THE SYNTHESIS AND CHARACTERIZATION OF A TECHNETIUM NITROSYL COMPLEX WITH CIS-(2-PYRIDYL,DIPHENYLPHOSPHINE) COLIGANDS - THE X-RAY CRYSTAL-STRUCTURE OF [TCCL2(NO)(PYPPH(2)-P,N)(PYPPH(2)-P)]

The reaction of the Tc(II) nitrosyl complex (Bu4N)[Tc(NO)Cl-4] with ex cess pyPPh(2) in refluxing MeOH gives the bis-pyridyl-diphenylphosphin e complex [TcCl2(NO)(pyPPh(2)-P,N)(pyPPh(2)-P)]. The IR spectrum of th e crystalline product shows a medium intensity band at 1092 cm(-1) and a very strong band at 1732 cm(-1) which is assigned to nu(Tc=N) from the nitrosyl core. The FAB(+) mass spectrum shows the protonated paren t ion of 725 m/z and the peak associated with the loss of a chloride l igand from the parent ion of 690 m/z. The H-1 NMR spectrum of the diam agnetic Tc(I) complex shows an extended series of multiplets in the ar yl 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 o f these phosphine ligands coordinated in a bidentate manner. The Tc-N bond length of 1.743(5) Angstrom is consistent with the multiple bondi ng expected for the linearly bonded nitrosyl ligand. The Tc-N-O bond a ngle of 177.2(5)degrees reflects the sp hybridization of the nitrosyl- nitrogen atom. The Tc-P bonds are 2.400(2) and 2.405(2) Angstrom, whic h are unexceptional, as are the Tc-Cl bonds of 2.447(2) and 2.441(2) A ngstrom. The coordination geometry of this complex is best described a s a very distorted octahedron. The P-Tc-N bond angle of the chelated p yridyl phosphine ligand is 66.1(1)degrees, which reflects the very sma ll bite angle imposed by the four-membered chelate ring of this phosph ine. This is compensated for by a large P-Tc-P angle of 107.82(5)degre es, imposed by the cis-phosphine coordination of these bulky tri-aryl phosphine ligands. Crystal data for C34.5H29Cl3N3OP2Tc: triclinic spac e group <P(1)over bar>, a=9.8440(3), b=13.4854(5), c=14.2401(5) Angstr om, alpha=106.406(1), beta=96.013(1), gamma=92.792(1)degrees, V=1797.3 5(11) Angstrom(3), with D-calc=1.419 g cm(-3). Structure solution base d on 5018 observed reflections converged at R=5.28%, for (1>2 sigma(I) ); GOF=1.73. (C) 1998 Elsevier Science S.A.