Ligand substitution reactions of [Tc(NO)Cl-2(PPh(3))(2)(NCCH3)] with pi-acceptor ligands

The reaction of [Tc(NO)Cl-2(PPh(3))(2)(NCCH3)] with carbon monoxide in chloroform yields [Tc(NO)Cl-2(PPh(3))(2)(CO)], in which the weakly coordinated acetonitrile ligand has been replaced by the carbon monoxide. The H-1 NMR spectrum of this complex displays equivalent triphenylphosphine ligands, indicating mutually trans coordination geometry. The FAB(+) mass spectrum of this complex contains the hydrated parent ion of 770 m/z plus various fragments associated with the loss of the chloride and carbon monoxide ligands. The reaction of [Tc(NO)Cl-2(PPh(3))(2)(NCCH3)] with excess tert-butylisonitrile in CH2Cl2 at room temperature yields [Tc(NO) Cl-2(PPh(3))(2)(CNtBu)], in which a single isonitrile ligand has replaced the coordinated acetonitrile. The IR spectrum of this complex displays the absorption from nu(N=O) at 1737 cm(-1). The FAB(+) mass spectrum of the species displays the parent ion of 806 m/z which corresponds to [Tc(NO)Cl-2(PPh(3))(2)(CNtBu)](+). The reaction of [Tc(NO)Cl-2(PPh(3))(2)(NCCH3)] with excess tert-butylisonitrile in refluxing CH2Cl2 yields [Tc(NO)Cl-2(PPh(3)) (CNtBu)(2)], in which two isonitrile ligands have replaced one of the triphenylphosphines and the coordinated acetonitrile. The IR spectrum of this complex displays the absorption from nu(N=O) at 1736 cm(-1). The FAB(+) mass spectrum of the species displays the parent ion of 627 m/z which corresponds to [Tc(NO)Cl-2(PPh(3)) (CNtBu)(2)](+). The reaction of [Tc(NO)Cl-2(PPh(3))(2)(NCCH3)] with excess tert-butylisonitrile in refluxing benzene yields [Tc(NO)Cl-2(CNtBu)(3)], in which three isonitrile ligands have replaced both of the phosphine ligands and the coordinated acetonitrile. The IR spectrum of this complex displays the absorptions from nu(N=O) at 1751 and 1725 cm(-1). The FAB (+) mass spectrum of the species displays the parent ion of 447 m/z which corresponds to [Tc(NO)Cl-2(CNtBu)(3)](+).