Syntheses and characterization of amino and amido–imido technetium(V) and rhenium(V) complexes with (o-aminophenyl)diphenylphosphine-N,P. Crystal structures of [TcNCl{PPh2(C6H4NH2-2)}2]Cl·MeCN and [Re{PPh2(C6H4N-2)}Cl2{PPh2(C6H4NH-2}]

Abstract

Reactions of [NBu₄][MOCl₄](M = Tc or Re) or [ReOX₂(OEt)(PPh₃)₂](X = Cl, Br or I) with the bidentate ligand (o-aminophenyl)diphenylphosphine (H₂L) under controlled reaction conditions gave neutral imido-metal(V) complexes of the type [M(L)Cl₂(HL)]; in particular, the neutral [Re(L)Cl₂(HL)] complex 3, the crystal structure of which has been determined contains HL^– and L^2– ligands ‘twisted’ relative to each other by 101.3°, with the imido group bonded trans to a Cl atom, while the other chloro is equatorial. Important molecular parameters are: Re–N(2) 1.780(7), Re–N(1) 1.973(7), Re–Cl(1) 2.404(2), Re–Cl(2) 2.384(2), Re–P(1) 2.438(2) and Re–P(2) 2.492(2)Å. The bent configuration of the imido core [Re–N(2)–C(12) 137.1(5)°] enforced by the intrinsic ligand geometry, along with the v(ReN–) stretch at 971 cm^–1, indicates the peculiarity of this nitrene core. The severe distortion from octahedral geometry is also represented by the Cl(2)–Re–N(2) angle of 157.0(2)° and by the ‘bite’ angles of 79.5(2) and 75.2(2)° for the HL^– and L^2– ligand, respectively. Substitution reactions on [NBu₄][TcNCl₄] and [MNCl₂(PPh₃)₂](M = Re or Tc) with H₂L give cationic nitrido–metal(V) complexes of the type [MNCl(H₂L)₂]Cl, in which the co-ordination of two bidentate H₂L chelates occurs with a mutual cis-P configuration and with the amino-N on the equatorial plane of a distorted octahedron; the site trans to the MN unit is occupied by a Cl ligand. The crystal structure of [TcNCl(H₂L)₂]Cl·MeCN 2 has also been determined. Relevant molecular parameters are: Tc–N(3) 1.627(3), Tc–N(1) 2.178(3), Tc–N(2) 2.205(4), Tc–Cl(1) 2.593(2), Tc–P(1) 2.427(2), Tc–P(2) 2.439(1)Å, N(3)–Tc–Cl(1) 179.5(1)°.