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Cp₂Ti(II) Mediated Rearrangement of Cyclopropyl Imines.

ABSTRACT: Ti-catalyzed oxidative alkyne carboamination with alkenes and azo compounds can yield either α,β-unsaturated imines or cyclopropyl imines through a common azatitanacyclohexene intermediate. Herein, we report the synthesis of a model azatitanacyclohexene complex (3) through the ring-opening of a cyclopropyl imine with Cp₂Ti(BTMSA) (BTMSA = bis(trimethylsilyl)acetylene). 3 readily undergoes thermal or reductant-catalyzed ring contraction to an azatitanacyclopentene (4), analogous to the proposed mechanism for forming α,β-unsaturated imines in the catalytic reaction. A cyclopropyl imine or an α,β-unsaturated imine could be liberated via the oxidation of 3 or 4 with azobenzene, respectively, further implicating the role of these metallacycles in the Ti-catalyzed carboamination reaction.

SUBMITTER: Kim J

PROVIDER: S-EPMC10619969 | biostudies-literature | 2023 Jun

REPOSITORIES: biostudies-literature

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Cp2Ti(II) Mediated Rearrangement of Cyclopropyl Imines.

Kim Jaekwan J Egger Dominic T DT Frye Connor W CW Beaumier Evan P EP Tonks Ian A IA

Organometallics 20230315 12

Ti-catalyzed oxidative alkyne carboamination with alkenes and azo compounds can yield either α,β-unsaturated imines or cyclopropyl imines through a common azatitanacyclohexene intermediate. Herein, we report the synthesis of a model azatitanacyclohexene complex (3) through the ring-opening of a cyclopropyl imine with Cp2Ti(BTMSA) (BTMSA = bis(trimethylsilyl)acetylene). 3 readily undergoes thermal or reductant-catalyzed ring contraction to an azatitanacyclopentene (4</ ...[more]

PMID: 37915831

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Project description:Neutral {CpFeII(CO)2[SnII(Pc•3-)]} {Cp is cyclopentadienyl (1, 2) or Cp* is pentamethylcyclopentadienyl (3); Pc: phthalocyanine}, {Cp*FeII(CO)2[SnII(Nc•3-)]} (4, Nc: naphthalocyanine), and {CpFeII(CO)2[SnII(TPP•3-)]} (5, TPP: tetraphenylporphyrin) complexes in which CpFeII(CO)2 fragments (Cp: Cp or Cp*) are coordinated to SnII(macrocycle•3-) have been obtained. The product complexes were obtained at the reaction of charge transfer from CpFeI(CO)2 (Cp: Cp or Cp*) to [SnII(macrocycle2-)] to form the diamagnetic FeII and paramagnetic radical trianionic macrocycles. As a result, these formally neutral complexes contain S = 1/2 spins delocalized over the macrocycles. This provides alternation of the C-Nimine or C-Cmeso bonds in the macrocycles, the appearance of new bands in the near-infrared spectra of the complexes, and blue shift of both Soret and Q-bands. The {CpFeII(CO)2SnII(macrocycle•3-)} units (Cp: Cp or Cp*, macrocycle: Pc or Nc) form closely packed π-stacking dimers in 1 and 3 or one-dimensional chains in 2 and 4 with effective π-π interaction between the macrocycles. Such packing allows strong antiferromagnetic coupling between S = 1/2 spins. Magnetic interaction can be described well by the Heisenberg model for the isolated dimers in 1 and 3 with exchange interaction J/k B = -78 and -85 K, respectively. Magnetic behavior of 2 and 4 is described well by the model that includes contributions from an antiferromagnetically coupled S = 1/2 dimer (J intra) and a Heisenberg S = 1/2 chain with alternating antiferromagnetic spin exchange between the neighbors (J inter). Compound 2 demonstrates large intradimer interaction of J intra/k B = -54 K and essentially weaker interdimer exchange interactions of J inter/k B = -6 K, whereas compound 4 shows strong magnetic coupling of spins within the dimers (J intra/k B = -170 K) as well as between the dimers (J inter/k B = -40 K). Compound {CpFeII(CO)2[SnII(TPP•3-)]} (5) shows no π-π interactions between the porphyrin macrocycles, and magnetic coupling is weak in this case (Weiss temperature is -5 K). Preparation of a similar complex with indium(III) chloride phthalocyanine yields {CpFe(CO)2[In(Pc2-)]} (6). In this complex, indium(III) atoms are reduced instead of the phthalocyanine macrocycles that explains electron paramagnetic resonance silence of 6 in the 4-295 K range.

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Cp₂Ti(II) Mediated Rearrangement of Cyclopropyl Imines.

Publications

Cp<sub>2</sub>Ti(II) Mediated Rearrangement of Cyclopropyl Imines.

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