Redox Chemistry of Heterobimetallic Polypnictogen Triple-Decker Complexes - Rearrangement, Fragmentation and Transfer

The redox chemistry of the heterobimetallic triple‐decker complexes [(Cp*Fe)(Cp′′′Co)(μ,η⁵:η⁴‐E₅)] (E=P (1), As (2), Cp*=1,2,3,4,5‐pentamethyl‐cyclopentadienyl, Cp′′′=1,2,4‐tri‐tertbutyl‐cyclopentadienyl) and [(Cp′′′Co)(Cp′′′Ni)(μ,η³:η³‐E₃)] (E=P (10), As (11)) was investigated. Compound 1 and 2 could be oxidized to the monocations 3 and 4 and further to the dications 5 and 6, while the initially folded cyclo‐E₅ ligand planarizes upon oxidation. The reduction leads to an opposite change in the geometry of the middle deck, which is now folded stronger into the direction of the other metal fragment (formation of monoanions 7 and 8). For the arsenic compound 8, a different behavior is found since a fragmentation into an As₆ (9) and As₃ ligand complex occurs. The Co and Ni triple‐decker complexes 10 and 11 can be oxidized initially to the heterometallic monocations 12 and 13, which are not stable in solution and convert selectively into the homometallic nickel complexes 14 and 15 and the cobalt complexes 16 and 17. This behavior was further proven by the oxidation of [(Cp′′′Co)(Cp′′Ni)(μ,η³:η²‐P₃)] (19, Cp′′=1,3‐di‐tertbutyl‐cyclopentadienyl) comprising two different Cp ligands. The transfer of {Cp^RM} fragments can be suppressed when a {W(CO)₅} unit is coordinated to the P₃ ligand (20) prior to the oxidation and the mixed cobalt and nickel cation 21 can be isolated. The reduction of 10 and 11 yields the heterometallic monoanions 22 and 23, where no transfer of the {Cp^RM} fragments is observed.

Coordination Chemistry of P4 S3 and P4 Se3 towards the Iron Fragments [Fe(Cp)(CO)2 ]+ and [Fe(Cp)(PPh3 )(CO)]. Chemistry 2019;25:12159-12168. [PMID: 31287589 PMCID: PMC6771638 DOI: 10.1002/chem.201902339]

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 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(ORF )4 ] (1 a), [Fp-P4 S3 ][F(Al(ORF )3 )2 ] (1 b), and [Fp-P4 Se3 ][Al(ORF )4 ] (2). Reactions with P4 S3 also yielded [FpPPh3 -P4 S3 ][Al(ORF )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 σ and π donation from the slightly P-P and P-E antibonding P4 E3 -cage HOMO (e symmetry) to the metal acceptor fragment.

Synthesis of Crystalline Chalcogenides in Ionic Liquids

Crystalline chalcogenides belong to the most promising class of materials. In addition to dense solid-state structures, they may form molecular cluster arrangements and networks with high porosity, as in the so-called "zeotype" chalcogenidometalates. The high structural diversity comes along with interesting physical properties such as semi-/photoconductivity, ion transport capability, molecular trapping potential, as well as chemical and catalytic activity. The great interest in the development of new and tailored chalcogenides has provoked a continuous search for new and better synthesis strategies over the years. The trend has clearly been towards lower temperatures for both economic and ecological reasons as well as for better reaction control. This led to the application of ionic liquids as a designer-like medium for materials synthesis. In this Review, we summarize recent developments and present a survey of different chalcogenide families along with their properties.

Redox and Coordination Behavior of the Hexaphosphabenzene Ligand in [(Cp*Mo)2 (μ,η(6) :η(6) -P6 )] Towards the "Naked" Cations Cu(+) , Ag(+) , and Tl(.)

Although the cyclo-P₆ complex [(Cp*Mo)₂(μ,η⁶:η⁶-P₆)] (1) was reported 30 years ago, little is known about its chemistry. Herein, we report a high-yielding synthesis of 1, the complex 2, which contains an unprecedented cyclo-P₁₀ ligand, and the reactivity of 1 towards the “naked” cations Cu⁺, Ag⁺, and Tl⁺. Besides the formation of the single oxidation products 3 a,b which have a bisallylic distorted cyclo-P₆ middle deck, the [M(1)₂]⁺ complexes are described which show distorted square-planar (M=Cu(4 a), Ag(4 b)) or distorted tetrahedral coordinated (M=Cu(5)) M⁺ cations. The choice of solvent enabled control over the reaction outcome for Cu⁺, as proved by powder XRD and supported by DFT calculations. The reaction with Tl⁺ affords a layered two-dimensional coordination network in the solid state.

Complexes of monocationic Group 13 elements with pentaphospha- and pentaarsaferrocene

Reactions of the sandwich complexes [Cp*Fe(η(5)-E5)] (Cp*=η(5)-C5Me5; E=P (1), As (2)) with the monovalent Group 13 metals Tl(+), In(+), and Ga(+) containing the weakly coordinating anion [TEF] ([TEF]=[Al{OC(CF3)3}4](-)) are described. Here, the one-dimensional coordination polymers [M(μ,η(5):η(1 -E5 FeCp*)3]n [TEF]n (E=P, M=Tl (3 a), In (3 b), Ga (3 c); E=As, M=Tl (4 a), In (4 b)) are obtained as sole products in good yields. All products were analyzed by single-crystal X-ray diffraction, revealing a similar assembly of the products with η(5)-bound E5 ligands and very weak σ-interactions between one P or As atom of the ring to the neighbored Group 13 metal cation. By exchanging the [TEF] anion of 4 a for the larger [FAl] anion ([FAl]=[FAl{OC6F10(C6F5)}3](-)), the coordination compound [Tl{(η(5)-As5)FeCp*}3][FAl] (5) without any σ-interactions of the As5-ring is obtained. All products are readily soluble in CH2 Cl2 and exhibit a dynamic coordination behavior in solution, which is supported by NMR spectroscopy and ESI-MS spectrometry as well as by osmometric molecular-weight determination. For a better understanding of the proceeding equilibrium DFT calculations of the cationic complexes were performed for the gas phase and in solution. Furthermore, the (31)P{(1)H} magic-angle spinning (MAS) NMR spectra of 3 a-c are presented and the first crystal structure of the starting material 2 was determined.