Vier- und Fünfgliedrige phosphorheterocyclen

Syntheses of 2‐Unsubstituted 1H‐1,3‐Benzazaphospholes from N‐Formyl‐2‐bromoanilides

“…The tungsten atoms deviate from the ring planes by 0.33Å, corresponding to 7.5 • and 7.8 • angles of the P-W vectors to the ring planes. In structurally related Cr(CO) 5 complexes with 1,5-dimethyl-1,2,3-diazaphosphole [11] and pivaloyl-2-phosphaindolizine [12] ligands, where phosphorus profits less from the π -donor effect of the σ 3 N atom, the deviation of the P-Cr bonds from the ring planes are small and not more significant, 2 • [11] and 1.5 • /0.12Å [12], respectively, as they are in the known o-substituted phosphinine W(CO) 5 complexes (0.7-3.3 • /0.02-0.12Å) [13]. The W-C bonds trans to the benzazaphospholes are shortened and the trans-C-O bonds elongated as compared with the corresponding bonds of cis-CO ligands.…”

Electron‐Rich Aromatic 1,3‐Heterophospholes – Recent Syntheses and Impact of High Electron Density at σ2P on the Reactivity

“…This indicates, in accordance with failed attempts to achieve P ‐protonation or BH 3 addition at σ 2 P, similarly low donicity and, in combination with relatively high thermal stability, rather π‐acidic ligand properties, such as discussed for the other types of σ 2 P ligands. The 31 P coordination chemical shifts (Δ δ ) of the benzazaphosphole complexes 59 M relative to those of the corresponding ligands ( 5a ,68 4b – d , 9b 11b,92) are small for M = Cr and show the same trends with respect to the metal as the analogous di‐ and triazaphosphole M(CO) 5 complexes 60 M ,63 61 M , and 62 M ,95 as well as the phosphinine complexes 63 M ,96 but the Δ δ values of 59 M indicate smaller net donicity, possibly through somewhat stronger backbonding towards phosphorus (Figure 5). The crystal structure analysis of the 1,5‐dimethylbenzazaphosphole complex ( 10a ) · W(CO) 5 displays small but significant deviations of the metal from the ring plane (bend angles of the W–P vector to the ring plane 7.5 and 7.8°)36 relative to those in the Cr(CO) 5 complexes of pivaloyl‐2‐phosphaindolizine (1.5°)93a and 1,5‐dimethyl‐1,2,3‐diazaphosphole (2°),95W(CO) 5 complexes of electron‐rich (+ M ) o ‐alkoxy‐ or 2‐hydroxy‐substituted phosphinines (0.7–3.3°),52b as well as to L 4 M 0 complexes (M = Pt, Ni) of P–N‐type azaphosphole ligands 98…”

“…The number of coordination compounds of azaphospholes (L) is comparably low, apart from a variety of metal(0) azaphosphole complexes, most of them of the (η 1 P‐L)M(CO) n type with (M = Cr, Mo, W; n usually 5, Fe, n = 4). [4,9b–9f,10a–10c] The (η 1 P‐ligand)M(CO) n complexes of benzo‐, [11b,39,40,62a,62b,68,92] pyrido[ b ]‐,38c and heterocyclic N ‐bridgehead‐anellated 1,3‐azaphospholes [10a–10c,51a,93] as well as of 1,2,4‐diazaphospholes63 and less electron‐rich mono‐,94 di‐, and triazaphospholes containing a P–N bond95 were prepared like the first 2,4,6‐triphenylphosphinine metal(0)carbonyl complexes96 from the ligand and M(CO) 5 (THF) or other M(CO) n (L′) precursors with good leaving group L′. M(CO) 5 complexes with the unsubstituted 1,2,4‐diazaphosphole 2a tend to coordinate a second M(CO) 5 fragment at the basic N atom,63 which for the pyrido[ b ]azaphosphole complexes38c occurs only in trace amounts.…”

Di‐ and Triazaphospholes as Ligands for Ruthenium(II) and Iridium(III) Complexes

“…One early study by Schmidpeter et al reports on the reaction of azaphospholes with different transition metals. However, in this study complexes with intact azaphospholes were obtained only with carbonyl complexes, especially of the chromium group 5. In the case of palladium and platinum complexes, the authors only identified intact and unreacted azaphosphole ligands in the 31 P and 195 Pt NMR spectra 6, 7.After subjoining nucleophiles (such as methanol) for addition reactions, single crystals of the reaction products were obtained, where the phosphorus atom had been affected by an 1,2‐addition and the heterocycle had lost its aromaticity.…”