Improved Access to Organo‐Soluble Di‐ and Tetrafluoridochlorate(I)/(III) Salts

Abstract A facile one‐pot gram‐scale synthesis of tetraalkylammonium tetrafluoridochlorate(III) [cat][ClF4] ([cat]=[NEt3Me]+, [NEt4]+) is described. An acetonitrile solution of the corresponding alkylammonium chloride salt is fluorinated with diluted fluorine at low temperatures. The reaction proceeds via the [ClF2]− anion which is structurally characterized for the first time. The potential application of [ClF4]− salts as fluorinating agents is evaluated by the reaction with diphenyl disulfide, Ph2S2, to pentafluorosulfanyl benzene, PhSF5. The CN moieties in acetonitrile and [B(CN)4]− are transferred in CF3 groups. Exposure of carbon monoxide, CO, leads to the formation of carbonyl fluoride, COF2, and elemental gold is dissolved under the formation of tetrafluoridoaurate [AuF4]−.

The other two sets were obtained at the B3LYP [12] -D3(BJ) [10] level of theory, also without and with COSMO solvent model. D3(BJ) stands for D3 atom-pairwise dispersion corrections with Becke-Johnson damping. [10] Subsequent nonrelativistic nuclear-shielding calculations at these structures used a recent improved DFT-GIAO [13] implementation in Turbomole, [14] extended to allow the use of local hybrid functionals. [15] We used two functionals, which had previously been demonstrated to provide accurate 19 F shieldings, [15,16] the global hybrid BHLYP, [12b,17] and the LH12ct-SsifPW92. [18] local hybrid functional with position-dependent exact-exchange admixture. [19] These computations used pcSseg-4 basis sets [20] for F, Cl, and Br and ANO-RCC-unc [21] basis sets for I. For each of the abovementioned sets of structures, shielding calculations with these two functionals were performed without or with COSMO. This allows the evaluation of the role of solvent effects acting either indirectly via the structure or directly. The nonrelativistic shielding/shift results are given in Tables S3, S4.
To evaluate the role of spin-orbit and scalar relativistic effects, we also carried out four-component relativistic computations (at the BP86-D3(BJ)(COSMO,CH 3 CN)/def2-TZVPPD optimized structures) using the matrix Dirac-Kohn-Sham (mDKS) method [22] implemented in the ReSpect program, version 5.1.0. [23] As neither local hybrids nor BHLYP are currently available for shielding computations in ReSpect, we used a modified B3LYP functional with 50% admixture of exact Hartree-Fock exchange (B3LYP50), which should give results that are close to BHLYP data. Uncontracted Dyall valence quadruple-ζ (Dyall-VQZ) [24] basis sets were used for all atoms. Relativistic shielding/shift results are shown in Table S5.

Synthesis of [NEt3Me][ClF2] in solution
[Net3Me]Cl (50 mg, 0,330 mmol, 1 eq) was dissolved in propionitrile (0.5 ml) and cooled to −50 °C. Dilute ClF (10 % in Ar) was bubbled through the solution (8.5 min, 20 ml min -1 , 2 eq). To remove residual amounts of reactive gases, Ar was bubbled through the solution for 15 min. A colorless solution was obtained. The reaction mixture was allowd to warm to −10 °C and subsequently slowly cooled to −80 °C in an ethanol bath Dewar to reduce the cooling rate. Single crystals were obtained after 4 days.

Nitrile activation
The acetonitrile boron trifluoride complex was synthesized by the addition of BF 3 to acetonitrile at r.  Figure S7) only shows the presence of starting material (CO) solvent (EtCN) and product (COF 2 ). The formation of COCl 2 or COClF was not observed.

Dissolution of gold
Gold metal (16 mg

Tetracyanoborate activation
Potassiumtetracyanoborate (500 mg, 3.25 mmol, 1 eq) was dissolved in acetonitrile (10 ml). A solution of triethylmethylaommonium chloride (0.493 mg, 3.25 mmol, 1 eq) in acetonitrile (5 ml) was added. The colourless precipitated was filtrated and the solvent was removed under reduced pressure to yield tetramethylammonium tetracyanoborate. Triethylmethylammonium tetracyanoborate (76.0 mg, 0.330 mmol, 0.5 eq) was dissolved in CHFCl 2 (1 ml) and boron trifluoride (67,0 mg, 0.989 mmol, 1.5 eq) was added. The solution was cooled to −60 °C. A cooled solution of Triethylmehtylammonium tetrafluoridochlorate(III) (1 ml, 0.659 mol*l −1 , 1 eq) was added at −60 °C, stirred for 5 min at −60 °C and let allowd to warm to r.t. Volatiles were removed and the residue was dissolved in CD 3 CN and analyzed via 19 Figure S16). This compound crystallizes in the space group 1 ̅ . In the asymmetric unit are four anionic moieties. One is a   202.17 a At B3LYP-D3(BJ)/def2-TZVPPD optimized structures. CFCl3 reference shieldings at the same level have been used to obtain the relative shifts. Nonrelativistic results with pcSseg-4 basis sets for F, Cl, Br, and ANO-RCC-unc for I.