Further Insights into the Structure of [M(η2(C,C‘)-C3O2)(PPh3)2] (M = Ni, Pd, Pt) by Quasi-Relativistic Density Functional Calculations and Solid-State CP/MAS NMR

Formation and infrared spectroscopic characterization of carbon suboxide complexes TM-η1 -C3 O2 and the inserted ketenylidene complexes OCTMCCO (TM=Cu, Ag, Au) in solid neon

The reactions of coinage metal atoms Cu, Ag and Au with carbon suboxide (C₃ O₂ ) are studied by matrix isolation infrared spectroscopy. The weakly bound complexes TM-η¹ -C₃ O₂ (TM=Cu, Ag, Au), in which the carbon suboxide ligand binds to the metal center in the monohapto fashion are formed as initial reaction products. The complexes subsequently isomerize to the inserted products OCTMCCO upon visible light (λ = 400-500 nm) excitation. The analysis of the electronic structure using modern quantum chemistry methods suggests that the linear OCTMCCO complexes are best described by the bonding interactions between the TM⁺ cation in the electronic singlet ground state and the [OC…CCO]^- ligands in the doublet state forming two TM⁺  ← ligands σ donation and two TM⁺  → ligands π backdonation bonding components. In addition, the CuCCO, AgCCO and AuCCO complexes are also formed, which are predicted to be bent.

Trimerisation of carbon suboxide at a di-titanium centre to form a pyrone ring system

Bis(pentalene)dititanium Ti₂(μ:η⁵,η⁵-Pn^†)₂ trimerises carbon suboxide (O Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> C Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> C Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> C Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> O) to form [{Ti₂(μ:η⁵,η⁵-Pn^†)₂}{μ-C₉O₆}], which contains a 4-pyrone core, via the monoadduct [Ti₂(μ:η⁵,η⁵-Pn^†)₂ (η²-C₃O₂)].

The reaction of the syn-bimetallic bis(pentalene)dititanium complex Ti₂(μ:η⁵,η⁵-Pn^†)₂ (Pn^† = C₈H₄(1,4-SiⁱPr₃)₂) 1 with carbon suboxide (O Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> C Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> C Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> C Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> O, C₃O₂) results in trimerisation of the latter and formation of the structurally characterised complex [{Ti₂(μ:η⁵,η⁵-Pn^†)₂}{μ-C₉O₆}]. The trimeric bridging C₉O₆ unit in the latter contains a 4-pyrone core, a key feature of both the hexamer and octamer of carbon suboxide which are formed in the body from trace amounts of C₃O₂ and are, for example, potent inhibitors of Na⁺/K⁺-ATP-ase. The mechanism of this reaction has been studied in detail by DFT computational studies, which also suggest that the reaction proceeds via the initial formation of a mono-adduct of 1 with C₃O₂. Indeed, the carefully controlled reaction of 1 with C₃O₂ affords [Ti₂(μ:η⁵,η⁵-Pn^†)₂ (η²-C₃O₂)], as the first structurally authenticated complex of carbon suboxide.

Activation of carbon suboxide (C3O2) by U(iii) to form a cyclobutane-1,3-dione ring

[U(η⁵-C₅H₄SiMe₃)₃] reductively couples three C₃O₂ molecules to form a tetranuclear complex with a central cyclobutane-1,3-dione ring, via an intermediate bridging ketene complex.

Heavier Carbon Subchalcogenides as C3 Sources for Tungsten-Capped Cumulenes: A Theoretical Study

Heavier carbon subchalcogenides C₃E₂ (E = S, Se) can bind to transition metals through either a C═C or a C═E double bond. These two binding modes on a reactive tungsten (PMe₃)₄WCl₂ site have been explored by density functional theory methods (M06-L/DZP+Lanl2DZ). The important step controlling the reaction direction is the initial binding of the C₃E₂ ligand. Of particular significance is the M═C═C═C═E fragment resulting from the C═E coordination mode. This fragment can bind to additional C₃E₂ molecules or bridge to other metals. Ultimately C₃E₂ serves as a source of C₃ units for building C_3n carbon sp-hybridized allotropes.

Infrared Photodissociation Spectroscopy and Density Functional Theory Study of Carbon Suboxide Complexes [M(CO)4(C3O2)](+) (M = Fe, Co, Ni)

Infrared photodissociation spectra are measured for mass-selected cation complexes with a chemical formula [MC7O6](+) (M = Fe, Co, Ni) formed via pulsed laser evaporation of metal target in expansions of helium gas seeded by CO. The geometries of the complexes are determined by comparison of the experimental spectra with the simulated spectra from density functional calculations. All of these complexes are identified to have [M(CO)4(C3O2)](+) structures involving a carbon suboxide ligand, which binds the metal center in an η(1) fashion. The antisymmetric CO stretching vibration of C3O2 is slightly red-shifted upon coordination. The donor-acceptor bonding interactions between C3O2 and the metal centers are analyzed using the EDA-NOCV method. The results show that M ← C3O2 σ donation is stronger than the M → C3O2 π back-donation in these cation complexes.

Differences between carbon suboxide and its heavier congeners as ligands in transition metal complexes: a theoretical study

The lowest energy structures for the [M](C₃E₂) complexes ([M] = Ir, Ni, Pt surrounded by ligands such as phosphines and halides; E = O, S, Se) are compared.

Cleavage of carbon suboxide to give ketenylidene and carbyne ligands at a reactive tungsten site: a theoretical mechanistic study

The reaction of (MePPh₂)₄WCl₂ with C₃O₂ results in stepwise cleavage of the two CC double bonds in C₃O₂ to give tungsten complexes containing phosphinoketenylidene and phosphinocarbyne ligands. The mechanism of this has been elucidated using density functional theory.