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

The pyridyldiazoles (L) used are 2,5-bis(2-pyridyl)-1,3,4-oxadiazole and 2,5-bis(2-pyridyl)-1,3,4-thiadiazole. The oxygen atom transfer reaction of [ReOCl3(L)] with PPh2R (R = Ph, Me) and Ph2P(CH2)xPPh2 (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)]Re04 and [Re(OPlP)Cl3(L)]Re04. Treatment of [Re(OPPh2R)Cl3(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 structure of 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