Nucleophilic Addition of CH, NH, and OH Bonds to the Phosphadiazonium Cation and Interpretation of ³¹P Chemical Shifts at Dicoordinate Phosphorus Centers

Abstract

The phosphadiazonium cation [MesNP](+) reacts quantitatively with the fluorenylide anion, MesNH(2), and MesOH (Mes = 2,4,6-tri-tert-butylphenyl), resulting in formal insertion of the N-P moiety into the H-Y (Y = C, N, O) bonds. Specifically, reaction of MesNPCl with fluorenyllithium gives the aminofluorenylidenephosphine [crystal data: C(31)H(38)NP, monoclinic, P2(1)/c, a = 9.568(8) Å, b = 24.25(2) Å, c = 11.77(1) Å, beta = 101.38(8) degrees, Z = 4]. Similarly, reaction of [MesNP][GaCl(4)] with MesNH(2) gives the diaminophosphenium salt [MesN(H)PN(H)Mes][GaCl(4)] [crystal data: C(36)H(60)Cl(4)GaN(2)P, monoclinic, C2/c, a = 24.921(2) Å, b = 10.198(4) Å, c = 16.445(2) Å, beta = 93.32(1) degrees, Z = 4], and reaction with MesOH gives the first example of an aminooxyphosphenium salt [MesN(H)POMes][GaCl(4)]. It is proposed that the reactions involve nucleophilic attack at phosphorus followed by a 1,3-hydrogen migration from Y to N. Experimental evidence for the formation of sigma-complex intermediates is provided by the isolation of [MesNP-PPh(3)][SO(3)CF(3)] [crystal data: C(37)H(44)F(3)NO(3)P(2)S, triclinic, P&onemacr;, a = 10.663(1) Å, b = 19.439(1) Å, c = 10.502(1) Å, alpha = 103.100(7) degrees, beta = 113.311(7) degrees, gamma = 93.401(7) degrees, Z = 2]. As part of the unequivocal characterization of the aminooxyphosphenium salt, detailed solid-state (31)P NMR studies and GIAO calculations on the phosphenium cations have been performed. Contrary to popular belief, the phosphorus shielding in dicoordinate cations is not caused by the positive charge but results from efficient mixing between the phosphorus lone pair and pi orbitals.

The N,N‐Bis(terphenyl)aminophosphenium Cation – A Sensitive Probe for Interactions with Different Anions

“…The only known aryl-substituted bis(amino)phosphenium cation 3 (E = Al, Scheme 2) was introduced by Niecke [9] and coworkers and further studied by Burford et al [10] As shown in Scheme 2, the phosphadiazonium cation [Mes*NP] + (2) reacts quantitatively with Mes*NH 2 (Mes* = 2,4,6-tri-tert-butylphenyl) to yield ECl 4 -salts with the bis(amino)phosphenium cation (Mes*3). The solid-state structures of Mes*3 [GaCl 4 ] and Mes*3 [AlCl 4 ] have been confirmed by X-ray crystallography and the structural parameters of the cation are essentially identical.…”

“…Synthesis of Mes*3 [ECl 4 ] (E = Al, Ga). [9,10] ride abstraction with Lewis acids in 2-chloro-1,3,2-diazaphospholenes (Scheme 3). [12] Chloride abstraction was also successfully applied in the isolation of salts that bear cyclo-1,3-diphospha-2,4-diazenium ions, which can also be regarded as carbene analogs (Scheme 3).…”

“…[2b, 9,10] In solution, 31 P NMR spectroscopy is a powerful tool for the identification of phosphenium ions. As might be anticipated from the low coordination number and the presence of a formal positive charge at phosphorus, the 31 P chemical shifts of phosphenium ions are rather deshielded and fall in the range 100-520 ppm.…”

An unusually large value of1J(31P,31P) for a solid triphenylphosphine phosphadiazonium cationic complex: determination of the sign ofJfrom 2D spin-echo experiments

“…Since the C-N-P bond angle is approximately linear, 169S0, it is reasonable to assume that the electric field gradient at the nitrogen centre will be nearly axially symmetric, with the largest component along the formal PN triple bond. From the known internuclear separation, rpTN = 1.486 (4) A (12), the dipolar coupling constant, R(1,S) = (p,d4.rr)(y,ysl r,,s3)(~/2.rr), can be calculated, 1070 Hz. With these values, analysis of the asymmetric doublets yields an upper limit for I ' J (~~P , '~N ) I of 25 Hz and a nitrogen nuclear quadrupolar coupling constant, X('~N), of -1.7(2) MHz.…”

“…The purpose of this communication is to demonstrate the power of solid-state ,'P NMR experiments in determining the absolute sign and magnitude of ' J (~' P , ~~P ) for an adduct composed of a phosphadiazonium cation, [Mes*NP]+ (Mes* = 2,4,6-tri-tert-butylphenyl), and triphenyl hosphine, bound by an unusually long P-P bond of 2.625 lf (12). The results of this study clearly demonstrate that there is no simple, general relationship between 'J(~'P,~'P) and P-P bond order.…”