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

Abstract

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 [ReOCl 3 (L)] with PPh 2 R (R = Ph, Me) and Ph 2 P(CH 2 ) x PPh 2 (PxP, x = 1-4) has afforded meridional [Re(OPPh 2 R)Cl 3 (L)] and [Re(OPxP)Cl 3 (L)] respectively. These (R = Ph, x = 1) are oxidised by HNO 3 yielding [Re(OPPh 3 )Cl 3 (L)]Re0 4 and [Re(OPlP)Cl 3 (L)]Re0 4 . Treatment of [Re(OPPh 2 R)Cl 3 (L)] with PPh 2 R has furnished facial [Re(PPh 2 R)Cl 3 (L)]. The [Re(OPxP)Cl 3 (L)] species undergo spontaneous twin isomerization in solution leading to [Re(PxPO)Cl 3 (L)]. All compounds have been characterized with the help of spectral and electrochemical data. The X-ray structure of a [Re(OPPh 3 )Cl 3 (L)]ReO 4 complex is reported. The rates and activation parameters of oxygen atom transfer and twin isomerization reactions have been determined and reaction models proposed.