Rhenium and technetium complexes with diphenyl(2-pyridyl)phosphine

Abstract

The potentially bidentate ligand diphenyl(2-pyridyl)phosphine (PPh 2py) reacted with (NEt 4) 2[M IX 3(CO) 3] complexes (M=Re, Tc; X=Cl, Br) to give (NEt 4)[M IX 2(CO) 3(PPh 2py-P)] or [M IX(CO) 3(PPh 2py-P) 2] depending on the amount of the ligand used. The reaction with (NBu 4)[Tc VINCl 4] yielded [Tc VNCl 2(PPh 2py-P) 2] whereas from the reaction with (NBu 4)[ReOCl 4] the complexes [Re VOCl 3(PPh 2py-P,N)], [Re VOCl 3(OPPh 2py-O,N)], [Re IVCl 4(OPPh 2py-O,N) and [Re IVCl 3(OH)(OPPh 2py-O,N)] have been isolated. Reduction of the metal center occurs using an excess of PPh 2py and heating of the reaction mixtures under reflux. The products have been characterised spectroscopically and by X-ray structure analysis. Monodentate co-ordination via phosphorus has been found for the rhenium(I) carbonyl complexes and [Tc VNCl 2(PPh 2py-P) 2]. In the latter compound a trigonal-bipyramidal coordination sphere is formed with the phosphines as axial ligands (bond angle P–Tc–P: 161.69(3)°). The chelated complexes show small N–Re–P and N–Re–O bite angles of 63.6° and 77.7–82.2° due to the four-membered or five-membered chelate rings. The pyridine nitrogen occupies the axial position ( trans to “O 2−”) in [ReOCl 3(PPh 2py-P,N)] whereas equatorial co-ordination is found in [ReOCl 3(OPPh 2py-O,N)].