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A Mechanistic Study on Reactions of Group 13 Diyls LM with Cp*SbX₂ : From Stibanyl Radicals to Antimony Hydrides.

ABSTRACT: Oxidative addition of Cp*SbX₂ (X=Cl, Br, I; Cp*=C₅ Me₅ ) to group 13 diyls LM (M=Al, Ga, In; L=HC[C(Me)N (Dip)]₂ , Dip=2,6-iPr₂ C₆ H₃ ) yields elemental antimony (M=Al) or the corresponding stibanylgallanes [L(X)Ga]Sb(X)Cp* (X=Br 1, I 2) and -indanes [L(X)In]Sb(X)Cp* (X=Cl 5, Br 6, I 7). 1 and 2 react with a second equivalent of LGa to eliminate decamethyl-1,1'-dihydrofulvalene (Cp*₂ ) and form stibanyl radicals [L(X)Ga]₂ Sb^. (X=Br 3, I 4), whereas analogous reactions of 5 and 6 with LIn selectively yield stibanes [L(X)In]₂ SbH (X=Cl 8, Br 9) by elimination of 1,2,3,4-tetramethylfulvene. The reactions are proposed to proceed via formation of [L(X)M]₂ SbCp* as reaction intermediate, which is supported by the isolation of [L(Cl)Ga]₂ SbCp (11, Cp=C₅ H₅ ). The reaction mechanism was further studied by computational calculations using two different models. The energy values for the Ga- and the In-substituted model systems showing methyl groups instead of the very bulky Dip units are very similar, and in both cases the same products are expected. Homolytic Sb-C bond cleavage yields van der Waals complexes from the as-formed radicals ([L(Cl)M]₂ Sb^. and Cp*^. ), which can be stabilized by hydrogen atom abstraction to give the corresponding hydrides, whereas the direct formation of Sb hydrides starting from [L(Cl)M]₂ SbCp* via concerted ?-H elimination is unlikely. The consideration of the bulky Dip units reveals that the amount of the steric overload in the intermediate I determines the product formation (radical vs. hydride).

SUBMITTER: Helling C

PROVIDER: S-EPMC7693246 | biostudies-literature | 2020 Oct

REPOSITORIES: biostudies-literature

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A Mechanistic Study on Reactions of Group 13 Diyls LM with Cp*SbX2 : From Stibanyl Radicals to Antimony Hydrides.

Helling Christoph C Wölper Christoph C Cutsail George E GE Haberhauer Gebhard G Schulz Stephan S

Chemistry (Weinheim an der Bergstrasse, Germany) 20200911 59

Oxidative addition of Cp*SbX2 (X=Cl, Br, I; Cp*=C5 Me5 ) to group 13 diyls LM (M=Al, Ga, In; L=HC[C(Me)N (Dip)]2 , Dip=2,6-iPr2 C6 H3 ) yields elemental antimony (M=Al) or the corresponding stibanylgallanes [L(X)Ga]Sb(X)Cp* (X=Br 1, I 2) and -indanes [L(X)In]Sb(X)Cp* (X=Cl 5, Br 6, I 7). 1 and 2 react with a second equivalent of LGa to eliminate decamethyl-1,1'-dihydrofulvalene (Cp*2 ) and form stibanyl radic ...[more]

PMID: 32428370

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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.

Dataset Information

A Mechanistic Study on Reactions of Group 13 Diyls LM with Cp*SbX₂ : From Stibanyl Radicals to Antimony Hydrides.

Publications

A Mechanistic Study on Reactions of Group 13 Diyls LM with Cp*SbX<sub>2</sub> : From Stibanyl Radicals to Antimony Hydrides.

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