The Continuing Development of the Chemistry of Phospholes

Quin, Louis D.

doi:10.2174/138527206775192997

Cited by 56 publications

(6 citation statements)

References 135 publications

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“…In both ligands, the phosphole ring is slightly bent with respect to the P(1)–C(5)–P(2) plane, making dihedral angles of 83.06(4)° for 4a and 82.44(7)° for 4c . The distances and angles in the phosphole ring are similar to those previously reported for common phosphole compounds . In each case, the phosphorus P(1) of the phosphole ring is slightly out of the C(1)C(2)C(3)C(4) plane by 0.140(1) and 0.262(3) Å, respectively, as already observed in phosphole ligands …”

Section: Resultssupporting

confidence: 85%

Modular Phosphole-Methano-Bridged-Phosphine(Borane) Ligands. Application to Rhodium-Catalyzed Reactions

et al. 2012

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The synthesis of the phospholyl(phosphinoborane)methane air-and moisture-stable hybrid ligands 4a−f, starting from 1-phenylphospholes 1a−d, was performed via P−C bond coupling on the methano bridge. Two strategies were investigated, according to the phospholyl moiety used as a nucleophilic or an electrophilic reagent. In the first pathway, the phospholyl anions react with the easily available (chloromethyl)diphenylphosphine−borane 3 to afford ligands 4a−d in 29−67% isolated yields. In the second pathway, the phospholyl(dicyclohexylphosphinoborane)methane ligands 4e,f were synthesized in 18−23% yields, through a nucleophilic substitution on the cyanophosphole. Removal of the BH 3 moiety on 4a−c assisted by DABCO leads to the hybrid phospholyl(diphenylphosphino)methanes 5a−c. Compounds 4 and 5 were fully characterized by multinuclear NMR spectroscopy ( 1 H, 31 P, 13 C, 11 B), mass spectrometry, and elemental analysis, and the X-ray crystal structures of 4a,c and 5a,b have been established. Ligands 5a,b were used to prepare the cationic rhodium complexes [Rh(η 4 -COD)(5a)] + (8a′), [Rh(η 4 -COD)(5b)] + (8b), [Rh(5a) 2 ] + (9a′), and [Rh(5b) 2 ] + (9b), containing four-membered chelate rings with BF 4 − or CF 3 SO 3 − as counterions. Ligands 4a−f were also used to synthesize the [Rh(η 4 -COD)(4)] + chelate complexes 10a−f, resulting from coordination of the phospholyl part and the BH 3 group via a η 2 mode with two bridging B−H−Rh 3c−2e bonds, as shown by the X-ray crystal structures of the complexes 10b,c. Rhodium complexes 8 and 10 isolated or formed in situ with ligands 4 and 5 were studied for catalytic hydrogenation of methyl 2-(acetamidomethyl)acrylate ( 11) and hydroboration of styrene (13) with catecholborane. In both reactions, the catalytic systems prepared either from the phospholyl(phosphinoborane)methane ligands 4 or the corresponding free ligands 5, gave good to excellent conversions. In addition, the regioselectivity of the catalyzed hydroboration is slightly influenced using these ligands. Finally, the use of hybrid phospholyl(phosphinoborane)methanes as ligands offers a new, efficient way to improve catalytic processes, for designing both the structure and the electronic properties of the catalyst, or still to implement it without removing the borane protecting group.

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Section: Resultssupporting

confidence: 85%

Modular Phosphole-Methano-Bridged-Phosphine(Borane) Ligands. Application to Rhodium-Catalyzed Reactions

et al. 2012

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“…Within the series of five-membered heterocycles, especially the phosphorus-containing heterocycles take an exceptional role because they are nonaromatic or only slightly aromatic. − The pyramidal phosphorus environment and the high inversion barrier of phospholes lead to a hindered interaction of the phosphorus lone pair with the dienic system . This results in a versatile reaction behavior: e.g., phospholes undergo Diels–Alder reactions of the dienic system, oxidation (P III → P V ), or complexation reactions of the phosphorus atom and/or the dienic system. ,− Due to the low delocalization within the phosphole ring, they typically behave as a classical diene or phosphine .…”

Section: Introductionmentioning

confidence: 99%

Transition-Metal Carbonyl Complexes of 2,5-Diferrocenyl-1-phenyl-1H-phosphole

et al. 2015

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Pentacarbonyl(2,5-diferrocenyl-1-phenyl-1H-phosphole)metal complexes 3a−c (3a, M = Cr; 3b, M = Mo; 3c, M = W) have successfully been synthesized by the reaction of 2,5-diferrocenyl-1-phenyl-1H-phosphole (1) with M-(CO) 5 (thf) (2a, M = Cr; 2b, M = Mo; 2c, M = W). Further irradiation of 3a−c with 1 equiv of 1 in tetrahydrofuran leads to tetracarbonylbis(2,5-diferrocenyl-1-phenyl-1H-phosphole)metal complexes 4a−c (4a, M = Cr; 4b, M = Mo; 4c, M = W). In addition, the reaction of 1 with Fe 2 (CO) 9 gave tetracarbonyl-(2,5-diferrocenyl-1-phenyl-1H-phosphole)iron (6) and heptacarbonyl[μ-(2,3,4,5-η)-1-(2,5-diferrocenyl-1-phenyl-1H-phosphole)]diiron (7), respectively. Treatment of 2,5-diferrocenyl-1-phenyl-1H-phosphole sulfide (8) with Fe 2 (CO) 9 afforded tricarbonyl[(2,3,4,5-η)-(2,5-diferrocenyl-1-phenyl-1H-phosphole 1-sulfide)]iron (9). Complexes 3b,c, 4c, 7, and 9 have been characterized by single-crystal X-ray diffraction. Molecules 3b,c and 4c exhibit a distorted-octahedral geometry, whereas in 4c the two phosphole units are cis-oriented. Coordination of the dienic system to Fe(CO) 3 in 7 and 9, respectively, resulted in a deflection of the phosphorus atom from the C 4 plane. Electrochemical measurements of 3a−c, 4a−c, and 9 demonstrated that the ferrocenyl units can be oxidized separately. The coordination of the dienic system to the Fe(CO) 3 building block leads to a decrease of the redox splitting (ΔE°′ = 190 mV) in comparison to 8 (ΔE°′ = 240 mV). Mixed-valence [3a−c] + , [4a−c] 2+ , and [9] + show IVCT absorptions of weak to moderate strengths. The coordination of the phosphorus atom to M(CO) 5 in 3a−c has no significant influence on the metal−metal interaction in the mixed-valent species. However, the coordination of the dienic system in 9 results in a significantly decreased electronic communication of the Fc/Fc + termini via the heterocyclic core. ■ INTRODUCTIONWithin the series of five-membered heterocycles, especially the phosphorus-containing heterocycles take an exceptional role because they are nonaromatic or only slightly aromatic. 1−6 The pyramidal phosphorus environment and the high inversion barrier of phospholes lead to a hindered interaction of the phosphorus lone pair with the dienic system. 7 This results in a versatile reaction behavior: e.g., phospholes undergo Diels− Alder reactions of the dienic system, oxidation (P III → P V ), or complexation reactions of the phosphorus atom and/or the dienic system. 1,8−12 Due to the low delocalization within the phosphole ring, they typically behave as a classical diene or phosphine. 1 In complexation reactions the metal atoms can be coordinated by the phosphorus atom (two-electron donor), the dienic system (four-electron donor), or both coordination sites (six-electron donor), resulting in the formation of multimetallic compounds. 1,8,13−16 In the development of new materials with promising photophysical properties, phosphorus-based molecules offer the opportunity to modify their features due to their versatile reaction behavior toward numerous trans...

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“…Recent reviews can be consulted for discussions of this work [6][7][8]. Rather, we will consider the phosphole system solely from the computational energy point of view.…”

Section: Introduction Phosphole Aromaticitymentioning

confidence: 99%