Steric and Electronic Control of the Spin State in Three-Fold Symmetric, Four-Coordinate Iron(II) Complexes

The three-fold symmetric, four-coordinate iron(II) phosphoraminimato complexes PhB(MesIm)3Fe− N=PRR′R″ (PRR′R″ = PMePh2, PMe2 Ph, PMe3, and PnPr3) undergo a thermally induced S = 0 to S = 2 spincrossover in fluid solution. Smaller phosphoraminimato ligands stabilize the low-spin state, and an excellent correlation is observed between the characteristic temperature of the spincrossover (T1/2) and the Tolman cone angle (θ)....

Tuning the Reactivity of TEMPO by Coordination to a Lewis Acid: Isolation and Reactivity of MCl₃(η¹‑TEMPO) (M = Fe, Al)

Addition of 2,2,6,6-tetramethylpiperidine-<i>N</i>-oxyl (TEMPO) to MCl₃ (M = Fe, Al) results in the formation of MCl₃(η¹-TEMPO) [M = Fe (<b>1</b>), Al (<b>2</b>)]. Both <b>1</b> and <b>2</b> oxidize alcohols to generate ketones or aldehydes along with the reduced complexes MCl₃(η¹-TEMPOH) [M = Fe (<b>3</b>), Al (<b>4</b>)]. Complexes <b>1</b>–<b>4</b> were fully characterized, including analysis by X-ray crystallography. Additionally, control experiments indicated that neither MCl₃ (M = Al, Fe) nor TEMPO are capable of effecting the oxidation of alcohols independently

Reaction of an Iron(IV) Nitrido Complex with Cyclohexadienes: Cycloaddition and Hydrogen-Atom Abstraction

The iron­(IV) nitrido complex PhB­(MesIm)₃FeN reacts with 1,3-cyclohexadiene to yield the iron­(II) pyrrolide complex PhB­(MesIm)₃Fe­(η⁵-C₄H₄N) in high yield. The mechanism of product formation is proposed to involve sequential [4 + 1] cycloaddition and retro Diels–Alder reactions. Surprisingly, reaction with 1,4-cyclohexadiene yields the same iron-containing product, albeit in substantially lower yield. The proposed reaction mechanism, supported by electronic structure calculations, involves hydrogen-atom abstraction from 1,4-cyclohexadiene to provide the cyclohexadienyl radical. This radical is an intermediate in substrate isomerization to 1,3-cyclohexadiene, leading to formation of the pyrrolide product

Steric and Electronic Control of the Spin State in Three-Fold Symmetric, Four-Coordinate Iron(II) Complexes

The three-fold symmetric, four-coordinate iron­(II) phosphoraminimato complexes PhB­(MesIm)₃Fe–NPRR′R″ (PRR′R″ = PMePh₂, PMe₂Ph, PMe₃, and PⁿPr₃) undergo a thermally induced <i>S</i> = 0 to <i>S</i> = 2 spin-crossover in fluid solution. Smaller phosphoraminimato ligands stabilize the low-spin state, and an excellent correlation is observed between the characteristic temperature of the spin-crossover (<i>T</i>_1/2) and the Tolman cone angle (θ). Complexes with <i>para</i>-substituted triaryl phosphoraminimato ligands (<i>p</i>-XC₆H₄)₃PN^– (X = H, Me and OMe) also undergo spin-crossover in solution. These isosteric phosphoraminimato ligands reveal that the low-spin state is stabilized by more strongly donating ligands. This control over the spin state provides important insights for modulating the magnetic properties of four-coordinate iron­(II) complexes

Reaction of a Polyphosphino Ruthenium(II) Acetate Complex with Grignard Reagents: Halogenation, Alkylation and β-Elimination

(PMe3)4Ru(H)OAc has been prepared from (PPh3)3Ru(H)OAc via phosphine exchange followed by solvent partitioning between acetonitrile and pentane. Complexes of the type (PMe3)4Ru(H)R (R = Et, nPr, nBu, iBu, H) have been synthesized through reaction with the corresponding Grignard reagents, RMgCl, and were found to be moderately stable provided the alkyl group is primary. Treatment with bulkier alkylmagnesium chlorides led instead to the dihydrido complex (PMe3)4RuH2. In some cases, the reaction was complicated by transfer of halide from the Grignard reagent to form, for example, (PMe3)4Ru(H)Cl