Transition Metal-Induced Cyclization of 1-Phosphabutadienes: Selective Formation of 1-Phosphet-2-ene or P═C-Substituted Phosphacyclohexene Ligands

Walsgrove, Henry T G; Patrick, Brian O.; Gates, Derek P.

doi:10.1021/acs.organomet.2c00340

Cited by 6 publications

(4 citation statements)

References 101 publications

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“…These observations are consistent with an isomeric mixture of meso-trans-4 and rac-trans-4 resulting from phosphine ligand exchange and this conclusion was further corroborated by 1 H and 13 C{ 1 H} NMR analysis to assign the resonances of both species. We have recently reported an analogous isomerization process at Pd II for related bis(1-phosphet-2-ene)Pd II complexes [32] and it has also been shown for mixtures of trans-[PhPd(PPh 3 ) 2 I] and trans-[PhPd(PPh 2 Me) 2 I]. [33] The ready ligand scrambling in 4 illustrates the potential of using labile dative covalent bonds to reversibly cross-link polymer 2 (see below).…”

Section: Molecular Model For Macromolecular Pd II Complexesmentioning

confidence: 80%

Palladium(II) Complexes of 1‐Phosphaisoprene Molecules and Polymers: Reversible Cross‐Linking of a Phosphorus‐Containing Polymer

et al. 2023

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The anionic polymerization of 1-phosphaisoprene [Mes*P=C-(Me)À CH=CH 2 (E-1)] affords poly(1-phosphaisoprene) 2 in high yield (75 %). Concentrated solutions of polymer 2 (M n = 21,800 g mol À 1 ; Đ = 1.02) a P-analogue of natural rubber, undergo gelation upon treatment with [Pd(cod)Cl 2 ] (0.15 P equiv). Evidence for P-coordination of 2 to Pd II was obtained by 31 P and 1 H NMR spectroscopy. The gelation is reversed by the addition of PMe 3 and the reformation of recoverable 2 along with [Pd II À PMe 3 ] complexes were confirmed by 31 P NMR spectro-scopy. The use of labile metal-ligand bonds to reversibly form gels is unprecedented and has relevance to self-healing materials. In contrast, coordination of 2 to [Pd(η 3 -C 3 H 5 )(μ-Cl)] 2 affords the well-defined complex 2 • [Pd(η 3 -C 3 H 5 )Cl] which was characterized by 31 P, 1 H, 13 C{ 1 H} NMR spectroscopy and GPC. This polymer chemistry was complemented by detailed molecular model studies of the coordination chemistry of monomer 1-phosphaisoprene E-1 with [Pd(cod)Cl 2 ] and [Pd(η 3 -C 3 H 5 )(μ-Cl)] 2 ].

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Section: Molecular Model For Macromolecular Pd II Complexesmentioning

confidence: 80%

Palladium(II) Complexes of 1‐Phosphaisoprene Molecules and Polymers: Reversible Cross‐Linking of a Phosphorus‐Containing Polymer

et al. 2023

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“…As yet, an analogous H + ‐mediated cyclization of 1‐phosphabutadienes has not been observed in bulk scale synthesis. We have recently reported 1‐phosphet‐2‐ene heterocycle formation upon ligation of 1 c to Pd II , [39] and note that cyclizations of P=C−C=C systems are well established, [40] albeit quite different to that proposed for 6 a – c .…”

Section: Tentative Assignment Of the Minor Signal Observed In The Tf‐...mentioning

confidence: 96%

“…The authors have cited additional references within the Supporting Information. [16,[28][29][30]39,[41][42][43][44] Experimental procedures, characterization data, NMR spectra, μSR description and data, DFT calculation details are given in the Supporting Information.…”

Section: Supporting Informationmentioning

confidence: 99%

Probing Radical Addition to 1‐Phosphabutadienes by Employing Muonium as a “Light Isotope” of Hydrogen

Walsgrove,

Percival,

Gates

2023

Chemistry A European J

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Understanding free radical addition to multiple bonds is important to elucidating the mechanistic details of addition polymerization reactions, albeit the fleeting radical intermediates are very difficult to detect by conventional methodologies. Muon spin spectroscopy (μSR) is a highly sensitive method that can detect radical species at 106 spins (cf. EPR: 1012 spins, NMR: 1018 spins). Herein, we employ μSR to detect the radical‐addition products from three 1‐phosphabutadiene monomers, P‐analogues of isoprene. We show that muonium (Mu), a “light” H‐atom surrogate, adds predominantly at the C4 position of the P1=C2−C3=C4 moiety to give unprecedented 1‐phosphaallyl radicals as the major products. Our structural assignments are supported by assignment of muon, phosphorus and proton hyperfine coupling constants using DFT‐calculations. A minor radical product is also detected that is tentatively assigned to an PC3‐heterocyclic free radical. On the basis of DFT‐predictions, we speculate that its formation may involve initial addition of Mu+ at the C3 position followed by electron capture. These studies provide rare insights into the prospective radical (or cationic) polymerization of 1‐phosphabutadienes, which have previously been polymerized using anionic initiation.

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“…A final ring-closure step affords 1 , with the overall reaction being 35.1 kcal mol –1 downhill in energy. Such formal intramolecular [2 + 2] cycloaddition is also known for 1-phosphabutadienes. − It is noteworthy that the reverse reaction from 1 back to 1c has a predicted barrier of 20.8 kcal mol –1 , making 1 a potential substrate for Danheiser benzannulation. , …”

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confidence: 96%

Synthesis of Phosphet-2-one Derivatives via Phosphinidene Transfer to Cyclopropenones

Xin,

Cummins

2023

J. Am. Chem. Soc.

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Transition Metal-Induced Cyclization of 1-Phosphabutadienes: Selective Formation of 1-Phosphet-2-ene or P═C-Substituted Phosphacyclohexene Ligands

Cited by 6 publications

References 101 publications

Palladium(II) Complexes of 1‐Phosphaisoprene Molecules and Polymers: Reversible Cross‐Linking of a Phosphorus‐Containing Polymer

Palladium(II) Complexes of 1‐Phosphaisoprene Molecules and Polymers: Reversible Cross‐Linking of a Phosphorus‐Containing Polymer

Probing Radical Addition to 1‐Phosphabutadienes by Employing Muonium as a “Light Isotope” of Hydrogen

Synthesis of Phosphet-2-one Derivatives via Phosphinidene Transfer to Cyclopropenones

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