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.     

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,crystal structure and some properties of new perrhenate and pertechnetate complexes of Nd and Am with 2,6-bis(tetramethylfurano)-1,2,4-triazin-3-yl)-pyridine,tris(2-pyridylmethyl)amine and N,N′-tetraethylmalonamide

The coordination complexes of trivalent f-element pertechnetates and perrhenates with some N-donor ligands were determined by using X-ray structural analysis: Nd³⁺ perrhenate with 2,6-bis(tetramethylfurano)-1,2,4-triazin-3-yl)-pyridine ([Nd(FBTP)₃ReO₄](ReO₄)₂ · 2H₂O (I)), tris(2-pyridylmethyl)amine ([Nd(TPA)(ReO₄)₃] (II)) and N,N′-tetraethylmalonamide ([Nd(TEMA)₄](ReO₄)₃ (III)). The coordination number of Nd is 10 in I, 9 in II and 8 in III. The complexes of Nd³⁺ pertechnetate and Am³⁺ pertechnetate with TPA have been also synthesized (Nd(TPA)(TcO₄)₃ (IV) and Am(TPA)(TcO₄)₃ (V)). The structure II does not change on replacement of perrhenate by pertechnetate and neodymium by americium.     

The influence of substituents (R) at the C carbon on bonding properties of thiosemicarbazones {RC(H)N-NH–C(S)–NH2} in palladium(II) complexes

Reactions of the trans-PdCl₂(PPh₃)₂ precursor with furan-2-carbaldehyde thiosemicarbazone (Hftsc) and thiophene-2-carbaldehyde thiosemicarbazone (Httsc), in 1:1 molar ratios in the presence of Et₃N base, removed one Cl and one PPh₃ group from the Pd^II center, and yielded the complexes [Pd(η²-N³,S-ftsc)(PPh₃)Cl] (1) and [Pd(η²-N³,S-ttsc)(PPh₃)Cl] (2), respectively. However, when a 1:2 molar ratio (M:L) was used, both Cl and PPh₃ ligands were removed, yielding the complexes trans-[Pd(η²-N³,S-ftsc)₂] (3) and trans-[Pd(η²-N³,S-ttsc)₂] (4). Complexes 1–4 have been characterized with the help of analytical data, spectroscopic techniques (IR, ¹H and ³¹P NMR) and single crystal X-ray crystallography. The thiosemicarbazone ligands behave as uninegative N³,S-chelating ligands in complexes 1–4. In contrast, pyrrole-2-carbaldehyde thiosemicarbazone (H₂ptsc) and salicylaldehyde thiosemicarbazone (H₂stsc) invariably formed the complexes [Pd(η³-N⁴,N³,S-ptsc)(PPh₃)] (5) and [Pd(η³–O, N³,S-stsc)(PPh₃)] (6), respectively, and the ligands acted as binegative tridentate donors (N⁴, N³, S, 5; O, N³, S, 6).     

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.     

Tethered silyl complexes from nucleophilic substitution reactions at the Si-Cl bond of the chloro(diphenyl)silyl ligand in Ru(SiClPh2)(κ-S2CNMe2)(CO)(PPh3)2

Crystal structure determination of RuH(κ²-S₂CNMe₂)(CO)(PPh₃)₂ (1) confirms that the triphenylphosphine ligands are arranged mutually trans. 1 reacts readily with HSiClPh₂ to eliminate H₂ and produce the six-coordinate silyl complex, Ru(SiClPh₂)(κ²-S₂CNMe₂)(CO)(PPh₃)₂ (2). Crystal structure determination of 2 reveals the same geometrical arrangement of ligands as in 1 with the silyl ligand replacing the hydride ligand. The chloride bound to silicon in 2 is replaced through reactions with 2-hydroxypyridine, 2-aminopyridine, and thallium acetate, producing, respectively, the mono-PPh₃ complexes, Ru(κ²(Si,N)-SiPh₂OC₅H₄N)(κ²-S₂CNMe₂)(CO)(PPh₃) (3), Ru(κ²(Si,N)-SiPh₂NHC₅H₄N)(κ²-S₂CNMe₂)(CO)(PPh₃) (4), and Ru(κ²(Si,O)-SiPh₂OCMeO)(κ²-S₂CNMe₂)(CO)(PPh₃) (5). Crystal structure determinations of 3, 4, and 5 confirm that in each case there is formation of a five-membered chelate ring tethering the silyl ligand to ruthenium. In the formation of 3, 4, and 5 the Si-ligand and the two S atoms of the dimethyldithiocarbamate ligand remain meridional but the remaining triphenylphosphine ligand and the carbonyl ligand are interchanged in position leaving the donor atom of the tether trans to the CO ligand. An alternative way of considering the tethered silyl ligands in 3, 4, and 5 is as tethered, base-stabilised, silylene ligands and the structural data give some support for a contribution from this bonding model.     

Synthesis and characterization of some novel ruthenium(II) complexes containing thiolate ligands

Reactions of the ruthenium complexes [RuH(CO)Cl(PPh₃)₃] and [RuCl₂(PPh₃)₃] with hetero-difunctional S,N-donor ligands 2-mercapto-5-methyl-1,3,5-thiadiazole (HL¹), 2-mercapto-4-methyl-5-thiazoleacetic acid (HL²), and 2-mercaptobenzothiazole (HL³) have been investigated. Neutral complexes [RuCl(CO)(PPh₃)₂(HL¹)] (1), [RuCl(CO)(PPh₃)₂(HL²)] (2), [RuCl(CO)(PPh₃)₂(HL³)] (3), [Ru(PPh₃)₂(HL¹)₂] (4), [RuCl(PPh₃)₃(HL²)] (5), and [RuCl(PPh₃)₃(HL³)] (6) imparting κ²-S,N-bonded ligands have been isolated from these reactions. Complexes 1 and 4 reacted with diphenyl-2-pyridylphosphine (PPh₂Py) to give neutral κ¹-P bonded complexes [RuCl(CO)(κ¹-P-PPh₂Py)₂(HL¹)] (7), and [Ru(κ¹-P-PPh₂Py)₂(HL¹)₂] (8). Complexes 1-8 have been characterized by analytical, spectral (IR, NMR, and electronic absorption) and electrochemical studies. Molecular structures of 1, 2, 4, and 7 have been determined crystallographically. Crystal structure determination revealed coordination of the mercapto-thiadiazole ligands (HL¹-HL³) to ruthenium as κ²-N,S-thiolates and presence of rare intermolecular S-S weak bonding interaction in complex 1.     

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.     

Selective synthesis of 2-pyridones and pyrimidine-2,4-diones by neutral rhodium(I) complex-catalyzed cyclocotrimerization of alkynes and isocyanates

A neutral rhodium(I) complex, ‘RhCl(PPh₃)₂’ generated by the combination of [RhCl(C₂H₄)₂]₂ with a fourfold amount of PPh₃, effectively catalyzed the cyclocotrimerization of alkynes (1) and isocyanates (2) to give 2-pyridones (3) and/or pyrimidine-2,4-diones (4), selectively, by controlling the molar ratio of alkynes (1) and isocyanates (2).     

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.     

Metallacyclic complexes with ortho-stannylated triphenylphosphine ligands, LnOs(κ(Sn,P)-SnMe2C6H4PPh2), derived from thermal reactions of the five-coordinate complex, Os(SnMe3)Cl(CO)(PPh3)2

Heating the five-coordinate trimethylstannyl complex, Os(SnMe₃)Cl(CO)(PPh₃)₂, in solution with triphenylphosphine induces an ortho-stannylation of one phenyl group of a triphenylphosphine ligand and an ortho-metallation of another triphenylphosphine ligand, to produce the metallacyclic complexes, Os(κ²(Sn,P)-SnMeClC₆H₄PPh₂)(κ²(C,P)-C₆H₄PPh₂)(CO)(PPh₃) (1) and Os(κ²(Sn,P)-SnMe₂C₆H₄PPh₂)(κ²(C,P)-C₆H₄PPh₂)(CO)(PPh₃) (2), suggesting the possible intermediacy of a complex with a coordinated stannylene ligand. Spectroscopic data indicate that only one diastereomer of 1 is formed and crystal structure determination of 1 reveals that this is the diastereomer with chloride directed towards the CO ligand. Complex 2 is converted to 1 through a redistribution reaction with SnMe₂Cl₂. Heating the six-coordinate trimethylstannyl complex, Os(SnMe₃)Cl(CO)₂(PPh₃)₂, in solution produces the osmium(II) methyl complex, Os(Me)(SnMe₂Cl)(CO)₂(PPh₃)₂ (3), through an exchange of methyl and chloride groups on the tin and osmium. In this rearrangement, the relative locations of the two CO ligands and the two PPh₃ ligands remains unchanged. However, when the six-coordinate trimethylstannyl complex, Os(SnMe₃)Cl(CO)₂(PPh₃)₂ is heated under CO, the same exchange reaction is observed but the mono-triphenylphosphine, tricarbonyl complex, Os(Me)(SnMe₂Cl)(CO)₃(PPh₃) (4), is produced and here the SnMe₂Cl ligand is located trans to the PPh₃ ligand. Crystal structure determinations for 1, 2, 3, and 4 have been obtained.     

Stabilization of the labile metal configuration in halfsandwich complexes [CpRh(PN)Hal]X

PN ligands 3 and 4, derived from 2-diphenylphosphanylmethylpyridine 2a, were synthesized, to which in the backbone a tether to a cyclopentadiene system and for comparison an ⁱPr substituent were attached. The chiral compounds were resolved by introduction of a menthoxy substituent into the 2-position of the pyridine system and/or palladium complexes with enantiomerically pure co-ligands. The tripod ligand 3b contains three different binding sites (Cp, P, N) connected by a resolved chiral carbon atom. (S_C)-configuration of this tripod ligand enforces (R_Rh)-configuration at the metal atom in the halfsandwich rhodium complex (L_Ment,S_C,R_Rh)-7b. The opposite metal configuration is inaccessible. Substitution of the chloro ligand in (L_Ment,S_C,R_Rh)-7b by halide (Br, I) or pseudohalide (N₃, CN, SCN) ligands occurs with retention of configuration to give complexes 8b-11b. However, in the reaction of (L_Ment,S_C,R_Rh)-7b with PPh₃ the pyridine arm of the tripod ligand in compound 13b becomes detached from the metal atom. In the Cp*Rh and CpRh compounds of the bidentate PN ligands 4a and 4b both metal configurations are accessible and in complexes 14a-17a and 14b-17b they equilibrate fast. The stereochemical assignments are corroborated by 9 X-ray analyses.     

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.     

Photophysical properties of copper(I) and zinc(II) complexes containing phosphinoquinoline ligands

Several copper(I) and zinc(II) complexes with 8-(diphenylphosphino)quinoline (PPh₂qn) or 8-diphenylphosphinoquinaldine (PPh₂qna) have been prepared. These ligands contain both imine and phosphine moieties, which can act as coordinating groups. X-ray analysis of the Cu(I) complexes reveals that [Cu(PPh₂qn)₂]PF₆ (Cu-1) and [Cu(PPh₂qn)₂]PF₆ (Cu-2), coordinated by two PPh₂qn and PPh₂qna ligands respectively, are obtained. In the Zn(II) complexes, a structural study shows that [ZnCl₂(PPh₂qn)] (Zn-1), [ZnBr₂(PPh₂qn)] (Zn-2) and [ZnI₂(PPh₂qn)] (Zn-3) are coordinated by one PPh₂qn ligand and two of the corresponding halogeno ligands (Cl⁻, Br⁻ and I⁻). In the solid state Cu-1 and Cu-2 show luminescence which is assigned to a ³MLCT transition involving π∗ of the quinoline group, as shown in the [Cu(dmp)(diphosphine)]⁺ complexes; due to the reduced bulkiness of the coordination sphere around the copper atom, no emission is observed in solution. Zn-1 shows a similar emission band to that of free PPh₂qn at both room temperature and 77 K. It suggests the emission bands should be assigned to a ligand-centered (LC) transition. In the solid state, it is found that the emissive energy of the complexes shift to lower energy and the energy depends on the halogeno ligands in the zinc complexes.     

Experimental and theoretical characterization of Ru(II) complexes with polypyridine and phosphine ligands

The synthesis and the experimental and theoretical characterization of ruthenium hydride complexes containing phosphorus and polypyridine ligands [RuH(CO)(N-N)(PPh₃)₂]⁺ with N-N = dppz 1, dppz-CH₃2 (2.1 isomer), dppz-Cl 3 (3.1 isomer), ppl 4, and 2,2′-biquinoline 5, (where dppz = dipyrido[3,2-a:2′,3′-c]phenazine), are presented. ¹H NMR, ³¹P NMR, ¹³C NMR, IR-FT, UV-Vis and elemental analysis are used to characterize the complexes. Optimized molecular geometries in the gas phase at the B3LYP/LACVP(d,p) level showed a distorted octahedral structure for ruthenium, the phosphine ligands are localized in a trans position, while the polypyridine ligand, which in all the cases is planar except in 5, adopt a trans position relative to the carbon monoxide and hydride ligands. The theoretical absorption spectra (one hundred excited states) were calculated for the seven complexes by the time dependent density functional theory (TD-DFT) in the gas phase. They predicted very well the UV-Vis spectra. It was possible to identify the character of each electronic transition and the fragments of the complexes involved in it. Theoretical evidence of the substituent effect in the polypyridine ligand and of the ligand effect (dppz, biq, ppl) was found, displayed mainly in the longer wavelength band. The theoretical results showed that the properties of these complexes can be tuned with changes localized in the polypyridine ligand covalently bonded to ruthenium.     

Rhenium chelate complexes with maltolate or kojate

Novel rhenium complexes containing the maltolate (mal) or kojate (koj) anions as chelating ligands have been synthesized: [ReOCl(mal)₂] (1), [ReOCl₂(mal)(PPh₃)] (2), [ReOBr₂(mal)(PPh₃)] (3), [ReOCl₂(koj)(PPh₃)] (4) and [ReOBr₂(koj)(PPh₃)] (5). The products have been characterized by FTIR, ¹H, ¹³C, and ³¹P NMR spectroscopies and elemental analysis. The crystal and molecular structures of all complexes were determined. Complex 1 crystallizes monoclinic, space group C2/c, Z = 8. It contains two O,O′-bidentate maltolate ligands and one chloro ligand at the (ReO)³⁺ unit, so that a distorted octahedral geometry is adopted by the six-coordinated rhenium(V) center. The chloro ligand occupies a cis position to the oxo ligand. Complexes 2 and 3 are isostructural and crystallize orthorhombic, space group Pbca and Z = 8. The isostructural complexes 4 and 5 crystallize monoclinic, space group P2₁/n and Z = 4. In complexes 2–5, the (ReO)³⁺ unit is coordinated by a monoanionic O,O-bidentate unit of the maltolate (2 and 3) or kojate (4 and 5) ligand, one triphenylphosphine and two halogeno ligands (Cl in 2 and 4; Br in 3 and 5), with the rhenium(V) center in a distorted octahedral environment. The halide ligands are in cis positions to each other.     

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.     

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.     

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.