Petr K. Sazonov

Halophilic reactions of pentafluorohalobenzenes with transition-metal carbonyl anions

Abstract In the present work we widen the scope of the halophilic mechanism of nucleophilic aromatic substitution, which we found earlier for the reaction of pentafluorochlorobenzene with [CpFe(CO) 2 ] − anion, to reactions of pentafluorohalobenzenes (Hal=Cl, Br, I) with various metal carbonyl anions [Re(CO) 5 ] − , [Mn(CO) 5 ] − and [CpFe(CO) 2 ] − . Nucleophilic aromatic substitution with the [CpFe(CO) 2 ] − anion yields C 6 F 5 Fe(CO) 2 Cp, while with [Re(CO) 5 ] − and [Mn(CO) 5 ] − anions the halo(acyl)metallates cis -[C 6 F 5 (CO)M(CO) 4 Hal]Na (M=Mn, Re) are obtained.

Nucleophilic vinylic substitution with transition metal carbonyl anions—a rare case of a halophilic reaction mechanism: Formation of halo(acyl)rhenate complexes and X-ray structure of cis-[CF2CF(CO)Re(CO)4Br]Na

Abstract Reactions of polyfluorinated alkenyl halides Z-(CF3)3CCFCFHal (Hal=Cl, I-Cl, Hal=Br, I-Br) and CF2CFBr (II-Br) with [CpFe(CO)2]K (FpK) and [Re(CO)5]Na proceed through the initial attack of metal carbonyl anion on halogen. Reaction with FpK gives minor amounts of σ-alkenyl complexes Z-RfCFCFFe(CO)2Cp (I-Fe, II-Fe) (3–30%), but primarily leads to dimer [CpFe(CO)2]2. Reaction with [Re(CO)5]Na produces anionic halo(acyl)rhenates cis-[Z-RfCFCF(CO)Re(CO)4Hal]Na (V-Cl, V-Br, VI) (70–90%) which were isolated, and halo(acyl)rhenate VI (Rf=F) was characterized by X-ray structure analysis. Halo(acyl)rhenates result from the attack of the intermediate carbanion [RfCFCF]− on the carbonyl ligand of Re(CO)5Hal. The involvement of [RfCFCF]− is demonstrated by their trapping with t-BuOH or CH-acid, which gives the protodehalogenated alkenes I-H and II-H, and suppresses the nucleophilic substitution reaction leading to I-Fe, II-Fe or V-Cl. Arguments against a radical/SET mechanism for the substitution reaction are also advanced.

The reaction of the [CpFe(CO)(2)](-) anion with pentafluorochlorobenzene: Nucleophilic aromatic substitution by halogen-metal exchange

The mechanism of the reaction of [CpFe(CO)2]− with pentafluorochlorobenzene is investigated in detail. The reaction is shown to proceed exclusively through the [C6F5]− intermediate (below), which can be trapped with proton donors or with an excess of C6F5Cl.

N-aryl- and N-vinyldiaza-18-crown-6: Synthesis and complexing ability

The nucleophilic aromatic and vinyl substitution using diaza-18-crown-6 as nucleophile afforded a number of its N,N’-diaryl-[aryl = 2,4-(NO2)2C6H3, 4-C5F4N, 4-CF3C6F4] and N,N’-dialkenyl-substituted derivatives [alkenyl = PhC(O)CH=CH, MeOCOCH=CH, (EtO2C)2C=C(Ph), etc.]. Arylation of diaza-18-crown-6 with nonactivated aryl bromides, such as 4-Me2NC6H4Br, 4-MeOC6H4Br, C6H5Br, and 4-CF3C6H4Br, was effected under catalysis by palladium complexes. N,N’-Diaryldiaza-18-crowns-6 having electron-acceptor substituents in the aromatic rings turned out to be incapable of forming complexes with metal cations, while their analogs containing electron-donor para-methoxy and para-dimethylamino groups gave complexes with barium perchlorate.

Anions of Transition Metals Carbonyls in Nucleophilic Vinyl Substitution: VII.2* Carbonylates Reaction with 1-Chloro-2-(trifluoromethyl)- and 1-Chloro-2-(perfluoro-tert-butyl)hexafluorocyclopent-1-enes, and with Z and E Isomers of ββ-Chloro-αα,ββ-difluorostyrenes. Halophilic and/or Nucleophilic Reaction mechanism2*2*

Reactions were studied between 1-chloro-2-(trifluoromethyl)-hexafluorocyclopent-1-ene with anions [CpFe(CO)2]-, [Re(CO)5]-, [Mn(CO)5]-, [CpMo(CO)3]-, and [CpW(CO)3]-. The effect of proton donors on the composition of reaction products was established. The reactions with [Re(CO)5]- and [Mn(CO)5]- were shown to proceed quantitatively along nucleophilic route (SN2Vin) resulting in σ-vinyl complexes of rhenium and manganese. The [CpMo(CO)3]- and [CpW(CO)3]- anions turned out to be 104 times less nucleophilic than [Mn(CO)5]-. In this case the main course of the reaction is the metal-halogen exchange with concurrent nucleophilic substitution. In reaction of [CpMo(CO)3]- and [CpW(CO)3]- with 1-chloro-2- (trifluoromethyl)-hexafluorocyclopent-1-ene the σ-vinyl complexes arise along an unusual autocatalytic mechanism: the reaction of carbonyl occurs not with the initial substrate but with pentafluoromethylcyclopent-1-ene that forms from the substrate under the action of a fluoride ion. In an extremely fast reaction of the same substrate with [CpFe(CO)2]K the main process is carbonylate oxidation along unestablished mechanism. The reaction between carbonylates and 1-chloro-2-(perfluoro-tert-butyl)hexafluorocyclopent-1-ene proceeds exclusively as metal-halogen exchange that with [Re(CO)5]- furnishes anionic acyl complex cis[C9F15C(O)Re(CO)4Cl]-. The reaction of Z and E isomers of β-chloro-α,β-difluorostyrenes with [CpFe(CO)2]- in the presence of proton donors confirmed the previously assumed (SN2Vin) mechanism of nucleophilic substitution and also the intermediate formation of alkenyl carbanions in the parallel redox process.

Arylation of phosphoryl-stabilized carbanions with metal π-complexes of aryl chlorides and fluorides

Abstract The nucleophilic aromatic substitution of halogen in metal arene π-complexes η6-(ArF)Cr(CO)3 and [η6-(ArHal)FeCp]+[PF6]− (Hal=F,Cl) with phosphoryl-stabilized carbanions ZCH2P(O)(OEt)2 (Z=COOEt, CN) allows the synthesis of metal π-complexes of α-EWG-substituted arylmethylphosphonates in high yields.

Polymer biquinolyl-containing complexes of Pd(II) as efficient catalysts for cyanation of aryl and vinyl halides with K4Fe(CN)6

A catalytic system for cyanation of aryl and vinyl halides with K4Fe(CN)6 based on a structurally tunable and nontoxic polymer backbone of polyamic type with biquinolyl fragments in the polymer chain capable of coordination to PdII ions is developed. The catalyst is eligible for thermal and microwave activation; in the latter case the reaction time is dramatically decreased. Cyanation of vinyl bromides occurs stereoselectively, and the configuration of the starting alkene is retained; even for Z-isomers the impact of configuration inversion is less than 5%. The polymer-based Pd catalyst is applicable for one-pot multi-step synthesis of the precursors of mesogenic structures of biphenyl type. Consecutive cross-coupling and cyanation reactions can be performed in the presence of the same portion of catalyst, in the same solvent, without isolation of intermediate products.

Stability and structure in solution of potassium and barium complexes with N,N'-diaryldiaza-18-crown-6 : Crystal structure of N,N'-bis(4-dimethylaminophenyl)diaza-18-crown-6 and its complex with barium perchlorate

It has been shown that N,N’-diaryldiaza-18-crown-6 ethers with p-dimethylamino-and p-methoxy groups in the benzene ring (aryl is 4-Mc2NC6H4) (I) and 4-MeOC6H4 (II) form complexes with potassium and barium salts. The influence of these salts on the UV and 1H NMR spectra of crown ethers I and II has been studied. The stability constants (logβ) of the complexes increase in the series II · Ba(ClO4)2 (2.0), I · Ba(ClO4)2 (2.3), II · KBr (2.8), I · KBr (3.0). N,N’-bis(4-dimethylphenylamine)diaza-18-crown-6 (L, I) and its complex with barium perchlorate Ba(ClO4)2 · L (III) are characterized by X-ray crystallography. The crystals of I are monoclinic: a = 13.778(2) Å, b = 5.9731(9) Å, c = 17.542(3) Å, β = 106.65(1)°, V = 1383.1(4) Å3, Z = 2, space group P21/n, R = 0.0374 for 990 reflections with I > 2σ(I). The crystals of III are monoclinic: a = 17.275(4) Å, b = 8.017(2) Å, c = 26.935(4) Å, β = 100.47(2)°, V = 3669(1) Å3, Z = 4, space group C2/c, R = 0.0320 for 1897 reflections with I > 2σ(I). The molecules of I and III are centrosymmetric. In III, the Ba atom is in the center of substituted diaza-18-crown-6 (DA18C6). The Ba atom is coordinated by all six donor atoms of diaza-18-crown-6 (av. Ba-O, 2.779(3) Å; Ba-N, 3.004(4) Å) and four oxygen atoms of two asymmetrically bound perchlorate groups (Ba-O, 2.832(4) and 3.031(4) Å) arranged below and above the plane of substituted diaza-18-crown-6. The conformations of the macrocycle in free and coordinated L are different.

Unexpected formation of [Z-PhCFCFRe2(CO)9]Na in the reaction of [Re(CO)5]Na with α,β,β-trifluorostyrene

Abstract The reaction of [Re(CO)5]Na with α,β,β-trifluorostyrene follows two concurrent pathways: nucleophilic vinylic substitution forming Z-PhCFCFRe(CO)5 and radical-chain process producing Z-[PhCFCFRe(CO)4Re(CO)5]Na. The intermediacy of metal carbonyl radicals in the radical process is evident from the fact that tertiary phosphines or an ‘electron trap’ inhibit, and Re2(CO)10, induce the production of Z-[PhCFCFRe(CO)4Re(CO)5]Na.

N,N′-bis(ortho-acylaryl)diaza-18-crown-6 ethers: Synthesis, complexation in solution, and crystal structure of the complex with lead perchlorate

Two new lariat ethers were obtained from N,N′-diaryldiaza-18-crown-6 (Ar = 2-formyl-4-methylphenyl (II) and 2-benzoyl-4-methylphenyl (III)). In the ethers obtained, the carbonyl O atoms act as additional electron-donating sites. Complexation of lariat ethers II and III with metal cations in solution was studied by 1H NMR spectroscopy (acetone-d6, methanol-d4). The stability constants of the resulting complexes were determined. For lariat ether III and its complexes, the magnetic anisotropy of the benzoyl groups substantially influences the chemical shifts of the protons of the macrocycle. The stability of the complexes increases from ether II to III and in the order K+ < Ba2+ < Pb2+. Complexes with La3+ were not obtained. The complex of lariat ether II(L) with Pb(ClO4)2, [PbL(H2O)](ClO4)2 · H2O, was characterized by X-ray diffraction. The Pb2+ cation is in the cavity of the lariat ether and is coordinated by the formyl O atoms on one side of the macrocycle plane and by the water molecule on the other side (C.N. 9).