The substitution chemistry of a useful new synthon with neutral donor ligands. Part 2. The reactions of [TcCl 3(NNPh 2)(PPh 3) 2] with neutral nitrogen and carbon ligands. The X-ray structure of [TcCl 2(NNPh 2)(bipy)(PPh 3)][PF 6], [TcCl 2(NNPh 2)(terpy)][BF 4] and [TcCl(NNPh 2)(CNCH 2Ph) 2(PPh 3) 2][PF 6

Abstract

The reaction of [TcCl 3(NNPh 2)(PPh 3) 2] complex with 2,2′ bipyridine in MeOH yields [TcCl(OMe)(NNPh 2)(PPh 3)(bipy)] + which is isolated as the (BPh 4) − salt. The X-ray structure shows the diphenylisodiazene ligand and methoxide in the axial sites, with the bipyridyl ligand, triphenylphosphine and chloride in the equatorial plane. The methoxide ligand is introduced from the reaction solvent. The TcN(1) bond length is 1.755(3) Å, while N(1)N(2) is 1.298(4) Å and the TcN(1)N(2) bond angle is 171.4(2)°, which reflects the multiple bonding through out the zwitterionic isodiazene moiety. The distorted octahedral geometry results from the small bite angle associated with the bipyridine ligand which is 75.98(10)°. In the reaction of [TcCl 3(NNPh 2)(PPh 3) 2] with terpyridine in MeOH, [TcCl 2(NNPh 2)(terpy)] + is isolated as the (BF 4) − salt. The X-ray structure shows the isodiazene ligand and terpyridine ligands in the equatorial plane and the chloride ligands in a mutually trans orientation. The TcN(1) bond length is 1.739(3) Å and the N(1)N(2) bond length is 1.301(4) Å again reflecting the multiple bonding throughout the metal–nitrogen–nitrogen framework. The TcN(1)N(2) bond angle is 174.3(3)° which, along with the N(1)N(2)C bond angles of 120.3(3)° and 115.8(3)°, are indicative of sp 2 hybridization on the β-nitrogen atom. The reaction of [TcCl 3(NNPh 2)(PPh 3) 2] with RNC {where R=CH 2Ph} yields [TcCl(NNPh 2)(PPh 3) 2(CNR) 2] +, which is isolated as the (PF 6) − salt. The reaction with isonitrile results in a one electron reduction of the technetium synthon, resulting in the clean isolation of the Tc(II) product. The TcN(1) bond length is 1.832(5) Å and the N(1)N(2) bond length is 1.287(6) Å, and the TcN(1)N(2) bond angle is 157.8(4)°. This new structural conformation approaches the ‘bent’ conformation of the isodiazene MNN linkage with sp 2 hybridization on both the α- and β-nitrogen atoms. There is no sign of an NH stretch in the IR and no evidence of a proton in the X-ray structure, so the addition of NH 4PF 6 as counter ion did not protonate the isodiazene ligand's α-nitrogen.