Cyano(triphenylsilyl)phosphanide as a Building Block for P,C,N Conjugated Molecules

Abstract

The cyano(triphenylsilyl)phosphanide anion was prepared as a sodium salt from 2‐phosphaethynolate. The electronic structure of this new cyano(silyl)phosphanide was studied via computational methods and its reactivity investigated using various electrophiles and Lewis acids, demonstrating its P‐ and N‐nucleophilicity. The ambident reactivity is in agreement with computations. The silyl group also shows lability and therefore the cyano(silyl)phosphanide can be considered as a phosphacyanamide synthon, [PCN]2−, and serves as building block for the transfer of a PCN moiety.

Cyano(triphenylsilyl)phosphanide as a Building Block for P,C,N Conjugated Molecules

“…[3a, 26] ]. The structure of Na(18-crown-6) [9] is shown in Figure 2 D. [27] The bond distances within the PCN unit closely resemble those of [8] À , with a P1-C1 distance of 1.77 and a C1-N1 distance of 1.15 . The only significant structural difference between [8] À and [9] À is the P-C-N angle which is closer in [9] À (1688) likely because of steric repulsion between the p-tolyl substituent at N2 and the bulky [Na(18-crown-6)] + cation which coordinates to the cyano group (Na-N1 distance 2.35 ).…”

“…The structure is shown in Figure 2 A. [27] Compound 4 decomposes in solution into an insoluble dark material over a few days (likely due to an auto-redox process). [23] The PÀC bond distance in 4 (1.68 ) is in the typical range of P = C double bonds [24] and significantly shorter than the one in [1] À (1.76 ).…”

“…Layering the reaction solution with hexane afforded crystals of this product. [27] In the anion [7] À , the boryl group binds to the nitrogen atom. As expected, the P À C bond (1.73 ) is shorter than in the anion [1] À , but significantly longer than in the neutral phospha-azaallene 4.…”

“…Crystallisation from DFB gave single crystals suitable for XRD. The structure of Na(18-C-6) [8] is displayed in Figure 2 C. [27] Anion [8] À is a phospha-cyanourea derivative [25] with a short CÀN bond (1.15 ), an elongated P= C double bond (1.77 ), and an almost linear PCN unit (1738). The 13 C-NMR resonance of the C2 carbon in [8] À is Scheme 3.…”

“…The structures of all compounds [Na(18-C-6)][1-3] were determined by X-ray diffraction (XRD) experiments (see the SI for details). [27] Selected bond lengths and angles are given in Table 1. Exemplary, the structure of [Na(18-C-6)][1] in a single crystal grown from 1,2-difluorobenzene (DFB) is shown in Figure 1 showing a dimeric aggregate in which one oxygen center in each 18-C-6 acts as a bridge between two sodium cations.…”