Carbon-Phosphorus Coupling from C^N Cyclometalated Au(III) Complexes.

With the aim of exploiting new organometallic species for cross-coupling reactions, we report here on the Au(III)-mediated Caryl-P bond formation occurring upon reaction of C^N cyclometalated Au(III) complexes with phosphines. The [Au(C^N)Cl2] complex 1 featuring the bidentate 2-benzoylpyridine (CCON) scaffold was found to react with PTA (1,3,5-triaza-7-phosphaadamantane) under mild conditions, including in water, to afford the corresponding phosphonium 5 via C-P reductive elimination. A mechanism is proposed for the title reaction based on in situ 31P{1H} NMR and HR-ESI-MS analyses combined with DFT calculations. The C-P coupling has been generalized to other C^N cyclometalated Au(III) complexes and other tertiary phosphines. Overall, this work provides new insights into the reactivity of cyclometalated Au(III) compounds and establishes initial structure-activity relationships to develop Au(III)-mediated C-P cross-coupling reactions.

Initially, spectra were acquired at room temperature at different time intervals (after the first hour, every 3 h for the subsequent 18 h and a final measurement at 24 h). The reaction yielding 6 was additionally studied at 15 ºC collecting spectra every 5 min over 100 min.
Computational studies. DFT calculations were performed on the structure of compound 1, as well as those of the species involved in its reaction pathways with the PTA ligand (see Scheme 2) following recently reported procedures, [5] using the M06-L DFT functional, [6] the Lanl2tz(f) basis set [7] for Au and the and the 6-31G(d,p) basis set [8] for P, Cl, O, N, C, and H atoms. Solvent effects were implicitly taken into account by full geometry optimization in the acetone solvent, reproduced by the polarizable continuum model (PCM). [9] The PF6counter-anion has not been included in the calculations. Transition-state structures were found by the synchronous transit guided quasi-Newton method. [10] Vibration frequency calculations, within the harmonic approximation, were performed to check that each optimized geometry corresponded to a minimum or to a first-order saddle point (for transition-state structures) in the potential energy surface, and to evaluate their standard Gibbs free energy values at 298.15 K. The Gibbs free energy values reported in Table S1were obtained by single point calculations on the optimized structures by using the Lanl2tz(f) for Au and expanding the all electron basis set to 6-311G(d,p) [11] for the other atoms. All calculations were performed by the Gaussian 09 program package. [12] Figures Figure S1. 1 H NMR spectrum of 5 in Acetone-d6.

6
Figure S20. 31 P { 1 H} NMR spectra of the reaction mixture of 2 with 3 eq. of PTA and 5 eq. of KPF6 in Acetone-d6 recorded over 24 h, compared to the spectrum of purified product 6. Figure S21. HR-ESI-MS spectra of the reaction mixture of 2 with 3 eq. of PTA and 5 eq. of KPF6 after 24 h in Acetone-d6, forming 6 and Au(I) coordination species resulting from the reductive elimination.          The structure was solved and the space group P21/n (# 14) determined by the ShelXT  structure solution program using Intrinsic Phasing and refined by Least Squares using version 2014/7 of ShelXL . All non-hydrogen atoms were refined anisotropically. Hydrogen atom positions were calculated geometrically and refined using the riding model.
There is a single molecule in the asymmetric unit, which is represented by the reported sum formula. In other words: Z is 4 and Z' is 1.

Structure Quality Indicators
Reflections:

Refinement:
A colourless block-shaped crystal with dimensions 0.360×0.280×0.120 mm 3 was mounted on a MITIGEN holder in perfluoroether oil. Data were collected using a Rigaku FRE+ diffractometer equipped with VHF Varimax confocal mirrors and an AFC12 goniometer and HyPix 6000HE detector, and equipped with an Oxford Cryosystems low-temperature device operating at T = 100.00 (10)  The structure was solved and the space group P21/n (# 14) determined by the ShelXT  structure solution program using Intrinsic Phasing and refined by Least Squares using version 2014/7 of ShelXL . All non-hydrogen atoms were refined anisotropically. Hydrogen atom positions were calculated geometrically and refined using the riding model.
There is a single molecule in the asymmetric unit, which is represented by the reported sum formula. In other words: Z is 4 and Z' is 1.

Structure Quality Indicators
Reflections:

Refinement:
A colourless block-shaped crystal with dimensions 0.320×0.240×0.150 mm 3 was mounted on a MITIGEN holder in perfluoroether oil. Data were collected using a Rigaku FRE+ diffractometer equipped with VHF Varimax confocal mirrors and an AFC12 goniometer and HyPix 6000HE detector, and equipped with an Oxford Cryosystems low-temperature device operating at T = 100.00 (10)  The structure was solved and the space group P21/c (# 14) determined by the ShelXT  structure solution program using Intrinsic Phasing and refined by Least Squares using version 2014/7 of ShelXL . All non-hydrogen atoms were refined anisotropically. Hydrogen atom positions were calculated geometrically and refined using the riding model. The PF6 was disordered.
There is a single molecule in the asymmetric unit, which is represented by the reported sum formula. In other words: Z is 4 and Z' is 1.         . All non-hydrogen atoms were refined anisotropically. Hydrogen atom positions were calculated geometrically and refined using the riding model.

Reflection Statistics
There is a single molecule in the asymmetric unit, which is represented by the reported sum formula. In other words: Z is 4 and Z' is 1.
The Flack parameter was refined to -0.0215(16). Determination of absolute structure using Bayesian statistics on Bijvoet differences using the Olex2 results in -0.0020(13). Note: The Flack parameter is used to determine chirality of the crystal studied, the value should be near 0, a value of 1 means that the stereochemistry is wrong and the model should be inverted. A value of 0.5 means that the crystal consists of a racemic mixture of the two enantiomers.