Heterometathesis of diphosphanes (R2P–PR2) with dichalcogenides (R'E–ER', E = O, S, Se, Te)

ESI 1: Experimental ...........................................................................................................................S2 ESI 2: 31P{1H}, 77Se{1H} and 1H NMR spectra of isolated products 1–7. .............................................S6 ESI 3: 31P{1H} NMR spectra of test reactions...................................................................................S13 ESI 4: Computational details. ..........................................................................................................S21 ESI 5: Crystallography .....................................................................................................................S36 ESI 6: References ............................................................................................................................S37


Diphenyl(phenylselanyl)phosphane (1):
Tetraphenyldiphosphane (190 mg, 0.513 mmol) and diphenyl diselenide (160 mg, 0.513 mmol) were added to a Schlenk flask and dissolved in THF (10 ml), immediately creating a pale-yellow solution, which was left to stir for 10 min. The solvent was then removed in vacuo affording 1 as an almost-colourless oily solid (323 mg, 92% yield). After storage under argon overnight the oily solid partially crystallised. Crystals suitable for single-crystal X-ray crystallography were grown over 1 week via CH 2 Cl 2 /n-hexane vapour diffusion. 1

Bis(4-methoxyphenyl)(phenylselanyl)phosphane (5):
Tetra(p-anisyl)diphosphane (150 mg, 0.305 mmol) and diphenyl diselenide (95 mg, 0.305 mmol) were added to a Schlenk flask, dissolved in THF (10 ml), and stirred for 10 min. The solvent was removed under reduced pressure affording 5 as a yellow oil (114 mg, 79% yield). 1        Note that each of these spectra correspond to NMR-scale reactions that were not stirred. The observed rates of reaction were slower than those reported in the syntheses of ESI 1. Chemical shift (ppm) CDCl 3 ), approximately 60% of the initial Ph 2 P-SePh remains. The major hydrolysis product at +32.5 ppm corresponds to Ph 2 P(O)OH. 5 The identity of the species responsible for the minor peak at +39.6 is unknown. S14 ESI 3.3. Top: molybdenum complexes of 1 (8 and 9) after attempted hydrolysis (4 days in watersaturated CD 2 Cl 2 ), though negligible change is observed compared with Figure 2 in main article.
Bottom: after heating to 60 °C for 3.5 h the pair of doublets assigned to complex 9 is the dominant species and the signal at ca. +16.9 (labelled X in Figure 2) has increased significantly in intensity.

ESI 4.2. Equilibria.
To establish an accurate computational method to predict the equilibria between X 2 PPX 2 and X 2 PY the smallest model system was considered, where X=H (Table S1). Comparing DFT energies to the coupled-cluster [DLPNO-CCSD(T)] reference values we find B3LYP to perform well, and that calculated free energy differences are very close to their potential energy analogues. For this reason, we select the B3LYP-D3BJ method and potential energies for optimal efficiency. The latter approximation also avoids any ambiguity in treating low-frequency phenyl rotation normal modes in the entropy calculation. An extended set of reaction energies presented in Table 1 are shown in Table S2. Table S1. Calculated reaction energies and enthalpies for H 2 PPH 2 + Y 2 → 2 H 2 PY at different levels of theory. Geometries and thermal corrections calculated at the PBE0-D3BJ/def2-SVP level of theory. DFT single points evaluated using the def2-TZVP basis set while DLPNO-CCSD(T) use the def2-TZVPP basis and default auxiliary basis sets.

∆E(DFT) / kcal mol -1 DLPNO-CCSD(T)
Entry Y With a view to investigating the possibility of RSe· radicals initiating the P/Se metathesis reaction the kinetic feasibility of thermal initiation was calculated (PhSe-SePh → 2 PhSe·, Table S3). The standard free energy change suggests an inaccessible thermally activated pathway, with a similar endergonicity to the analogous Ph 2 P-PPh 2 homolysis, which we found to be photoinitiated. 1

ESI 5: Crystallography
Crystallography X-ray diffraction experiments on 1 were carried out at 100(2) K on a Bruker APEX II diffractometer using Mo-K α radiation (λ = 0.71073 Å). Intensities were integrated in SAINT 17 and absorption corrections based on equivalent reflections were applied using SADABS. 18 The structures was solved using Superflip 19,20 and refined by full matrix least squares against F 2 in ShelXL 21,22 using Olex2. 23 All of the non-hydrogen atoms were refined anisotropically. While all of the hydrogen atoms were located geometrically and refined using a riding model. Crystal structure and refinement data are given in