Synthesis and Structures of Stable Pt<sup>II</sup> and Pt<sup>IV</sup> Alkylidenes: Evidence for π‐Bonding and Relativistic Stabilization

LaPierre, Etienne A.; Piers, Warren E.; Lin, Jian‐Bin; Gendy, Chris

doi:10.1002/chem.201806065

Cited by 7 publications

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“…The first ligand of this type, I , incorporates relatively less basic −PPh 2 groups as the pincer arms and was reported some time ago by Roper et al when they observed its serendipitous self-assembly in the coordination sphere of the ruthenium complex [RuCBr 2 (PPh 3 ) 2 (CO) 2 Br] + [BBr 4 ] − through sequential S E Ar reactions . The modern era of the study of these ligands began in 2012 when our group intentionally prepared the more electron rich −P(iPr) 2 -substituted version II (Chart ) and explored its chemistry with group 9 and 10 metals (Ir, − Rh, , Ni, − Pt). In addition, Young et al have utilized the original ligand I for a number of studies involving Rh − and the first-row congeners based on Co, , while Iluc et al have used II to elaborate the Pd chemistry of these PC carbene P ligand systems − and more recently opened the chemistry of this ligand with Fe …”

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confidence: 99%

Carbene Character in a Series of Neutral PC_carbeneP Cobalt(I) Complexes: Radical Carbenes versus Nucleophilic Carbenes

et al. 2022

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Cobalt(I) complexes supported by a series of PC carbene P pincer ligands of varying donicity, differing in the aryl group linking the phosphine arms with the anchoring carbon donor, are described. Addition of the proligands to cobalt bromide results in the formation of a series of cobalt(II) tetrahedral complexes, Ln-1, which serve as excellent precursors to the corresponding PC alkyl P and PC carbene P complexes. The square-planar cobalt PC carbene P complexes L2 R -3-X (X = Cl, Br) are readily synthesized by addition of a bulky aryloxide radical to the corresponding PC alkyl P complex L1-2-Br, via addition of L2 R to ClCo(PPh 3 ) 3 in the presence of trityl radical, or by addition of NaHBEt 3 and trityl radical to isolated L2 R -1. For the L2 NMe2 PC carbene P complexes, salt metathesis reactions with CsOH•H 2 O, LiCH 2 TMS, or LiNH 2 result in the corresponding hydroxo, alkyl, and amine complexes L2 NMe2 -3-R (R = OH, CH 2 TMS, NH 2 ). Reaction of L2 NMe2 -3-OH with benzoic acid affords the κ 2 -O 2 CPh derivative The nature of the carbene bond in either ligand platform and the effects of the X-type capping ligand on the CoC bond are explored using CASSCF and CASPT2 calculations and show that triplet structures are relatively more stable for the less electron donating ligand L1 while singlet Co(I) carbenes dominate for the more electron rich L2 derivatives. For L2 NMe2 complexes, the effect of the trans ligand X was also probed. π donors imbue the carbene with singlet character, while the strongly σ donating alkyl derivative exhibits significant triplet character.

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Section: Introductionmentioning

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Carbene Character in a Series of Neutral PC_carbeneP Cobalt(I) Complexes: Radical Carbenes versus Nucleophilic Carbenes

et al. 2022

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“…Noticeably, the satisfactorily characterised non-heretoatom-substituted alkylidene complexes of Pt(II) and Pt(0) (Chart 1) bear di(isopropyl)-substituted phosphines as ancillary ligands, and were reported only recently by some of us in 2012, 3 and some years later by Iluc 4 and Piers. 5 To date, the reactivity of the carbene complexes shown in Chart 1 remains mostly undisclosed. The behaviour of the cationic species 1a 3,6 and 1b 5 was assayed towards P-, N-, and C-donating neutral Lewis bases, dihydrogen, ethyldiazoacetate, and PhICl 2 , the latter permitting the isolation of a Pt(IV) alkylidene from 1b by formal oxidative addition of Cl 2 .…”

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“…Noticeably, the satisfactorily characterised non-heretoatom-substituted alkylidene complexes of Pt( ii ) and Pt(0) (Chart 1) bear di(isopropyl)-substituted phosphines as ancillary ligands, and were reported only recently by some of us in 2012, 3 and some years later by Iluc 4 and Piers. 5…”

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“…To date, the reactivity of the carbene complexes shown in Chart 1 remains mostly undisclosed. The behaviour of the cationic species 1a 3,6 and 1b 5 was assayed towards P-, N-, and C-donating neutral Lewis bases, dihydrogen, ethyldiazoacetate, and PhICl 2 , the latter permitting the isolation of a Pt( iv ) alkylidene from 1b by formal oxidative addition of Cl 2 . Complex 1c was found to react with CH 3 I and SiH 2 Ph 2 , 4 a whereas treatment of 1d with I 2 afforded the paramagnetic alkylidene complex 1f .…”

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Electrophilic activation of alkynes promoted by a cationic alkylidene complex of Pt(ii)

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Access to and Reactivity of Fe⁰, Fe^−I, Fe^I, and Fe^II PC_carbeneP Pincer Complexes

et al. 2021

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Despite their promising metal–ligand cooperative reactivity, PCcarbeneP pincer ligands are rarely reported for first‐row transition‐metal centres. Using a dehydration methodology, we report access to an Fe0 PCcarbeneP pincer complex (1) that proceeds via an isolated α‐hydroxylalkyl hydrido complex (3). Reversible carbonyl migration to the carbene position in 1 is found to allow coordination chemistry and E−H bond addition (E=H, B, Cl) across the iron–carbene linkage, representing a unique mechanism for metal–ligand cooperativity. The PCcarbeneP pincer ligand is also found to stabilize formal FeII, FeI, and Fe−I oxidation states, as demonstrated with synthesis and characterization of the complexes [11‐X][BArF20] (X=Br, I), 12, and K[13]. Compound K[13] is found to be highly reactive, and abstracts hydrogen from a range of aliphatic C−H sources. Computational analysis by DFT suggests that the formal FeI and Fe−I complexes contain significant carbene radical character. The ability of the PCcarbeneP ligand scaffold to partake in metal–ligand cooperativity and to support a range of iron oxidation states renders it as potentially useful in many catalytic applications.

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Synthesis and Structures of Stable Pt^II and Pt^IV Alkylidenes: Evidence for π‐Bonding and Relativistic Stabilization

Cited by 7 publications

References 48 publications

Carbene Character in a Series of Neutral PC_carbeneP Cobalt(I) Complexes: Radical Carbenes versus Nucleophilic Carbenes

Carbene Character in a Series of Neutral PC_carbeneP Cobalt(I) Complexes: Radical Carbenes versus Nucleophilic Carbenes

Electrophilic activation of alkynes promoted by a cationic alkylidene complex of Pt(ii)

Access to and Reactivity of Fe⁰, Fe^−I, Fe^I, and Fe^II PC_carbeneP Pincer Complexes

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Synthesis and Structures of Stable PtII and PtIV Alkylidenes: Evidence for π‐Bonding and Relativistic Stabilization

Cited by 7 publications

References 48 publications

Carbene Character in a Series of Neutral PCcarbeneP Cobalt(I) Complexes: Radical Carbenes versus Nucleophilic Carbenes

Carbene Character in a Series of Neutral PCcarbeneP Cobalt(I) Complexes: Radical Carbenes versus Nucleophilic Carbenes

Electrophilic activation of alkynes promoted by a cationic alkylidene complex of Pt(ii)

Access to and Reactivity of Fe0, Fe−I, FeI, and FeII PCcarbeneP Pincer Complexes

Contact Info

Product

Resources

About

Synthesis and Structures of Stable Pt^II and Pt^IV Alkylidenes: Evidence for π‐Bonding and Relativistic Stabilization

Carbene Character in a Series of Neutral PC_carbeneP Cobalt(I) Complexes: Radical Carbenes versus Nucleophilic Carbenes

Carbene Character in a Series of Neutral PC_carbeneP Cobalt(I) Complexes: Radical Carbenes versus Nucleophilic Carbenes

Access to and Reactivity of Fe⁰, Fe^−I, Fe^I, and Fe^II PC_carbeneP Pincer Complexes