Reactions of cyclonickelated complexes with hydroxylamines and TEMPO˙: isolation of new TEMPOH adducts of Ni(II) and their reactivities with nucleophiles and oxidants.

This contribution describes a study on the reactivities of the complexes [{κP,κC-(i-Pr)PO-Ar}Ni(μ-Br)], 1a-d (Ar: CH, a; 3-Cl-CH, b; 3-OMe-CH, c; 4-OMe-napthalenyl, d), with hydroxylamines in the presence of TEMPO˙ (TEMPO˙ = (2,2,6,6-tetramethylpiperidinyl-1-yl)oxyl). The results of this study showed that treating 1a-d with a mixture of EtNOH and TEMPO˙ did not afford the desired oxidation-induced functionalization of the Ni-aryl moiety in 1a-d, giving instead the corresponding κO-TEMPOH adducts [{κP,κC-(i-Pr)PO-Ar}Ni(Br)(κO-TEMPOH)], 3a-d (TEMPOH = -hydroxy-2,2,6,6-tetramethylpiperidine). The TEMPOH moiety in these zwitterionic compounds 3 can be displaced by a large excess of acetonitrile (MeCN), 10 equiv.

Reactivities of cyclonickellated complexes with hydroxylamines: formation of κ-hydroxylamine and κ-imine adducts and a κ, κ-aminoxide derivative.

This report discusses the reactivities of hydroxylamines with a family of nickellacyclic complexes prepared by C-H nickellation of aryl phosphinites. Treating the dimeric complexes κ,κ-{2-OPR,4-R'-CH}Ni(μ-Br) (R = i-Pr; R' = H, Cl, OMe, NMe) or their monomeric acetonitrile adducts κ,κ-{2-OPR,4-R'-CH}Ni(Br)(NCMe) with hydroxylamines showed three types of reactivities depending on the Ni complex, the reaction solvent, and the substrate used: (1) the benzyl-protected substrate PhCHONH gave simple N-bound adducts with all Ni complexes; (2) the parent Ni dimer (R' = H) reacted with EtNOH and (PhCH)NOH in CHCl to give, respectively, the zwitterionic amine oxide κ,κ-{2-OPR-CH}Ni(κ-ONHEt)Br and the bidentate aminoxide (i-RPOPh)Ni{κ,κ-ON(CHPh)}Br; (3) the analogous reaction of substituted Ni complexes (R' = Cl, OMe, NMe) with hydroxylamines in acetonitrile gave adducts of imines derived from dehydration of EtNOH and (PhCH)NOH. The latter reactivity proceeds optimally in acetonitrile, but it also occurs to a lesser extent in CD if the reaction is allowed to go for more than 24 h.

Improvement of the Photophysical Performance of Platinum-Cyclometalated Complexes in Halogen-Bonded Adducts.

Three groups of luminescent platinum complexes [Pt(C^N)(L)(Y)] [C^N=benzothienyl-pyridine (1), bezofuryl-pyridine (2), phenyl-pyridine (3); L/Y=DMSO/Cl (a), PPh /Cl (b), PPh /CN (c)] have been probed as halogen-bond (XB) acceptors towards iodofluorobenzenes (IC F and I C F ). Compounds 1 a and 2 a (L/Y=DMSO/Cl) afford the adducts 1 a⋅⋅⋅I C F and 2 a⋅⋅⋅I C F , which feature I⋅⋅⋅S /I⋅⋅⋅π and I⋅⋅⋅O /I⋅⋅⋅Cl short contacts, respectively. The phosphane-cyanide derivatives 1 c and 2 c (L/Y=PPh /CN) co-crystallise with both IC F and I C F .