Intra- and Intermolecular [3+2] Cycloaddition Reactions of P-Cp-Substituted Nitrilium Phosphane-Ylide Tungsten Complexes

• Published in: Organometallics Vol. 19; no. 4; pp. 475 - 481
• Main Authors: Streubel, Rainer, Schiemann, Udo, Hoffmann, Nils, Schiemann, Yvonne, Jones, Peter G, Gudat, Dietrich
• Format: Journal Article
• Language: English
• Published: WASHINGTON American Chemical Society 21.02.2000; Amer Chemical Soc
• Subjects: Chemistry; Chemistry, Inorganic & Nuclear; Chemistry, Organic; Physical Sciences; Science & Technology; CHEMISTRY; PHOSPHORUS
• ISSN: 0276-7333; 1520-6041
• DOI: 10.1021/om990801e

Thermal ring opening of {pentacarbonyl[2-pentamethylcyclopentadienyl-3-phenyl-2H-azaphosphirene-κP]tungsten(0)} (1) in toluene in the presence of either 1-piperidinonitrile or ethyl cyanoformate yields predominantly tricyclic P-heterocycle complexes 4a,b via intramolecular trapping reactions of transiently formed nitrilium phosphane-ylide complexes 3a,b; complex 4a was isolated and fully characterized. On prolonged heating, complexes 4a,b transformed into 2H-1,3,2-diazaphosphole complexes 5a,b, which were also characterized by NMR spectroscopy. In the case of 1-piperidinonitrile, acyclic dinuclear complex 6 was formed as byproduct via a 2-fold 1,3-addition reaction of complex 3a with water. Furthermore, preliminary studies on ring opening of complex 4a showed retro-[2+1] and retro-[3+2] cycloaddition reactions, depending on the substrate. If dimethyl acetylenedicarboxylate was employed, the tetracyclic phosphorus−carbon cage complex 10 was obtained, and if 1-piperidinonitrile was used, the 2H-1,3,2-diazaphosphole complex 5a was formed selectively. The structures of 2H-1,3,2-diazaphosphole complex 5a, the acyclic dinuclear complex 6, and the tetracyclic P-heterocycle complex 10 were determined by single-crystal X-ray diffraction.