Interfragment transmission of electronic effects of π-acceptor ligands in heterometallic triad complexes with trans-[Ru(Py)4(CN)2] as a central unit

The complex trans-[RuPy₄(CN)₂] cleaves chloride bridges in the binuclear rhodium(i) and palladium(ii) complexes [Rh(CO)₂Cl]₂, [Rh(η⁴-C₈H₁₂)Cl]₂, [(η⁴-C₈H₁₂)Rh(μ-Cl)₂Rh(CO)₂], [Pd(η³-C₃H₅)Cl]₂, and [(η₃-C₃H₅)Pd(μ-Cl)₂Rh(CO)₂] to form heterometallic triad complexes [(CO)₂ClRh(NC)RuPy₄(CN)RhCl(CO)₂] (1), [(η⁴-C₈H₁₂)ClRh(NC)RuPy₄(CN)RhCl-(η⁴-C₈H₁₂)] (2), [(CO)₂ClRh(NC)RuPy₄(CN)RhCl(η⁴-C₈H₁₂)] (3), [(η³-C₃H₅)ClPd(NC)-Ru(Py)₄(CN)PdCl(η³-C₃H₅)] (4), and [(CO)₂ClRh(NC)Ru(Py)₄(CN)PdCl(η₃-C₃H₅)] (5), respectively. In solutions, complex 3 coexists with equilibrium amounts of compounds 1 and 2; complex 5 is in the equilibrium with compounds 4 and 1. In both cases, the ratio of concentrations is close to binomial. Complexes 2 and 5 treated with [Rh(CO)₂Cl]₂ are converted into 1 with the simultaneous formation of [Rh(η⁴-C₈H₁₂)Cl]₂ and [Pd(η³-C₃H₅)Cl]₂, respectively. The δ_H and δ_C values for the ligands η⁴-C₈H₁₂, η³-C₃H₅, and CO are sensitive to the nature of the remote triad unit. The ligand effects are shown to be transmitted along the chain L′-M′-(NC)-Ru-(CN)-M″-L″.     

A novel reaction producing the rhodium(I) complexes with π-coordinated tetraphenylborate anion, (π-PhBPh3). X-ray study of [Rh(PPh3)2(π-PhBPh3)]

Treating the complexes [Rh(TFA)(PPh₃)₂], [Rh(HFA)(PPh₃)₂], and [Rh(TFA)(Cod)] (TFA - trifluoroacetylacetonate, HFA - hexafluoroacetylacetonate, Cod - 1,5 cyclooctadiene) with an excess of NaBPh₄ in acetonitrile yields the rhodium(I) complexes with coordinated [BPh₄]⁻ anion, [Rh(PPh₃)₂(π-PhBPh₃)] · 2MeCN (I) and [Rh(Cod)(π-PhBPh₃)] (II). The reactions present a new example of β-diketonate ligand replacement. The ¹H, ³¹P, and ¹¹B NMR spectra of I and II are discussed. [Rh(PPh₃)₂(π-PhBPh₃)] has been characterized by single crystal X-ray analysis.     

Conformational behaviour of dinuclear Rh(I) complexes of the open-chain tetrapyrrolic ligand 2,2′-bidipyrrin (H2BDP)

The reaction of 2,2′-bidipyrrins H₂BDP with the Rh^I complexes [Rh(COD)(μ-OMe)]₂ and [Rh(CO)₂(μ-Cl)]₂ yields the neutral species [{Rh(COD)}₂BDP] (7, 8) and [{Rh(CO)₂}₂BDP] (2, 9), respectively. Treatment of the COD complexes with carbon monoxide results in the exchange of all COD ligands against CO. Ligand exchange studies on the carbonyl complexes 2 and 9 with different phosphane donors reveal the regioselective exchange of one CO per metal ion. In most cases, the reaction is accompanied by a large conformational change of the tetrapyrrole from a syn to an anti conformation. This conformational change was resolved by a combination of NMR spectroscopy and X-ray diffraction studies.     

Rhodium(I) carbonyl complexes of quinoline carboxaldehyde ligands and their catalytic carbonylation reaction

The dimeric rhodium precursor [Rh(CO)₂Cl]₂ reacts with quinoline (a) and its three isomeric carboxaldehyde ligands [quinoline-2-carboxaldehyde (b), quinoline-3-carboxaldehyde (c), and quinoline-4-carboxaldehyde (d)] in 1:2 mole ratio to afford complexes of the type cis-[Rh(CO)₂Cl(L)] (1a-1d), where L = a-d. The complexes 1a-1d have been characterised by elemental analyses, mass spectrometry, IR and NMR (¹H, ¹³C) spectroscopy together with a single crystal X-ray structure determination of 1c. The X-ray crystal structure of 1c reveals square planar geometry with a weak intermolecular pseudo dimeric structure (Rh?Rh = 3.573 Å). 1a-1d undergo oxidative addition (OA) with different electrophiles such as CH₃I, C₂H₅I and I₂ to give Rh(III) complexes of the type [Rh(CO)(COR)Cl(L)I] {R = -CH₃ (2a-2d), R = -C₂H₅ (3a-3d)} and [Rh(CO)Cl(L)I₂] (4a-4d) respectively. 1b exhibits facile reactivity with different electrophiles at room temperature (25 °C), while 1a, 1c and 1d show very slow reactivity under similar condition, however, significant reactivity was observed at a temperature ∼40 °C. The complexes 1a-1d show higher catalytic activity for carbonylation of methanol to acetic acid and methyl acetate [Turn Over Frequency (TOF) = 1551-1735 h⁻¹] compared to that of the well known Monsanto’s species [Rh(CO)₂I₂]⁻ (TOF = 1000 h⁻¹) under the reaction conditions: temperature 130 ± 2 °C, pressure 33 ± 2 bar, 450 rpm and time 1 h. The organometallic residue of 1a-1d was also isolated after the catalytic reaction and found to be active for further run without significant loss of activity.     

Synthesis and structural studies of Rh, Pd, Ni complexes and one-pot synthesis of binuclear Ru complex [(η-p-cymene)Ru(μ2-Cl)3Ru{PhN(P(OC6H4OMe-o)2)2}Cl]

The Rh^I, Ru^II, Pd^I and Ni^II complexes of the aminobis(phosphonite), PhN(P(OC₆H₄OMe-o)₂)₂ (1) are reported. The reactions of 1 with [Rh(COD)Cl]₂ in 1:1 and 2:1 molar ratio afford the mono- and diolefin substituted chloro bridged chelate complexes, [(COD)Rh₂(μ₂-Cl)₂{PhN(P(OC₆H₄OMe-o)₂)₂}] (2) and [Rh(μ₂-Cl){PhN(P(OC₆H₄OMe-o)₂)₂}]₂ (3), respectively. Similarly, the cationic mono- and bis-chelate complexes, [Rh(COD){PhN(P(OC₆H₄OMe-o)₂)₂}]OTf (4) and [Rh{PhN(P(OC₆H₄OMe-o)₂)₂}₂]OTf (5) are obtained by treating 1 with [Rh(COD)Cl]₂ in the presence of AgOTf in appropriate ratios. The dinuclear Rh^I carbonyl complex, [RhCl(CO){μ-PhN(P(OC₆H₄OMe-o)₂)₂}]₂ (6) is prepared by treating 1 with 0.5 equiv. of [Rh(CO)₂Cl]₂. Reaction of 1 with cis-[NiBr₂(DME)] (DME = 1,2-dimethoxyethane) affords [{PhN(P(OC₆H₄OMe-o)₂)₂}NiBr₂] (7) whereas with [Ru-(η⁶-p-cymene)Cl₂]₂ in refluxing THF medium produces an interesting and rare bimetallic Ru^II complex, [(η⁶-p-cymene)Ru(μ₂-Cl)₃Ru{PhN(P(OC₆H₄OMe-o)₂)₂}Cl] (8). Redox condensation of the Pd⁰ and Pd^II derivatives with 1 affords the dinuclear Pd^I complex, [PdBr{μ-PhN(P(OC₆H₄OMe-o)₂)₂}]₂ (9). The formation and structure of complexes 2-9 are assigned through various spectroscopic and micro analysis data. The molecular structures of 5 and 7-9 are confirmed by single crystal X-ray diffraction studies.     

Synthesis and characterization of new Rh complexes bearing CO, PPh3 and chelating P,O- or Se,Se-ligands: Application to hydroformylation of styrene

The complexes [Rh(CO)(PPh₃){Ph₂PNP(O)Ph₂-P,O}] (3), [Rh(CO)₂{Ph₂P(Se)NP(Se)Ph₂-Se,Se′}] (5), and [Rh(CO)(PPh₃){Ph₂P(Se)NP(Se)Ph₂-Se,Se′}] (6), were synthesised by stepwise reactions of CO and PPh₃ with [Rh(cod){Ph₂PNP(O)Ph₂-P,O}] (2) and [Rh(cod){Ph₂P(Se)NP(Se)Ph₂-Se,Se′}] (4), respectively. The complexes 3, 5 and 6 have been studied by IR, as well as ¹H and ³¹P NMR spectroscopy. The ν(CO) bands of complexes 3 and 6 appear at approximately 1960 cm⁻¹, indicating high electron density at the Rh^I centre. The structure of complexes 3 and 6 has been determined by X-ray crystallography, and the ³¹P NMR chemical shifts have been resolved via low temperature NMR experiments. Both complexes exhibit square planar geometry around the metal centre, with the five-membered ring of complex 3 being almost planar, and the six-membered ring of complex 6 adopting a slightly distorted boat conformation. The C-O bond of the carbonyl ligand is relatively weak in both complexes, due to strong π-back donation from the electron rich Rh^I centre. The catalytic activity of the complexes 2, 3 and 6 in the hydroformylation of styrene has been investigated. Complexes 2 and 3 showed satisfactory catalytic properties, whereas complex 6 had effectively no catalytic activity.     

Synthesis and structural characterisation of rhodium hydride complexes bearing N-heterocyclic carbene ligands

Addition of excesses of N-heterocyclic carbenes (NHCs) IEt₂Me₂, IⁱPr₂Me₂ or ICy (IEt₂Me₂ = 1,3-diethyl-4,5-dimethylimidazol-2-ylidene; IⁱPr₂Me₂ = 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene; ICy = 1,3-dicyclohexylimidazol-2-ylidene) to [HRh(PPh₃)₄] (1) affords an isomeric mixture of [HRh(NHC)(PPh₃)₂] (NHC = IEt₂Me₂ (cis-/trans-2), IⁱPr₂Me₂ (cis-/trans-3), ICy (cis-/trans-4) and [HRh(NHC)₂(PPh₃)] (IEt₂Me₂(cis-/trans-5), IⁱPr₂Me₂ (cis-/trans-6), ICy (cis-/trans-7)). Thermolysis of 1 with the aryl substituted NHC, 1,3-dimesityl-4,5-dihydroimidazol-2-ylidene (IMesH₂), affords the bridging hydrido phosphido dimer, [{(PPh₃)₂Rh}₂(μ-H)(μ-PPh₂)] (8), which is also the reaction product formed in the absence of carbene. When the rhodium precursor was changed from 1 to [HRh(CO)(PPh₃)₃] (9) and treated with either IMes (=1,3-dimesitylimidazol-2-ylidene) or ICy, the bis-NHC complexes trans-[HRh(CO)(IMes)₂] (10) and trans-[HRh(CO)(ICy)₂] (11) were formed. In contrast, the reaction of 9 with IⁱPr₂Me₂ gave [HRh(CO)(IⁱPr₂Me₂)₂] (cis-/trans-12) and the unusual unsymmetrical dimer, [(PPh₃)₂Rh(μ-CO)₂Rh(IⁱPr₂Me₂)₂] (13). The complexes trans-3, 8, 10 and 13 have been structurally characterised.     

Cationic methyl complexes of rhodium(III): synthesis, structure, and some reactions

Cationic methyl complex of rhodium(III), trans-[Rh(Acac)(PPh₃)₂(CH₃)(CH₃CN)][BPh₄] (1) is prepared by interaction of trans-[Rh(Acac)(PPh₃)₂(CH₃)I] with AgBPh₄ in acetonitrile. Cationic methyl complexes of rhodium(III), cis-[Rh(Acac)(PPh₃)₂ (CH₃)(CH₃CN)][BPh₄] (2) and cis-[Rh(BA)(PPh₃)₂(CH₃)(CH₃CN)][BPh₄] (3) (Acac, BA are acetylacetonate and benzoylacetonate, respectively), are obtained by CH₃I oxidative addition to rhodium(I) complexes [Rh(Acac)(PPh₃)₂] and [Rh(BA)(PPh₃)₂] in acetonitrile in the presence of NaBPh₄. Complexes 2 and 3 react readily with NH₃ at room temperature to form cis-[Rh(Acac)(PPh₃)₂(CH₃)(NH₃)][BPh₄] (4) and cis-[Rh(BA)(PPh₃)₂(CH₃)(NH₃)][BPh₄] (5), respectively. Complexes 1-5 were characterized by elemental analysis, ¹H and ³¹P{¹H} NMR spectra. Complexes 1, 2, 3 and 4 were characterized by X-ray diffraction analysis. Complexes 2 and 3 in solutions (CH₂Cl₂, CHCl₃) are presented as mixtures of cis-(PPh₃)₂ isomers involved into a fluxional process. Complex 2 on heating in acetonitrile is converted into trans-isomer 1. In parallel with that isomerization, reductive elimination of methyl group with formation of [CH₃PPh₃][BPh₄] takes place. Replacement of CH₃CN in complexes 1 and 2 by anion I⁻ yields in both cases the neutral complex trans-[Rh(Acac)(PPh₃)₂(CH₃)I]. Strong trans influence of CH₃ ligand manifests itself in the elongation (in solid) and labilization (in solution) of rhodium-acetonitrile nitrogen bond.     

Generation of Ir-Sn and Rh-Sn bonds from the oxidative addition of tin(IV) halides to [Ir(μ-Cl)(1,5-COD)]2 and [Rh(μ-Cl)(1,5-COD)]2

Facile oxidative addition of SnCl₄, MeSnCl₃, and SnBr₄ across Ir(I) and Rh(I) cyclooctadiene complexes resulted in the formation of the corresponding Ir-Sn and Rh-Sn heterobimetallic complexes. Treatment of SnCl₄ with [Ir(COD)(μ-Cl)]₂ and [Rh(COD)(μ-Cl)]₂ afforded [Ir(COD)(μ-Cl)Cl(SnCl₃)]₂ (1) and [Rh(COD)(μ-Cl)Cl(SnCl₃)]₂ (2), respectively. Reaction of the organotin halide MeSnCl₃ with [Ir(COD)(μ-Cl)]₂ led to the formation of [Ir(COD)(μ-Cl)Cl(MeSnCl₂)]₂ (3). The reaction of SnBr₄ to Ir^I and Rh^I precursors gave [Ir(COD)(μ-Br)Br(SnBr₃)]₂ (4) and [Rh(COD)(μ-Br)Br(SnBr₃)]₂ (5) respectively, which indicates halide exchange at post-oxidative addition stage. The structures of complexes 1-5 were confirmed by X-ray crystallography. A cis-addition of Sn-X bond across Ir^I/Rh^I is proposed from the analysis of the geometrical features of “X-M-Sn” triangular units in 1-5.     

Reactivity of cationic methyl rhodium(III) complexes cis-[Rh(β-diket)(PPh3)2(CH3)(CH3CN)][BPh4] toward ligands of different character: pyridine, carbon monoxide, and triphenylphosphine

Cationic methyl complex of rhodium(III), cis-[Rh(Acac)(PPh₃)₂(CH₃)(Py)][BPh₄] (1) as a single isomer with Py in the trans to PPh₃ position, is formed upon the reaction of cis-[Rh(Acac)(PPh₃)₂(CH₃)(CH₃CN)][BPh₄] with pyridine in methylene chloride solution.Complex 1 was characterized by elemental analysis and by ³¹P{¹H} and ¹H NMR spectra.Cationic pentacoordinate acetyl complexes, trans-[Rh(Acac)(PPh₃)₂(COCH₃)][BPh₄] (2) and trans-[Rh(BA)(PPh₃)₂(COCH₃)][BPh₄] (3), are prepared by action of carbon monoxide on cis-[Rh(Acac)(PPh₃)₂(CH₃)(CH₃CN)][BPh₄] and cis-[Rh(BA)(PPh₃)₂(CH₃)(CH₃CN)][BPh₄], respectively, in methylene chloride solutions.Complexes 2 and 3 were characterized by elemental analysis and by IR, ³¹P{¹H}, ¹³C{¹H} and ¹H NMR. According to NMR data, 2 and 3 in solution are non-fluxional trigonal bipyramids with β-diketonate and acetyl ligands in the equatorial plane and axial phosphines.In solutions, 2 and 3 gradually isomerize into octahedral methyl carbonyl complexes trans-[Rh(Acac)(PPh₃)₂(CO)(CH₃)][BPh₄] (4) and trans-[Rh(BA)(PPh₃)₂(CO)(CH₃)][BPh₄] (5), respectively.Complexes 4 and 5 were characterized by IR, ³¹P{¹H}, ¹³C{¹H} and ¹H NMR, without isolation.Upon the action of PPh₃ on cis-[Rh(Acac)(PPh₃)₂(CH₃)(CH₃CN)][BPh₄] and cis-[Rh(BA)(PPh₃)₂(CH₃)(CH₃CN)] [BPh₄], reductive elimination of the methyl ligand as a phosphonium salt, [CH₃PPh₃][BPh₄], occurs to give square planar rhodium(I) complexes [Rh(Acac)(PPh₃)₂] and[Rh(BA)(PPh₃)₂], respectively. The reaction products were identified in the reaction mixtures by ³¹P{¹H} and ¹H NMR.     

New cationic palladium (II) and rhodium (I) complexes of [Ph2PCH2C(Ph)N(2,6-Me2C6H3)]

Treatment of the bulky iminophosphine ligand [Ph₂PCH₂C(Ph)N(2,6-Me₂C₆H₃)] (L) with [M(CH₃CN)₂(ligand)]⁺ⁿ, where for M = Pd(II): ligand = η³-allyl, n = 1, and for M = Rh(I), ligand: 2(C₂H₄), 2(CO) or cod, n = 0, yields the mono-cationic iminophosphine complexes [Pd(η³-C₃H₅)(L)][BF₄] (1), [Rh(cod)(L)][BF₄] (2), [Rh(CO)(CH₃CN)(L)][BF₄] (3), and cis-[Rh(L)₂][BF₄] (4). All the new complexes have been characterised by NMR spectroscopy and X-ray diffraction. Complex 1 shows moderate activity in the copolymerisation of CO and ethene but is inactive towards Heck coupling of 4-bromoacetophenone and n-butyl acrylate.     

Coordination properties of N2S (1,5-bis(3,5-dimethyl-1-pyrazolyl)-3-thiapentane) or N2S2 (1,8-bis(3,5-dimethyl-1-pyrazolyl)-3,6-dithiaoctane or 1,2-bis[3-(3,5-dimethyl-1-pyrazolyl)-2-thiapropyl]benzene) donor ligands toward Rh(I)

The 1,5-bis(3,5-dimethyl-1-pyrazolyl)-3-thiapentane ligand (bdtp) reacts with [Rh(COD)(THF)₂][BF₄] to give [Rh(COD)(bdtp)][BF₄] ([1][BF₄]), which is fluxional in solution on the NMR time scale. Its further treatment with carbon monoxide leads to a displacement of the 1,5-cyclooctadiene ligand, generating a mixture of two complexes, namely, [Rh(CO)₂(bdtp)][BF₄] ([2][BF₄]) and [Rh(CO)(bdtp-κ³N,N,S)][BF₄] ([3][BF₄]). In solution, [2][BF₄] exists as a mixture of two isomers, [Rh(CO)₂(bdtp-κ²N,N)]⁺ ([2a]⁺) and [Rh(CO)₂(bdtp-κ³N,N,S)]⁺ ([2b]⁺; major isomer) rapidly interconverting on the NMR time scale. At room temperature, [2][BF₄] easily loses one molecule of carbon monoxide to give [3][BF₄]. The latter is prone to react with carbon monoxide to partially regenerate [2][BF₄]. The ligands 1,2-bis[3-(3,5-dimethyl-1-pyrazolyl)-2-thiapropyl]benzene (bddf) and 1,8-bis(3,5-dimethyl-1-pyrazolyl)-3,6-dithiaoctane (bddo) are seen to react with two equivalents of [Rh(COD)(THF)₂][BF₄] to give the dinuclear complexes [Rh₂(bddf)(COD)₂][BF₄]₂ ([4][BF₄]₂) and [Rh₂(bddo)(COD)₂][BF₄]₂ ([5][BF₄]₂), respectively. In such complexes, the ligand acts as a double pincer holding two rhodium atoms through a chelation involving S and N donor atoms. Bubbling carbon monoxide into a solution of [4][BF₄]₂ results in loss of the COD ligand and carbonylation to give [Rh₂(bddf)(CO)₄][BF₄]₂ ([6][BF₄]₂). The single-crystal X-ray structures of [3][CF₃SO₃], [5][BF₄]₂ and [6][BF₄]₂ are reported.     

Synthesis, coordination studies and redox properties of a novel ditertiary phosphine bearing two ferrocenyl groups

The new ferrocenyl substituted ditertiary phosphine {FcCH₂N(CH₂PPh₂)CH₂}₂ [Fc = (η⁵-C₅H₄)Fe(η⁵-C₅H₅)] (1) was prepared, in 72% yield, by Mannich based condensation of the known bis secondary amine {FcCH₂N(H)CH₂}₂ with 2 equiv. of Ph₂PCH₂OH in CH₃OH. Phosphine 1 readily coordinates to various transition-metal centres including Mo⁰, Ru^II, Rh^I, Pd^II, Pt^II and Au^I to afford the heterometallic complexes {RuCl₂(p-cym)}₂(1) (2), (AuCl)₂(1) (3), cis-PtCl₂(1) (4), cis-PdCl₂(1) (5), cis-Mo(CO)₄(1) (6), trans,trans-{Pd(CH₃)Cl(1)}₂ (7) and trans,trans-{Rh(CO)Cl(1)}₂ (8). In complexes 2, 3, 7 and 8 ligand 1 displays a P,P′-bridging mode whilst for 4-6 a P,P′-chelating mode is observed. All new compounds have been fully characterised by spectroscopic and analytical methods. Furthermore the structures of 1, 2 · 2CH₂Cl₂, 3 · CH₂Cl₂, 4 · CH₂Cl₂, 6 · 0.5CHCl₃ and 8 have been elucidated by single crystal X-ray crystallography. Electrochemical measurements have been undertaken, and their redox chemistry discussed, on both noncomplexed ligand 1 and representative compounds containing this new ditertiary phosphine.     

Nucleophilic substitution reactions at the Si-Cl bonds of the dichloro(methyl)silyl ligand in five- and six-coordinate complexes of ruthenium(II) and osmium(II)

Treatment of either RuHCl(CO)(PPh₃)₃ or MPhCl(CO)(PPh₃)₂ with HSiMeCl₂ produces the five-coordinate dichloro(methyl)silyl complexes, M(SiMeCl₂)Cl(CO)(PPh₃)₂ (1a, M = Ru; 1b, M = Os). 1a and 1b react readily with hydroxide ions and with ethanol to give M(SiMe[OH]₂)Cl(CO)(PPh₃)₂ (2a, M = Ru; 2b, M = Os) and M(SiMe[OEt]₂)Cl(CO)(PPh₃)₂ (3a, M = Ru; 3b, M = Os), respectively. 3b adds CO to form the six-coordinate complex, Os(SiMe[OEt]₂)Cl(CO)₂(PPh₃)₂ (4b) and crystal structure determinations of 3b and 4b reveal very different Os-Si distances in the five-coordinate complex (2.3196(11) Å) and in the six-coordinate complex (2.4901(8) Å). Reaction between 1a and 1b and 8-aminoquinoline results in displacement of a triphenylphosphine ligand and formation of the six-coordinate chelate complexes M(SiMeCl₂)Cl(CO)(PPh₃)(κ²(N,N)-NC₉H₆NH₂-8) (5a, M = Ru; 5b, M = Os), respectively. Crystal structure determination of 5a reveals that the amino function of the chelating 8-aminoquinoline ligand is located adjacent to the reactive Si-Cl bonds of the dichloro(methyl)silyl ligand but no reaction between these functions is observed. However, 5a and 5b react readily with ethanol to give ultimately M(SiMe[OEt]₂)Cl(CO)(PPh₃)(κ²(N,N-NC₉H₆NH₂-8) (6a, M = Ru; 6b, M = Os). In the case of ruthenium only, the intermediate ethanolysis product Ru(SiMeCl[OEt])Cl(CO)(PPh₃)(κ²(N,N-NC₉H₆NH₂-8) (6c) was also isolated. The crystal structure of 6c was determined. Reaction between 1b and excess 2-aminopyridine results in condensation between the Si-Cl bonds and the N-H bonds with formation of a novel tridentate “NSiN” ligand in the complex Os(κ³(Si,N,N)-SiMe[NH(2-C₅H₄N)]₂)Cl(CO)(PPh₃) (7b). Crystal structure determination of 7b shows that the “NSiN” ligand coordinates to osmium with a “facial” arrangement and with chloride trans to the silyl ligand.     

Trifluoroacetylacetonate rhodium(III) methyl complexes, cis-[Rh(TFA)(PPh3)2(CH3)(L)][BPh4] and cis-[Rh(TFA)(PPh3)2(CH3)(I)] (L = CH3CN, NH3, pyridine), in comparison with their acetylacetonate analogs

The oxidative addition of CH₃I to planar rhodium(I) complex [Rh(TFA)(PPh₃)₂] in acetonitrile (TFA is trifluoroacetylacetonate) leads to the formation of cationic, cis-[Rh(TFA)(PPh₃)₂(CH₃)(CH₃CN)][BPh₄] (1), or neutral, cis-[Rh(TFA)(PPh₃)₂(CH₃)(I)] (4), rhodium(III) methyl complexes depending on the reaction conditions. 1 reacts readily with NH₃ and pyridine to form cationic complexes, cis-[Rh(TFA)(PPh₃)₂(CH₃)(NH₃)][BPh₄] (2) and cis-[Rh(TFA)(PPh₃)₂(CH₃)(Py)][BPh₄] (3), respectively. Acetylacetonate methyl complex of rhodium(III), cis-[Rh(Acac)(PPh₃)₂(CH₃)(I)] (5), was obtained by the action of NaI on cis-[Rh(Acac)(PPh₃)₂(CH₃)(CH₃CN)][BPh₄] in acetone at −15 °C. Complexes 1-5 were characterized by elemental analysis, ³¹P{¹H}, ¹H and ¹⁹F NMR. For complexes 2, 3, 4 conductivity data in acetone solutions are reported. The crystal structures of 2 and 3 were determined. NMR parameters of 1-5 and related complexes are discussed from the viewpoint of their isomerism.     

The reaction of manganese carbonyl with tert-butylisocyanide: Synthesis and characterization of cis- and trans-[Mn(BuNC)4(CN)(CO)]

The reaction of Mn₂(CO)₁₀ with tert-butyl isocyanide in the presence of 10 bar of carbon monoxide leads to the formation of cis- and trans-[Mn(^tBuNC)₄(CN)(CO)], 1a and 1b, in good yields together with [Mn(^tBuNC)₆]CN (2), as a minor product. Nevertheless, the reaction pathway highly depends on the reaction conditions. An interesting side-product is obtained, if chloroform is used during the workup procedure. Compound 3 is composed of cationic [Mn(^tBuNC)₅(CO)] units as well as dinuclear anionic [Mn(^tBuNC)₄(CO)(μ-CN)MnCl₃] moieties. If no additional CO pressure is applied to the system, the organic product N,N′-di-tert-butyl-3,5-bis-tert-butylimino-4-phenyl-cyclopent-1-ene-1,2-diamine (4), is formed in considerable amount. Compound 4 most probably is produced via a double benzylic C-H activation of the solvent toluene and the oligomerization of four isocyanide moieties. The reaction of 1b with Co(NO₃)₂ leads to the isolation of the trinuclear cyanide bridged coordination compound {[Mn(^tBuNC)₄) (CO) (μ-CN)]₂Co(NO₃)₂}, 5, in which the cobalt atoms are tetrahedrally surrounded by the two cyanide ligands and the η¹-coordinated nitro groups. In contrast to the reaction of 1b, treatment of the dicyano complexes cis- or trans-[Ru(^tBuNC)₄(CN)₂] with Co(NO₃)₂ results in the formation of the coordination polymers {[Ru(^tBuNC)₄(CN)₂]Co(NO₃)₂}_n, 7 (trans) and 9 (cis). All new compounds are characterized by X-ray diffraction experiments.     

Novel Re(I) tricarbonyl complexes of chelating ligands with aromatic N-heterocycle ring and aliphatic amine donor - Synthesis, spectroscopic characterization, X-ray structure and DFT calculations

Three novel tricarbonyl rhenium(I) complexes of chelating ligands with aromatic N-heterocycle ring and aliphatic amine donor (2-aminomethylpyridine (ampy), 2-(2-aminophenyl)-1H-benzimidazole (apbi) and 2-(2-aminophenyl)benzothiazole (apbt)) have been synthesized and characterized. The compounds [Re(CO)₃(ampy)Cl] (1), [Re(CO)₃(apbi)Cl] (2) and [Re(CO)₃(apbt)Cl] (3) have been identified by IR, UV-Vis spectroscopy and X-ray analysis. The experimental studies on the complexes 1, 2 and 3 have been accompanied computationally by the density functional theory (DFT) calculations.     

Synthesis and characterization of heterometallic Rh/Ru complexes supported by 1,2-dichalcogenolato-o-carborane ligands

The 16-electron half-sandwich complexes Cp^∗Rh[E₂C₂(B₁₀H₁₀)] (E = S, 1a; Se, 1b) react with [Ru(COD)Cl₂]_x under different conditions to give different types of heterometallic complexes. When the reactions were carried out in THF for 24 h, the binuclear Rh/Ru complexes [Cp^∗Rh(μ-Cl)₂(COD)Ru][E₂C₂(B₁₀H₁₀)] (E = S, 2a; Se, 2b) bridged by two Cl atoms and the binuclear Rh/Rh complexes (Cp^∗Rh)₂[E₂C₂(B₁₀H₁₀)] (E = S, 3a; Se, 3b) with direct Rh-Rh bond can be isolated in moderate yields. [Ru(COD)Cl₂] fragments in 2a and 2b have inserted into the Rh-E bond. If the [Ru(COD)Cl₂]_x was reacted with 1a in the presence of K₂CO₃ in methanol solution, the product [Cp^∗Rh(COD)]Ru[S₂C₂(B₁₀H₁₀]] (4a), K[(μ-Cl)(μ-OCH₃)Ru(COD)]₄ (5a) and 3a were obtained. The B(3)-H activation in complex 4a was found. However, when the reaction between 1b and [Ru(COD)Cl₂]_x was carried out in excessive NaHCO₃, the carborane cage opened products {Cp^∗Rh[S₂C₂(B₉H₁₀)]}Ru(COD) (6b), {Cp^∗Rh[S₂C₂(B₉H₉)]}Ru(COD)(OCH₃) (7b) and 3b were obtained. All complexes were fully characterized by their IR, ¹H NMR and elemental analyses. The molecular structures of 2a, 2b, 3b, 4a, 5a, and 7b have been determined by X-ray crystallography.     

Rhodium(I) complexes with 1′-(diphenylphosphino)ferrocenecarboxylic acid as active and recyclable catalysts for 1-hexene hydroformylation

The rhodium complex trans-[Rh(CO)(Hdpf-κP)(dpf-κ²O,P)] (1), (Hdpf = 1′-(diphenylphosphino)ferrocenecarboxylic acid) was used as an efficient and recyclable catalyst for 1-hexene hydroformylation producing ca. 80% of aldehydes at 10 atm CO/H₂ and 80 °C. After the reaction, unchanged complex 1 was separated from the reaction mixture and used again three times with the same catalytic activity. The effect of modifying ligands, phosphines and phosphites, on the reactivity of 1 was investigated. The active catalytic systems containing 1 or trans-[Rh(CO)(L)(dpf-κ²O,P)] (2) were formed in situ from acetylacetonato rhodium(I) precursors [Rh(CO)₂(acac)] (3) or [RhL(CO)(acac)] (4) and Hdpf or Medpf (L = phosphine, Medpf = methyl ester of Hdpf).     

Rhodium(I) carbonyl complexes of tetradentate chalcogen functionalized phosphines, [P(X)(CH2CH2P(X)Ph2)3] {X = O, S, Se}: Synthesis, reactivity and catalytic carbonylation reaction

The reaction of [Rh(CO)₂Cl]₂ with 0.5 mol equivalent of the ligands [P^′(X)(CH₂-CH₂P(X)Ph₂)₃](P^′P₃X₄) {where X = O(a), S(b) and Se(c)} affords tetranuclear complexes of the type [Rh₄(CO)₈Cl₄(P^′P₃X₄)] (1a-1c). The complexes 1a-1c have been characterized by elemental analyses, mass spectrometry, IR and multinuclear NMR spectroscopy, and the ligands b and c are structurally determined by single crystal X-ray diffraction. 1a-1c undergo oxidative addition (OA) reactions with CH₃I to generate Rh(III) oxidised products. Kinetic data for the reaction of 1a and 1b with excess CH₃I indicate a pseudo first order reaction. The catalytic activity of 1a-1c for the carbonylation of methanol to acetic acid and its ester show a higher Turn Over Frequency (TOF = 1349-1748 h⁻¹) compared to the well-known species [Rh(CO)₂I₂]⁻ (TOF = 1000 h⁻¹) under the similar experimental conditions. However, 1b and 1c exhibit lower TOF than 1a, which may be due to the desulfurization and deselinization of the ligands in the respective complexes under the reaction conditions.