Ligating properties of thionitrosoamines: III. Carbonyl complexes of rhodium(I) and rhodium(III) containing N-thionitrosodimethylamine

Me₂NNS reacts with [Rh(CO)₂Cl]₂ to produce the complex cis-Rh(SNNMe₂)(CO)₂Cl (1). The latter undergoes reversible CO substitution by Me₂NNS to give the complex trans-Rh(SNNMe₂)₂(CO)Cl (2a). Complexes 1 and 2a, in solution lose CO and Me₂NSS, respectively, to give the complex trans-(μ-Cl)₂[Rh(SNNMe₂)(CO)]₂ (3). Complex 1 can also be prepared by bubbling CO through a CH₂Cl₂ solution of Rh(SNNMe₂)(diene)Cl (diene = 1,5-cyclooctadiene (4a), norbornadiene (4b)) obtained by a bridge-splitting reaction of Me₂NNS with [Rh(diene)Cl]₂. 1 and 2a react with EPh₃ (E = P, As, Sb) to give the complexes trans-Rh(EPh₃)₂(CO)Cl. The complexes trans-Rh(E′Ph₃)₂(CO)X (X = Cl, E′ = As, Sb; X = Br, NCS, E′ = As) undergo reversible E′Ph₃ displacement upon treatment with Me₂NNS to give the complexes trans-Rh(SNNMe₂)₂(CO)X (X = Cl (2a), Br (2b), NCS (2c)). Oxidative additions of Br₂, I₂, or HgCl₂ to 2a produce stable adducts, while the reaction of 2a with CH₃I gives an inseparable mixture of the adduct Rh(SNNMe₂)₂(CO)(CH₃)ClI and the acetyl derivative Rh(SNNMe₂)₂(CH₃CO)ClI. A mixture of the acetyl derivative (μ-Cl)₂[Rh(SNNMe₂)(CH₃CO)I]₂ and the adduct (μ-Cl)₂[Rh(SNNMe₂)(CO)(CH₃)I]₂ is obtained by treating 1 with CH₃I. The IR spectra of all the compounds are consistent with S-coordination of Me₂NNS. Because of the restricted rotation around the NN bond, the ¹H NMR spectra of the new compounds exhibit two quadruplets in the range 3.5–4.3δ when ⁴J(HH) = 0.7–0.5 Hz. When ⁴J(HH) < 0.5 Hz, the perturbing effect of the quadrupolar relaxation of the ¹⁴N nucleus obscures the spin-spin coupling and two broad signals are observed in the range 3.6–4δ.     

Carbonyl complexes of rhodium(I) and rhodium(III) with 2,2′-biquinoline

Novel carbonyl complexes of rhodium(I) and rhodium(III) containing the bidenate nitrogen donor ligand 2,2′-biquinoline (biq) have been prepared; they are of the types RhX(CO)₂ biq and RhX(CO)biq (X = Cl, Br, I). Cationic carbonyl and substituted carbonyl complexes of the types [Rh(CO)₂biq]ClO₄ and [Rh(CO)biqL₂]ClO₄, where L is tertiary phosphine or arsine have also been isolated. In spite of considerable steric crowding around the nitrogen atoms, 2,2′-biquinoline behaves much like 2,2′-bipyridine in forming carbonyl complexes of rhodium.     

Ligating properties of thionitrosoamines: IV. Cationic complexes of rhodium(I), rhodium(III), and ruthenium(II) containing N-thionitrosodimethylamine

The solvento species obtained by treatment of the complexes [Rh(1,5-cyclooctadiene)Cl]₂, [Rh(norbornadiene)Cl]₂, [Rh(CO)₂Cl]₂, C₅H₅Rh(CO)I₂, [C₅Me₅RhCl₂]₂, and [Ru(C₆H₆)Cl₂]₂ with AgPF₆ in acetone or acetonitrile react with a large excess of Me₂NNS to give the compounds [Rh(1,5-C₈H₁₂)-(SNNMe₂)₂]PF₆ (1a), [Rh(C₇H₈)(SNNMe₂)₂]PF₆ (1b), [Rh(CO)₂(SNNMe₂)₂]PF₆ (2), [C₅H₅Rh(SNNMe₂)₃](PF₆)₂ (3), [C₅Me₅Rh(SNNMe₂)₃](PF₆)₂ (4), and [Ru(C₆H₆(SNNMe₂)₃](PF₆) (5). If the thionitroso ligand is not preent in large excess decomposition often occurs. The use of AgClO₄ allows isolation of the perchlorate salts of 1a, 1b, 2, 4, and 5, and the complexes [C₅H₅Rh-(SNNMe₂)₂(ClO₄)ClO₄ (6) and Rh(1,5-C₈H₁₂)(SNNMe₂)(ClO₄) (7). In the H¹ NMR spectra the methyl protons of Me₂NNS are observed as two quadruplets, in the range δ 3.75–4.25 (⁴J(HH) ca. 0.7 Hz) because of restricted rotation around the NN bond. The rhodium(I) complexes (1a, 1b, and 2) reacts with PPh₃ or p-tolylPPh₂ to give labile products, and only [Rh(1,5-C₈H₁₂)(SNNMe₂)(PPh₃)]ClO₄ (8) and [Rh(1,5-C₈H₁₂)(SNNMe₂)(p-tolylPPh₂)]ClO₄ (9) were isolated and characterized.     

Aqueous rhodium(III) hydrides and mononuclear rhodium(II) complexes

In aqueous solutions, as in organic solvents, rhodium hydrides display the chemistry of one of the three limiting forms, i.e. {Rh(I)+ H+}, {Rh(II)+ H.}, and {Rh(III)+ H-}. A number of intermediates and oxidation states have been generated and explored in kinetic and mechanistic studies. Monomeric macrocyclic rhodium(II) complexes, such as L(H2O)Rh2+ (L = L1 = [14]aneN4, or L2 = meso-Me6[14]aneN4) can be generated from the hydride precursors by photochemical means or in reactions with hydrogen atom abstracting agents. These rhodium(II) complexes are oxidized rapidly with alkyl hydroperoxides to give alkylrhodium(III) complexes. Reactions of Rh(II) with organic and inorganic radicals and with molecular oxygen are fast and produce long-lived intermediates, such as alkyl, superoxo and hydroperoxo complexes, all of which display rich and complex chemistry of their own. In alkaline solutions of rhodium hydrides, the existence of Rh(I) complexes is implied by rapid hydrogen exchange between the hydride and solvent water. The acidity of the hydrides is too low, however, to allow the build-up of observable quantities of Rh(I). Deuterium kinetic isotope effects for hydride transfer to a macrocyclic Cr(v) complex are comparable to those for hydrogen atom transfer to various substrates.     

Synthesis and reactivity of substituted cyclopentadienyl rhodium(I) and (III) complexes

New cyclopentadienyl derivatives of rhodium COD complexes [Cp*=C₅H₄COOCH₂CHCH₂ (1); C₅H₄CH₂CH₂CHCH₂ (2); C₅H(i-C₃H₇)₄ (3)] and carbonyl complex [Cp*=C₅H(i-C₃H₇)₄ (4)] were synthesized from [RhCl(COD)]₂ and [RhCl(CO)₂]₂. 1, 2 and 3 oxidized by iodine gave iodine bridged dimers 5, 6 and 7, respectively. Triphenyl phosphine, carbon monoxide and carbon disulfide molecules broke down the iodine bridged structure easily and produced monomer products Cp*RhI₂L [Cp*=C₅H₄COOCH₂CHCH₂, L=CS₂ (8); L=PPh₃ (9). Cp*=C₅H(i-C₃H₇)₄, L=CO (10)]. All of these new compounds were characterized by elemental analysis, ¹H NMR, IR, UV-Vis and mass spectroscopy. The crystal structure of 1 was solved in the triclinic space group with one molecule in the unit cell, the dimensions of which are a=7.082(9) Å, b=8.392(3) Å, c=13.889(5) Å, α=101.19(3)°, β=99.06(6)°, γ=105.11(5)°, and V=763(1) ų. The crystal structure of 3 was solved in the orthorhombic space group Pn21a with four molecules in the unit cell, the dimensions of which are a=9.748(3) Å, b=16.054(5) Å, and V=2319(1) ų. Least squares refinement leads to values for the conventional R₁ of 0.0251 for 1 and 0.0558 for 3, respectively. Compared to that in 1, a shorter metal-ligand bond length in 3 was observed and this is attributed to the rich electron density on Rh(I) metal center piled up by the C₅H(i-C₃H₇)₄ ligand.     

Substituted dipyridylpyridazine rhodium(III) complexes

3,6-Bis(2-pyridyl)pyridazine derivatives (n-dppn) react with hydrated rhodium(III) chloride and bromide (prepared in situ) to give cis-[Rh(n-dppn)₂Cl₂]PF₆·xH₂O (n = 5, 6, 7, 8) and cis-[Rh(n-dppn)₂Br₂]Br·xH₂O (n = 5, 7) complexes, which have been characterized by elemental analyses, conductivity measurements, i.r., electronic and ¹H- and ¹³C-n.m.r. spectra.     

Monocarbonyl cationic rhodium(I) complexes

Summary The preparations and characterisation of cationic complexes of the type [Rh(CO)(MeCN)(PR₃)₂]ClO₄, [Rh(CO)L(PR₃)₂]ClO₄ (L=py or 2-MeOpy), [Rh(CO)(L-L)(PR₃)₂]ClO₄ (L-L = bipy or phen) and [Rh(CO)(PR₃)₃]ClO₄ with PR₃ = P(p-YC₆H₄)₃ (Y=Cl, F, Me or MeO) are described.     

Polymerization of propadiene. III. Catalyst systems based on various rhodium (I) complexes

The polymerization of propadiene to 1,2-polyallene by various Rh(I) based catalysts is described and discussed. Also the interrelations between these Rh(I) complexes are discussed and an overall reaction scheme is given. A mechanism is put forward in which the formation of a common intermediate from propadiene and different Rh(I) complexes is the rate determining step. It is found that the activity decreases in the order: cis-Rh(CO)₂P(C₆H₅)₃Cl > [Rh(CO)₂Cl]₂ > Rh(CO)₃Cl. The complexes Rh[P(C₆H₅)₃]₂(CO)Cl and Rh[P(C₆H₅)₃]₃Cl proved to be inactive in the polymerization of propadiene.     

N-substituted salicylaldimine complexes of rhodium(III) and related rhodium(III) organometallic derivatives

A series of new Rh^III complexes with N-substituted salicylaldimines have been prepared of the form [RhSBPy₂]PF₆ where SB is a tetradentate N,N′-substituted bis(salicylaldimine) or represents two molecules of a corresponding bidentate derivative. Several of these complexes have been reduced with 0.5% sodium amalgam and the products reacted with CH₃I to yield the organometallic derivatives CH₃RhSBPy.     

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.     

Rhodium(I) and rhodium(III) arene complexes with N-carbazolyltriphenylphosphinegold(I) and other polycyclic arene ligands

The new heteronuclear arene complexes [(COD)Rh(μ-cbz)AuPPh₃]ClO₄, [{(COD)Rh}₂(μ-cbz)AuPPh₃](ClO₄)₂, [(C₅Me₅)Rh(μ-cbz)AuPPh₃](ClO₄)₂ and [{C₅Me₅) Rh}₂(μ-cbz)AuPPh₃](ClO₄)₄ (COD = 1,5-cyclooctadiene, cbz = carbazolyl), and the mononuclear arene complexes [(COD)Rh(arene)]ClO₄ (arene = tetralin, biphenyl, fluorene, indene, 9,10-dihydroanthracene or carbazole) have been prepared by reaction of the acetone solvated complexes [(COD)Rh(Me₂CO)_x]ClO₄ or [(C₅Me₅)Rh(Me₂CO)₃](ClO₄)₂ with (cbz)AuPPh₃ or the appropriate polycyclic arene ligand.     

Some new rhodium(I)-iridium(III) complexes with bridging hydride and chloride ligands

[IrH₅(PEt₃)₂] reacts with [(PR₃)₂Rh(μ₂-Cl)₂(PR₃)₂] (PR₃ = PEt₃ or 2 PR₃ = Ph₂PCH₂CH₂PPh₂) to give the hydrido-bridged binuclear species [(PR₃)₂Rh(μ₂-H)(μ₂-Cl)IrH₂(PR₃)₂] which show catalytic activity in alkene hydrogenation.     

Cationic thiocarbonyl complexes of rhodium(I)

The syntheses are described of a range of cationic rhodium(I) thiocarbonyl complexes containing tertiary phosphine, phosphinite, phosphonite and phosphonite ligands.     

Theoretical study of rhodium(III)-catalyzed hydrogenation of carbon dioxide into formic acid. Significant differences in reactivity among rhodium(III), rhodium(I), and ruthenium(II) complexes

The title reaction was theoretically investigated, where cis-[RhH(2)(PH(3))(3)](+) and cis-[RhH(2)(PH(3))(2)(H(2)O)](+) were adopted as models of the catalyst. The first step of the catalytic cycle is the CO(2) insertion into the Rh(III)-H bond, of which the activation barrier (E(a)) is 47.2 and 28.4 kcal/mol in cis-[RhH(2)(PH(3))(3)](+) and cis-[RhH(2)(PH(3))(2)(H(2)O)](+), respectively, where DFT(B3LYP)-calculated E(a) values (kcal/mol unit) are given hereafter. These results indicate that an active species is not cis-[RhH(2)(PH(3))(3)](+) but cis-[RhH(2)(PH(3))(2)(H(2)O)](+). After the CO(2) insertion, two reaction courses are possible. In one course, the reaction proceeds through isomerization (E(a) = 2.8) of [RhH(eta(1)- OCOH)(PH(3))(2)(H(2)O)(2)](+), five-centered H-OCOH reductive elimination (E(a) = 2.7), and oxidative addition of H(2) to [Rh(PH(3))(2)(H(2)O)(2)](+) (E(a) = 5.8). In the other one, the reaction proceeds through isomerization of [RhH(eta(1)-OCOH)(PH(3))(2)(H(2)O)(H(2))](+) (E(a) = 5.9) and six-centered sigma-bond metathesis of [RhH(eta(1)-OCOH)(PH(3))(2)(H(2)O)](+) with H(2) (no barrier). RhH(PH(3))(2)-catalyzed hydrogenation of CO(2) proceeds through CO(2) insertion (E(a) = 1.6) and either the isomerization of Rh(eta(1)-OCOH)(PH(3))(2)(H(2)) (E(a) = 6.1) followed by the six-centered sigma-bond metathesis (E(a) = 0.3) or H(2) oxidative addition to Rh(eta(1)-OCOH)(PH(3))(2) (E(a) = 7.3) followed by isomerization of RhH(2)(eta(1)-OCOH)(PH(3))(2) (E(a) = 6.2) and the five-centered H-OCOH reductive elimination (E(a) = 1.9). From these results and our previous results of RuH(2)(PH(3))(4)-catalyzed hydrogenation of CO(2) (J. Am. Chem. Soc. 2000, 122, 3867), detailed discussion is presented concerning differences among Rh(III), Rh(I), and Ru(II) complexes.     

1,3-diaryltriazenido complexes of ruthenium(I), (II) and (III), and of osmium(III), rhodium(III) and iridium(III)

The synthesis and characterization of the platinum metal—1,3-diaryltriazenido complexes [Ru(ArNNNAr)(CO)₃]₂, [Ru(ArNNNAr)₂]₂, cis-Ru(ArNNNAr)₂(CO)₂, MX₂(ArNNNAr)(PPh₃)₂ (M = Ru, Os; X = Cl, Br) and M′(ArNNNAr)₃ (M′= Ru, Os, Rh and Ir) are reported. Axial ligand substitution in [Ru(ArNNNAr)(CO)₃]₂ and adduct formation by [Ru(ArNNNAr)₂]₂ are described. In contrast to other known Ru(II)/Ru(II) “lantern” molecules, the species [Ru(ArNNNAr)₂]₂ have measured magnetic moments equivalent to ca one unpaired electron per dimer, which are presumably due to population of the spin states σ²π⁴δ²π^*4 and σ²π⁴δ²π^*3σ^*1.     

Bacterial activity of cobalt(III) complexes. Part IV: Diethylenetriaminemonoacetatocobalt(III) complexes

Summary The activities of the diethylenetriaminemonoacetatocobalt(III) complexes, [Co(en)(DTMA)]I₂, [CoX₂(DTMA)] and [CoCO₃(DTMA)]·H₂O (DTMA=diethylenetriaminemonoacetato or formally 3-amino-3, 6-diazaoctanato; en=ethylenediamine, X=Cl^–, NO ₂ ^– , NCS^–) were studied onEscherichia coli B growing in a minimal glucose medium in both lag- and log-phases. Activities decrease in the order: [Co(NCS)₂(DTMA)]> [Co(NO₂)₂(DTMA)]>[Co(en)(DTMA)]I₂>[CoCl₂(DTMA)] >[CoCO₃(DTMA)]·H₂O. The antagonistic activities of the complexes were also studied.     

Studies on ruthenium(III), rhodium(III) and iridium(III) complexes of indazoles

Summary New complexes of the general formula M(L)₃Cl₃ and M(5-AInz)₂Cl₃ · n H₂O (where M = Ru^III, Rh^III and Ir^III; L = indazole and 5-nitroindazole; n=1–2) have been synthesized and characterised by elemental analysis, molar conductance, magnetic susceptibility and i.r. and electronic spectral measurements. All the complexes are covalent and apparently have an octahedral geometry. The ligands are monocoordinated through the pyrrole nitrogen. From the far i.r. spectra amer configuration has been assigned to the indazole and 5-nitroindazole complexes.     

Polymerization of propadiene. IV. Kinetics and mechanism of polymerization under the influence of rhodium(I) complexes

The kinetics and mechanisms of propadiene polymerization under the influence of [Rh(CO)₂Cl]₂, Rh(CO)₂P(C₆H₅)₃Cl, Rh(CO)₃Cl are reported. The reaction rates are first-order in Rh(CO)₂P(C₆H₅)₃Cl and Rh(CO)₃Cl and half-order in [Rh(CO)₂Cl]₂. They are second-order in the substrate for Rh(CO)₃Cl and [Rh(CO)₂Cl]₂ and first-order for Rh(CO)₂P(C₆H₅)₃Cl. The data are interpreted in terms of a common intermediate mechanism. The formation of this common intermediate is the rate-determining step. A solvent effect is also discussed.