Sterically Crowded Tris(2‐(trimethylsilyl)phenyl)phosphine – Is it Still a Ligand?

Abstract

Tris(2‐(trimethylsilyl)phenyl)phosphine, P(o‐TMSC6H4)3, was synthesised and characterised in solution and in the solid state. The large steric bulk prevents most reactions of the phosphorus donor and makes the compound air stable both in the solid state as well as in solution. This shielded phosphine can still undergo three reactions, namely protonation, oxidation to the phosphine oxide under harsh conditions and complexation to AuI, thus forming a complex with linear coordination. Unexpectedly, complexation was unsuccessful with a range of other metal cations. Neither PdII, PtII, ZnII nor HgII reacted and even the remaining coinage metal cations CuI and AgI could not be coordinated. Both the parent molecule as well as the reaction products were structurally characterised by single crystal X‐ray diffraction, and the conformational change of geometry required to accommodate the additional atoms was analysed in detail. Apart from chemical oxidation with H2O2, P(o‐TMSC6H4)3 displays reversible electrochemical oxidation with a potential not unlike the one of sterically unencumbered phosphines for which the oxidation is usually not reversible. P(o‐TMSC6H4)3 can thus be considered a model compound for the investigation of the electronic properties of sterically unencumbered phosphines.

Fusing Triphenylbismuth and PnPh3 (Pn = P–Bi): Synthesis, Isolation, and Characterization of 9-Bisma-10-Pnictatriptycenes

“…The triaryl pnictanes 1-Pn (Pn = As, Sb, Bi) were prepared as colorless crystalline solids (As: 38%, Sb: 43%, Bi: 99%; Scheme ) from 1-bromo-2-iodobenzene, which was reacted with i -PrMgCl and subsequently treated with the respective pnictogen­(III) chloride (As, Sb) or bromide (Bi). The triaryl phosphine 1-P was prepared following a literature-known Cu­(I) catalytic procedure . The 1 H NMR spectra (in benzene- d 6 ) of compounds 1-Pn exhibit two (apparent) doublets of doublets and two (apparent) triplets of doublets.…”

“…2.152(5) Å, Bi: 2.264(7) Å) and increasing pyramidalization of the pnictogen atom (Pn = P: av. 101°, As: av. 98°, Sb: av.…”

“… a CuI (3 mol %) was added, and the reaction temperature was maintained at −40 °C until PCl 3 was added . Note, that neither the choice of the bismuth halide nor the reaction temperature during lithiation (within the given range) had a significant influence on the yield. …”

“…1-P was prepared following a literature protocol. 5 Yield: 59% (5.85 g). 1 H NMR (500 MHz, 298 K, C 6 D 6 ): δ 6.68 (td, 3 J H,H = 7.6, 4 J H,H = 1.8 Hz, 3H, C4-H), 6.75 (td, 3 J H,H = 7.5, 4 J H,H = 1.3 Hz, 3H, C3-H), 6.88 (dt, 3 J H,H = 7.6, 4 J H,H = 1.9 Hz, 3H, C2-H), 7.34 (ddd, 3 J H,H = 7.9, 4 J P,H = 3.9, 4 J H,H = 1.3 Hz, 3H, C5-H) ppm.…”

Tri(N-carbazolyl)phosphine Gold(I) Complexes: Structural and Catalytic Activity Studies

“…The steric properties of tri­( N -carbazolyl)­phosphine ligands were next evaluated by calculating the values of V bur % using SambVca 2.1 based on the X-ray structures of the corresponding L–Au–Cl complexes, and the results are depicted in Table . For comparison, the V bur % values of triaryl-substituted ligand PPh 3 and trialkyl-substituted phosphine ligand PAd 3 are also presented. , Tri­( N -carbazolyl)­phosphine ligand 1 exhibits a relatively large V bur % value of 43.0, larger than that of PAd 3 , similar to the value of tris­(2,4,6-trimethoxyphenyl)­phosphine (43.6), indicating that this ligand is a sterically demanding ligand. Tri­[ N -(3,6-dibromo-carbazolyl- d 6 )]­phosphine 2 also exhibit a large V bur % value of 40.2, similar to bulky PAd 3 and P­( t -Bu) 3 (40.0) ligands.…”