Catalytic and selective ring expansion reactions of o-phenyl-substituted 2H-azaphosphirene tungsten complexes

ortho-Phenyl-substituted ethoxy- and aminocarbene pentacarbonyltungsten complexes 2a–c and 3a–c are synthesized and the latter are reacted with chloromethylenephosphane 4 in diethyl ether in the presence of triethylamine to yield the ortho-phenyl-substituted 2H-azaphosphirene complexes 6a–c via elimination of triethylammonium chloride; remarkable are the prolonged reaction times in the case of the methoxy- and dimethylamino-substituted complexes 6b,c. The 2H-azaphosphirene complexes 6a–c and 7d are reacted with benzonitrile in dichloromethane in the presence of ferrocenium hexafluorophosphate to furnish the 2H-1,2,4-diazaphosphole complexes 8a–d (8a: R=Me, 8b: R=OMe, 8c: R=NMe2, 8d: R=H); the reaction course will be discussed. All complexes were unambiguously confirmed by NMR spectroscopy and elemental analysis and, additionally complexes 2b, 5 and 6b by X-ray analysis.