Tetradentate bis-phosphine ligands (P(2)N(2) and P(2)S(2)) and their Rh(III), Ni(II) and (105)Rh complexes: X-ray crystal structures of trans-[RhCl(2)(L2)]PF(6), [Ni(L2)](PF(6))(2) and μ-O(2)SO(2)-[Ni(L5)](2)(PF(6))(2)

Abstract

Introduction: Tetradentate acyclic and macrocyclic diphosphine ligands (P(2)N(2) and P(2)S(2)) have been synthesized and characterized as potential chelates for Rh(III).

Methods: The coordination complexes [RhCl(2)(L1)]Cl, trans-[RhCl(2)(L2)]PF(6), [Ni(L2)](PF(6))(2), [Ni(L3)](PF(6))(2), [RhCl(2)(L4)]PF(6) and [RhCl(2)(L5)]PF(6) have been synthesized and characterized. In addition, radiochemistry studies of the (105)Rh complexes with the ligands N,N'-bis[2-(diphenylphosphino)phenyl]-1,3-diaminopropane (L1), 4,8-diphenyl-1,11-diaza-4,8-diphosphaundecane (L2), 5,9-diphenyl-5,9-diphospha-2,12-dithiatridecane (L3) and 1,4,8,11-tetraphenyl-4,8-diphospha-1,11-dithiaundecane (L4) are reported, including normal mouse biodistributions of (105)Rh-L2.

Results: trans-[RhCl(2)(L2)]PF(6) crystallized in the monoclinic space group P2(1)/c with a = 9.9353(5) Å, b = 9.0929(5) Å, c = 28.689(1) Å, β = 93.1400(10) deg, Z = 4, R = 0.037 and R(w) = 0.053. [Ni(L2)](PF(6))(2) crystallized in the monoclinic space group P2(1)/c with a = 11.9665(6) Å, b = 14.8903(7) Å, c = 31.148(1) Å, β = 91.587(1) deg, Z = 8, R = 0.056 and R(w) = 0.083. μ-O(2)SO(2)-[Ni(L5)](2)(PF(6))(2), an unusual sulfate-bridged Ni(II) dimer, crystallized in the triclinic space group P1 bar with a = 15.179(2) Å, b = 15.514(2) Å, c = 16.128(2) Å, α = 105.280(7) deg, β = 113.074(6) deg, γ = 101.657(8) deg, Z = 2, R = 0.050 and R(w) = 0.072.

Conclusions: Phosphine-containing ligands allowed for lower temperatures and lower ethanol concentrations in the formulations for (105)Rh(L) complexation, but at the expense of higher ligand concentrations.