A 2-iridathiophene from reaction between IrCl(CS)(PPh3)2 and Hg(CHCHPh)2

The thiocarbonyl analogue of Vaska’s compound is produced in high yield by first treating IrCl(CO)(PPh₃)₂ with CS₂ and methyl triflate to give [Ir(κ²-C[S]SMe)Cl(CO)(PPh₃)₂]CF₃SO₃ (1), secondly, reacting 1 with NaBH₄ to give IrHCl(C[S]SMe)(CO)(PPh₃)₂ (2), and finally heating 2 to induce elimination of both MeSH and CO to produce IrCl(CS)(PPh₃)₂ (3). When IrCl(CS)(PPh₃)₂ is treated with Hg(CHCHPh)₂ the novel 2-iridathiophene, Ir[SC₃H(Ph-3)(CHCHPh-5)]HCl(PPh₃)₂ (4) is produced. The X-ray crystal structure of the iodo-derivative of 4, Ir[SC₃H(Ph-3)(CHCHPh-5)]HI(PPh₃)₂ (5) confirms the unusual 2-metallathiophene structure. Treatment of IrCl(CS)(PPh₃)₂ with Hg(CHCPh₂)₂ produces both a coordinatively unsaturated 1-iridaindene, Ir[C₈H₅(Ph-3)]Cl(PPh₃)₂ (6) and a chelated dithiocarboxylate complex, Ir(κ²-S₂CCHCPh₂)Cl(CHCPh₂)(PPh₃)₂ (7). X-ray crystal structure determinations for 6 and 7 are reported.     

On the reactivity of [IrCl(N2)(PPh3)2] with alkynylsilanes - A new route to vinylidene iridium(I) complexes

The iridium dinitrogen complex [IrCl(N₂)(PPh₃)₂] (1) was found to react with alkynylsilanes to form the vinylidene iridium(I) complexes trans- (R/R′ = Ph/Me, 2; Me/Me, 3; Bn/Me, 4; SiMe₃/Me, 5; SiEt₃/Et, 6; ⁱPr/Me, 7) and with Me₃SiCCC(O)R to yield the iridium η²-alkyne complexes trans-[IrCl{η²-Me₃SiCCC(O)R}(PPh₃)₂] (R = OEt, 9; Me, 11). Complex 9 was found to isomerize upon heating or upon UV irradiation yielding the vinylidene complex trans-[IrCl{CC(SiMe₃)CO₂Et}(PPh₃)₂] (10). The reaction of 1 with Me₃SiCCCCSiMe₃ yielded the complex trans-[IrCl{CC(SiMe₃)CCSiMe₃}(PPh₃)₂] (8), whereas with MeO₂CCCCO₂Me the iridacyclopentadiene complex [Ir{C₄(CO₂Me)₄}Cl(PPh₃)₂] (13) was formed. The complexes were characterized by means of ¹H, ¹³C and ³¹P NMR spectroscopy as well as by IR spectroscopy and microanalysis.     

Synthesis of ruthenium phenylindenylidene, carbyne, allenylidene and vinylmethylidene complexes from (PPh3)3−4RuCl2: A mechanistic and structural investigation

The reaction of (Ph₃P)₃RuCl₂ with 1,1-diphenyl-2-propyn-1-ol was investigated in various solvents. The reaction in thf under reflux is reported to produce the (PPh₃)₂Cl₂Ru(3-phenylindenylidene) complex (3) which has undergone rearrangement of the allenylidene C₃-spine. We have improved the reliability of the reported synthesis by adding acetyl chloride which converts the formed water of the reaction and thus increases the acidity of the reaction solution. Without the additive, we observed the exclusive formation of an intermediate of the transformation and identified it as dinuclear (PPh₃)₂ClRu(μ-Cl)₃(PPh₃)₂RuCCCPh₂ complex (5). The reaction of (Ph₃P)₃₋₄RuCl₂ with 1,1-diphenyl-2-propyn-1-ol in CH₂Cl₂ or C₂H₄Cl₂ under reflux in the presence of excess conc. aqueous HCl afforded the new, neutral (PPh₃)₂Cl₃RuC-CHCPh₂ carbyne complex (7), an HCl adduct of previously elusive (PPh₃)₂Cl₂RuCCCPh₂ complex 6 in high yields. In contrast to the formation of complex 3, the reaction in a non-coordinating solvent did not afford the rearrangement of the allenylidene C₃-spine. Complex 7 was converted into complex 3 in thf under reflux under loss of a molecule HCl. Complex 7 was converted with triethylamine under loss of HCl to complex 6. Pentacoordinate complex 6 was crystallized in the presence of O-donor ligands (EtOH, MeOH and H₂O) to give hexacoordinate (PPh₃)₂Cl₂(ROH)RuCCCPh₂ (R = H, CH₃, C₂H₅) complexes (9)-(11) with the O-donor coordinating in trans-position to the allenylidene moiety. The reaction of complex 7 with 2 equiv. of 4-(N,N-dimethylamino)pyridine (DMAP) gave hexacoordinate (PPh₃)₂Cl₂(DMAP)RuCCCPh₂complex (12) with one molecule DMAP also coordinating in trans-position to the allenylidene group. Methanol and acetic acid in the absence of strong bases afforded the Fischer-carbene complexes (PPh₃)₂Cl₂RuC(OCH₃)-CHCPh₂ (14) and (PPh₃)₂Cl₂RuC(OAc)-CHCPh₂ (15) where the nucleophile added to the α-carbon atom. The structures of complexes 5, 7, 9-11, 14, and 15 were solved via X-ray crystallography.     

Synthesis and characterisation of the amidine complexes trans-[PtCl(NH3){HNC(NH2)R}2]Cl (R = Me, Ph, CH2Ph) derived from addition of NH3 to the coordinated nitriles in trans-[PtCl2(NCR)2]

The di-nitrile complexes trans-[PtCl₂(NCR)₂] (R = Me, Ph, CH₂Ph) react with an excess of gaseous NH₃ in CH₂Cl₂ at −10 °C to form, in high yield, the corresponding di-amidine complexes trans-[PtCl(NH₃){HNC(NH₂)R}₂]Cl in which also one chlorine ligand has been displaced by NH₃. The ¹H NMR spectra in DMSO showed the formation of different species which were characterized through NOESY, TOCSY and ¹H/¹³C heteronuclear correlations as trans-[Pt(NH₃){HNC(NH₂)R}₂(DMSO)]Cl₂ and trans-[PtCl{HNC(NH₂)R}₂(DMSO)]Cl.     

Synthesis and structures of bimetallic silicon-containing imido alkylidene complexes of tungsten (R′O)2(ArN)WCH-SiR2-CHW(NAr)(OR′)2 (R = Me, Ph) and (R′O)2(ArN)WCH-SiMe2SiMe2-CHW(NAr)(OR′)2

Bimetallic alkylidene complexes of tungsten (R′O)₂(ArN)WCH-SiR₂-CHW(NAr)(OR′)₂ (R = Me (1), Ph (2)) and (R′O)₂(ArN)WCH-SiMe₂SiMe₂-CHW(NAr)(OR′)₂ (3) (Ar = ; R′ = CMe₂CF₃) have been prepared by the reactions of divinyl silicon reagents R₂Si(CHCH₂)₂ with known alkylidene compounds R′′-CHMo(NAr)(OR′)₂. (R′′ = Bu^t, PhMe₂C) Complexes 1-3 were structurally characterized. Ring opening metathesis polymerization (ROMP) of cyclooctene using compounds 1-3 as initiators led to the formation of high molecular weight polyoctenamers with predominant trans-units content in the case of 1 and 3 and predominant cis-units content in the case of 2.     

Silicon version of enamines: Amino-substituted disilenes by the reactions of the disilyne RSiSiR (R = SiPr[CH(SiMe3)2]2) with amines

The reaction of 1,1,4,4-tetrakis[bis(trimethylsilyl)methyl]-1,4-diisopropyltetrasila-2-yne 1 with secondary or primary amines produced amino-substituted disilenes R(R₂′N)SiSiHR 2a-d (R = SiⁱPr[CH(SiMe₃)₂]₂, R₂′NEt₂N (2a), (CH₂CH₂)₂N (2b), ^tBu(H)N (2c), and Ph₂N (2d)). Spectroscopic and X-ray crystallographic analyses of 2 showed that 2a-c have a nearly coplanar arrangement of the SiSi double bond and the amino group, giving π-conjugation between the SiSi double bond and the lone pair on the nitrogen atom, whereas 2d has a nearly perpendicular arrangement precluding such conjugation. Theoretical calculations indicate that π-conjugation between the π-orbital of the SiSi double bond and the lone pair on the nitrogen atom is markedly influenced by the torsional angle between the SiSi double-bond plane and the amino-group plane.     

Synthesis and characterization of bimetallic ruthenium complexes connected through linear (CH)14 chain

Treatment of RuHCl(CO)(PPh₃)₃ with (3E,5E,7E,9E,11E)-HCC-(CHCH)₅- CCH produces [RuCl(CO)(PPh₃)₂]₂[μ-(CHCH)₇]. The later complex reacts with PMe₃ to give [RuCl(CO)(PMe₃)₃]₂[μ-(CHCH)₇], the structure of which has been confirmed by X-ray diffraction. The through-space distance from one Ru to the other is 19.88 Å.     

The stereoselective synthesis of (Z)-HFCCFZnI and stereospecific preparation of (E)-1,2-difluorostyrenes from (Z)-HFCCFZnI via an unusual Pd(PPh3)4-Cu(I)Br co-catalysis approach or (Z)-HFCCFSnBu3

(Z)-HFCCFZnI was stereoselectively synthesized from activated zinc dust and (Z)-HFCCFI that was synthesized from chlorotrifluoroethene in a sequential manner. Compared to (E)-HFCCFZnI, (Z)-HFCCFZnI was more challenging to prepare in terms of sluggish metallation and formation of by-products, and underwent slower and incomplete Negishi coupling with aryl iodides. In a modification of Negishi coupling, (E)-α,β-difluorostyrenes were stereospecifically prepared in good to excellent yields under mild conditions from aryl iodides and (Z)-HFCCFZnI with the co-catalysis of Pd(PPh₃)₄/Cu(I)Br. Experimental investigation and mechanistic rationalization suggested that Cu(I)Br would be a scavenger of free ligands for the facilitation of Pd(PPh₃)₂ formation, and a supplier of ligand for the metathesis process. Alternatively, (Z)-HFCCFSnBu₃ and aryl iodides with an electron-withdrawing group underwent Stille-Liebiskind coupling to afford (E)-α,β-difluorostyrenes.     

The synthesis and single-crystal X-ray structures of palladium(II) and platinum(II) complexes of the difluorovinyl and 1-chloro-2-fluorovinyl-substituted phosphines, PPh2(Z-CFCFH) and PPh2(E-CClCFH)

The coordination chemistry of the fluorovinyl substituted phosphines PPh₂(Z-CFCFH) and PPh₂(E-CClCFH) with K₂MX₄ (M = Pd, Pt; X = Cl, Br, and I) salts has been investigated resulting in the first reported palladium(II) and platinum(II) complexes of phosphines containing partially fluorinated vinyl groups. The complexes have been characterised by a combination of multinuclear [¹H, ¹³C{¹H}, ¹⁹F, ³¹P{¹H}] NMR spectroscopy, and IR/Raman spectroscopy. The single-crystal X-ray structures of trans-[PdX₂{PPh₂(CFCFH)}₂], X = Cl (1), Br (2), I (3), trans-[PdCl₂{PPh₂(CClCFH)}₂] (4), cis-[PtX₂{PPh₂(CFCFH)}₂], X = Cl (5), Br (6), trans-[PtI₂{PPh₂(CFCFH)}₂] (7), and both cis- and trans-[PtCl₂{PPh₂(CClCFH)}₂] (8), have been determined. Results obtained from spectroscopic and crystallographic data suggest that replacement of a β-fluorine by hydrogen, whilst reducing the steric demand of the ligand, has little effect on the electronic character of the ligand. The presence of a proton in the vinyl group results in short proton-halide secondary interactions in the solid state (d(H?X) = 2.72(3) for 1, and 2.92(5) Å for 2) forming an infinite chain ribbon motif.     

Synthesis and characterization of (CHCH)n-bridged (n = 1, 2, 3) heterobimetallic and trimetallic ferrocene-ruthenium complexes

A series of heterobinuclear ferrocene-ruthenium complexes Fc(CHCH)_nRuCl(CO)(PMe₃)₃ (n = 1, 3; n = 2, 12), Fc(CHCH)RuCl(CO)(Py)(PPh₃)₂ (4), and trimetallic Fc(CHCH)RuCl(CO)(PPh₃)₂(Py-E-(CHCH)Fc) (6) have been prepared. The length of the molecular rods is extended by successive insertion of CHCH spacers in the bridging ligands or the ancillary ligands. The respective products have been fully characterized and the structures of 3 and 12 have been established by X-ray crystallography. Electrochemical studies have revealed that ethenyl heterobimetallic complexes display two successive one-electron processes, and that intermetallic electronic communication between the two endgroups is attenuated with the increase of the length of the conjugated bridge. The electrochemical behavior of the trimetallic complex reveals strong electronic communication between ruthenium and ferrocene transmitted through the ethenyl bridge, however, it also reveals a very weak interaction between ruthenium and ferrocene transmitted through the (E)-CHCH-Py bridge.     

A well feasible and general route to (organoethynyl)difluoroboranes, RHCCBF2, and their perfluorinated analogues, RFCCBF2

A representative series of (organoethynyl)difluoroboranes RCCBF₂ (RC₄H₉, (CH₃)₃C, CF₃, C₃F₇, (CF₃)₂CF, CF₃CFCF, C₄F₉CFCF, C₆F₅) was prepared by abstraction of fluoride from the corresponding K[RCCBF₃] salts with BF₃ in appropriate solvents (1,1,1,3,3-pentafluoropropane, 1,1,1,3,3-pentafluorobutane, or dichloromethane).     

Germylene complexes of tungsten pentacarbonyls W(CO)5GeCl2 and W(CO)5GeW(CO)5: Electrochemical synthesis and quantum-chemical computations

Convenient synthetic route to prepare the germylene complexes of tungsten pentacarbonyls, W(CO)₅GeCl₂ and W(CO)₅GeW(CO)₅, electrochemically is developed. Combined quantum-chemical/IR spectroscopic approach is used for identification of the synthesized compounds. Good agreement between theoretical and experimental spectra can be regarded as one of the proofs of their supposed structures.     

Triosmium compounds containing the oxametallacycle [Os(CO)3{C(R)CHC(O)CHC(H)C5H4FeC5H5}] moiety. Synthesis and electrochemical studies

The compounds [Os₃(CO)₁₀{μ,η³-(SCH₂CH₂SCCHC(O)CHCH(C₅H₄)Fe (C₅H₅)}] (2), [Os₃(CO)₉{μ,η³-(SCH₂CH₂SCCHC(O)CHCH(C₅H₄)Fe(C₅H₅)}] (3) and [Os₃(CO)₈{μ₃,η²-{CCHC(O)CHCH(C₅H₄)Fe(C₅H₅)}(SCH₂CH₂S)}] (4) have been obtained by rupture of S-C bonds in the ketene dithioacetal [C₅H₅FeC₅H₄CHCHC(O)CHC(SCH₂CH₂S)], in their reaction with the activated cluster [Os₃(CO)₁₀(NCMe)₂]. The presence of an oxametallacycle in these derivatives has been confirmed by an X-ray diffraction analysis. The electrochemical study has indicated the ability of these compounds to modify the electrode surfaces.     

The first evidence for a transient stibaallene ArSbCCR2

Dechlorofluorination of ArSb(F)-C(Cl)CR₂ (CR₂ = fluorenylidene, Ar = 2,4,6-tri-tert-butylphenyl) by tert-butyllithium afforded a 3,4-bis(fluorenylidene)-1,2-distibacyclobutane. The formation of the latter probably involves the transient stibaallene ArSbCCR₂ followed by a head-to-head dimerization via two SbC double bonds. Molecular orbital calculations at the ab initio and DFT levels support the head-to-head dimerization of ArSbCCR₂ with the formation of a 1,2-distibacyclobutane.     

A new mechanism of nucleophilic vinylic substitution and unexpected products in the reaction of chlorotrifluoroethylene with [Re(CO)5]Na and [CpFe(CO)2]K

The mechanism of chloride substitution in CF₂CFCl with [Re(CO)₅]⁻ and [CpFe(CO)₂]⁻ anions is investigated experimentally and theoretically. The substitution reaction begins with the nucleophile addition to CF₂CFCl producing the carbenoid anion [MCF₂CFCl]⁻ (A) (M = Re(CO)₅, CpFe(CO)₂). This is shown by trapping the intermediate A with electrophiles - proton donor (t-BuOH) to give MCF₂CFClH or with CF₂CFRe(CO)₅ to give acylmetallate III, and by the formation of the substitution products CF₂CFM from the anion A, generated by the deprotonation of MCF₂CFClH with t-BuOK. 1,2-Shift of metal carbonyl group concerted with the α-elimination of chloride anion is proposed as the transformation pathway of carbenoid A into CF₂CFM. A competing process of carbene insertion into Fe-CO bond is proposed to explain the formation of (XI). The feasibility of these two pathways is confirmed by DFT (B3LYP/SDD and 6-31G^∗) calculations of the carbenes [MCF₂CF:] and carbenoid anions [MCF₂CFCl]⁻. Transition states (TS) for 1,2-shift (+3.2 kcal/mol) and for nucleophilic addition at CO ligand (+5.4 kcal/mol) are located for [(CO)₅ReCF₂CFCl]⁻, but only one TS corresponding to carbene insertion into Fe-CO bond (+2.1 kcal/mol) is located for [(CO)₂CpFeCF₂CFCl]⁻. The formation of other newly observed products, F(CO)CHFRe(CO)₅ (V) and Cp(CO)₂FeCCFeCp(CO)₂ (VIII) is also discussed.     

Highly chemo- and stereoselective glycosidation of permethacrylated O-glycosyl trichloroacetimidate reagents promoted by TMSNTf2

TMSNTf₂ has been used efficiently as a promoter in glycosidation reaction involving permethacrylated Schmidt reagents. While TMSNTf₂ is known to be a powerful activator for CO double bonds, we have discovered that this reagent can activate CN double bond selectively, even in the presence of excess CO groups of permethacrylated O-glycosyl trichloroacetimidate substrates. Glycosides are synthesized in moderate to reasonable yields with an excellent overall β-stereoselectivity.     

Carbon-carbon and carbon-chlorine bond formation on reaction of iodine(III) reagents with the bis(alkynyl)palladium(II) motif, and structural chemistry of trans-Pd(CC-o-Tol)2(PMe2Ph)2] and trans-[PdCl(CC-o-Tol)(PMe2Ph)2]

Trans-di(ortho-tolylethynyl)bis(dimethylphenylphosphine)palladium(II) reacts above −20 °C with the iodonium reagent IPhCl₂ to give predominantly o-Tol-CC-Cl, above 15 °C with IPh₂(OTf) (OTf = triflate) to give o-Tol-CC-Ph and (o-Tol-CC)₂ in ca. 3:1 ratio, and above 10 °C with IPh(CCR)(OTf) (R = Bu^t, SiMe₃) to give predominantly o-Tol-CC-CC-R and (o-Tol-CC)₂. ³¹P NMR spectra provide evidence for detection of intermediates. The complexes trans-[Pd(CC-o-Tol)₂(PMe₂Ph)₂] and trans-[PdCl(CC-o-Tol)(PMe₂Ph)₂] are obtained on reaction of trans-[PdCl₂(PMe₂Ph)₂] with Li(CC-o-Tol) and o-Tol-CCH/Et₃N, respectively, and have been characterised by X-ray crystallography.     

Rearrangement of phosphinohydrazide ligand -NPh-N(PPh2)2 in transition metal coordination sphere: Synthesis and characterization of nickel and cobalt spirocyclic complexes M(NPh-PPh2N-PPh2)2 and their properties

The reaction of diphosphinohydrazine PhNH-N(PPh₂)₂ (1) with cobalt(II) silylamide, Co[N(SiMe₃)₂]₂, proceeds via formation of unstable phosphinohydrazide complex Co[NPh-N(PPh₂)₂]₂ followed by rearrangement to a new chelating compound Co(NPh-PPh₂N-PPh₂)₂ (2). Disproportionation of nickel(I) silylamide, (Ph₃P)₂Ni-N(SiMe₃)₂, in the presence of 1, yields Ni(0) and Ni(II) phosphinoamide complexes: Ni[(Ph₂P)₂N-NPhH]₂ (3), Ni(NPh-PPh₂N-PPh₂)₂ (4). X-ray analysis reveals tetrahedral environment of the cobalt atom in 2 and square-planar environment of the nickel atom in cis-4. In contrast to the crystalline patterns, the solutions of 2 in THF or toluene have EPR signal which is typical to square-planar low-spin d⁷ cobalt complex. The reactions of 2 with dioxygen, elemental sulfur and diphenyldiazomethane led to the spirocyclic insertion products Co(NPh-PPh₂N-PPh₂X)₂ (X = O, S, NNCPh₂) while the absorption of carbon monoxide is reversible.     

Further reactions of some bis(vinylidene)diruthenium complexes

Whereas {Ru(dppm)Cp*}₂(μ-CCCC) (2) is the only product formed by deprotonation of [{Ru(dppm)Cp*}₂{μ(CCHCHC)}]⁺ with dbu, a mixture of 2 with Ru{CCCHCH(PPh₂)₂[RuCp*]}(dppm)Cp* (3) and {Cp*Ru(PPh₂CHCCH-)}₂ (4) is obtained with KOBu^t. A similar reaction with [{Ru(dppm)Cp*}₂{μ(CCMeCMeC)}]⁺ (5) gave Ru{CCCMeCH(PPh₂)₂[RuCp*]}(dppm)Cp* (6). X-ray structures of 4, 5 and 6 confirm the presence of the 1-ruthena-2,4-diphosphabicyclo[1.1.1]pentane moiety, which is likely formed by an intramolecular attack of the deprotonated dppm ligand on C(1) of the vinylidene ligand. Protonation of {Ru(dppe)Cp*}₂(μ-CCCC) (8-Ru) regenerates its precursor [{Ru(dppe)Cp*}₂{μ(CCHCHC)}]²⁺ (7-Ru). Ready oxidation of the bis(vinylidene) complex affords the cationic carbonyl [Ru(CO)(dppe)Cp*]PF₆ (9) (X-ray structure).