Ferromagnetic interactions and polymorphism in radical-substituted gold phosphine complexes

Abstract

A series of gold() complexes containing aminoxyl radical-substituted phosphine ligands has been prepared. Complexes chloro{2-[(p-diphenylphosphino)phenyl]-4,4,5,5-tetramethylimidazoline 1-oxyl 3-oxide}gold and [tertbutyl(p-diphenylphosphinophenyl)aminoxyl]chlorogold were prepared by reaction of the free radical phosphine with AuClؒTHT (THT = tetrahydrothiophene) or by complexation of the radical precursor of the ligands to AuClؒTHT followed by oxidation of the resulting gold complex. The first complex forms two distinct polymorphic crystal phases: in CH 2 Cl 2 -Et 2 O 2 crystallizes as green plates (α) in the triclinic space group P1 ¯ and in CH 2 Cl 2 -hexanes as blue prisms (β) in the monoclinic space group P2 1 /a. The crystal structures of both polymorphs and that of the complex 4 have been solved. The different solid-state arrangement of the molecules in the two polymorphic forms yields different magnetic behaviour; both exhibit intermolecular antiferromagnetic interactions but α exhibits a maximum in χ m at 3.5 K while β shows no maximum. The favourable overlap of aminoxyl N-oxide groups in α causes this stronger interaction, which was modelled as a 1-D antiferromagnetic Heisenberg chain to give J = Ϫ3.2 cm Ϫ1 . The magnetic behaviour of the complex 4 was investigated down to 50 mK, showing dominant intermolecular ferromagnetic interactions but long range antiferromagnetic ordering at very low temperatures.

Stable Organopalladium(II) and Organoruthenium(II) Complexes with Spin-Labeled Phosphine Ligands

“…Note that the radical-substituted phosphine 2 cannot be isolated in the solid state in the absence of a coordinating metal . Phosphine 2 has also been stabilized by coordination to a gold(I) center . The Pd−Cl and Pd−P bond lengths of 2.2865(7) and 2.3298(6) Å, respectively (Table ), are comparable to those found in the parent compound PdCl 2 (PPh 3 ) 2 , illustrating that the addition of a remote radical group does not significantly alter the coordination sphere of the metal.…”

Spin Transfer and Magnetic Interaction via Phosphorus in Nitronyl Nitroxide Radical-Substituted Triphenylphosphine Derivatives

“…Two of such monosubstituted phosphine derivatives have already been briefly described . These were shown to be able to coordinate to a metal center by means of either the phosphorus atom − or the aminoxyl unit. , The presence of two phenyl groups available for further substitution prompted us to envisage the corresponding polyradical derivatives. Herein, we report on the synthesis and magnetic characteristics of a series of mono-, di-, and tri- p -nitronyl nitroxide triphenylphosphine derivatives.…”

Synthesis, Structure, and Magnetism of Mono- and Binuclear Manganese(II) Compounds of Nitronyl Nitroxide Substituted Phosphine Oxides

“…In response, we have recently described the synthesis of novel phosphine , and phosphine oxide substituted nitronyl nitroxides. The phosphine derivatives were shown to coordinate selectively via the P atom to soft, low-valent metal centers without alteration of the radical moiety. , Here we focus on the triphenylphosphine oxide ligands. As a useful comparison to the pyridine systems, the coordination chemistry of both o - and p -nitronyl nitroxide substituted triphenylphosphine oxides with Mn(hfac) 2 is hereby presented and reveals differences in both structure and magnetic properties.…”