A diamino-substituted carbodiphosphorane as strong C-donor and weak N-donor: isolation of monomeric trigonal-planar L·ZnCl2

Phosphine/sulfoxide-carbone, a ligand with a flexible bonding mode for early to late transition metals

In recent years, carbones have emerged as a new exciting class of carbon-based ligands. We report here a series of organometallic complexes demonstrating the versatility in coordination mode of phosphine/sulfoxide carbone 1. Indeed, 1 is able to chelate both early and late transition metals, in a mono- or bidentate fashion depending on the oxyphilic character of metal center thanks to the presence of the sulfoxide moiety. All complexes have been fully characterized by X-ray diffraction analysis and by NMR spectroscopy (except hafnium complex because of its extreme insolubility). It is noteworthy that silver(I) and zirconium(IV) complexes are efficient transmetalating reagents toward copper(I) complexes.

Synthesis, Structural Characterization, and Phosphorescence Properties of Trigonal Zn(II) Carbene Complexes

The sterically demanding N-heterocyclic carbene ITr (N,N'-bis(triphenylmethyl)imidazolylidene) was employed for the preparation of novel trigonal zinc(II) complexes of the type [ZnX2(ITr)] [X = Cl (1), Br (2), and I (3)], for which the low coordination mode was confirmed in both solution and solid state. Because of the atypical coordination geometry, the reactivity of 1-3 was studied in detail using partial or exhaustive halide exchange and halide abstraction reactions to access [ZnLCl(ITr)] [L = carbazolate (4), 3,6-di-tert-butyl-carbazolate (5), phenoxazine (6), and phenothiazine (7)], [Zn(bdt)(ITr)] (bdt = benzene-1,2-dithiolate) (8), and cationic [Zn(μ2-X)(ITr)]2[B(C6F5)4]2 [X = Cl (9), Br (10), and I (11)], all of which were isolated and structurally characterized. Importantly, for all complexes 4-11, the trigonal coordination environment of the ZnII ion is maintained, demonstrating a highly stabilizing effect due to the steric demand of the ITr ligand, which protects the metal center from further ligand association. In addition, complexes 1-3 and 8-11 show long-lived luminescence from triplet excited states in the solid state at room temperature, according to our photophysical studies. Our quantum chemical density functional theory/multireference configuration interaction (DFT/MRCI) calculations reveal that the phosphorescence of 8 originates from a locally excited triplet state on the bdt ligand. They further suggest that the phenyl substituents of ITr are photochemically not innocent but can coordinate to the electron-deficient metal center of this trigonal complex in the excited state.

Diversification of the Carbodicarbene Class by Embedding an Anionic Component in its Scaffold

Carbodicarbene (CDC) has become an emerging ligand in many fields due to its strong σ-donating ability. Collapse

Key Words

• Anionic carbodicarbene
• carbone
• dative bonding model
• geminal bimetallic complexes

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MESH Headings Collapse

Grants

• NSTC 112-2123-M-001-007 National Science Council
• AS-GC-111-M04 Academia Sinica

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Affiliation(s)

Cheng-Han Yu Institute of chemistry, Academia Sinica, Taipei, Taiwan (R.O.C., 115201
Ka-Chun Au-Yeung Institute of chemistry, Academia Sinica, Taipei, Taiwan (R.O.C., 115201 Corporate R&D Center, LCY Chemical Corporation, Kaohsiung, Taiwan (R.O.C
Ruiqin Liu School of Chemistry and Molecular Engineering, State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing Tech University, Nanjing, China
Chao-Hsien Lee Institute of chemistry, Academia Sinica, Taipei, Taiwan (R.O.C., 115201
Dandan Jiang School of Chemistry and Molecular Engineering, State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing Tech University, Nanjing, China
Bamlaku Semagne Aweke Institute of chemistry, Academia Sinica, Taipei, Taiwan (R.O.C., 115201 Department of Applied Chemistry, National Yang Ming Chiao Tung University, Hsinchu, Taiwan (R.O.C Sustainable Chemical Science and Technology, Taiwan International Graduate Program, Academia Sinica, Taipei, Taiwan (R.O.C
Chia-Hung Wu Institute of chemistry, Academia Sinica, Taipei, Taiwan (R.O.C., 115201 Department of Chemistry, National Taiwan University, Taipei, Taiwan (R.O.C
Yu-Jou Wang Institute of chemistry, Academia Sinica, Taipei, Taiwan (R.O.C., 115201 Department of Chemistry, National Taiwan University, Taipei, Taiwan (R.O.C
Ting-Hsuan Wang Institute of chemistry, Academia Sinica, Taipei, Taiwan (R.O.C., 115201
Kien Voon Kong Department of Chemistry, National Taiwan University, Taipei, Taiwan (R.O.C
Glenn P A Yap Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware, United States
Wen-Ching Chen Institute of chemistry, Academia Sinica, Taipei, Taiwan (R.O.C., 115201
Gernot Frenking School of Chemistry and Molecular Engineering, State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing Tech University, Nanjing, China Fachbereich Chemie, Philipps-Universität Marburg, Hans-Meerwein-Strasse, D-35043, Marburg, Germany
Lili Zhao School of Chemistry and Molecular Engineering, State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing Tech University, Nanjing, China
Tiow-Gan Ong Institute of chemistry, Academia Sinica, Taipei, Taiwan (R.O.C., 115201 Department of Chemistry, National Taiwan University, Taipei, Taiwan (R.O.C Department of Medicinal and Applied Chemistry, Kaohsiung Medical University, Kaohsiung, Taiwan (R.O.C

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Carbodicarbenes and Striking Redox Transitions of their Conjugate Acids: Influence of NHC versus CAAC as Donor Substituents

Herein, a new type of carbodicarbene (CDC) comprising two different classes of carbenes is reported; NHC and CAAC as donor substituents and compare the molecular structure and coordination to Au(I)Cl to those of NHC-only and CAAC-only analogues. The conjugate acids of these three CDCs exhibit notable redox properties. Their reactions with [NO][SbF6 ] were investigated. The reduction of the conjugate acid of CAAC-only based CDC with KC8 results in the formation of hydrogen abstracted/eliminated products, which proceed through a neutral radical intermediate, detected by EPR spectroscopy. In contrast, the reduction of conjugate acids of NHC-only and NHC/CAAC based CDCs led to intermolecular reductive (reversible) carbon-carbon sigma bond formation. The resulting relatively elongated carbon-carbon sigma bonds were found to be readily oxidized. They were, thus, demonstrated to be potent reducing agents, underlining their potential utility as organic electron donors and n-dopants in organic semiconductor molecules.

Phosphorus-Containing Superbases: Recent Progress in the Chemistry of Electron-Abundant Phosphines and Phosphazenes

The renaissance of Brønsted superbases is primarily based on their pronounced capacity for a large variety of chemical transformations under mild reaction conditions. Four major set screws are available for the selective tuning of the basicity: the nature of the basic center (N, P, …), the degree of electron donation by substituents to the central atom, the possibility of charge delocalization, and the energy gain by hydrogen bonding. Within the past decades, a plethora of neutral electron-rich phosphine and phosphazene bases have appeared in the literature. Their outstanding properties and advantages over inorganic or charged bases have now made them indispensable as auxiliary bases in deprotonation processes. Herein, an update of the chemistry of basic phosphines and phosphazenes is given. In addition, due to widespread interest, their use in catalysis or as ligands in coordination chemistry is highlighted.

Isolation of a Uranium(III)-Carbon Multiple Bond Complex

Low-valent uranium-element multiple bond complexes remain scarce, though there is burgeoning interest regarding to their bonding and reactivity. Herein, isolation of a uranium(III)-carbon double bond complex [(Cp*)2 U(CDP)](BPh4 ) (1) comprising a tridentate carbodiphosphorane (CDP) was reported for the first time. Oxidation of 1 afforded the corresponding U(IV) complex [(Cp*)2 U(CDP)](BPh4 )2 (2). The distance between U and C in 2 is 2.481 Å, indicating the existence of a typical U=C double bond, which is further confirmed by quantum chemical calculations. Bonding analysis suggested that the CDP also serves as both σ- and π-donor in complex 1, though a longer U-C bond (2.666(3) Å) is observed. It implies that 1 is the first isolable mononuclear uranium(III) carbene complex. Moreover, these results suggest that CDPs are promising ligands to establish other low-valent f-block metal-carbon multiple bond complexes.

From carbones to carbenes and ylides in the coordination sphere of iridium

The carbodiphosphorane-based iridium pincer complex (2) is demonstrated to rearrange in chlorinated organic solvents under cleavage of a P-C-bond to give a chelating phosphine ylide ligand. A detailed mechanistic investigation reveals that these types of donor groups are prone for P-C-bond cleavage in the coordination sphere of transition metal hydrido complexes. Finally, complex 2 is demonstrated to be an efficient hydrogen-borrowing catalyst.

Cationic Phosphorus Compounds Based on a Bis(1-piperidinyl)-Substituted Carbodiphosphorane: Syntheses, Structures, and Csp3–H Activation

The use of the bis(1-piperidinyl)-substituted carbodiphosphorane (Ph₂(Pip)P)₂C (1) as an NCN ligand for the stabilization of phosphorus cations was studied. A simple ligand for halide exchange allowed the synthesis and isolation of a series of phosphorus monocations of the type [1-PR₂]⁺ (with R = Cl, Br, I, CyCl, Ph). These cations exhibit characteristic NMR and structural properties which nicely correlate with the charge at the central phosphorus atom and the interaction between the ligand and the PR₂ moiety. Halide abstraction from the monocations does not result in isolable dicationic compounds but in an unexpected intramolecular C_sp³–H activation in the piperidinyl group. DFT studies show that the selective activation of the CH₂ group next to the nitrogen atom instead of a CH group at the phenyl substituents proceeds via an iminium intermediate formed by hydride transfer from the carbon atom to the cationic phosphorus center. This observation clearly demonstrates the pronounced π acidity of the dicationic phosphorus species in comparison to compounds with a further π-donor substituent.

Carbones and Carbon Atom as Ligands in Transition Metal Complexes

This review summarizes experimental and theoretical studies of transition metal complexes with two types of novel metal-carbon bonds. One type features complexes with carbones CL₂ as ligands, where the carbon(0) atom has two electron lone pairs which engage in double (σ and π) donation to the metal atom [M]⇇CL₂. The second part of this review reports complexes which have a neutral carbon atom C as ligand. Carbido complexes with naked carbon atoms may be considered as endpoint of the series [M]-CR₃ → [M]-CR₂ → [M]-CR → [M]-C. This review includes some work on uranium and cerium complexes, but it does not present a complete coverage of actinide and lanthanide complexes with carbone or carbide ligands.