peri-Substituted Phosphino-Phosphonium Salts: Synthesis and Reactivity

Abstract

The clean reaction of 5-lithio-6-(diisopropylphosphino)acenaphthene with dichlorophosphines RPCl2 gives the peri-substituted phosphino-phosphonium salts [Acenap(PiPr2)(PR)]+Cl– (2, R = Ph; 3, R = Fc; 4, R = NMe2; 5, R = iPr; Acenap = acenaphthene-5,6-diyl). Their ionic structure is maintained in solution and in the solid state. The reduction of 2 and 3 with LiAlH4 led to the formation of mixed tertiary/secondary chelating bis(phosphines) Acenap(PiPr2)(PRH) (6 and 7), which were subsequently reacted with PtCl2(cod) to give the complexes [(6)/(7)PtCl2] (8 and 9). Reaction of 2 and 3 with a large excess of MeOTf at elevated temperature gave the chiral 1,2-diphosphoniums [Acenap(PiPr2)(PRMe)]2+([TfO]−)2 (10 and 11), which were reduced with LiAlH4 to the heteroleptic bis(phosphines) Acenap(PiPr2)(PRMe) (12 and 13); these were then reacted with [(nor)Mo(CO)4] to give the complexes [(12)/(13)Mo(CO)4] (14 and 15). The heteroleptic bis(phosphines) 6, 7, 12, and 13 display large through-space couplings (formally 4 J PP = 163–199 Hz), comparable in magnitude to 1 J PP couplings observed in phosphino-phosphonium salts 2–5 (303–412 Hz). Single-crystal X-ray structures of 2, 3, 7–9, 14, and 15 are reported.

Intramolecular pnicogen interactions in phosphorus and arsenic analogues of proton sponges

“…19 Important reviews on naphthalene and related systems, peri-substituted by group 15 and 16 elements, have been published. [22][23][24][25][26][27][28][29][30] Numerous review articles have appeared devoted to the different aspects of the hydrogen bond that occurred between N atoms after proton trapping, [31][32][33] but so far there are no theoretical studies on pnicogen derivatives, with P and As instead of N atoms in structures similar to DMAN, and how the intramolecular non-covalent interaction between the heteroatoms alters in the absence of that proton. In particular, the field of compounds related to DMAN but with phosphorus instead of nitrogen atoms has been studied since their discovery in 1993 till today.…”

Hydride Abstraction and Deprotonation – an Efficient Route to Low Coordinate Phosphorus and Arsenic Species

“…A solution of 1a in CDCl 3 showed decomposition to a mixture of products (by 31 P{ 1 H} NMR spectroscopy) within minutes, whilst 1b showed no decomposition initially and decomposed to a complex mixture (albeit less complex than in the case of 1a) over 3 days. In both cases crystals were obtained from the solutions and found, by X-ray diffraction, to be analogues of the salts 2a and 2b with chloride counterions (7a and 7b).…”

“…This is somewhat lower in magnitude than that seen with similar phosphino-phosphonium salts, where the phosphorus-bound hydrogen is substituted for a phenyl ( 1 J P,P = 303 Hz) or ferrocenyl group ( 1 J P,P = 311 Hz). [31] In the 31 P NMR spectrum, the signal at δ P −132.0 splits into a doublet of doublets with 1 J P,H = 208 Hz. This 1 J P,H coupling constant is comparable to that observed in the primary phosphine 1b ( 1 J P,H = 204 Hz).…”

“…The P1-P9 distance of 2.229(1) Å is typical of a P-P single bond [24] and is very similar to that observed in previously published peri-substituted phosphino-phosphonium salts. [31] In addition to X-ray diffraction, 1 H, 31 P and 31 P{ 1 H} NMR; 2b was further characterised by 13 C{ 1 H} and 11 B NMR spectroscopy, Raman spectroscopy, ES MS and elemental analysis.…”

“…Compounds 1a and 1b were synthesised according to literature procedures. [23,30] Where possible, new compounds were fully characterized by 31 …”