Rhenium chemistry of pyridyldiazoles : oxygen atom transfer, oxidation, substitution and twin isomerization involving oxo, phosphine oxide and phosphine coordination

Department of Inorganic Chemistry, Indian Association for the Cultivation of Science, Kolkata-700 032, India E-mail : icac@mahendra.iacs.res.in Fax : 91-33-24732805 Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore-560 064, India Manuscript received 27 June 2006, accepted 28 June 2006 The pyridyldiazoles (L) used are 2,5-bis(l-pyridyl)-1,3,4-oxadiazole and 2,5-bis(2-pyridyl)-1,3,4-thiadiazole. The oxygen atom transfer reaction of [Re0Cl3(L)] with PPh2R (R = Ph, Me) and Ph2P(CH1l2PPh2 (PxP, x = 1-4) has afforded meridional [Re(OPPh2R)Cl3(L)] and [Re(OPxP)Cl3(L)] respectively. These (R = Ph, x = 1) are oxidised by HNO3 yielding [Re(OPPh3)Cl3(L)]ReO4 and [Re(OP1P)Cl3(L)]ReO4. Treatment of [Re(OPPhzR)Cll(L)] with PPh2R has furnished facial [Re(PPh2R)Cl3(L)]. The [Re(OPxP)Cl3(L)] species undergo spontaneous twin isomerization in solution leading to [Re(PxPO)Cl3(L)]. All compounds have been characterized with the help of spectral and electrochemical data. The X-ray structurr or a [Re(OPPh3)Cl3(L)]ReO4 complex is reported. The rates and activation parameters of oxygen atom transfer and twin isomerization reactions have been determined and reaction models proposed