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Coordination Chemistry of P₄ S₃ and P₄ Se₃ towards the Iron Fragments [Fe(Cp)(CO)₂ ]⁺ and [Fe(Cp)(PPh₃ )(CO)].

ABSTRACT: The complexes Ag(L)_n [WCA] (L=P₄ S₃ , P₄ Se₃ , As₄ S₃ , and As₄ S₄ ; [WCA]=[Al(OR^F )₄ ]^- and [F{Al(OR^F )₃ }₂ ]^- ; R^F =C(CF₃ )₃ ; WCA=weakly coordinating anion) were tested for their performance as ligand-transfer reagents to transfer the poorly soluble nortricyclane cages P₄ S₃ , P₄ Se₃ , and As₄ S₃ as well as realgar As₄ S₄ to different transition-metal fragments. As₄ S₄ and As₄ S₃ with the poorest solubility did not yield complexes. However, the more soluble silver-coordinated P₄ S₃ and P₄ Se₃ cages were transferred to the electron-poor Fp⁺ moiety ([CpFe(CO)₂ ]⁺ ). Thus, reaction of the silver salt in the presence of the ligand with Fp-Br yielded [Fp-P₄ S₃ ][Al(OR^F )₄ ] (1?a), [Fp-P₄ S₃ ][F(Al(OR^F )₃ )₂ ] (1?b), and [Fp-P₄ Se₃ ][Al(OR^F )₄ ] (2). Reactions with P₄ S₃ also yielded [FpPPh₃ -P₄ S₃ ][Al(OR^F )₄ ] (3), a complex with the more electron-rich monophosphine-substituted Fp⁺ analogue [FpPPh₃ ]⁺ ([CpFe(PPh₃ )(CO)]⁺ ). All complex salts were characterized by single-crystal XRD, NMR, Raman, and IR spectroscopy. Interestingly, they show characteristic blueshifts of the vibrational modes of the cage, as well as structural contractions of the cages upon coordination to the Fp/FpPPh₃ moieties, which oppose the typically observed cage expansions that lead to redshifts in the spectra. Structure, bonding, and thermodynamics were investigated by DFT calculations, which support the observed cage contractions. Its reason is assigned to ? and ? donation from the slightly P-P and P-E antibonding P₄ E₃ -cage HOMO (e symmetry) to the metal acceptor fragment.

SUBMITTER: Weis P

PROVIDER: S-EPMC6771638 | biostudies-literature | 2019 Sep

REPOSITORIES: biostudies-literature

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Coordination Chemistry of P4 S3 and P4 Se3 towards the Iron Fragments [Fe(Cp)(CO)2 ]+ and [Fe(Cp)(PPh3 )(CO)].

Weis Philippe P Riddlestone Ian M IM Scherer Harald H Krossing Ingo I

Chemistry (Weinheim an der Bergstrasse, Germany) 20190823 52

The complexes Ag(L)n [WCA] (L=P4 S3 , P4 Se3 , As4 S3 , and As4 S4 ; [WCA]=[Al(ORF )4 ]- and [F{Al(ORF )3 }2 ]- ; RF =C(CF3 )3 ; WCA=weakly coordinating anion) were tested for their performance as ligand-transfer reagents to transfer the poorly soluble nortricyclane cages P4 S<su ...[more]

PMID: 31287589

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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.

Project description:The mixed-valence triiron complexes [Fe3(CO)7-x (PPh3) x (μ-edt)2] (x = 0-2; edt = SCH2CH2S) and [Fe3(CO)5(κ2-diphosphine)(μ-edt)2] (diphosphine = dppv, dppe, dppb, dppn) have been prepared and structurally characterized. All adopt an anti arrangement of the dithiolate bridges, and PPh3 substitution occurs at the apical positions of the outer iron atoms, while the diphosphine complexes exist only in the dibasal form in both the solid state and solution. The carbonyl on the central iron atom is semibridging, and this leads to a rotated structure between the bridged diiron center. IR studies reveal that all complexes are inert to protonation by HBF4·Et2O, but addition of acid to the pentacarbonyl complexes results in one-electron oxidation to yield the moderately stable cations [Fe3(CO)5(PPh3)2(μ-edt)2]+ and [Fe3(CO)5(κ2-diphosphine)(μ-edt)2]+, species which also result upon oxidation by [Cp2Fe][PF6]. The electrochemistry of the formally Fe(I)-Fe(II)-Fe(I) complexes has been investigated. Each undergoes a quasi-reversible oxidation, the potential of which is sensitive to phosphine substitution, generally occurring between 0.15 and 0.50 V, although [Fe3(CO)5(PPh3)2(μ-edt)2] is oxidized at -0.05 V. Reduction of all complexes is irreversible and is again sensitive to phosphine substitution, varying between -1.47 V for [Fe3(CO)7(μ-edt)2] and around -1.7 V for phosphine-substituted complexes. In their one-electron-reduced states, all complexes are catalysts for the reduction of protons to hydrogen, the catalytic overpotential being increased upon successive phosphine substitution. In comparison to the diiron complex [Fe2(CO)6(μ-edt)], [Fe3(CO)7(μ-edt)2] catalyzes proton reduction at 0.36 V less negative potentials. Electronic structure calculations have been carried out in order to fully elucidate the nature of the oxidation and reduction processes. In all complexes, the HOMO comprises an iron-iron bonding orbital localized between the two iron atoms not ligated by the semibridging carbonyl, while the LUMO is highly delocalized in nature and is antibonding between both pairs of iron atoms but also contains an antibonding dithiolate interaction.

Dataset Information

Coordination Chemistry of P₄ S₃ and P₄ Se₃ towards the Iron Fragments [Fe(Cp)(CO)₂ ]⁺ and [Fe(Cp)(PPh₃ )(CO)].

Publications

Coordination Chemistry of P<sub>4</sub> S<sub>3</sub> and P<sub>4</sub> Se<sub>3</sub> towards the Iron Fragments [Fe(Cp)(CO)<sub>2</sub> ]<sup>+</sup> and [Fe(Cp)(PPh<sub>3</sub> )(CO)].

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