Synthesis and molecular structures of dinuclear complexes with 1,2-dihydro-1,2-diphenyl-naphtho[1,8-c,d]1,2-diphosphole as a bridging ligand

A bisphosphine in which a PhP-PPh bond bridges 1,8-positions of naphthalene, 1,2-dihydro-1,2-diphenyl-naphtho[1,8-cd]-1,2-diphosphole (1), was used as a bridging ligand for the preparation of dinuclear group 6 metal complexes. Free trans-1, a more stable isomer having two phenyl groups on phosphorus centers mutually trans with respect to a naphthalene plane, was allowed to react with two equivalents of M(CO)₅(thf) (M = W, Mo, Cr) at room temperature to give dinuclear complexes (OC)₅M(μ-trans-1)M(CO)₅ (M = W (2a), Mo (2b), Cr (2c)). The preparation of the corresponding dinuclear complexes bridged by the cis isomer of 1 was also carried out starting from the free trans-1 in the following way. Mono-nuclear complexes M(trans-1)(CO)₅ (M = W (3a), Mo (3b), Cr (3c)) which had been prepared by a reaction of trans-1 with one equivalent of the corresponding M(CO)₅(thf) (M = W, Mo, Cr) complex, were heated in toluene, wherein a part of the trans-3a-c was converted to their respective cis isomer M(cis-1)(CO)₅. Each cis trans mixture of the mono-nuclear complexes 3a-c was treated with the corresponding M(CO)₅(thf) to give a cis trans mixture of the respective dinuclear complexes 2a-c. The cis isomer of the ditungsten complex 2a was isolated, and its molecular structure was confirmed by X-ray analysis, showing a shorter W?W distance of 5.1661(3) Å than that of 5.8317(2) Å in trans-2a.     

Synthesis and structure of {{amino(triorganosilyl)carbene}pentacarbonyltungsten(0)} complexes and attempted synthesis of {[2-bis(trimethylsilyl)methyl-3-triorganosilyl-2H-azaphosphirene-κP]pentacarbonyltungsten(0)}

First examples of tungsten aminocarbene complexes [(OC₅)W{C(SiR¹_nR²_3-n)NH₂}] 2a-d (R¹ = Ph, R² = Me) were synthesized via ammonolysis of the corresponding methoxycarbene complexes 1a-d. They were characterized by NMR spectroscopy, MS, IR, UV/Vis and elemental analysis, and in the case of the C-triphenylsilyl derivative 2a by single-crystal X-ray structure analysis. The reaction of P-chloro alkylidenephosphane 3 with complexes 2a-d, meant to give 2H-azaphosphirene complexes, was monitored by ³¹P NMR spectroscopy to reveal the formation of the products 4-7, which were presumably formed via decomposition of the transient complexes 10a-d.     

3-Amino- and 3-acylamido-2-phosphonopyridines: synthesis by Pd-catalyzed P-C coupling, structure and conversion to pyrido[b]-anellated PC-N heterocycles

Palladium catalyzed cross-coupling of 3-amino- and 3-acylamido-2-bromopyridines 1a-f with triethyl phosphite allowed the synthesis of 3-amino- and 3-acylamido pyridine-2-phosphonic acid diethyl esters 2a-f, whereas nickel catalysts, although providing access to related anilido-2-phosphonates, proved inactive. Reduction of the aminophosphonate 2a with LiAlH₄ afforded 3-amino-2-phosphinopyridine (3a), which was cyclocondensed with dimethylformamide dimethyl acetal (DMFA) via phosphaalkene intermediates 4a to the novel pyrido[b]-anellated 1,3-azaphosphole 5a. Reaction of amidophosphonates 2b-f with LiAlH₄ did not result in the expected reductive cyclization, as shown by closely related anilido-2-phosphonates, but led to product mixtures containing N-secondary 3-amino-2-phosphinopyridines 3b-f as the main or major component. The conversion of 3b,d,e with DMFA to 5b,d,e provides first examples of N-substituted pyrido[b]-anellated azaphospholes. Structures were confirmed by multinuclear NMR and X-ray crystallography (for 2c, 3b).     

Columnar/smectic metallomesogens derived from heterocyclic benzoxazoles

The synthesis, mesomorphic behavior, and optical properties of two new series of metal complexes 1a,b-M (M=Pd, Cu, Zn) derived from benzoxazoles 2a,b are reported. The crystal and molecular structures of mesogenic 5-decyloxy-2-(6-decyloxybenzooxazol-2-yl)phenol and nonmesogenic bis[5-octyloxy-2-(6-octyloxybenzooxazol-2-yl) phenol]Pd(II) were determined by means of X-ray structural analysis. Two benzoxazoles 2a exhibited monotropic SmA phases, and all benzoxazoles 2b were nonmesogenic. On the other hand, metal complexes 1a-M exhibited distinctly different mesomorphism from complexes 1b-M. Complexes 1a-Pd formed SmC phases; complexes 1a-Cu and 1a-Zn formed crystal phases. In contrast, complexes 1b-Zn exhibited columnar phases, and complexes 1b-Cu and 1b-Pd were nonmesogenic. The difference of the mesomorphism in 1a-M and 1b-M was probably attributed to the geometry and/or the overall molecular shape created by 2a and 2b. The electronic configuration of metal ion might play an important role in forming the mesophases. The fluorescent properties of these compounds were also examined.     

From platina-β-diketones to diacetylplatinum(II) complexes - Synthesis, characterization and structural features

The reaction of the electronically unsaturated platina-β-diketone [Pt₂{(COMe)₂H}₂(μ-Cl)₂] (1a) with N^?N donors led to the formation of diacetyl(hydrido)platinum(IV) complexes [Pt(COMe)₂Cl(H)(N^?N)] (2). By the reaction of these complexes with NaOH in a two-phase system (H₂O/CH₂Cl₂) diacetylplatinum(II) complexes [Pt(COMe)₂(N^?N)] (N^?N = bpy, 4a; 4,4′-Me₂-bpy, 4b; 4,4′-t-Bu₂-bpy, 4c; 4,4′-Ph₂-bpy, 4d; 4,4′-t-Bu₂-6-n-Bu-bpy, 4e; bpym, 4f; bpyr, 4g; phen, 4h; 4-Me-phen, 4i; 5-Me-phen, 4j) were obtained. All complexes were characterized by microanalysis, IR and ¹H and ¹³C NMR spectroscopy. Additionally, complexes 4a, 4c, 4d and 4e were characterized by single-crystal X-ray diffraction analysis. The observed variety of packing patterns resulting from π-π stacking and hydrogen bonding is discussed.     

2-(1-Isopropyl-2-benzimidazolyl)-6-(1-aryliminoethyl)pyridyl transition metal (Fe, Co, and Ni) dichlorides: Syntheses, characterizations and their catalytic behaviors toward ethylene reactivity

A series of 2-(1-isopropyl-2-benzimidazolyl)-6-(1-aryliminoethyl)pyridyl metal complexes [iron (II) (1a-6a), cobalt (II) (1b-6b) and nickel (II) (1c-6c)] were synthesized and fully characterized by elemental and spectroscopic analyses. Single-crystal X-ray diffraction analyses of five coordinated complexes 5a, 3b, 5b, 1c and 2c reveal 5a and 5b as distorted trigonal-bipyramidal geometry, and 3b, 1c and 2c as distorted square pyramidal geometry. All complexes performed ethylene reactivity with the assistance of various organoaluminums. The iron complexes displayed good activities in the presence of MAO and MMAO. Upon activated by Et₂AlCl, the cobalt analogues showed moderate ethylene reactivity, while the nickel analogues exhibited relatively higher activities.     

Syntheses, spectroscopic and structural characterizations and metal ion binding properties of Schiff bases derived from 4′-aminobenzo-15-crown-5

A series of benzyloxybenzaldehyde derivatives (1-4) were synthesized by the reactions of 4-(bromomethyl)benzonitrile with 4-hydroxy-3-methoxybenzaldehyde (vanillin), 2-hydroxy-3-methoxybenzaldehyde (o-vanillin), 2-hydroxy-4-methoxybenzaldehyde and 2-hydroxy-5-methoxybenzaldehyde. Condensation reactions among the new benzyloxybenzaldehyde derivatives (1-4) with 4′-aminobenzo-15-crown-5 yielded the new Schiff base compounds (5-8). Sodium complexes (5a-8a) and potassium complexes (5b-8b) were prepared with NaClO₄ and KI, respectively. All of these synthesized compounds were characterized on the basis of FT-IR, ¹H and ¹³C NMR, mass spectrometry and elemental analyses data. The solid state structures of compounds 8 and 5a were determined by X-ray crystallography. The extraction abilities of compounds 5-8 were also evaluated in CH₂Cl₂ by using several main group and transition metal picrates, such as Na⁺, K⁺, Pb²⁺, Cr³⁺, Ni²⁺, Cu²⁺ and Zn²⁺.     

Hydrogen-bonded networks from η-semiquinone complexes of manganese tricarbonyl

The cationic manganese tricarbonyl complexes containing η⁶-2-methylhydroquinone (2a), η⁶-2,3-dimethylhydroquinone (3a), η⁶-2-t-butylhydroquinone (4a), η⁶-tetramethylhydroquinone (5a) and η⁶-4,4′-biphenol (6a) are readily deprotonated to the corresponding neutral (η⁵-semiquinone)Mn(CO)₃ (2b-6b) and anionic (η⁴-quinone)Mn(CO)₃⁻ (2c-5c) complexes. The X-ray structures of 2b-6b feature strong intermolecular hydrogen bonding interactions that result in the formation of supramolecular organometallic networks. Significantly, the substitution pattern at the semiquinone ring affects the stereochemistry of the hydrogen bonding interactions. NMR spectra of 2b, 3b and 5b reveal dynamic hydrogen bonding in solution.     

Synthesis and properties of novel 5-(cyclohepta-2′,4′,6′-trienylidene)pyrimidine-2(1H),4(3H),6(5H)-triones: methodology for synthesizing cyclohepta[b]pyrimido[5,4-d]furan-8(7H),10(9H)-dionylium tetrafluoroborates

Novel condensation reaction of tropone with N-substituted and N,N′-disubstitued barbituric acids in Ac₂O afforded 5-(cyclohepta-2′,4′,6′-trienylidene)pyrimidine-2(1H),4(3H),6(5H)-trione derivatives (8a-f) in moderate to good yields. The ¹³C NMR spectral study of 8a-f revealed that the contribution of zwitterionic resonance structures is less important as compared with that of 8,8-dicyanoheptafulvene. The rotational barriers (ΔG^‡) around the exocyclic double bond of mono-substituted derivatives 8a-c were obtained to be 14.51-15.03 kcal mol⁻¹ by the variable temperature ¹H NMR measurements. The electrochemical properties of 8a-f were also studied by CV measurement. Upon treatment with DDQ, 8a-c underwent oxidative cyclization to give two products, 7 and 9-substituted cyclohepta[b]pyrimido[5,4-d]furan-8(7H),10(9H)-dionylium tetrafluoroborates (11a-c·BF₄⁻ and 12a-c·BF₄⁻) in various ratios, while that of disubstituted derivatives 8d-f afforded 7,9-disubstituted cyclohepta[b]pyrimido[5,4-d]furan-8(7H),10(9H)-dionylium tetrafluoroborate (11d-f·BF₄⁻) in good yields. Similarly, preparation of known 5-(1′-oxocycloheptatrien-2′-yl)-pyrimidine-2(1H),4(3H),6(5H)-trione derivatives (14a-d) and novel derivatives 14e,f was carried out. Treatment of 14a-c with aq. HBF₄/Ac₂O afforded two kinds of novel products 11a-c·BF₄⁻ and 12a,c·BF₄⁻ in various ratios, respectively, while that of 14d-f afforded 11d-f. The product ratios of 11a-c·BF₄⁻ and 12a-c·BF₄⁻ observed in two kinds of cyclization reactions were rationalized on the basis of MO calculations of model compounds 20a and 21a. The spectroscopic and electrochemical properties of 11a-f·BF₄⁻ and 12a-c·BF₄⁻ were studied, and structural characterization of 11c·BF₄⁻ based on the X-ray crystal analysis and MO calculation was also performed.     

Chiral binuclear copper(II) catalyzed nitroaldol reaction: scope and mechanism

Chiral binuclear copper(II) Schiff base complexes 4a-g have been prepared from aldehydes 1a,b, (S)-amino alcohols 2a-f, and Cu(OAc)₂·1H₂O in high yield. Their catalysis is studied for the addition of nitroalkanes to aldehydes at ambient conditions with 76:24 er.     

Some novel observations on the reaction of 2-hydrazino-3-methylquinoxaline with trifluoromethyl-β-diketones

The reaction of 2-hydrazino-3-methylquinoxaline 1 with trifluoromethyl-β-diketones 2 not only yields the expected 5-trifluoromethyl-5-hydroxy-Δ²-pyrazolines 3a-3f and/or 3-trifluoromethylpyrazoles 4c-4f but also the unexpected products 1,2,4-triazolo[4,3-a]quinoxalines 5a-5f and/or 3(5)-trifluoromethyl-1H-pyrazoles 6c-6f. Furthermore, the acid-catalyzed dehydration of 5-hydroxypyrazolines 3a-3b resulted in the formation of unexpected 5a-5b along with the expected corresponding pyrazoles 7a-7b. These unprecedented observations provide evidence for the existence of equilibrium between the hydroxypyrazoline 3 and its open chain tautomer, ketoimine 9 in the mechanistic path leading to the formation of pyrazoles 7 and triazoles 5.     

Ruthenium piano-stool complexes containing mono- or bidentate pyrrolidinylalkylphosphines and their reactions with small molecules

Ruthenium piano-stool complexes incorporating the new bidentate aminoalkylphosphine ligand 1,2-bis(dipyrrolidin-1-ylphosphino)ethane (dpyrpe, I) or its monodentate counterpart bis(pyrrolidin-1-yl)methylphosphine (pyr₂PMe, II) have been prepared, [(C₅R₅)RuCl(PP)] (R = Me and PP = dpyrpe, 1; R = Me and PP = (pyr₂PMe)₂, 2; R = H and PP = dpyrpe, 3). Complexes 2 and 3 have been characterized by X-ray crystallography. Complexes 1 and 2 react with NaBAr₄^f in the presence of ligand L to yield [Cp^∗Ru(L)(dpyrpe-κ²P)][BAr^f₄] (L = MeCN, 4a; CO, 4b; N₂, 4c) and [Cp^∗Ru(L)(pyr₂PMe)₂][BAr₄^f] (L = MeCN, 5a; CO, 5b; N₂, 5c). Complex 4a was crystallographically characterized. The CO complexes 4b and 5b were examined using IR spectroscopy in an attempt to establish the electron-donating capabilities of I and II. Complex 1 oxidatively adds H₂ in the presence of NaBAr₄^f to yield the Ru(IV) dihydride [Cp^∗RuH₂(dpyrpe-κ²P)][BAr₄^f], 7.     

Phosphorus-nitrogen compounds part 22. Syntheses, structural investigations, biological activities and DNA interactions of new mono and bis (4-fluorobenzyl) spirocyclophosphazenes

The reactions of hexachlorocyclotriphosphazene, N₃P₃Cl₆, with mono (1 and 2) and bis(4-fluorobenzyl) diamines (3-5), FPhCH₂NH(CH₂)_nNHR (RH or FPhCH₂-), produce mono (1a and 2a) and bis(4-fluorobenzyl) monospirocyclophosphazenes (3a-5a). The tetraaminomonospirocyclophosphazenes (1b-2d) are obtained from the reactions of the partly substituted phosphazenes (1a and 2a) with excess pyrrolidine, morpholine and 1,4-dioxa-8-azaspiro[4,5]decane (DASD), respectively. The tetrachlorobis(4-fluorobenzyl) monospirocyclophosphazenes (4a and 5a) with excess pyrrolidine, morpholine and DASD afford the fully substituted bis(4-fluorobenzyl) monospirocyclophosphazenes (4b, 4d-5d) in boiling THF. In addition, monochlorobis(4-fluorobenzyl) monospirocyclophosphazenes (4e and 4f) have also been isolated from the reactions with excess morpholine and DASD in boiling THF. The structural investigations of the compounds have been verified by elemental analyses, MS, FTIR, ¹H, ¹³C, ¹⁹F (for 1d and 2d), ³¹P NMR, HSQC and HMBC techniques. The crystal structures of 3a, 4a, 5a and 2b have been determined by X-ray crystallography. The compounds 2a-5a, 1b-2d, 4b, 4d-5d, 4e and 4f have been screened for antibacterial effects on bacteria and for antifungal activity against yeast strains. The compounds 1b and 4b showed antimicrobial activity against three species of bacteria, Bacillus subtilis, Bacillus cereus and Staphylococcus aureus, and two fungi, Candida albicans and Candida tropicalis. Minimum inhibitory concentrations (MIC) were determined for 1b and 4b. The MIC values were found to be 5000 μM for each bacteria. The most effective compound, 4b has exhibited activity with a MIC of 312 μM for C. albicans and 625 μM for C. tropicalis. DNA-binding and the nature of the interaction with pBR322 plasmid DNA are studied. All of the compounds induce changes on the DNA mobility and intensity. Prevention of HindIII digestion with the compounds indicates that the compounds bind with AT nucleotides in DNA.     

Aluminum and zinc complexes supported by functionalized phenolate ligands: Synthesis, characterization and catalysis in the ring-opening polymerization of ε-caprolactone and rac-lactide

A series of aluminum and zinc complexes supported by functionalized phenolate ligands were synthesized and characterized. Reaction of 2-(3,5-R₂C₃N₂)C₆H₄NH₂ (R = Me, Ph) with salicylaldehyde or 3,5-di-tert-butylsalicylaldehyde afforded 2-((2-(1H-pyrazol-1-yl)phenylimino)methyl)phenol derivatives 2a-2d. Treatment of 2a-2d with an equiv. of AlR²₃ (R² = Me, Et) gave corresponding aluminum aryloxides 3a-3e, while reaction with an equiv. of ZnEt₂ afforded zinc aryloxides 4a-4d. Treatment of 2c with 0.5 equiv. of ZnEt₂ formed diphenolato zinc complex 5. All new compounds were characterized by ¹H and ¹³C NMR spectroscopy and elemental analyses. The structures of complexes 3a, 4a and 5 were further characterized by single crystal X-ray diffraction techniques. The catalytic activity of complexes 3-5 toward the ring-opening polymerization of ε-caprolactone was studied. The zinc complexes (4a-4d) exhibited higher catalytic activity than the aluminum complexes (3a-3e). The diphenolato zinc complex 5 showed lower catalytic activity than the ethylzinc complexes 4a-4d. The aluminum complex (3b) is inactive to initiate the ROP of rac-lactide, while the zinc complex (4d) is active initiator for the ROP of rac-lactide, giving atactic polylactide.     

Mononuclear rearrangements of heterocycles in water/β-CD: information on the real site of reaction from structural modifications of substrates and from proton concentration dependence of the reactivity

The effect of β-cyclodextrin (β-CD) on the reactivity in the base-catalyzed pathway for the rearrangement in water of some (Z)-hydrazones of 3-benzoyl-1,2,4-oxadiazoles (1b-f) into the relevant triazoles (2b-f) was investigated, finding different behavior as a function of the proton concentration. ESIMS and ¹H NMR data evidence the formation of host-guest complexes. The whole of the experimental and calculated (MM2) data enabled us to draw some intriguing conclusions concerning the influence of the structures of the substrates and the nature of the formed host-guest complexes on the real site of the reaction.     

Preference of di-n-butyltin compounds to build O?Sn bonds in fused rings with five-six members

The reaction of salicylaldehyde (1), o-aminophenols (2a-2f), and di-n-butyltin^IV oxide (3) to give six di-n-butyltin^IV compounds (4a-4f) was achieved in good yields. All compounds were characterized by ¹H, ¹³C, ¹⁵N, ¹¹⁹Sn NMR, mass spectrometry, IR, elemental analysis and in the case of compounds 4a, 4b, 4d and 4e by X-ray diffraction analysis. Compound 4a crystallized with trigonal bipiramidal (TPB) geometry surrounding the tin atom while 4b and 4e crystallized as dimeric molecules joined by two O?Sn bonds with distorted octahedron (DOC) geometry. The X-ray structure of 4d presents one cocrystallized monomeric TBP with one dimeric DOC molecule. Correlations of σ_Hammett vs. spectroscopic values were found for 4a-4b and 4d-4f, indicating the substituents in the aromatic ring derived from o-aminophenol serve as modulators of the O?Sn supramolecular interaction. The O?Sn bond formation is selective for the five-membered ring oxygen atom.     

Syntheses, structures and electrochemistry of some 1-(η-allylamino)-1-ferrocenylcarbene complexes of chromium(0), molybdenum(0) and tungsten(0) : Part 13: The chemistry of metallacyclic alkenylcarbene complexes

The metallacyclic complexes (OC)₄MC(η²-NHCH₂CHCHX)Fc (4; X = H) and (5; X = CH₂OH) [M = Cr: a; Mo: b; W: c; Fc = ferrocenyl = CpFe(C₅H₄)] were obtained in good yields upon photo-decarbonylation of the bimetallic allylaminocarbene complexes (OC)₅MC(NHCH₂CHCHX)Fc (2; X = H)/(3; X = CH₂OH). At room temperature complexes 2/3 exist as mixtures of E- and predominantly Z-isomers with regard to the C-N bond. The molecular structures of 4b and 4c were determined by X-ray diffraction analyses. The intermetallic communicative effects and the interplay of Fc and η²-alkene moieties of 4a and 4b were assessed by cyclovoltammetry. All complexes were also characterized in solution by one- and two-dimensional NMR spectroscopy (¹H, ¹³C, ¹H NOE, ¹H/¹H COSY, ¹³C/¹H HETCOR).     

Aminobis(phenolate)s of imidomolybdenum(VI) and -tungsten(VI)

The reactions of trans-[MoO(ONO^Me)Cl₂] 1 (ONO^Me = methylamino-N,N-bis(2-methylene-4,6-dimethylphenolate) dianion) and trans-[MoO(ONO^tBu)Cl₂] 2 (ONO^tBu = methylamino-N,N-bis(2-methylene-4-methyl-6-tert-butylphenolate) dianion) with PhNCO afforded new imido molybdenum complexes trans-[Mo(NPh)(ONO^Me)Cl₂] 3 and trans-[Mo(NPh)(ONO^tBu)Cl₂] 4, respectively. As analogous oxotungsten starting materials did not show similar reactivity, corresponding imido tungsten complexes were prepared by the reaction between [W(NPh)Cl₄] with aminobis(phenol)s. These reactions yielded cis- and trans-isomers of dichloro complexes [W(NPh)(ONO^Me)Cl₂] 5 and [W(NPh)(ONO^tBu)Cl₂] 6, respectively. The molecular structures of 4, cis-6 and trans-6 were verified by X-ray crystallography. Organosubstituted imido tungsten(VI) complex cis-[W(NPh)(ONO^tBu)Me₂] 7 was prepared by the transmetallation reaction of 6 (either cis or trans isomer) with methyl magnesium iodide.     

Reactivity studies of (η-arene)ruthenium dimeric complexes towards pyrazoles: isolation of amidines, bis pyrazoles and chloro bridged pyrazole complexes

The complex [(η⁶-p-cymene)Ru(μ-Cl)Cl]₂1 reacts with pyrazole ligands (3a-g) in acetonitrile to afford the amidine derivatives of the type [(η⁶-p-cymene)Ru(L)(3,5-HRR′pz)](BF4)₂ (4a-f), where L = {HNC(Me)3,5-RR′pz}; R, R′ = H (4a); H, CH₃ (4b); C₆H₅ (4c); CH₃, C₆H₅ (4d) OCH₃ (4e); and OC₂H₅ (4f), respectively. The ligand L is generated in situ through the condensation of 3,5-HRR′pz with acetonitrile under the influence of [(η⁶-p-cymene)RuCl₂]₂. The complex [(η⁶-C₆Me₆)Ru(μ-Cl)Cl]₂2 reacts with pyrazole ligands in acetonitrile to yield bis-pyrazole derivatives such as [(η⁶-C₆Me₆)Ru (3,5-HRR′pz)₂Cl](BF₄) (5a-b), where R, R′ = H (5a); H, CH₃ (5b), as well as dimeric complexes of pyrazole substituted chloro bridged derivatives [{(η⁶-C₆Me₆)Ru(μ-Cl) (3,5-HRR′pz)}₂](BF₄)₂ (5c-g), where R, R′ = CH₃ (5c); C₆H₅ (5d); CH₃, C₆H₅ (5e); OCH₃ (5f); and OC₂H₅ (5g), respectively. These complexes were characterized by FT-IR and FT-NMR spectroscopy as well as analytical data. The molecular structures¹ of representative complexes [(η⁶-C₆Me₆)Ru{3(5)-Hmpz}₂Cl]⁺5b, [(η⁶-C₆Me₆)Ru(μ-Cl)(3,5-Hdmpz)]₂²⁺5c and [(η⁶-C₆Me₆)Ru(μ-Cl){3(5)Me,5(3)Ph-Hpz}]₂²⁺5e were established by single crystal X-ray diffraction studies.     

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.