The substitution chemistry of a useful new synthon with neutral donor ligands. The reactions of [TcCl 3(NNPh 2)(PPh 3) 2] with phosphine ligands. The X-ray crystal structures of [TcCl 2(NNPh 2)(PMe 2Ph) 3][PF 6], [TcCl(NNPh 2)(dppe) 2][PF 6] 2 and [TcCl 2(NNPh 2)(TRIPHOS)][BPh 4

Abstract

The reaction of (Bu 4N)[TcOCl 4] with 1,1-diphenylhydrazine .HCl and PPh 3 in refluxing MeOH yields the neutral, Tc(III) isodiazene complex [TcCl 3(NNPh 2)(PPh 3) 2]. The reaction of this complex with PMe 2Ph in MeOH yields the cationic complex [TcCl 2(NNPh 2)(PMe 2Ph) 3] + which is isolated as the hexafluorophosphate salt. The X-ray structure of this complex shows a meridional arrangement of phosphine ligands with the diphenylisodiazene ligand and a chloride in the axial sites. The Tc–N(1) bond length is 1.741(3) Å, while N(1)–N(2) is 1.287(4) Å and the Tc–N(1)–N(2) bond angle is 176.4(3)°, which reflects the multiple bonding through out the zwitterionic isodiazene moiety. The distorted octahedral geometry results from the steric congestion associated with the three phosphine ligands in the equatorial plane. In the reaction of [TcCl 3(NNPh 2)(PPh 3) 2] with a three molar excess of dppe, {dppe=1,2 bis(diphenylphosphino)ethane} the dicationic isodiazene complex [TcCl(NNPh 2)(dppe) 2] 2+ is isolated as the bis hexafluorophosphate salt. The X-ray structure of this dication shows an equatorial arrangement of phosphine ligands with the isodiazene ligand and chloride in the axial positions. The Tc–N(1) bond length is 1.758(7) Å and the N(1)–N(2) bond length is 1.312(9) Å again reflecting the multiple bonding throughout the M–N–N framework. The Tc–N(1)–N(2) bond angle is 179.7(9)° which is indicative of sp 2 hybridization on the β-nitrogen atom. The reaction of [TcCl 3(NNPh 2)(PPh 3) 2] with TRIPHOS {TRIPHOS=bis(2-diphenylphosphinoethyl)phenylphosphine} yields the cationic product, structurally analogous to the Tris–PMe 2Ph cation described above, [TcCl 3(NNPh 2)(TRIPHOS)] +, which is isolated as the tetraphenylborate salt. The bonding constraints put on the coordination geometry by the tridentate ligand cause significant distortion from an ideal octahedron. The Tc–N(1) bond length is 1.752(3) Å and the N(1)–N(2) bond length is 1.286(4) Å, and the Tc–N(1)–N(2) bond angle is 176.2(3)°, again reflecting the multiple bonding throughout the isodiazene M–N–N linkage and the sp 2 hybridization on the β-nitrogen atom.