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

The potentially bidentate ligand diphenyl(2-pyridyl)phosphine (PPh2py) reacted with (NEt4)2[MIX3(CO)3] complexes (M=Re, Tc; X=Cl, Br) to give (NEt4)[MIX2(CO)3(PPh2py-P)] or [MIX(CO)3(PPh2py-P)2] depending on the amount of the ligand used. The reaction with (NBu4)[TcVINCl4] yielded [TcVNCl2(PPh2py-P)2] whereas from the reaction with (NBu4)[ReOCl4] the complexes [ReVOCl3(PPh2py-P,N)], [ReVOCl3(OPPh2py-O,N)], [ReIVCl4(OPPh2py-O,N) and [ReIVCl3(OH)(OPPh2py-O,N)] have been isolated. Reduction of the metal center occurs using an excess of PPh2py 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 [TcVNCl2(PPh2py-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 “O2−”) in [ReOCl3(PPh2py-P,N)] whereas equatorial co-ordination is found in [ReOCl3(OPPh2py-O,N)].