Ir(β-diketonate)(diolefin)] and [Ir(β-diketonate-C³)(diolefin)(LL)] (β-diketone = acetyl acetone (Hacac), 1-phenyl, butane-1,3-dione (HBzac), 1,3-diphenyl,propane-1,3-dione (HBz₂ac); diolefin = tetraflurobenzobarrelene (TFB), trimethyltetrafluorobenzobarrelene (Me₃TFB); LL = 1,10-phenanthroline (phen), 2,2′-bipyridine (bipy) (not all possible combinations)) are reported. The neutral complexes [IrI(TFB)₂] and [IrI(TFB)(phen)] were prepared by metathetical reactions from the corresponding chlorides. The oxidative addition of iodine to [Ir(acac-C³)(TFB)-(phen)] or (Ir(TFB)(phen)][ClO₄] results in formation of the trans or cis isomers of the iridium(III) cation [IrI₂(TFB)(phen)]⁺, respectively. The rans isomer has been structurally characterized by X-ray diffraction methods; the lattice constants of the monoclinic P2₁/n cell are a 12.6841(4), b 17.7550(7), c 13.8500(4) Å with β 108.874(2)°. The R factor was 0.058 for 3552 observed reflections. The octahedral coordination of the metal is distorted as to make an I-Ir-I angle of 160.43(4)°.     

Indolylgold(I) derivatives and indole as π-arene ligands in cationic rhodium(I) complexes

The reaction of LAuIn (L = P(C₆H₅)₃, P(2-MeC₆H₄)₃ or P(4-MeC₆H₄)₃; In = indolyl group) with the solvated complexes [(diolefin)Rh(Me₂CO)_x]ClO₄ gives the novel heterometallic complexes [(diolefin)Rh(μ-In)AuL]ClO₄. The mononuclear arene derivatives [(diolefin)Rh(η⁶-HIn)]ClO₄ react with methanolic KOH to give the binuclear complexes [(diolefin)Rh(μ-OMe)]₂, while [(COD)Rh(η⁶-HIn)]ClO₄ reacts with KOH in water/acetone to give the hydroxo-bridged complex [(COD)Rh(μ-OH)]₂.     

Rhodium and iridium complexes containing the anion of 1-phenyl-3-methyl-4-benzoyl- pyrazolone-5, a sophisticated analogue of β-diketones

Several (diolefin)M(A) complexes (M = Rh, Ir) were prepared, where AH is 1-phenyl-3-methyl- 4-benzoylpyrazolone-5, a very stable asymmetric analogue of acetylacetone. In these complexes the diolefin could be replaced by one mole of (Ph₂PCH₂CH₂)₂, two of CO or of PPh₃, or three of CNBu^t, while 1,10-phenanthroline displaced the chelating ligand to yield [(cyclooctadiene)Rh(phen)]⁺ (A)^?. Some compounds X?Y (X?Y = iodine or MeI) added oxidatively yielding the corresponding trivalent species. Using ³¹P NMR spectra the presence of the expected steric isomers was detected in (Ph₃P)(CO)Rh(A) and in (Ph₃P) (CO)Rh(A)(X)(Y).     

Reactions of dimethyl(dimethylsulphoxide)pentamethylcyclopentadienyl-rhodium and -irridum with acids

The complexes [C₅Me₅MMe₂(Me₂SO)] (Ia, M = Rh; Ib, M = Ir) react with p-toluenesulphonic acid in acetonitrile to give [C₅Me₅MMe(Me₂SO)(MeCN)]⁺, (II), and with trifluoroacetic acid to give first [C₅Me₅MMe(Me₂SO)(O₂CCF₃)] and then [C₅Me₅M(Me₂SO)(O₂CCF₃)₂]. Complexes II react with halide (X^?) to give the halomethyl complexes [C₅Me₅MMe(X)(Me₂SO)]. The IR, far-IR, ¹H and ¹³C NMR spectra are all in agreement with structures proposed.     

Bidentate amine N-oxides and phosphine oxides as ligands in rhodium(I) chemistry

Cationic rhodium(I) complexes of the general formula [Rh(COD)L₂]ClO₄ (L₂ = bipyO₂, phenO, dpeO₂ and dpmO₂) are prepared from the solvated species [Rh(COD)(Me₂CO)_x]⁺ and the appropriate ligand. Complexes of the type [Rh_n(COD)_n](ClO₄)_n (CNPyO = 4-cyano and 2-cyanopyridine N-oxide) are obtained similarly. Reaction of [RhCl(COD)]₂ with the potassium salt of 2-picolinic acid N-oxide leads to the neutral complex Rh(COOPyO)(COD). The mononuclear rhodium diolefinic compounds react with carbon monoxide to give complexes of the type [Rh(CO)₂L₂]ClO₄ and Rh(COOPyO)(CO)₂, which on treatment with triphenylphosphine yield monocarbonyl derivatives.The catalytic activities of the diolefin complexes and related derivatives in hydrogen-transfer catalytic reactions have been studied.     

2,2′-biimidazole, 2,2′-bibenzimidazole and imidazoles as ligands in cationic rhodium(I) complexes

Summary Cationic rhodium(I) complexes of the type [Rh(diolefin)(L-L)]ClO₄ and [Rh(diolefin)L₂]ClO₄, (diolefin = 1,5-cyclooctadiene, 2,5-norbornadiene and tetrafluorobenzobarrelene; L-L = 2,2-biimidazole, 2,2-bibenzimidazole; L = pyrazole or imidazoles) are described. [Rh(CO)₂(L-L)]-C1O₄ complexes, which can be obtained by reaction of cyclooctadiene derivatives with CO, react with P-donor ligands in equimolar ratios to yield [Rh(CO)(P-donor)(L-L)]ClO₄ monocarbonyl derivatives. The catalytic activity of some of these complexes is considered.     

Spectroscopic and structural characterization of cationic N-(2-aminoethyl)aziridine-N,N′ chelate complexes of the d-metals Rh(III) and Ir(III)

The syntheses of the compounds [M(Cp^∗)(aeaz)(az)](OTf)₂ (4, 5) (M = Rh(III), Ir(III); aeaz = C₂H₄NC₂H₄NH₂, az = C₂H₄NH (3)) containing cationic N-(2-aminoethyl)aziridine-N,N′ chelate complexes are described. The bis-aziridine complexes [MCl(Cp^∗)(az)₂]Cl (M = Rh (1), M = Ir (2)) react with an excess of the aziridine (az) in the presence of AgO₃SCF₃ (=AgOTf) via AgCl precipitation and az addition followed by a metal-mediated coupling reaction, to give the compounds [M(Cp^∗)(aeaz)(az)](OTf)₂ (4, 5). The new aeaz ligand is formally the dimerisation product of az. Using the same reaction conditions with the analogous, but weaker Lewis acidic ruthenium(II) complex [RuCl(C₆Me₆)(az)₂]Cl (6) an anion exchange reaction yielding [RuCl(C₆Me₆)(az)₂]OTf (8) is observed. After purification, all compounds are fully characterized using IR, FAB-MS, ¹H and ¹³C NMR spectroscopy. The single crystal X-ray structure analysis reveals a distorted octahedral geometry for all complexes.     

A novel access to the anionic permethylated fac-tripod ligand [C5Me5Co&P(O)(OEt)2&3]−, and its derived trinuclear and binuclear complexes

[C₅Me₅Co&P(O)(OEt)₂&₃]Co(II) was obtained in high yield from the reaction of C₅Me₅Li with Co(acac)₃ and diethylphosphite in a one-step synthesis. This provides high-yield synthetic routes to several decamethylated triple-decker sandwiches [C₅Me₅Co&P(O)(OEt)₂&M [M = Co(III) or Ti(IV)], and pentamethylated binuclear complexes [C₅Me₅Co&P(O)(OEt)₂&₃]M′L_n, &M′L_n = [Re(CO)₃]⁺, [VO(acac)]⁺ or [Ru(η-C₆Me₆)]²⁺&.     

New Pentacoordinated Rhodium Species as Unexpected Products during the In Situ Generation of Dimeric Diphosphine‐Rhodium Neutral Catalysts

Dimeric rhodium complexes of the type [Rh(PP)(μ₂‐Cl)]₂ (PP=diphosphine) are often used as precatalysts and are generated “in situ” from the corresponding diolefin complexes by exchange of the diene with the desired diphosphine. Herein, we report that the “in situ” procedure also leads to unexpected monomeric pentacoordinated neutral complexes of the type [RhCl(PP)(diolefin)], for the first time herein characterized by NMR spectroscopy and X‐ray crystallography for the ligands 1,4‐bis(diphenylphosphino)propane (DPPP), 1,4‐bis(diphenylphosphino)butane (DPPB), and 2,2′‐bis(diphenylphosphino)‐1,1′‐binaphthyl (BINAP). The pentacoordinated complexes are in equilibrium with the dimeric target compound [Rh(PP)(μ₂‐Cl)]₂. The equilibrium is influenced by the rhodium‐diolefin precursor, the solvent and the temperature. Based on the results of NMR and UV/Vis spectroscopic analysis (kinetics) it could be shown that the pentacoordinated complex [RhCl(PP)(diolefin)] may arise both from the “in situ”‐generated neutral complex [Rh(PP)(μ₂‐Cl)] by reaction with the free diolefin and, more surprisingly, directly from [Rh(diolefin)(μ₂‐Cl)]₂ and the diphosphine.     

Rhodium(I) complexes with pyridazine, 4,6-dimethyl-pyrimidine, 4,6-bis(3,5-dimethylpyrazol-1-yl)pyrimidine, 3,6-bis(3,5-dimethylpyrazol-1-yl)pyridazine and 3-(3,5-dimethylpyrazol-1-yl)-6-chloropyridazine

The synthesis and properties of rhodium(I) complexes of formulae [“RhCl(diolefin)”₂(L)] (or [Rh(Cl(diolefin)(L)]), and [Rh(diolefin)(L)]_n(ClO₄)_n are reported. These complexes react with carbon monoxide to yield the related carbonyl derivatives. Ligands used were pyridazine, 4,6-dimethyl-pyrimidine, 4,6-bis(3,5-dimethylpyrazol-1-yl)pyrimidine, 3,6-bis(3,5-dimethylpyrazol-1-yl)pyridazine and 3-(3,5-dimethyl-pyrazol-1-yl)-6-chloropyridazine. Related iridium(I) and gold(I) compounds are also reported.     

Cationic complexes of rhodium(I) as catalysts in the homogeneous O2-oxidation of terminal alkenes to methyl ketones

[Rh(LL)₂]⁺, [Rh(LL)(diene)]⁺ and [Rh(LL)S₂]⁺ complexes are effective as catalysts for the oxidation by dioxygen of terminal olefins to methyl ketones. The complexes act as monooxygenases, the second oxygen atom being transferred to the alcohol solvent.     

Metallkomplexe mit biologisch wichtigen Liganden. XCV. η5- Pentamethylcyclopentadienyl-Rhodium-, -Iridium-, (η6-Benzol)-Ruthenium- und Phosphan-Palladium-Komplexe von Prolinmethylester und Prolinamid

Metal Complexes of Biologically Important Ligands. XCV. η⁵-Pentamethylcyclopentadienyl Rhodium, Iridium, η⁶- Benzene Ruthenium, and Phosphine Palladium Complexes of Proline Methylester and Proline Amide Proline methylester (L¹) and proline amide (L²) give with the chloro bridged complexes [(η⁵ -C₅Me₅)MCl₂]₂ (M ? Rh, Ir), [(η⁶ -benzene)RuCl₂]₂ and [Et₃PPdCl₂]₂ N and N,O coordinated compounds: (η⁵ -C₅Me₅)M(Cl₂)L¹ ( 1, 2 M ? Rh, Ir), [(η⁵-C₅Me₅) Rh(Cl)(L²)]⁺Cl^? ( 5 ), [(η⁶- C₆Me₆) Ru(Cl)(L²)]⁺Cl^? ( 6 ), [(η⁶-p-cymene)Ru(Cl)(L²)]⁺Cl^? ( 7 ), [(eta;⁵-C₅Me₅)M(Cl)(L²-H⁺)] ( 9, 10 M ? Rh, Ir), (Et₃P)Pd(Cl)₂L¹ ( 3 ), and [(Et₃P)Pd(Cl)(L²)]⁺Cl^? ( 8 ). The NMR spectra indicate that for 5 and 6 only one diastereoisomer is formed. The complexes 1, 2, 3 and 5 were characterized by X-ray diffraction.     

Trichlorostannato(diphosphine)rhodium(I) complexes. Crystal structure of [Rh(SnCl3)(1,5-cyclooctadiene)(dppp)]

The molecular structure of [Rh(SnCl₃)(1,5-cyclooctadiene)(dppp)] [dppp = 1,3-bis(diphenylphosphino)propane] has been determined to R_F = 3.6% single-crystal X-ray techniques. The crystal contains two discrete molecules 1 and 2 per asymmetric unit. Molecule 1 is best described as distorted trigonal bipyramidal with the diolefin and the diphosphine occupying both apical and equatorial positions and the SnCl₃ group on an equatorial position, and molecule 2 as distorted square pyramidal with the equatorial positions occupied by the diolefin and the diphosphine, respectively, and the SnCl₃ fragment in the apical position. In solution at room temperature, complexes [Rh(SnCl₃)(COD)(diphosphine)] exhibit tin dissociation and various intramolecular rearrangements.     

Protonated diolefin complexes: Model systems for C?;h activation via metal complexation

On protonation of the diolefin complexes [M(C₅R₅)(diene)] (R = H, CH₃; M = Co, Rh, Ir; diene = 2,3-dimethylbutadiene, 1,3-cyclohexadiene) with HBF₄, cationic species are isolated which, at room temperature, show fluxional behaviour on the NMR time scale. Depending on R and M, three different ground states are observed for these cationic complexes in the NMR spectra at low temperatures. While for M = Ir a classical metal-hydride structure M–H is observed, the Co and Rh complexes show ground states with ‘agostic’ H-bridges M‥H‥C. The protonated species are characterized by ¹H-, ¹³C- and ¹⁰³Rh-NMR spectra. Total line-shape analysis of the ¹H and ¹³C spectra in the 298–154 K range gave the free enthalpies of activation ΔG ^≠ for methyl rotation and 1, 4-H shift in the agostic structures 2b , 2b′ , 2c , and 2c′ . The Rh complexes show the lowest ΔG^± values for the 1,4-H shift, and the strength of the agostic bond appears to decrease in the order CoC₅H₅ > CoC₅Me₅ > RhC₅H₅ > RhC₅Me₅. Only for R = H and M = Rh and in the presence of traces of Lewis bases (H₂O, Pyridine, or acetone), variable amounts of coordinatively saturated allyl complexes competing with the agostic species are observable. Morethan equimolar amounts of basic solvents lead to irreversible deprotonation and recovery of the starting complexes. Stable allyl-halide complexes are formed on reaction with HCI, while protonation with HBF₄, in the presence of CO, gives high yields of complexes [M(CO)(allyl)(C₅R₅)] [BF₄]. The different ground states observed for the protonated complexes and the dynamic behaviour in solution are compared with other hydride-transfer reactions observed in organometallic chemistry, specifically with the β-hydride elimination and the catalytic hydrogenation of olefins.