N,N′-Fused Bisphosphole: Heteroaromatic Molecule with Two-Coordinate and Formally Divalent Phosphorus. Synthesis, Electronic Structure, and Chemical Properties

Abstract

The reduction of 6,12-dichloro-1,2,3,4,7,8,9,10-octahydro-6H,12H-[1,2,3]benzodiazaphospholo[2,1-a][1,2,3]benzodiazaphosphole (3) by metallic magnesium in tetrahydrofuran (THF) affords the N,N'-fused bisphosphole 1 in 92% yield. The compound reveals a novel type of 10π-electron heteroaromatic system [NICS(0) = -11.4], containing a two-coordinate and formally divalent phosphorus atom. Compound 1 possesses a much higher coordination activity than many other diazaphospholes. This is caused by a novel type of complexation to a metal ion wherein the lone phosphorus pairs are not involved in metal coordination. Instead, the 10π-electron heteroaromatic system provides two electrons for P → M bond formation. Polarization of the ligand results in the formation of extended molecular associates or cluster compounds. Complexes of 1 with mercury dichloride [{(1)3HgCl}2(μ6-Cl)](+)Cl(-) (7) and tin dichlorides [1·SnCl2(PhMe solvate)] (8a) and [1·SnCl2] (8b) are, in fact, supramolecular in nature, containing multiple intermolecular short contacts. Crystals of complex 8a containing short Sn···Sn packing interactions were converted reversibly to metallic tin after workup with THF. The simple mixing of 1 and 3 (1:1) gave a P-P bridging dimeric species prone to easy dissociation. The addition of GeCl2(diox) to the equimolar mixture of 1 and 3 shifted the equilibrium to the formation of a poorly soluble salt-like dimer 6, which is, in fact, a stacked 18π-electron dication having a through-space delocalization of π electrons.

Organophosphorus Compounds in Organic Electronics

“…The electronic spectrum of this compound is dominated by a single strong absorption centered at 438 nm. The reaction of the dichloro precursor 52 (Figure ) in the presence of GeCl 2 gives a face‐to‐face dimer, which is formally an 18 π‐electron dication 53 (Figure ) with “π‐stacked aromaticity” . A similar P−P bridged dimer formation was reported by the same authors for a related P,N,N‐heterocyclic compound, though not being aromatic .…”

Phenylpyrazole‐Based Hypervalent Phosphorus Compounds: From Positional Isomerism to Stacking Interactions

“…Taking into consideration the steric factors and charge distribution, it may be supposed that the arrangement of the two positively charged heterocyclic units in 10 would be most favorable in the anti position relative to each other. The stacked arrangement of diazaphosphole units has a close analogy to the previously described stacked 18π-electron dication based on N,NЈ-fused bis-phosphole [21] with [GeCl 3 ] -counterions in which through-space delocalization of π electrons is assumed.…”

“…We proposed that compound 3 under reducing conditions may give a unique 10π-electron system (6), similar to the N,NЈ-fused bis-phosphole 7 described recently [21] containing two-coordinate and formally divalent phosphorus atoms.…”

π-Rich σ2P-Heterocycles: Bent η1-P- and μ2-P-Coordinated 1,3-Benzazaphosphole Copper(I) Halide Complexes

“…Removal of the solvent from the filtrate gave 180 mg of a yellow viscous residue. 1 H NMR (CD 3 OD): δ = 0.90 (s, 9 H, CMe 3 ), 4.08 (s, 2 H, NCH 2 ), 7.11 (tdd, 3 J = 7.9, 7.2, 4 J PH = 1.2, 4 J = 0.6 Hz, 1 H, H-5), 7.38 (br t, 3 J = 8.3, 7.2 Hz, 1 H, H-6), 7.72 (d, 3 J = 8.3 Hz, 1 H, H-7), 7.93 (dd, 3 J = 7.9, 3 J PH = 4.5 Hz, 1 H, H-4), 8.46 (d, 2 J PH = 35.9 Hz, 1 H, H-2). 13 C{ 1 H} NMR (CD 3 OD): δ = 28.57 (s, CH 3 ), 35.36 (s, CMe 3 ), 61.64 (s, NCH 2 ), 115.46 (s, C-7), 121.59 (d, 3 J = 11.9 Hz, C-5), 125.96 (s, C-6), 129.93 (d, 2 J = 18.6 Hz, C-4), 144.93 (d, 2 J = 4 Hz, C q -7a), 163.48 (d, 1 J = 30.5 Hz, CH-2); C q -3a at noise level.…”