Chlorine Monofluoride Research Articles

High-pressure crystal structure and properties of chlorine monofluoride

Chlorine Monofluoride (ClF) is a good fluoride that can react with tungsten, selenium, and other simple substances to generate fluoride and chlorine, but it is very unstable under environmental pressure. The pressure-induced structural phase transition of halogen compound ClF at high pressure was studied using the crystal structure AnaLYsis by Particle Swarm Optimization (CALYPSO) structure prediction method. The order of phase transition for ClF under high pressure was found as P1 → Cmc21 → P2/m → Imma, with corresponding phase transition pressures observed at 6 GPa, 54 GPa, and 130 GPa, respectively. The physical properties of each predicted phase were thoroughly studied, finding that the P1 phase is unstable at the Brillouin zone. Furthermore, the energy band structure and density of states showed that P2/m phase and Imma phase with a metal structure. The present studies provide a foundation and insight into the structural phase transition of other halogen compounds at high pressures.

Non-classical polyinterhalides of chlorine monofluoride: experimental and theoretical characterization of [F(ClF)3

We present the synthesis and characterization of the first non-classical Cl(i) polyinterhalide [NMe4][F(ClF)3] as well as the homologous polychloride [NPr3Me][Cl7]. Both salts were obtained from the reaction of the corresponding ammonium chlorides with ClF or Cl2, respectively. Quantum-chemical investigations predict an unexpected planar structure for the [F(ClF)3]− anion.

Isolation of a Halogen-Bonded Complex Formed between Methane and Chlorine Monofluoride and Characterisation by Rotational Spectroscopy and Ab Initio Calculations.

A halogen-bonded complex formed between methane and chlorine monofluoride has been isolated in the gas phase before the reaction between the components and has been characterised through its rotational spectrum, which is of the symmetric-top type but only exhibits K = 0 type transitions at the low effective temperature of the pulsed-jet experiment. Spectroscopic constants for two low-lying states that result from internal rotation of the CH4 subunit were detected for each of the two isotopic varieties H4C···35ClF and H4C···37ClF and were analysed to show that ClF lies on the symmetry axis with Cl located closer than F to the C atom, at the distance r0(C···Cl) Å and with an intermolecular stretching force constant kσ 4 N m−1. Ab initio calculations at the explicitly correlated level CCSD(T)(F12c)/cc-pVTZ-F12 show that in the equilibrium geometry, the ClF molecule lies along a C3 axis of CH4 and Cl is involved in a halogen bond. The Cl atom points at the nucleophilic region identified on the C3 axis, opposite the unique C–H bond and somewhere near the C atom and the tetrahedron face centre, with re(C···Cl) = 3.191 Å. Atoms-in-molecules (AIM) theory shows a bond critical point between Cl and C, confirming the presence of a halogen bond. The energy that is required to dissociate the complex from the equilibrium conformation into its CH4 and ClF components is only De 5 kJ mol−1. A likely path for the internal rotation of the CH4 subunit is identified by calculations at the same level of theory, which also provide the variation of the energy of the system as a function of the motion along that path. The barrier to the motion along the path is only 20 cm−1.

Improved multiparameter exponential‐type potential for diatomic molecules

AbstractWe report an improved multiparameter exponential‐type potential (MPETP) energy model for diatomic molecules. It is found that this potential is identical to the Tietz potential in the realm of diatomic molecules. The efficiency of the improved MPETP is clarified by simulating the internuclear interaction potential curve for the A (3Π1) state of the chlorine monofluoride molecule.

Electrophilic Addition of Chlorine Monofluoride for PET tracers

We have studied the utility of [(18)F]ClF electrophilic addition to the carbon-carbon double bond of analogues of a model positron emission tomography (PET) tracer, [(18)F]EF5. The consequence of simultaneous chlorine/fluorine addition on lipophilicity and biological activity of the molecule is evaluated. Post-target produced [(18)F]F2 was reacted with Cl2 to produce [(18)F]ClF, which was used in electrophilic addition. [(18)F]ClF was produced and used to label chlorinated analogues of [(18)F]EF5. The chlorinated analogues, [(18)F]EF4Cla and [(18)F]EF4Clb, were synthesized simultaneously. The in vivo uptake of the analogues compared well with [(18)F]EF5 uptake in tumor-bearing mice. [(18)F]ClF is a suitable labeling reagent for electrophilic addition to double bonds of PET tracers. The results show that the modification of the pentafluoro group of [(18)F]EF5 by monofluorine-for-chlorine exchange affected the lipophilicity, but the hypoxia avidity of these molecules was not apparently altered.

Symmetry of chloronium ions from ionic reaction of chlorine, chlorine monofluoride gas, and chlorine monofluoride complex with terminal alkenes

Ionic chlorination of 1H,1H,7H-perfluorohept-1-ene ( 2) and heptafluoropropyl trifluorovinyl ether ( 4) with chlorine monofluoride (ClF) gas in aprotic solvent; and alkenes 2, 1H-perfluorohept-1-ene ( 3E), and 4 with chlorine (Cl 2) in protic solvent were investigated. Regiochemical data from SN 2-like ring-opening of the intermediate was used to predict the symmetry of the chloronium ion. The chloronium ions from perfluorohydroalkene 2 with two terminal hydrogens were found to be unsymmetrical with positive charge localized on the terminal carbon. However, reaction of ClF (g) with 3E containing a single terminal fluorine atom gave data suggesting a symmetrical chloronium ion. Alkene 4 contains a heptafluoropropyl ether group that stabilizes positive charge on the number-2 carbon and it is reactive enough to give products with the sluggish ClF complex generated in situ. Reactive eletrophiles ClF (g), Cl 2(g), or the less reactive ClF complex, give an unsymmetrical chloromium ion with charge localized on the internal number-2 carbon.

Pre-reactive complexes in mixtures of water vapour with halogens: characterisation of H2O...ClF and H2O...F2 by a combination of rotational spectroscopy and ab initio calculations.

Complexes H2O...ClF and H2O...F2 were detected by means of their ground-state rotational spectra in mixtures of water vapour with chlorine monofluoride and difluorine, respectively. A fast-mixing nozzle was used in conjunction with a pulsed-jet, Fourier-transform microwave spectrometer to preclude the vigorous chemical reaction that these dihalogen species undergo with water. The ground-state spectra of seven isotopomers (H2 16O...35ClF, H2 16O...ClF, H2 18O...35ClF, D2 16O... 35ClF, D2 16O...37ClF, HDO...35ClF and HDO...37ClF) of the ClF complex and five isotopomers (H2O...F2, H2 18O...F2, D2O...F2, D2 18O...Fi and HDO...F2) of the F2 complex were analysed to yield rotational constants, quartic centrifugal distortion constants and nuclear hyperfine coupling constants. These spectroscopic constants were interpreted with the aid of simple models of the complexes to give effective geometries and intermolecular stretching force constants. Isotopic substitution showed that in each complex the H2O molecule acts as the electron donor and either CIF or F2 acts as the electron acceptor, with nuclei in the order H2O...ClF or H2O...F2. For H2O...ClF, the angle phi between the bisector of the HOH angle and the O...Cl internuclear line has the value 58.9(16)degrees, while the distance r(O...Cl)= 2.6081(23) A. The corresponding quantities for H2O...F2 are phi = 48.5(21)degrees and r(O...Fi) = 2.7480(27) A, where Fi indicates the inner F atom. The potential energy V(phi) as a function of the angle phi was obtained from ab initio calculations at the aug-cc-pVDZ/MP2 level of theory for each complex by carrying out geometry optimisations at fixed values of phi in the range +/-80degrees. The global minimum corresponded to a complex of Cs symmetry with a pyramidal configuration at O in each. The function V(phi) was of the double-minimum type in each case with equilibrium values phie = +/-55.8degrees and +/-40.5degrees for H2O...ClF and H2O...F2, respectively. The barrier at the planar C2v conformation was V0= 174cm(-1) for H2O...ClF and 7cm(-1) for H2O...F2. For the latter complex, the zero-point energy level lies above the top of the barrier.

Electrophilic versus free radical reactions of halogens and halogen systems with perfluoroalkenes and a perfluoroalkylethylene

Ionic and free radical addition of halogen systems were carried out with perfluoroheptene-1 ( 1), octafluorocyclopentene ( 2), 1H,1H,2H-perfluorooctene-1 ( 3) and perfluoro-4-methyl-2-pentene ( 4). The terminal alkene 1 was treated with chlorine in tert-butyl alcohol as solvent with mercury catalyst under reaction conditions that assure an ionic pathway. Bromine did not react with 1 under similar conditions. Chlorine monofluoride reacts with 1 in methylene chloride to give 2-chloroperfluoroheptane. Alkene 3 is more reactive and gives products with electrophiles Cl 2, Br 2, BrCl, and ICl from ring-opening of the halonium ions at the terminal carbon. Disubstituted perfluoroalkenes 2 and 4 did not react ionically with Cl 2, Br 2, BrCl, or ICl. Free radical reactions of Cl 2, Br 2, BrCl, and ICl give good yields of dihaloproducts with 1 and 3. Yields are poor for the photochemical bromination of disubstituted perfluoroalkenes 2 and 4 since the dibromoproducts are in photochemical equilibrium with the alkene.

Rotational spectrum of CH3CN⋯ClF and evidence for the +I effect of a CH3 group on the ‘chlorine’ bond N⋯ClF

The ground-state rotational spectra of the isotopomers CH3C14N⋯35ClF, CH3C14N⋯37ClF, CD3C14N⋯35ClF and CH3C15N⋯35ClF of a symmetric-rotor complex formed by methyl cyanide and chlorine monofluoride have been observed and analysed to give the spectroscopic constants B0, DJ, DJK, χaa(14N), χaa(Cl) and Mbb. Interpretations of these quantities on the basis of simple models enabled the geometry and strength of binding of the complex to be determined. It is found that the atoms C–CN⋯ClF lie on the C3 axis of this complex of C3v symmetry and that the distance r(N⋯Cl)=2.561(2)Å. The quadratic force constants associated with the intermolecular stretching mode and with the bending motion of the CH3CN subunit pivoted at its mass centre were determined from the centrifugal distortion constants DJ and 2 DJ+DJK. Their values were kσ=13.9(3)Nm−1 and kα=3.0(1)×10−20Jrad−2, respectively. A comparison of r(N⋯Cl) values and of kσ values establishes that the +I effect of the CH3 group when it replaces H in HCN leads to a similar shortening of r(N⋯Cl) and to a similar increase in kσ in the two series RCN⋯ClF and RCN⋯HCl (R=H or CH3).

Density functional studies of the pseudo-π.aσ charge-transfer complex between cyclopropane and chlorine monofluoride

The pseudo-π.aσ charge-transfer complex formed by cyclopropane and chlorine monofluoride was studied with various approximate pure and hybrid density functional methods and the second-order Moller–Plesset (MP2) theory. The calculations demonstrate that one hybrid method, namely the so-called B3LYP, leads to reasonably good estimates of the experimentally measured rotational constants. In addition, the predicted B3LYP intermolecular distance is found also to be close to the experimental value. This lends confidence to the prediction of the intermolecular interaction energy, which is found to be 1.42 kcal mol-1. It was also possible to calculate the number and energies of the vibrational states supported by the intermolecular stretching mode. Only five such states have been found. The performances of the various approximate density functionals and MP2 theory are compared and discussed. Finally, the analysis of the natural bond orbitals, which has been found to be very valuable in understanding the nature of the weak intermolecular interaction is discussed.

Density Functional Studies of the n·aσ Charge-Transfer Complex between Sulfur Dioxide and Chlorine Monofluoride

The n·aσ charge-transfer complex formed by sulfur dioxide and chlorine monofluoride has been studied with various approximate pure and hybrid density functional methods and the second-order Moller−Plesset (MP2) theory. The calculations demonstrate that one pure method and one hybrid method, namely, the so-called BLYP and BHHLYP, respectively, lead to reasonably good estimates of the experimentally measured rotational constants. However, the predicted BHHLYP intermolecular distance is found to be noticeably closer to the experimental value. Our best estimation for the intermolecular interaction energy is 1.93 kcal/mol. We have also been able to calculate the number and energies of the vibrational states supported by the intermolecular stretching mode. Only 11 such states have been found. The performance of the various approximate density functionals and the MP2 theory is compared and discussed. Finally, we comment on the analysis of the natural bond orbitals, which has been found to be very valuable to shed light on the nature of weak intermolecular interactions.

Rotational spectrum of the nitrogen trifluoride–chlorine monofluoride complex and the inductive effect of groups R=CH 3, H, F on R 3N/ClF interactions

Rotational constants B 0, centrifugal distortion constants D J and D JK , and nuclear quadrupole coupling constants χ aa( 14 N) and χ aa (Cl) were determined by pulsed-nozzle, Fourier transform microwave spectroscopy for the isotopomers F 3 14 N⋯ 35 ClF and F 3 14 N⋯ 37 ClF of a complex formed by nitrogen trifluoride and chlorine monofluoride. The distance r(N⋯Cl) and the intermolecular stretching force constant k σ for this symmetric-top species are compared with those of several axially symmetric complexes B⋯ClF in which a nitrogen atom of the base B interacts with ClF. In particular, it is shown that r(N⋯Cl) decreases along the series R 3N⋯ClF, where R=F, H or CH 3, while k σ increases dramatically.

Angular geometries of complexes containing the O⋯Cl–F linkage: Rotational spectrum of formaldehyde⋯chlorine monofluoride

Ground-state rotational spectra of the three isotopomers H2CO⋯35ClF, H2CO⋯37ClF and D2CO⋯35ClF of a complex formed by formaldehyde and chlorine monofluoride were observed with a Balle–Flygare, Fourier-transform microwave spectrometer. A fast-mixing nozzle, specially modified to generate a continuous supply of H2CO from paraformaldehyde in situ close to the nozzle exit, was used to preclude the chemical reaction of H2CO and ClF. The rotational constants A0, B0, and C0, centrifugal distortion constants ΔJ, ΔJK, and δJ, components χaa, χbb−χcc, χab of the Cl-nuclear quadrupole tensor, and the spin–rotation coupling constant 1/2(Mbb+Mcc) were determined. Interpretation of the spectroscopic constants led to the conclusion that H2CO⋯ClF is a planar complex of Cs symmetry with r(O⋯Cl)=2.523(7) Å, with an angle 180−φ=69.1(7)° between the C2 axis of H2CO and the O⋯Cl internuclear line, but with a deviation θ of the O⋯Cl–F nuclei from collinearity of only 3.2(7)°. A family relationship between the angular geometries of several complexes B⋯XY, where B is 2,5-dihydrofuran, oxirane, or formaldehyde, and XY is ClF or HCl, is discussed. It is shown that for a given B the angle 180-φ is the same for XY=HCl or ClF, while the nonlinearity θ of the O⋯X–Y system is almost negligible for XY is ClF but significant when XY is HCl. Reasons for this family relationship and the nonlinear O⋯H–Cl hydrogen bonds are discussed.

Evidence concerning the relative nucleophilicities of non-bonding and π-bonding electrons in furan from the rotational spectrum of furan···ClF

The rotational spectra of the three isotopomers C4H4O···35ClF, C4H4O···37ClF and C4D4O···35ClF of a complex formed between furan and chlorine monofluoride have been observed by means of a pulsed-nozzle, Fourier-transform microwave spectrometer fitted with a fast-mixing nozzle to preclude any chemical reaction among the component gases. Transitions allowed by all three components µa, µb and µc of the electric dipole moment were observed, those associated with µc exhibiting a small doubling (ca. 20 kHz). Spectral analysis yielded rotational constants, centrifugal distortion constants and (for the isotopomers C4H4O···35ClF and C4H4O···37ClF) all five independent components of the Cl nuclear quadrupole coupling tensor χαβ (α, β = a, b, c). Diagonalisation of the tensor χαβ led to the values of the components χii (i = x, y, z) in the ClF principal axis system and the direction cosines θαz (α = a, b, c) relating the ClF axis (z) to the principal inertial axis system. The geometry obtained by fitting the principal moments of inertia of the three observed isotopomers is consistent with the θαz values and has the ClF subunit approximately perpendicular to one of the C(2)–C(3) bonds of furan. The end δ+Cl of ClF thus appears to interact with the π electron density between these two atoms. The distance of the Cl atom from the point of intersection of the extrapolated ClF axis with the ring is r(···Cl) = 2.726 A. The doubling of the c-type transitions is interpreted in terms of a motion in which the interaction switches from C(2)–C(3) to C(2′)–C(3′). The contrast between the angular geometries of furan···HCl and furan···ClF is discussed in the context of the relative nucleophilicities of the n-pair and the aromatic π-electrons of furan.

Interaction of benzene and halogens in the gas-phase: rotational spectrum of C6H6···ClF

Ground-state rotational spectra of three isotopomers, C6H6···35ClF, C6H6···37ClF and C6D6···35ClF, of a complex formed by benzene with chlorine monofluoride have been observed by pulsed-nozzle, Fourier-transform microwave spectroscopy. Chemical reaction between the two components was precluded by use of a fast-mixing nozzle. A vibrational satellite associated with a low lying state (v=1) was also observed for the C6H6···35ClF and C6D6···35ClF isotopomers. The spectra were established to be of the symmetric-top type, but with large centrifugal distortion effects associated both with the frequencies of the unperturbed line centres and with the Cl nuclear quadrupole hyperfine structure. In the ground state, these effects were reflected in a large centrifugal distortion constant DJK, in higher order distortion constants of significant magnitude, and in a strong dependence of the Cl nuclear quadrupole coupling constant on the quantum number K. In the v=1 state, the constant DJK and the centrifugal distortion terms χK and χD that affect the nuclear quadrupole hyperfine structure were a similar magnitude to those of the v=0 state, but of opposite sign. The nuclear quadrupole coupling constants, χR, appropriate to the J=0, K=0 states, and the changes in the rotational constants B0 with isotopic substitution, were interpreted in terms of a model for the complex in which, at equilibrium, the ClF axis is inclined at an angle ϑ≈14° to the C6 axis of benzene, with the two axes intersecting at the ClF centre of mass. The Cl atom lies closer to the benzene ring than does the F atom. The extrapolation of the ClF internuclear axis intersects the plane of the benzene ring at a point (*) that lies at a distance of ca. 0.24 Ainside the ring from the centre of a C–C bond. The conformation with ϑ=0° (ClF axis and benzene C6 axis coincident) corresponds to a potential energy maximum, concentric with which is an approximately circular valley corresponding to ϑ≈14°. This type of potential energy surface is consistent with the symmetric-top nature of the observed spectra, with the relatively small energy separation of the v=0 and v=1 states, and with large, but oppositely signed, centrifugal distortion effects in the two states originating in a Coriolis interaction between them. The distance r(*···Cl)=3.313 Awas also determined.

Density Functional Studies of the bπ.aσ Charge-Transfer Complex Formed between Ethyne and Chlorine Monofluoride

The bπ.aσ charge-transfer complex formed by ethyne and chlorine monofluoride has been studied with various approximate pure and hybrid density functional methods and the second-order Moller−Plesset...

Properties of a complex of carbon dioxide and chlorine monofluoride from rotational spectroscopy: identification of an extremely weak interaction

The ground-state rotational spectra of three isotopomers, 12C 16O 2⋯ 35ClF, 12CO 2⋯ 37ClF and 13CO 2⋯ 35ClF, of a complex formed by carbon dioxide with chlorine monochloride have been observed by pulsed-nozzle, Fourier-transform microwave spectroscopy. The following values of the spectroscopic constants B 0, D 0, H 0, χ aa (Cl) and M bb (Cl) have been determined for this linear (or nearly linear) molecule. 12C 16O 2⋯ 35ClF 12CO 2⋯ 37ClF 13CO 2⋯ 35ClF B 0 (MHz) 916.1184(2) 909.7692(2) 906.2644(5) D 0 (kHz) 5.435(5) 5.381(6) 5.31(2) H 0 (Hz) 0.37(3) 0.34(5) 0.4(1) χ aa (Cl) (MHz) −136.804(4) −107.812(5) −136.820(8) M bb (Cl) (kHz) −2.5(4) −0.9(4) −3.4(5) Interpretation of the spectroscopic constants reveals that the nuclei lie in the order OCO⋯ClF, with r(O⋯Cl)=2.699(2) Å, and that the intermolecular bond is very easily distorted both radially and angularly. A comparison of the series B⋯HF and B⋯ClF for B=Ar, N 2, CO or CO 2 establishes that CO 2⋯ClF is anomalous in respect of the strength of its binding.

The rotational spectrum and angular geometry of a pre-reactive complex of allene and chlorine monofluoride

Ground-state rotational constants, centrifugal distortion constants and Cl nuclear quadrupole coupling constants were determined from the rotational spectra of two isotopomers (allene⋯ 35ClF and allene⋯ 37ClF) of a pre-reactive complex of allene and chlorine monofluoride. Chemical reaction between the components was avoided by using a fast-mixing nozzle in a Fourier transform microwave spectrometer. It is concluded that the observed complex is of the weakly bound, Mulliken outer type in which the Cl of ClF interacts with the π-bond of allene to give an L-shaped geometry with the heavy atoms coplanar.

Identification and characterization of a gas-phase complex of methylenecyclopropane and chlorine monofluoride by rotational spectroscopy

The rotational spectrum of a complex formed between methylenecyclopropane (mecp) and chlorine monofluoride was observed by using a fast-mixing nozzle in combination with a Balle–Flygare microwave spectrometer. Rotational constants A0, B0 and C0, quartic centrifugal distortion constants ΔJ, ΔJK, δJ and δK, and the components χaa, χbb − χcc and χab of the Cl nuclear quadrupole coupling tensor were evaluated for each of the isotopomers mecp···35ClF and mecp···37ClF. Interpretations of the various spectroscopic constants demonstrated that the observed species is a Mulliken outer complex which may be described formally as of the bπ.aσ type, i.e. with the electrophilic end δ+Cl of ClF interacting weakly with the π bond of mecp and with only minor electric charge redistribution within the ClF subunit. The geometry of the complex was established to be of Cs symmetry. The ClF molecule lies in the principal inertial plane ab, which is the molecular symmetry plane and is perpendicular to the plane of the four carbon atoms of mecp. The angle ϕ, subtended at the centre (*) of the π bond by the unique carbon atom of the mecp ring and the Cl atom, is 92.5(5)° and the distance r(*···Cl) = 2.675(10) A. The system *···Cl–F deviates from collinearity by 4.9(1)°. These properties of mecp···ClF are discussed in the context of two different series of B···ClF complexes. In the first, the molecules B are the prototype π or pseudo-π electron donors ethene, cyclopropane, allene, mecp and buta-1,3-diene. The molecules B in the second series are the three-membered rings (CH2)2Y, where Y is either one of the n-pair donors O or S or the π donor CCH2.

A pseudo-π analogue of a Mulliken bπ.aσ type complex: The rotational spectrum of cyclopropane–chlorine monofluoride

The rotational spectrum of an asymmetric-rotor complex formed by cyclopropane with chlorine monofluoride has been observed by using a pulsed-nozzle, Fourier-transform microwave spectrometer. A fast-mixing nozzle was employed to preclude any chemical reaction between the components. Ground-state spectroscopic constants A 0 , B 0 , C 0 , Δ J , Δ JK , δ J , χ aa (Cl), [χ bb (Cl)-χ cc (Cl)] and 12[M bb (Cl)+M cc (Cl)] were obtained by fitting observed transition frequencies for each of the two isotopomers (CH 2 ) 3 ··· 35 ClF and (CH 2 ) 3 ··· 37 ClF. A detailed interpretation of these constants leads to the conclusion that the three C nuclei, the Cl nucleus and the F nucleus are coplanar and that in the equilibrium conformation the axis of ClF coincides or nearly coincides with the a-axis of the complex, with Cl closer than F to the cyclopropane ring. The distance from the cyclopropane centre of mass to the Cl nucleus is 3.395(1) A. Although the principal moments of inertia of the observed isotopomers of the complex are independent of the angle of rotation ϕ of the cyclopropane subunit about its local C 3 axis, it is most likely that the a-axis coincides with a median of the C 3 equilaterial triangle. In that case, the electrophilic end of δ+ ClF δ- interacts with the pseudo-π electron density of the C–C single bond, with r(*···Cl)=2.958(1) A, where * defines the mid-point of the C–C bond. Comparison of the series B···HCl and B···ClF, where B is ethyne, ethene or cyclopropane, reveals that cyclopropane···HCl has an enhanced binding strength (as measured by the force constant k σ ) relative to other members of the B···HCl series that results from a secondary interaction between the nucleophilic Cl atom of HCl and the four equivalent H atoms at the binding edge of the cyclopropane subunit. The corresponding H···F secondary interactions are negligible in cyclopropane···ClF.