Reactivity of electrophilic terminal phosphinidene complexes toward phosphorus ylides

Stabilised phosphorus ylides react with transient terminal phosphinidene complexes [RP---W(CO)₅] (R=Ph, Me) to give products resulting from a formal insertion of P into a C---H bond via an initial nucleophilic attack of the ylidic carbon.     

Synthesis and characterization of diiron ethanedithiolate complexes with monosubstituted phosphine ligands

Reactions of (μ-edt)Fe₂(CO)₆ (edt = SCH₂CH₂S) (1) with the monophosphine ligands Ph₂PCH₂Ph, Ph₂PC₆H₁₁, Ph₂PCH₂CH₂CH₃, or P(2-C₄H₃O)₃ in the presence of Me₃NO?2H₂O afforded (μ-edt)Fe₂(CO)₅L [L = Ph₂PCH₂Ph, 2; Ph₂PC₆H₁₁, 3; Ph₂PCH₂CH₂CH₃, 4; P(2-C₄H₃O)₃, 5] in 70–88% yields. Complexes 2–5 were characterized by spectroscopy and single crystal X-ray diffraction analysis. The phosphorus of 2–5 is in an apical position of the distorted octahedral geometry of iron.     

Cyclometalation of phosphorus ligands by UV irradiation of complexes having transition metal---silicon bonds

UV irradiation of complexes of the type (η⁵-C₅H₅)(CO)_nMSiR₃ (n = 2, M = Fe; n = 3, M = Mo) in the presence of phosphorus ligands such as P(XC₆H₅)₃ (X = O, S, CH₂) and phosphines containing allyl, 1-naphthyl or tolyl groups gives cyclometalated complexes, R₃SiH being eliminated with retention of configuration at Si. In the cyclometalation five-membered rings are formed in preference to six-membered rings, and metalation occurs more easily at sp² than at sp³ carbon atoms. Methylphenyl-1-naphthylphosphine undergoes rapid racemization upon UV irradiation at room temperature.     

Synthesis and electrochemistry of phenyl-functionalized diiron propanedithiolate complexes with bidentate phosphine ligands

Carbonyl substitution reactions of [μ-(SCH₂)₂CHC₆H₅]Fe₂(CO)₆ with bidentate phosphine ligands, cis-1,2-bis(diphenylphosphine)ethylene (cis-dppv) and N,N-bis(diphenylphosphine)propylamine [(Ph₂P)₂N-Pr-n], yielded an asymmetrically substituted chelated complex [(μ-SCH₂)₂CHC₆H₅]Fe₂(CO)₄(k ²-dppv) and a symmetrically substituted bridging complex [(μ-SCH₂)₂CHC₆H₅]Fe₂(CO)₄[μ-(PPh₂)₂N-Pr-n] under different reaction conditions. Both complexes were fully characterized by spectroscopic methods and by X-ray crystallography. Their electrochemical behaviors were observed by cyclic voltammetry, and the catalytic electrochemical reduction of protons from acetic or trifluoroacetic acid to give dihydrogen mediated by complex [(μ-SCH₂)₂CHC₆H₅]Fe₂(CO)₄(k ²-dppv) was investigated.     

A promising method for phosphinidene generation: complexes of phosphinidenes with N-donor ligands

1,3,2-diazaphospholenes and related compounds can formally be regarded as complexes of phosphinidenes (R-P) with 1,4-diazabutadienes. The dissociation Gibbs free energies of these "complexes" were calculated by using density functional theory (B3LYP/3-21G(*) and B3LYP/6-311+G**). The dissociation Gibbs free energies show systematic dependence on the phosphorus substituent as well as on the stability of the N-donor ligand formed as a byproduct. The thermodynamics and kinetics of the dissociations were thoroughly examined. The results allow us to conclude that novel routes of phosphinidene generation can be developed.     

Synthetic and structural studies of the diiron toluenedithiolate carbonyl complexes with monophosphine ligands

Four diiron toluenedithiolate complexes 2–5 with monophosphine ligands are reported. Treatment of [μ-SC₆H₃(CH₃)S-μ]Fe₂(CO)₆ (1) with tris(3-chlorophenyl)phosphine, tris(4-chlorophenyl)phosphine, tris(4-methylphenyl)phosphine or 2-(diphenylphosphino)benzaldehyde, and Me₃NO?2H₂O in MeCN resulted in the formation of [μ-SC₆H₃(CH₃)S-μ]Fe₂(CO)₅[P(3-C₆H₄Cl)₃] (2), [μ-SC₆H₃(CH₃)S-μ]Fe₂(CO)₅[P(4-C₆H₄Cl)₃] (3), [μ-SC₆H₃(CH₃)S-μ]Fe₂(CO)₅[P(4-C₆H₄CH₃)₃] (4), and [μ-SC₆H₃(CH₃)S-μ]Fe₂(CO)₅[Ph₂P(2-C₆H₄CHO)] (5) in 64–82% yields. Complexes 2–5 have been characterized by elemental analysis, IR, ¹H NMR, ³¹P{¹H} NMR, ¹³C{¹H} NMR and further confirmed by single crystal X-ray diffraction analysis. The molecular structures show that 2–5 contain a butterfly diiron toluenedithiolate cluster coordinated by five terminal carbonyls and an apical monophosphine.     

Activation of white phosphorus in the coordination sphere of nickel complexes with σ-donor ligands

Routes of white phosphorus activation in the coordination sphere of the nickel complexes with different ligands are shown. The first route is based on the coordination of a P₄ molecule with the metal, resulting in the deformation of the P₄ tetrahedron without destruction. This case is characteristic of the NiX₂L complexes, which are reduced at higher cathodic potentials (|E_red| > 0.9 V) (X = BF₄, Br, and Cl; L is bpy in DMF, MeCN, and acetone; 2,9-dimethyl-1,10-phenanthroline (phen) and PPh₃ in DMF and acetone). To cleave the P—P bonds in the P₄ molecule, this complex should be reduced on the electrode. The second route is the oxidation of white phosphorus in the coordination sphere of the Ni^II complex. It occurs when the complex has a sufficiently high oxidizing ability and is reduced rather easily (|E_red| < 0.9 V) (X = BF₄, L is 1,1,1-tris(diphenylphosphinomethyl)ethane (triphos) in acetone; 1,1′,5,5′-bis[methylenedi(p-phenylene)]di(3,7-diphenyl-1,5-diaza-3,7-diphosphacyclooctane) (n²p²) in DMF; phen and PPh₃ in MeCN). The P₄ molecule opening is observed to form a new Ni^I complex containing the (P₃) fragment, for example, [(triphos)Ni(P₃)Ni(triphos)](BF₄)₂. Dedicated to the Academician V. I. Minkin on the occasion of his 70th birthday. __________ Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 919–924, April, 2005.     

Activation of C-H / H-H bonds by rhodium(II) porphyrin bimetalloradicals

Reactivity, kinetic, and thermodynamic studies are reported for reactions of a rhodium(II) bimetalloradical with H(2), and with the methyl C-H bonds for a series of substrates CH(3)R (R = H, CH(3), OH, C(6)H(5)) using a m-xylyl diether tethered diporphyrin ligand. Bimolecular substrate reactions involving the intramolecular use of two metalloradical centers and preorganization of the four-centered transition state (M*...X...Y*...M) result in large rate enhancements as compared to termolecular reactions of monometalloradicals. Activation parameters and deuterium kinetic isotope effects for the substrate reactions are reported. The C-H bond reactions become less thermodynamically favorable as the substrate steric requirements increase, and the activation free energy (DeltaG++) decreases regularly as DeltaG degrees becomes more favorable. An absolute Rh-H bond dissociation enthalpy of 61.1 +/- 0.4 kcal mol(-1) is directly determined, and the derived Rh-CH(2)R BDE values increase regularly with the increase in the C-H BDE.     

Benzoate-functionalized diiron propanedithiolate complexes with mono- and di-phosphine ligands as catalysts for reduction of protons

Reaction of the diiron propanedithiolate complex [μ-(SCH₂)₂CHO₂CC₆H₅]Fe₂(CO)₆ (A) with triphenylphosphine (PPh₃) or cis-1,2-bis(diphenylphosphine)ethylene (cis-dppv) in the presence of one equivalent of Me₃NO·2H₂O yielded a mono-substituted complex [μ-(SCH₂)₂CHO₂CC₆H₅]Fe₂(CO)₅(PPh₃) (1) or an asymmetrically substituted complex [(μ-SCH₂)₂CHO₂CC₆H₅]Fe₂(CO)₄(κ²-dppv) (2), respectively. The structures of both complexes were characterized by spectroscopic methods and X-ray crystallography. In the solid state, the PPh₃ ligand in 1 occupies an apical position of the square pyramidal geometries of the Fe2, while the cis-dppv in 2 coordinates Fe2 in an apical-basal manner. The electrochemistry of both complexes was investigated. The electron-withdrawing benzoate functionality on the bridgehead carbon of the propanedithiolate bridge shifts the oxidation and reduction potentials of 1 or 2 slightly. Both complexes can catalyze the reduction of protons from CF₃COOH but with a higher efficiency for 2.     

Reaction of a phosphaketene with diiron enneacarbonyl: Possible intermediacy of a terminal phosphinidene complex

Evidence is presented for the intermediacy of a terminal phosphinidene complex, [2,4,6-(t-Bu)₃C₆H₂]PFe(CO)₄, in the reaction of [2,4,6-(t-Bu)₃C₆H₂]PCO with Fe₂(CO)₉.     

Facile activation of H-H and Si-H bonds by boranes

The borane B(C(6)F(5))(3) is a precatalyst for H/Dexchange between H(2) and deuterium-labeled silanes (D(3)SiPh, D(2)SiMePh, DSiMe(2)Ph, DSiEt(3)). Experimental and DFT studies reveal that B(C(6)F(5))(3) itself cannot activate dihydrogen but converts to HB(C(6)F(5))(2) under the action of hydrosilane. The latter species easily activates H-H and Si-H bonds by a σ-bond metathesis mechanism, which was further confirmed by the reactions of BD(3)·THF with H(2).     

Addition of alkynes at bridging vinyliminium ligands in diiron complexes: Unprecedented diene formation by enyne-like metathesis

The zwitterionic bridging vinyliminium complex [Fe₂{μ-η¹:η³-C(Tol)C(CS₂)CN(Me)₂}(μ-CO)(CO)(Cp)₂] (5a) undergoes the addition of two equivalents of MeO₂C-CC-CO₂Me affording the bridging bis-alkylidene complex [Fe₂{μ-η¹:η³-C(Me)C{C(CO₂Me)C(CO₂Me)CSC(CO₂Me)C(CO₂Me)S}CNMe₂}(μ-CO)(CO)(Cp)₂] (6). One alkyne unit inserts into a C-CS₂ bond of the bridging ligand, with consequent rearrangement that leads to the formation of a diene. The reaction shows analogies with the enyne metathesis. The second alkyne is incorporated into the bridging frame via cycloaddition at the thiocarboxylate function, affording a 1,3-dithiolene. The complexes [Fe₂{μ-η¹:η³-C(R′)C(CS₂)CN(Me)(R)}(μ-CO)(CO)(Cp)₂] (R = Xyl, R′ = Tol, 5b; R = p-C₆H₄OMe, R′ = Me, 5c; Xyl = 2,6-Me₂C₆H₃), treated with MeO₂C-CC-CO₂Me and then with HBF₄, undergo the cycloaddition of the alkyne with the dithiocarboxylate group and protonation of the dithiocarboxylate carbon, affording the complexes [Fe₂{μ-η¹:η³-C(R′)C{C(H)SC(CO₂Me)C(CO₂Me)S}CN(Me)(R)}(μ-CO)(CO)(Cp)₂][BF₄] (R = Xyl, R′ = Tol, 7a; R = p-C₆H₄OMe, R′ = Me, 7b), respectively.The X-ray molecular structure of 6 has been determined.     

Hydrogen-atom abstraction from Ni(I) phosphido and amido complexes gives phosphinidene and imide ligands

Hydrogen-atom abstraction from M-E(H) to generate M═E-containing complexes (E = PR, NR) is not well studied because only a few complexes are known to undergo such reactions. Hydrogen-atom abstraction from nickel(I) phosphide and amide complexes led to the corresponding phosphinidene and imide compounds. These reactions are unparalleled in the organometallic chemistry of nickel and feature an unusual example of a transition-metal phosphinidene synthesized by hydrogen-atom abstraction.     

Thermal stability of some new complexes bearing ligands with polymerizable groups

A series of new complexes with mixed ligands of the type M(4,4’-dipy)(C₃H₃O₂)₂(H₂O)_y ((1) M=Mn, y=2; (2) M=Ni, y=2; 4,4’-dipy: 4,4’-dipyridyl and C₃H₃O₂ is acrylate anion) and respectively M₂(4,4’-dipy)(C₃H₃O₂)₄(H₂O)_y ((3) M=Cu, y=0; (4) M=Zn, y=1). The modification evidenced in IR spectra was correlated with the presence of acrylate ion as unidentate in the case of complex (1) and as bidentate for others complexes. The electronic reflectance spectra showed the d–d transition for complex (1) and (2) characteristic for the octahedral surrounding while the spectrum for complex (3) have the characteristic pattern for square-pyramidal stereochemistry. The thermal behaviour steps were investigated. The thermal transformations are complex processes according to TG and DTG curves including dehydration, acrylate ion oxidative degradation and thermolysis process of aromatic amine. The final products of decomposition are the most stable metal oxides.     

Insertion reactions of phenyl isocyanate into hafnium nitrogen bonds: synthesis and reactivity of hafnium complexes bearing substituted pyrrolyl ligands

A bis(diethylamido)hafnium compound [C₄H₃N(CH₂NMe₂)-2]₂Hf(NEt₂)₂ (1) has been prepared in 79% yield by reacting Hf(NEt₂)₄ with 2 equiv. of [C₄H₃NH(CH₂NMe₂)-2] in heptane via deamination. Reacting compound 1 with 2 equiv. of phenyl isocyanate at room temperature in diethyl ether results in the PhNCO being inserted seletively into hafnium-NEt₂ bonds to generate [C₄H₃N(CH₂NMe₂)-2]₂Hf[PhNC(NEt₂)O]₂ (2) in 56% yield. Similarly, while reacting 1 with 2 equiv. of phenyl isocyanate for a week in toluene produces a mixture of 2 and [C₄H₃N(CH₂NMe₂)-2]Hf[PhNC(NEt₂)O]₃ (3). For comparison, reacting Hf(NEt₂)₄ with 4 equiv. of PhNCO in a toluene solution at room temperature results in the PhNCO inserted into Hf-N bonds, and forms a tetrakis-ureato hafnium compound Hf[PhNC(NEt₂)O]₄ (4) in 88% yield. A theoretical calculation found that the unpaired electrons of the ureato fragments of 2 are resonance delocalized between the C-O, C-NPh, and C-NEt₂ bonds, which are all partially doubly bonded.     

Thermal behavior of some new complexes bearing ligands with polymerisable groups

This paper reports the investigation of the thermal stability of a series of new complexes with mixed ligands of the type M(dipy)(C₃H₃O₂)₂(H₂O)_y ((1) M: Mn, y=1; (2) M: Ni, y=2; (3) M: Cu, y=1; (4) M: Zn, y=2; dipy: 2,2’-dipyridine and C₃H₃O₂ is acrylate anion). The thermal behaviour steps were investigated. The thermal transformations are complex processes according to TG and DTG curves including dehydration, oxidative condensation of acrylate and thermolysis processes. The final products of decomposition are the most stable metal oxides.     

Thiocarbonyl rhodium complexes with tricyclohexylphosphine and other nitrogen and phosphorus donor ligands

Summary The preparation of the covalent Rh(OCIO₃)(CS)(PCy₃)₂ and Rh(OClO₃)(CS)(PPh₃)(PCy₃) perchlorato complexes is described, These complexes react with mono- or bidentate nitrogen donor ligands to give new cationic complexes of the [Rh(CS)(PCY₃)₂L]ClO4 and [Rh(CS)(PPh,)(PCy₃)L]ClO₄ types,