Syntheses of Tungsten Diazoalkane Complexes from a Dinitrogen Complex and Diketones. Conversion of Molecular Nitrogen into Pyrazoles via the Diazoalkane Complexes as Intermediates

Abstract

Abstract The hydrazido(2-) complexes [WCl2(NNH2)(L)(PMe2Ph)2] (L = PMe2Ph, CO), derived from the dinitrogen complex cis-[W(N2)2(PMe2Ph)4] (1), reacted with β-diketones R1COCHR2COR3 (R1 = Me, But, Ph; R2 = H, Me; R3 = Me, Et, But, Ph) to afford a series of diazoalkane complexes [WCl2(NN=CR1CHR2COR3)(L)(PMe2Ph)2]. The detailed structure of cis,mer-[WCl2(NN=CMeCH2COPh)(PMe2Ph)3] has been determined by X-ray analyses. These diazoalkane complexes were treated with a KOH/EtOH mixture to produce pyrazoles in moderate yields, whereas the reaction of 1 with a MeCOCH2COPh/KOH/EtOH mixture resulted in the direct formation of 5-methyl-3-phenylpyrazole.