258826-16-3Relevant academic research and scientific papers
Identification of [M(II)(arene)2]2+ (M = V, Cr) as the key intermediate in the formation of V[TCNE](x)(·)ySolvent magnets and Cr[TCNE](x) (·) Solvent
Gordon, Douglas C.,Deakin, Laura,Arif, Atta M.,Miller, Joel S.
, p. 290 - 299 (2000)
To elucidate the mechanism of the reaction between V0(C6H6)2 and tetracyanoethylene (TCNE) that leads to the room-temperature magnet V[TCNE]](x)(·)yCH2Cl2 (x ~2; y ~ 1/2 ), reactions between bis(arene)- vanadium (arene = 1,3,5-trimethylbenzene, 1,3,5-tri-tert-butylbenzene) and its cations and TCNE and its anion were studied. The reaction of V°(arene)2 with TCNE yields magnets with critical temperatures ranging from 28 to 400 K. Products from the reaction of [V(I)(arene)2]+ with [TCNE](·)-) were not magnets; however, reaction of [V(I)(arene)2]+ with [TCNE](·)-) in the presence of TCNE forms a magnetically ordered material. The reaction of V0(1,3,5-C6H3Me3)2 with 2 equiv of one-electron oxidant [Fe(III)(C5H5)2]+, and subsequently with [TCNE](·)-, also leads to a magnetic material. The results of these investigations suggest that V0(arene)2 undergoes two one-electron oxidation reactions with TCNE to form sequentially [V(I)(arene)2]+ and '[V(II)(arene)2]2+', the latter being the key intermediate that reacts with [TCNE](·) - to produce the magnetic product. [V(I)(arene)2]+ has been isolated, whereas and '[V(II)(arene)2]2+' has not. The one-electron oxidation of V0[C6H3(t- Bu)3]2 with Ag-[BPh4] produces {V(I)[C6H3(t-Bu)3]2}+[BPh4]-. The stoichiometric reaction of V0[C6H3(t-Bu)3]2 with TCNE leads to paramagnetic {V(I)[1,3,5-C6H3(tBu)3]2}+[TCNE](·) -. {V(I)[C6H3(t- Bu)3]2}+[BPh4]- and {V(I)[1,3,5-C6H3-(tBu)3]2}+[TCNE](·) - have been structurally characterized. When [V(II)(NCMe)6]{B[3,5- C6H3(CF3)2]4}2 is reacted with [TCNE](·) -, a route that does not use bis(arene)vanadium complexes, a magnetic precipitate is also produced. As established earlier, the reaction of Cr0(arene)2 with TCNE forms nonmagnetically ordered [Cr(I)(arene)2](·)+-[TCNE](·) -. Reaction of lower oxidation potential Cr0Np2 (Np = naphthalene) with TCNE putatively forms '[Cr(II)Np2]2+' which reacts with [TCNE](·)- to form Cr[TCNE](x)·yS, which was isolated and, unexpectedly, does not magnetically order. Similar results are obtained when [Cr(II)(NCMe)4][BF4]2 or [Cr(II)(NCMe)6][B(3,5-C6H3(CF3)2)4]2 is reacted with [n-Bu4N][TCNE].
