Syntheses, Structures, and Reactions ofC-Methoxycarbonyl-Functionalized Small- and Medium-Sized P-Heterocycle Complexes

Abstract

Thermal ring‐opening of [{2‐bis(trimethylsilyl)methyl‐3‐ phenyl‐2H‐azaphosphirene‐ĸP}pentacarbonyltungsten(0)] (8a) in the presence of dimethyl acetylenedicarboxylate (DMAD) led to the 2,3‐bifunctionalized 1H‐phosphirene complex 9a and the 4‐phenyl‐substituted 2H‐1,2‐azaphosphole complex 10a, the latter as a by‐product. If a small amount of benzonitrile was added, complex 10a was obtained as the main product, along with a small amount of the decomplexed 2H‐1,2‐azaphosphole 11, which could not be isolated. Reaction of complex 10a with elemental sulfur furnished the corresponding PV sulfide 13. When the ring‐opening of complex 8a was performed in the presence of two equivalents of DMAD and two equivalents of dimethyl cyanamide, we obtained the 4‐dimethylamino‐substituted 2H‐1,2‐azaphosphole complex 10b, together with the diastereomeric Δ3‐1,3,2‐oxazaphospholene complexes 14a,b. On reaction of [{2‐pentamethylcyclopentadienyl‐3‐phenyl‐2H‐azaphosphirene‐ĸP}pentacarbonyltungsten(0)] (8b) and DMAD in toluene, the corresponding 1H‐phosphirene complex 9b was only formed as a transient species and the P‐coordinated P,C‐cage compound 15 was the final product. Using benzonitrile as solvent, the 4‐phenyl‐substituted 2H‐1,2‐azaphosphole complex 10c was obtained, together with the 7‐aza‐1‐phosphanorbornadiene complex 16, the latter through partial decomposition of 10c coupled with rearrangement and a Diels–Alder reaction; the ratio 10c/16 was found to depend strongly on the molar ratio of complex 8b to DMAD. A cycloaddition reaction of the 2,3‐bifunctionalized 1H‐phosphirene complex 9a with 2,3‐dimethylbutadiene furnished the bicyclic phosphirane complex 19, along with a small amount of the noncoordinated bicyclic phosphirane 20. Reaction of complex 9a with diethylamine yielded the phosphirane complex 21 as a 1,2‐addition product, the diorganophosphane complex 22 through ring‐opening of 9a, and the 3,4‐functionalized 1,2‐dihydro‐1‐phosphet‐2‐one complex 23 through an unprecedented ring‐expansion reaction; the products 21, 22, 23 were formed in a ratio of ca. 1:1:1. The structures of the 1H‐phosphirene complex 9a, the 4‐dimethylamino‐substituted 2H‐1,2‐azaphosphole complex 10b, the bicyclic phosphirane complex 19, the phosphirane complex 21, and the 1,2‐dihydro‐1‐phosphet‐2‐one complex 23 have been determined by single‐crystal X‐ray diffraction analysis.

Transition Metal-Induced Cyclization of 1-Phosphabutadienes: Selective Formation of 1-Phosphet-2-ene or P═C-Substituted Phosphacyclohexene Ligands

“…The sum of the ring angles within the 1-phosphet-2-ene ring shows minimal deviation from the idealized 360° for a planar four-membered ring {[Au­( 4b )­Cl] = 359.8(5); [Pd­( 4b )­(η 3 -C 3 H 5 )­Cl] = 360.0(3); [Pd­( 4b ) 2 Cl 2 ] = 360.0(5)°}. For comparison, the sum of the ring angles within known 1-phosphet-2-ene W 0 and Au I complexes ranges from 358.8(4) to 360(1)°. ,,,− The C(1)–P(1)–C(3) angles are the most acute within the 1-phosphet-2-ene ring {angle (deg): [Au­( 4b )­Cl] = 75.11(19); [Pd­( 4b )­(η 3 -C 3 H 5 )­Cl] = 74.51(9); [Pd­( 4b ) 2 Cl 2 ] = 73.40(18)}. This is in agreement with the aforementioned known 1-phosphet-2-ene-W 0 and Au I complexes [range = 70.9(2) to 75.4(1)°].…”

Phosphetene: Synthesis and reactivity

“…They thus studied the reaction of phosphirene complexes with various reactant in order to expand the phosphorous ring. [33] In particular, the reaction of the phosphirene complexe 12 with diethylamine lead to the formation of three products (in a ratio near to 1:1:1): the 1,2-addition product 13, the secondary vinylphosphane complex 14, and the 1,2-dihydro-1-phosphet-2-one complex 15 (Scheme 3) The following year, Mathey et al also worked on the synthesis of 1,2-dihydrophosphete starting from in situ generated tungsten or chromium pentacarbonyl phosphinidene complex (Scheme 6). [38,39,40] The dihydrophosphete derivative 27 was obtained by reacting the phosphinidene precursor 25 with the carbene complex 26.…”

Synthesis of a 1-aza-2-phospha-acenaphthene complex profiting from coordination enabled chloromethane elimination

“…, in a 1,2 H -azaphosphole of Cain in 2018 ( d (P–N) = 1.74 Å) 35 or a respective complex from our earlier work ( d (P–N) = 1.67 Å). 36…”

“…The P-N distance of 1.6970 Å is typical for a single bond as observed in similar systems, e.g., in a 1,2H-azaphosphole of Cain in 2018 (d(P-N) = 1.74 Å) 35 or a respective complex from our earlier work (d(P-N) = 1.67 Å). 36 At this point, we assumed that a further destabilization of the (elongated) P-Cl bond occurs due to the complexation at phosphorus, thus leading to a heterolytic P-Cl bond cleavage and, eventually, to the elimination of chloromethane to form 5 from 4, a transient phosphenium complex (see Fig. 5).…”