An unexpected Staudinger reaction at an N-heterocyclic carbene-carbon center

Abstract

The previously unreported carbene-phosphine adduct (IPr)PCl2N3 [IPr = (HCNDipp)2C:; Dipp = 2,6-iPr2C6H3] was synthesized and used as a synthon toward the elusive dichlorophosphazene monomer unit, [Cl2P=N]. (IPr)PCl2N3 was found to undergo halide and azide abstraction when combined with various electrophiles and its thermolysis yielded the unexpected Staudinger reaction product (IPr=N)PCl2.

Isolation of N‐Heterocyclic Carbene‐Stabilized Phosphorus and Arsenic Mononitride

“…The corresponding arsenic derivative [(IDipp)NAsCl 2 ] ( 1b ) was prepared from AsCl 3 in a similar fashion and isolated in 78 % yield as a colorless solid. The 31 P NMR spectrum of 2a in C 6 D 6 exhibits the expected singlet at δ = 167 ppm . The 1 H NMR spectra of 2a and 2b are very similar and reveal dynamic behavior with C 2 v symmetry on the NMR timescale.…”

“…The 31 P NMR spectrum of 2a in C 6 D 6 exhibits the expected singlet at δ = 167 ppm. [23] The 1 H NMR spectra of 2a and 2b are very similar and reveal dynamic behavior with C 2v symmetry on the NMR timescale. Rivard and co-workers determined the crystal structure of 2a at 173 K in the triclinic space group type P1 [Z = 2, a = 9.2023(3) Å, b = 9.4927(3) Å, c = 17.3362(5) Å, α = 90.4763(16)°, β = 91.8703 (14)°, γ = 116.5497 (14)°].…”

“…The preparation of [(IDipp)NPCl 2 ] ( 2a ) follows the synthetic approach first reported by Kuhn , who described the reaction of [(IMe)NSiMe 3 ] (IMe = 1,3‐dimethylimidazolin‐2‐ylidene) with PCl 3 in diethyl ether affording [(IMe)NPCl 2 ] . Independently, Rivard reported the synthesis of 2a via the same approach from [(IDipp)NSiMe 3 ] ( 1 ) and PCl 3 in toluene solution at room temperature . 1 was also used by Dielmann for the reaction with various chlorophosphines (ClPR 2 ) to form strongly electron‐donating phosphine ligands .…”

“…[22] Independently, Rivard reported the synthesis of 2a via the same approach from [(IDipp)NSiMe 3 ] (1) and PCl 3 in toluene solution at room temperature. [23] 1 was also used by Dielmann for the reaction with various chlorophosphines (ClPR 2 ) to form strongly electron-donating phosphine ligands. [24] In our hands, 2a was isolated in 90 % yield as a colorless solid by performing the reaction in THF (Scheme 1).…”

“…Rivard and co-workers determined the crystal structure of 2a at 173 K in the triclinic space group type P1 [Z = 2, a = 9.2023(3) Å, b = 9.4927(3) Å, c = 17.3362(5) Å, α = 90.4763(16)°, β = 91.8703 (14)°, γ = 116.5497 (14)°]. [23] At 100 K, we found a monoclinic polymorph in C2/c with half a molecule of 2a in the asymmetric unit [Z = 4, a = 16.711(2) Å, b = 9.2085(10) Å, c = 17.420(3) Å, β = 91.750 (14)°]. The molecule resides on a twofold rotation axis with the phosphorus atom being disordered over two positions ( Figure 2).…”