Nuclear magnetic resonance spectra of polyfluorobuta-1,3-dienes. Part II [1]. Variable temperature study of two 2-azabutadienes

The two perfluoro-azadienes CF₂N.CRCF₂ (R = CF₃ or CF₂Cl) show temperature dependent ¹⁹F n.m.r. spectra, with non-equivalent fluorine nuclei of the CF₂N portion at low temperatures, which coalesce due to inversion at the nitrogen at higher temperatures (ΔG3 = 60 kJ mol^?1). N.m.r. parameters have been obtained. One of the five-bond FF coupling constants is much larger ($\text{ca}$. 24 Hz) than the remainder (0·5–5·5 Hz), possibly due to ‘through-space’ coupling of fluorines in the $\text{cis}$-skew conformation.     

Spektroskopische Charakterisierung und Kristallstruktur von Trifluormethylchloriod(III)‐trifluoracetat (CF3I(Cl)OCOCF3)

Spectroscopic Characterization and Crystal Structure of Trifluoromethyl Iodine(III) Chloride Trifluororacetate (CF₃I(Cl)OCOCF₃) The ternary iodine(III) compound CF₃I(Cl)OCOCF₃ is obtained by reaction between CF₃I(Cl)F and (CH₃)₃SiOCOCF₃ at –50 °C. The molecule was characterized by vibrational spectra, NMR‐spectra, and a crystal structure analysis. CF₃I(Cl)OCOCF₃ crystallizes monoclinic in the space group P2₁/c with a = 1102.7(1) pm, b = 785.6(1) pm, c = 989.7(1) pm, and β = 101.34(1)°.     

Preparation and synthetic utility of fluorinated phosphonium salts,bisphosphonium salts and phosphoranium salts

The synthesis and mechanism of formation of phosphonium salts of the type [R₃$\text{P}\text{+}$CFXY]Z^? (where X = F, Cl, Br; Y = Br, Cl; Z = Br, Cl), $\text{bis}$-phosphonium salts of the type [R₃$\text{P}\text{+}$CF₂$\text{P}\text{+}$R₃]2Br^?, and phosphoranium salts of the type [R₃$\text{P}\text{+}$$\text{C}\text{?}$F$\text{P}\text{+}$R₃]X^? (X = Br, Cl) will be presented. The applicability of these substrates in the generation of useful nucleophilic or electrophilic synthetic intermediates will be discussed.     

Synthesis,Raman and NMR spectroscopy of the trimetallic complexes [IrCl(SnCl3)(HgCl)(CO)(PR3)2]

Synthesis, Raman and NMR studies are presented for the new octahedral trimetallic complexes with composition [IrCl(SnCl₃)(HgCl)(CO)(PR₃)₂], R = p-XC₆H₄; X = H, CH₃O, F, Cl. Only the isomer containing the Cl₃SnIrHgCl fragment and trans phosphine ligands is observed. Force constants for the IrSn and IrHg bonds as well as ³¹P, ¹¹⁹Sn and ¹⁹⁹Hg NMR data are reported. The presence of a spin-spin coupling constant of more than 40,000 Hz between the ¹⁹⁹Hg and ¹¹⁹Sn atoms is shown to originate from a two-bond and not a one-bond interaction.     

Gas-phase electron diffraction determination of the molecular structure of perfluoro(methyloxirane)

The molecular geometry of perfluoro(methyloxirane) has been studied using gas-phase electron diffraction data, effective least-squares refinement of the structure being achieved with the aid of constraints to limit the number of variable parameters. With the CCF₃ bond constrained to be 0.078 Å longer than the ring CC, the refined bond- length values CF (av.) = 1.323(2), CO (av.) = 1.410(8), and CC (ring) = 1.467(7) Å ($\text{r}$_g values, with e.s.d. in parentheses) were obtained; the angles between ring bonds and substituent CF bonds were CCF (av.) 121(1) and OCF (av.) 114(1)^o, the corresponding parameters involving the bulkier CCF₃ fragment being larger by 3^o in each case [∠CCCF₃ 124(1)^o∠OCCF₃ 117(2)^o]. The remaining refined parameters were ∠CCF(of CF₃) = 110.6(4)^o and τ , a torsion angle defining the orientation of the CF bonds of the CF₃ group with respect to ring bonds, = 29(2)^o. Dependent bond angles possessed the values 62.7 (COC), 58.7 [OCC (ring)], 108.3 [FCF (CF₃ group)], 114 [FCF (ring CF₂)], and 111^o (FCCF₃).     

Force constants in molecular crystals of methyl-and perdeuteriomethylmercury(II) halides

Force constants for the internal vibrations involving the metal and for the lattice vibrations of Hg(CH₃)X and Hg(CD₃)X (X = Cl, Br or I) are calculated on the basis of a D_4h⁷ layer structure. The internal HgX stretching force constants are much lower than for these molecules in solution, but HgC stretching force constants are slightly higher. The HgX and longitudinal translatory force constants within the lattice layer are close in value to the strong and weak HgX bond stretching force constants respectively in the unsymmetrical [Hg(CH₃)X₂]^? complex ions.     

Nitroxide chemistry. Part XVII [1]. Reaction of bistrifluoromethyl nitroxide with some halogenoalkanes and related alkenes

The mono (bistrifluoromethylamino-oxy)alkanes (CF₃)₂NOCXYZ (X = Y = F, Z = Cl; X = H, Y = F or Cl, Z = CH₃; X = Y = F, Z = CH₃; X = H, Y = Cl or Br, Z = CF₃; X = Cl, Y = Br, Z = CF₃) have been synthesised by treatment of appropriate halogenoalkanes, CHXYZ, with bistrifluoromethyl nitroxide. The 1,2-bis(bistrifluoromethylamino-oxy)alkanes (CF₃)₂NOCH₂CXYON(CF₃)₂ were obtained as by-products in the reactions involving the ethanes CH₃CHXY (X = H, Y = F or Cl; X = Y = F); these products, like their analogues (CF₃)₂NOCHFCF₂ON(CF₃)₂ and (CF₃)₂NOCH₂CCl₂ON(CF₃)₂, were also prepared $\text{via}$ attack of bistrifluoromethyl nitroxide on the corresponding ethenes.     

Force field studies of some trifluoromethyl- and trichloromethyl-mercury-II) compounds

Force constants of [Hg(CF₃)₂], [Hg(CCl₃)₂], [Hg(CF₃)X] (X = Cl, Br, or I) and [Hg(CCl₃)X] (X = Cl or Br) have been calculated using a valence force field and wavenumber data from solutions. The potential energy distributions show substantial mixing between the symmetrical stretching and umbrella deformation coordinates of the trihalomethyl groups. The high degree of mixing of HgC and HgX stretching coordinates in [Hg(CF₃)Br] and [Hg(CF₃)I] accounts for the discontinuous frequency and intensity trends in the [Hg(CF₃)X] series.The results are discussed in comparison with methylmercury and other trifluoromethyl systems.     

Fluorocarbon derivatives of nitrogen. Part 10. Preparation of heptafluoro- and 1-chlorohexafluoro-2-nitrosopropane,and conversion on the latter to chloropentafluoroacetone oxime

Details are given for the preparation of heptafluoro-2-nitrosopropane and 1-chlorohexafluoro-2-nitrosopropane $\text{via}$ the routes CF₃CFCF₂ → [with CsFR_FCO₂Ag (R_F = CF₃, nC₃F₇)] (CF₃)₂CFAg → (with NOCl) (CF₃)₂CFNO and CF₃CFCF₂ → (with CsClNOCl) CF₃(CF₂Cl)CFNO, respectively, and for conversion of the latter nitroso-compound to chloropentafluoroacetone oxime $\text{via}$ reduction with aqueous potassium hydrogen sulphite.     

The effect of the solvent upon the rates and mechanisms of organometallic reactions: VI. The complexation of dibenzylmercury in solutions studied by PMR spectroscopy

The concentration and temperature dependence of J(¹¹⁹HgC¹H) values for solutions of dibenzylmercury in various solvents show dearly that if the solvent is of the monodentate electron-donating type $\text{1}\text{1}$ complexes are formed predominantly, the $\text{1}\text{2}$ complexes existing only at very low temperatures. The results suggest that the $\text{1}\text{1}$ complexes are very weak and have planar T-shaped structures, whereas the $\text{1}\text{2}$ complexes are probably tetragonal pyramids. In complexes of the former type the relative content of s-electrons in the HgCH site is higher than in the $\text{1}\text{2}$ complexes.     

A series of hydridoplatinum(II) complexes stabilized with tribenzylphosphines: their preparation,and an empirical approach to the mutual influence of ligands

The preparation, IR and NMR spectra of 123 platinum hydrides of the general formula, trans-PtHX(PBz₃)₂ or trans-PtHL(PBz₃)₂BPh₄ (X = a uninegative anionic ligand, L = a neutral donor molecule, Bz = benzyl), are described. Neutral platinum hydrides have been synthesized by the reduction of trans-PtCl₂-(PBz₃)₂ with NaBH₄, by the Michaelis—Arbuzov rearrangement, or by metathesis. Cationic hydridoplatinum(II) complexes are obtained from the reaction of trans-PtHX(PBz₃)₂ (X = Cl or NO₃) with a donor molecule (L) in the presence of NaBPh₄, or by coordinating a donor molecule through use of PtH(PBz₃)₂BPh₄ · $\text{1}\text{2}$CH₂Cl₂. The observed trends in ν(PtH), τ(H), ¹J(PtH) and ¹J(PtP) in a series of the hydridobenzylphosphineplatinum(II) complexes are discussed in terms of “trans- or cis-influences”, defined as the ability of a ligand to weaken the bond trans or cis to itself. The data support the view that a donor atom trans to the hydridic ligand is important in determining the strength of the PtH bond in this series. Some remarks on the distinctive characteristics of some complexes, e.g., dissociation of coordinated cycloalkanone from platinum(II) or stereochemical non-rigidity of the sym-dimethylurea ligand, are included. Tricyclohexylphosphine analogs also have been prepared for comparison.     

Reactions of the carbonyl complexes M(CO)3(L)3 (L = py,M = Mo,W; L = NH3, M = Mo) and M(CO)4(2-Mepy)2 (M = Mo,W) with HgX2 (X = Cl,CN, SCN)

The reactions of the substituted Group VI metal carbonyls of the type M(CO)₄(2-Mepy)₂ (M = Mo, w) and M(CO)₃(L)₃ (L = py, M = Mo, W; L = NH₃, M = Mo) with mercuric derivatives HgX₂ (X = Cl, CN, SCN) have given rise to three series of tricarbonyl complexes: M(CO)₃(py)HgCl₂ · 1/2HgCl₂ (M = Mo, W); 2[M(CO)₃(L)]Hg(CN)·nHg(CN)_x (L = py, M = Mo, W, n = $\text{1}\text{2}$, × = 2; L = 2- Mepy, × = 1; M = Mo, n = 3; M = W, n = 1); and [M(CO)₃(L)Hg(SCN)₂ · nHg(SCN)₂] (L = py, M = Mo,W, n = 0; L = 2-Mepy, M = Mo, W, n = $\text{1}\text{2}$; L = NH₃, M = Mo, n = 0) depending on which mercuric compound is employed. All the reactions with Hg(SCN)₂ give isolable products whereas those with Hg(CN)₂ and HgCl₂ did so far only the reactions with [M(CO)₄(2-Mepy)₂] and M(CO)₃(py)₃. The greater reactivity of Hg(SCN)₂ than of Hg(CN)₂ and HgCl₂ is consistent with the various acceptor capacities of the groups bonded to the mercury atom.The reactions studied always involve displacement of the N-donor ligand of the original complex and partial or total displacement of the halide or pseudohalide groups of the mercury compound to give in all cases compounds containing MHg bonds. In addition, elimination of a CO group in the tetracarbonyl complexes M(CO)₄(2-Mepy)₂occurs.     

Isotopic selectivity in the sensitized dissociation of SF5Cl and CF3I by multiphoton excitation of SF6

The dissociation of SF₅Cl and CF₃I sensitized by multiphoton excitation of SF₆ by a pulsed CO₂ laser has been studied versus pressure, laser fluence, inert gas and optical frequency. Isotopic effects have been observed between ³²SF₅Cl/³³SF₅Cl and between ¹³CF₃I/¹²CF₃I and selectivity factors as high as α^?1_{$\text{33}\text{32}$} = 1.57 or α_{$\text{13}\text{12}$} = 1.23 obtained.     

Group IB organometallic chemistry: XVI. Complex formation between 2-(dimethylamino)-phenylcopper with copper(I) or silver halides. Synthesis and structural characterization of hexanuclear (2-Me2NC6H4)4Cu6-nMnX2 (M = Cu or Ag) cluster compounds

The $\text{2}\text{1}$ complexes (2RCu · MX) between 2-(dimethylamino)phenylcopper (RCu) and CuX (X = Cl, Br or I) or AgBr have been prepared in two ways (i) from the $\text{2}\text{3}$ reaction of 2-(dimethylamino)phenyllithium with cuprous halide and (ii) from the reaction of RCu with excess of the metalIB halide.The structure of bis[(2-dimethylamino)phenylcopper] cuprous bromide, which is dimeric (R₄Cu₆Br₂) in the solid state, has been determined by X-ray analysis. The bonding in this hexanuclear cluster (CuCu ranging from 2.48 to 2.70 Å, multicenter bonded aryl groups) is discussed. Molecular weight determinations and ¹H NMR spectroscopy reveal a similar hexanuclear structure for the R₄Cu₆X₂ complexes in benzene solution. NMR spectroscopy indicates that in solution the mixed-metal cluster compounds R₄Cu_6-nAg_nBr₂ are not stable but enter into interaggregate exchange reactions. A possible pathway involving trinuclear species R₂Cu_3-nAg_nX as intermediates is proposed.     

Electrochemical behaviour and chemical oxidation study of the thio- and phosphido-bridge binuclear iron complexes

The electrochemical behaviour of thio and phosphido complexes of iron(I): Fe₂XY(CO)_6nL_n (X = Y = SR, PR₂ and X = SR, Y = PR₂, L = PR₃) has been studied on platinum and mercury electrodes, in organic solvent. These complexes are reduced in a two-electron irreversible process. A large difference is observed between their oxidation potentials on mercury and platinum electrodes; this is ascribed to the formation of a mercury complex in which mercury is inserted into the metalmetal bond. In oxidation on platinum electrodes, two mono-electronic waves are observed. The influece of the ligand basicity on the cathodic E_{$\text{1}\text{2}$} values is discussed. A parallel shift is observed between the E_{$\text{1}\text{2}$} and the IR ν(CO) of the totally symmetrical mode. Chemical oxidation of the complexes shows that the dications cannot be isolated, and leads to isolation of the following species: [FeP(CH₃)₂(CO)₃]₂AgNO₃, [FeSCH₃(CO)₂P(CH₃)₃]₂(NO₃)₂, {[FeSCH₃(CO)₂P(CH₃)₃]₂F} PF₆, where NO₃^? and F^? act as ligands.     

The syntheses and coordination properties of M(CO)3X(DAB) (M = Mn,Re; X = Cl,Br, I; DAB = 1,4-diazabutadiene)

M(CO)₅X (M = Mn, Re; X = Cl, Br, I) reacts with DAB (1,4-diazabutadiene = R₁N=C(R₂)C(R₂)′=NR′₁) to give M(CO)₃X(DAB). The ¹H, ¹³C NMR and IR spectra indicate that the facial isomer is formed exclusively. A comparison of the ¹³C NMR spectra of M(CO)₃X(DAB) (M = Mn, Re; X = Cl, Br, I; DAB = glyoxalbis-t-butylimine, glyoxyalbisisopropylimine) and the related M(CO)₄DAB complexes (M = Cr, Mo, W) with Fe(CO)₃DAB complexes shows that the charge density on the ligands is comparable in both types of d⁶ metal complexes but is slightly different in the Fe-d⁸ complexes. The effect of the DAB substituents on the carbonyl stretching frequencies is in agreement with the A′(cis) > A″ (cis) > A′(trans) band ordering.Mn(CO)₃Cl(t-BuNCHCHNt-Bu) reacts with AgBF₄ under a CO atmosphere yielding [Mn(CO)₄(t-BuNCHCHN-t-Bu)]BF₄. The cationic complex is isoelectronic with M(CO)₄(t-BuNCHCHNt-Bu) (M = Cr, Mo, W).     

On the sign of the dipole moment derivatives in CH3X (X = F, Cl, Br, I)

It is shown in this paper that the principal methods for reducing the indeterminacy of the sign of (δ M/δ$\text{O}$_i) (isotropic invariance of M, quantum mechanical calculations, determination of (δM/δ$\text{O}$_i) via high resolution data or the Stark effect) lead, in the case of CH₃X (X = F, Cl, Br, I) molecules, to contradictory conclusions. The discrepancies are illustrated and discussed. It is also pointed out that either a revision of the previous results or a calculation of electro-optical parameters on a set of chemically similar molecules including CH₃X could possibly lead to a unique determination of the sign.     

Formation of an iridium σ-cyclopropane complex by the intramolecular activation of a cyclopropylphosphine: Rearrangement to a chelating σ-vinyl complex

When (t-Bu)₂PCH₂CHCH₂CH₂ is combined with [IrCl(C₈H₁₄)₂]₂ in toluene, the σ-bound cyclopropane complexes

(P(t-Bu)₂CH₂$\text{CHCH}{}_2\text{C}$H₂) (1a, 1b) are formed. Complexes 1a,1b react readily with H₂ to form IrClH₂P(t-Bu)₂CH₂$\text{CHCH}{}_2\text{C}$H₂)₂ (2). In polar solvents 1a,1b isomerize to the σ-vinyl chelated complex $\text{IrClH(P(t-Bu)}{}_2\text{CH}{}_2\text{C(CH}{}_3\text{)C}$H)(P(t-Bu)₂CH₂$\text{CHCH}{}_2\text{C}$H₂) (3). The structure of this 5-coordinate, 16-electron Ir^III complex was deduced from spectroscopic data, reaction chemistry, and from the crystal structure of its CO adduct (4). Compound 4 crystallizes in the monoclinic space group C_2h⁵-P2₁/n (a 15.610(14), b 15.763(16), c 11.973(13) Å, and β 104.74(5)°) with 4 molecules per unit cell. The final agreement indices for 2326 reflections having F_o² > 3σ(F_o²) are R(F) = 0.089 and R_w(F) = 0.095 (271 variables) while R(F²) is 0.148 for the 3423 unique data. Bond lengths in the 5-atom chelate ring $\text{IrPCCC}$ are IrP 2.341(4), PC 1.857(26), CC 1.520(30), CC 1.341(25), and CIr 1.994(21) Å. The IrCl distance is 2.479(5) Å.     

Heterocyclic polyfluoro-compounds. Part 36 [1]. The reaction of 2,2-bis(trifluoromethyl)-3,4-difluoro-oxetan with aluminium trichloride

2,2-Bis(trifluoromethyl)-3,4-difluoro-oxetan, when treated with aluminium trichloride at 30 to 90 °C, undergoes $\text{cis}$ to $\text{trans}$ isomerisation, non-stereospecific exchange of the 4-fluorine by chlorine, and more slowly of the 3-fluorine, and ring opening to give preferentially the alcohols (CF₃)₂C(OH)CXCHCl (X  F or Cl), together with the aldehydes (CF₃)₂CClCHXCHO and acid chlorides (CF₃)₂CClCHXCClO (X  F or Cl). A large number of unidentified minor products were also obtained from the reactions carried out at the higher temperatures.     

Substituent effects and stereochemical mechanisms for substitution reactions of 18F for halogen atoms in CF3X, (CH3)3−n CHnX,and CH3X

No thermal substitutions of ¹⁸F for X (X  halogen atom) are observed with CF₃X and (CH₃)_3?nCH_nX substrates in excess SF₆. The absence of thermal yield increasing with weaker CX bond energies, as found with CH₃X substrates, is attributed to the much larger mass versus H of F and CH₃ substituents. The thermal substitution of ¹⁸F/X in CH₃X molecules probably occurs by an inversion mechanism.