On the Basicity of Carboranylphosphines

Abstract

Three new carboranylphosphines, [1-(1′-closo-1′,7′-C2B10H11)-7-PPh2-closo-1,7-C2B10H10], [1-(1′–7′-PPh2-closo-1′,7′-C2B10H10)-7-PPh2-closo-1,7-C2B10H10], and [1-{PPh-(1′-closo-1′,2′-C2B10H11)}-closo-1,2-C2B10H11], have been prepared, and from a combination of these and literature compounds, eight new carboranylphosphine selenides were subsequently synthesized. The relative basicities of the carboranylphosphines were established by (i) measurement of the 1 J PSe NMR coupling constant of the selenide and (ii) calculation of the proton affinity of the phosphine, in an attempt to establish which of several factors are the most important in controlling the basicity. It is found that the basicity of the carboranylphosphines is significantly influenced by the nature of other substituents on the P atom, the nature of the carborane cage vertex (C or B) to which the P atom is attached, and the charge on the carboranylphosphine. In contrast, the basicity of the carboranylphosphines appears to be relatively insensitive to the nature of other substituents on the carborane cage, the isomeric form of the carborane, and whether the cage is closo or nido (insofar as that does not alter the charge on the cluster). Such information is likely to be of significant importance in optimizing future applications of carboranylphosphines, e.g., as components of frustrated Lewis pairs.

Predicting Dinitrogen Activation by Carborane-Based Frustrated Lewis Pairs

“…However, the adduct P1 is reluctant to form, as indicated by positive Gibbs reaction energies (Δ G s, Figures and S1), whenever E is Si or C. For type 2 FLP, when the closed form was chosen as a reference reactant, the Δ G values of P1 and P2 were 13.8 and −38.4 kcal mol –1 , respectively. Additionally, it has been well established that the C-bound carboranyl group acts as an electron withdrawing group, while the B-bound carboranyl group acts as an electron donating group. ,− Therefore, type 2 should be the best choice for P1 , owing to the electron withdrawing effect of B­(SiMe 3 ) 2 and the electron donating effect of carbene, supported by the least negative Δ G value of P1 (Figure ). Then, P1 can rearrange into the highly stable product P2 via SiMe 3 transfer and ring opening. , The high exothermicity of P2 should be attributed to the extended conjugation in the N–C–N–N­(R)–B framework reported previously .…”

Sterically Demanding Novel Triazole Based Tertiary Phosphines: Synthesis, Transition Metal Chemistry and Catalytic Applications

“…The oxidation reactions of 3 and 4 with chalcogens was carried out in order to understand the Lewis basicity and donor properties by using the 31 J PSe = 729 Hz), [28] [CH 2 (1,2-C 3 H 2 N 2 PPh 2 Se) 2 ] ( 1 J PSe = 746 Hz), [28] [CH 2 (1,2,4-C 2 HN 3 PPh 2 Se) 2 ] ( 1 J PSe = 754 Hz) [28] and also others. [46][47][48] The larger 1 J PSe coupling of 761 Hz in 7 a suggests that the phosphorus lone pairs have a larger scharacter. This might be due to the combined electron- The molecular structures of 3-5 were established by singlecrystal X-ray analysis.…”

Reactivity Studies of Phosphinines: The Selenation of Diphenyl-Phosphine Substituents and Formation of a Chelating Bis(Phosphinine) Palladium(II) Complex

“…The oxidation of phosphines with sulphur and selenium is well-known [26,27] with phosphine selenides being particularly useful in determining the electronic properties of the parent phosphines via the measurement of phosphorus-selenium coupling constants [28][29][30]. With respect to phosphinine chemistry, oxidation with sulfur and selenium is usually difficult with phosphinine sulfides initially only tentatively characterised as intermediates in the reaction of S with 2-Ph-4,5-Me 2 PC 5 H 2 (via trapping reactions with 2,3-dimethylbutadiene) and S with 2,3-(PPh 2 ) 2 -6-PhPC 5 H (ca.…”