Preparation of new 'diazo' complexes of manganese stabilised by phosphite ligands

A series of mono- and binuclear aryldiazene complexes [Mn(ArN=NH)(CO)(n)P5- n]BPh4 and [{Mn(CO)(n)P5-n}(2)(mu -HN=NAr-ArN=NH)](BPh4)(2) [P = P(OMe)(3), P(OEt)(3) or P(OPh)(3); Ar = C6H5, 4-CH3C6H4; Ar-Ar = 4,4'-C6H4-C6H4, 4,4' -C6H4-CH2-C6H4; n = 1, 2 or 3] were prepared by allowing hydride species Mn H(CO)(n)P5-n to react with the appropriate aryldiazonium salts at -80 degre esC. Characterisation of the complexes by IR and variable-temperature H-1-, P-31-, N-15-NMR spectra (with N-15 isotopic substitution) are reported. Tr eatment of aryldiazene derivatives containing both the tricarbonyl Mn(CO)(3 )P-2 and the dicarbonyl Mn(CO)(2)P-3 fragments with NEt3 affords the pentac oordinate dicarbonyl aryldiazenido Mn(ArN2)(CO)(2)P-2 and [Mn(CO)(2)P-2](2) (mu -N2Ar-ArN2) derivatives. Instead, the aryldiazene bonded to the monocar bonyl fragment Mn(CO)P-4 is unreactive towards base and does not give aryld iazenido species. Hydrazine complexes [Mn(RNHNH2)(CO)(n)P5-n]BPh4 [R = H, C H3 or C6H5; P = P(OMe)(3), P(OEt)(3) or P(OPh)(3); n = 1, 2 or 3] were prep ared by reacting hydride species MnH(CO)(n)P5-n first with Bronsted acid (H BF, or CF,SO,PI) and then with an excess of the appropriate hydrazine. The binuclear complex [{Mn(CO)(3)[P(PEt)(3)](2)}(2)(mu -NH2NH2)](BPh4)(2) was a lso prepared. Oxidation reactions of phenylhydrazine cations [Mn(C6H5NHNH2) (CO)(n)P5-n](+) with Pb(OAc)(4) at -40 degreesC give the phenyldiazene [Mn( C6H5N=NH)(CO)(n)P5-n](+) derivatives, whereas the oxidation of methylhydraz ine [Mn(CH3NHNH2)(CO)(n)P5-n](+) complexes allows the synthesis of the firs t methyldiazene [Mn(CH3N=NH)(CO){P(OMe)(3)}(4)]BPh4 derivative of manganese . (C) 2001 Elsevier Science B.V. All rights reserved.