The synthesis and characterization of a technetium nitrosyl complex with cis-{2-pyridyl,diphenylphosphine} coligands. The X-ray crystal structure of [TcCL 2(NO) (pyPPh 2- P, N) (pyPPh 2- P)

Abstract

The reaction of the Tc(II) nitrosyl complex (Bu 4N) [Tc(NO)Cl 4] with excess pyPPh 2 in refluxing MeOH gives the bis-pyridyl-diphenylphosphine complex [TcCl 2(NO)(pyPPh 2- P, N) (pyPPh 2- P)]. The IR spectrum of the crystalline product shows a medium intensity band at 1092 cm −1 and a very strong band at 1732 cm −1 which is assigned to v(Tc=N) from the nitrosyl core. The FAB(+) mass spectrum shows the protonated parent ion of 725 m/ z and the peak associated with the loss of a chloride ligand from the parent ion of 690 m/ z. The 1H NMR spectrum of the diamagnetic Tc(1) complex shows an extended series of multiples in the aryl region between 7.0 and 9.15 ppm. The X-ray crystal structure shows an unusual cis arrangement of these bulky phosphine ligands with one of these phosphine ligands coordinated in a bidentate manner. The Tc-N bond length of 1.743(5) Å is consistent with the multiple bonding expected for the linearly bonded nitrosyl ligand. The Tc-N-O bond angle of 177.2(5)° reflects the sp hybridization of the nitrosyl-nitrogen atom. The Tc-P bonds are 2.400(2) and 2.405(2) Å, which are unexceptional, as are the Tc-Cl bonds of 2.447(2) and 2.441(2) Å. The coordination geometry of this complex is best described as a very distorted octahedron. The P-Tc-N bond angle of the chelated pyridyl phosphine ligand is 66.1(1)°, which reflects the very small bite angle imposed by the four-membered chelate ring of this phosphine. This is compensated for by a large P-Tc-P angle of 107.82(5)°, imposed by the cis-phosphine coordination of these bulky tri-aryl phosphine ligands. Crystal data for C 34 5H 29 Cl 4 N 4 OP 3Tc: triclinic space group P1, a=9.8440(3), b=13.4854(5), c=14.2401(5) A ̊ , α=106.406(1), β=96.013(1), γ=92.792(1) 2 V=1797.35(11) A ̊ 3 , with D calc=1.419 g cm −3. Structure solution based on 5018 observed reflections converged at R=5.28%, for (1>2 σ(1)); GOF=1.73.