Late‐Transition‐Metal Complexes as Tunable Lewis Bases

Bauer, Jürgen; Braunschweig, Holger; Brenner, Peter; Kraft, Katharina; Radacki, Krzysztof; Schwab, Katrin

doi:10.1002/chem.201001228

Cited by 76 publications

(51 citation statements)

References 95 publications

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“…The need for such elevated temperatures for the isomerization to proceed is further corroborated by the DFT‐calculated energy of activation of 34.9 kcal mol −1 (see the optimized transition state in the Supporting Information) required for reductive elimination of the alkyne ligands. It is important to note that, although rare, well‐defined Pt 0 species bearing carbene ligands have recently been isolated and characterized by Braunschweig and co‐workers 46. In order to further confirm our hypothesis, we performed a scrambling experiment between two cis complexes bearing different carbene ligands.…”

Section: Resultsmentioning

confidence: 59%

“…It is important to note that, although rare, well-defined Pt 0 species bearing carbene ligands have recently been isolated and characterized by Braunschweig and co-workers. [46] In order to further confirm our hypothesis, we performed a scrambling experiment between two cis complexes bearing different carbene ligands. To this end, we synthesized complex 9 a bearing the IBIM ligand instead of the DBIM ligand as in the case of complex 5 a.…”

Section: Mechanistic Investigationsmentioning

confidence: 84%

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Highly Efficient Deep‐Blue Emitters Based on cis and trans N‐Heterocyclic Carbene Pt^II Acetylide Complexes: Synthesis, Photophysical Properties, and Mechanistic Studies

Zhang

Blacque

Venkatesan

2013

Chemistry A European J

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We have synthesized cis and trans N-heterocyclic carbene (NHC) platinum(II) complexes bearing σ-alkynyl ancillary ligands, namely [Pt(dbim)2 (CCR)2 ] [DBIM=N,N'-didodecylbenzimidazoline-2-ylidene; R=C6 H4 F (4), C6 H5 (5), C6 H2 (OMe)3 (6), C4 H3 S (7), and C6 H4 CCC6 H5 (8)] and [Pt(ibim)2 (CCC6 H5 )2 ] (9) (ibim=N,N'-diisopropylbenzimidazoline-2-ylidene), starting from [Pt(cod)(CCR)2 ] (COD=cyclooctadiene) and 2 equivalents of [dbimH]Br ([ibimH]Br for complexes 9) in the presence of tBuOK and THF. Mechanistic investigations aimed at uncovering the cis to trans isomerization reaction have been performed on the representative cis complex 5 a [Pt(dbim)2 (CCC6 H5 )2 ] and revealed the isomerization to progress smoothly in good yield when 5 a was treated with catalytic amounts of [Pt(cod)(CCR)2 ] at 75 °C in THF or when 5 a was heated at 200 °C in the solid state under an inert atmosphere. Detailed examination of the reactions points to the possible involvement, in a catalytic fashion, of a solvent-stabilized Pt(II) dialkyne complex in the former case and a Pt(0) NHC complex in the latter case, for the transformation of the cis isomer to the corresponding trans complex. Thermal stability and the isomerization process in the solid state have been further investigated on the basis of TGA and DSC measurements. X-ray diffraction studies have been carried out to confirm the solid-state structures of 4 b, 5 a, 5 b, and 9 b. All of the synthesized dialkyne complexes 4-9 exhibit phosphorescence in solution, in the solid state at room temperature (RT), and also in frozen solvent glasses at 77 K. The emission wavelengths and quantum yields have been found to be highly tunable as a function of the alkynyl ligand. In particular, the trans isomer of complex 9 in a spin-coated film (10 wt % in poly(methyl methacrylate), PMMA) exhibits a high phosphorescence quantum yield of 80 %, which is the highest reported for Pt(II) -based deep-blue emitters. Experimental observations and time-dependent density functional theory (TD-DFT) calculations are strongly indicative of the emission being mainly governed by metal-perturbed interligand ((3) IL) charge transfer.

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Section: Resultsmentioning

confidence: 59%

Section: Mechanistic Investigationsmentioning

confidence: 84%

Highly Efficient Deep‐Blue Emitters Based on cis and trans N‐Heterocyclic Carbene Pt^II Acetylide Complexes: Synthesis, Photophysical Properties, and Mechanistic Studies

Zhang

Blacque

Venkatesan

2013

Chemistry A European J

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“…In order to further examine the interactions between platinum complexes and fluoroboranes, theoretical calculations were performed using the functionals B3LYP and M05-2X. The first functional was chosen due to its frequent application in the calculation of bond dissociation enthalpies (BDE) in Lewis pairs with transition metals, [45][46][47][48] the second was chosen due to its ability to reproduce weak interactions in Lewis pairs, as demonstrated for example in the calculation of the FLP [(ItBu)A C H T U N G T R E N N U N G (BPf 3 )] (ItBu = N,N'-bis(tert-butyl)imidazol-2-ylidene, 27 opt ). [49] The free formation energies (DDG) of the complexes [(Et 3 P) 3 (Figure 4 and Table 5).…”

Section: Resultsmentioning

confidence: 99%

Reactivity of Lewis Basic Platinum Complexes Towards Fluoroboranes

Bauer¹,

Braunschweig²,

Dewhurst³

et al. 2013

Chemistry A European J

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We herein report detailed investigations into the interaction of Lewis acidic fluoroboranes, for example BF2Pf (Pf=perfluorophenyl) and BF2Ar(F) (Ar(F)=3,5-bis(trifluoromethyl)phenyl), with Lewis basic platinum complexes such as [Pt(PEt3)3] and [Pt(PCy3)2] (Cy=cyclohexyl). Two presumed Lewis adducts could be identified in solution and corresponding secondary products of these Lewis adducts were characterized in the solid state. Furthermore, the concept of frustrated Lewis pairs (FLP) was applied to the activation of ethene in the system [Pt(BPf3)(CH2CH2)(dcpp)] (dcpp=1,3-bis(dicyclohexylphosphino)propane; Pf=perfluorophenyl). Finally, DFT calculations were performed to determine the interaction between the platinum-centered Lewis bases and the boron-centered Lewis acids. Additionally, several possible mechanisms for the oxidative addition of the boranes BF3, BCl3, and BF2Ar(F) to the model complex [Pt(PMe3)2] are presented.

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“…The Z-type ligands in the so-formed T-shape, tri-coordinate complexes include BeCl 2 [328] (Fig. 60, center top), AlCl 3 [329][330][331], GaCl 3 [332] (Fig. 60, center bottom), and ZrCl 4 [333].…”

Section: C-3 Direct Quantum-chemical Calculation Of Osmentioning

confidence: 99%

Toward a comprehensive definition of oxidation state (IUPAC Technical Report)

Karen

McArdle

Takats

2014

Pure and Applied Chemistry

111

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A generic definition of oxidation state (OS) is formulated: "The OS of a bonded atom equals its charge after ionic approximation". In the ionic approximation, the atom that contributes more to the bonding molecular orbital (MO) becomes negative. This sign can also be estimated by comparing Allen electronegativities of the two bonded atoms, but this simplification carries an exception when the more electronegative atom is bonded as a Lewis acid. Two principal algorithms are outlined for OS determination of an atom in a compound; one based on composition, the other on topology. Both provide the same generic OS because both the ionic approximation and structural formula obey rules of stable electron configurations. A sufficiently simple empirical formula yields OS via the algorithm of direct ionic approximation (DIA) by these rules. The topological algorithm works on a Lewis formula (for a molecule) or a bond graph (for an extended solid) and has two variants. One assigns bonding electrons to more electronegative bond partners, the other sums an atom's formal charge with bond orders (or bond valences) of sign defined by the ionic approximation of each particular bond at the atom. A glossary of terms and auxiliary rules needed for determination of OS are provided, illustrated with examples, and the origins of ambiguous OS values are pointed out. An electrochemical OS is suggested with a nominal value equal to the average OS for atoms of the same element in a moiety that is charged or otherwise electrochemically relevant.

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Late‐Transition‐Metal Complexes as Tunable Lewis Bases

Cited by 76 publications

References 95 publications

Highly Efficient Deep‐Blue Emitters Based on cis and trans N‐Heterocyclic Carbene Pt^II Acetylide Complexes: Synthesis, Photophysical Properties, and Mechanistic Studies

Highly Efficient Deep‐Blue Emitters Based on cis and trans N‐Heterocyclic Carbene Pt^II Acetylide Complexes: Synthesis, Photophysical Properties, and Mechanistic Studies

Reactivity of Lewis Basic Platinum Complexes Towards Fluoroboranes

Toward a comprehensive definition of oxidation state (IUPAC Technical Report)

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Late‐Transition‐Metal Complexes as Tunable Lewis Bases

Cited by 76 publications

References 95 publications

Highly Efficient Deep‐Blue Emitters Based on cis and trans N‐Heterocyclic Carbene PtII Acetylide Complexes: Synthesis, Photophysical Properties, and Mechanistic Studies

Highly Efficient Deep‐Blue Emitters Based on cis and trans N‐Heterocyclic Carbene PtII Acetylide Complexes: Synthesis, Photophysical Properties, and Mechanistic Studies

Reactivity of Lewis Basic Platinum Complexes Towards Fluoroboranes

Toward a comprehensive definition of oxidation state (IUPAC Technical Report)

Contact Info

Product

Resources

About

Highly Efficient Deep‐Blue Emitters Based on cis and trans N‐Heterocyclic Carbene Pt^II Acetylide Complexes: Synthesis, Photophysical Properties, and Mechanistic Studies

Highly Efficient Deep‐Blue Emitters Based on cis and trans N‐Heterocyclic Carbene Pt^II Acetylide Complexes: Synthesis, Photophysical Properties, and Mechanistic Studies