Tokyo Institute of Technology · Materials Science
Professor Shigekazu Ito's research lab specializes in the design and synthesis of stable open-shell P-heterocyclic systems, particularly phosphorus-centered radicals and biradicals, with a focus on steric and electronic stabilization strategies. The lab develops novel phosphorus-containing heterocycles—such as 1,3-diphosphacyclobutenes and triphosphafulvenes—using sterically encumbered aryl groups (e.g., Mes* = 2,4,6-tri-tert-butylphenyl) to achieve exceptional kinetic and thermodynamic stability. Their work explores the tuning of electronic properties through aryl and heteroaryl substitution, enabling applications in organic electronics, spintronics, and materials science. The lab combines advanced spectroscopic techniques (EPR, X-ray crystallography), computational modeling, and transition-metal coordination to understand and exploit the unique electronic structures of these systems.
Figures are computed from collected data and may differ slightly.
Radically stable: An extremely stable P-heterocyclic organic radical was isolated after oxidation of a sterically encumbered 1,3-diphosphacyclobutenyl anion generated from Mes*CP (Mes*=2,4,6-tBu3C6H2). The structure of the 1,3-diphosphacyclobuten-4-yl radical, as determined by X-ray analysis, was comparable to data obtained from EPR analysis and a computational model. Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2002/2006/z600950_s.pd
A trimer of the phosphanylidene carbenoid, generated from Mes*P=CBr2 with tert-butyllithium, is the novel route to the title compound. The 1,3,6-triphosphafulvene bears three 2,4,6-tri-tert-butylphenyl (Mes*) groups, which contribute to the kinetic stabilization. Coordination of this phosphorus-substituted fulvene derivative to pentacarbonyltungsten furnishes complex 1. The structure of the deep red prismatic crystals of 1 was established.
Biradical chromophore bridge: Di- and trimethylenephenyl moieties facilitate a through-space interaction between sterically demanding biradical subunits (see picture), enabling the design of new electronic materials. The solid-state structure of a bis(biradical) derivative illustrates the proximal positioning of two biradical subunits, allowing for direct interaction between them.
We have developed methods for installing aryl substituents directly on the phosphino groups of the 1,3-diphosphacyclobutane-2,4-diyl system. The aryl substituents tuned the electronic and structural characteristics of the biradical unit both in solution and in the solid state. 1-tert-butyl-2,4-bis(2,4,6-tri-tert-butylphenyl)-1,3-diphosphacyclobuten-4-yl anion, prepared from phosphaalkyne (Mes*C≡P; Mes* = 2,4,6-tBu3C6H2) and t-butyllithium, was allowed to react with an electron-deficient N-hetero
Tuning of the physicochemical properties of the 1,3-diphosphacyclobutane-2,4-diyl unit is attractive in view of materials applications. The use of arynes is shown to be effective for installing relatively electron rich aryl substituents into the open-shell singlet P-heterocyclic system. Treatment of the sterically encumbered 1,3-diphosphacyclobuten-4-yl anion with ortho-silylated aryl triflates in the presence of fluoride under appropriate conditions afforded the corresponding 1-aryl 1,3-diphosp
Radikal stabil: Ein äußerst stabiles P-heterocyclisches organisches Radikal lieferte die Oxidation eines sterisch belasteten 1,3-Diphosphacyclobutenylanions, das aus Mes*CP (Mes*=2,4,6-tBu3C6H2) erzeugt wurde. Die röntgenographisch ermittelte Struktur des 1,3-Diphosphacyclobuten-4-yl-Radikals ist vergleichbar mit Daten, die aus einer EPR-Analyse und einem Computermodell erhalten wurden. Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_200
2-(2,4,6-Tri-tert-butylphenyl)-1-phosphaethyne was allowed to react with 0.5 eq. of alkyllithium to afford 2,4-bis(2,4,6-tri-tert-butylphenyl)-1,3-diphosphacyclobutenes through an intramolecular cyclisation of a 1,3-diphosphabuta-1,3-diene intermediate.
(E)-3,3-Diphenyl-1-(2,4,6-tri-tert-butylphenyl)-2-(trimethylsilyl)-1,3-diphosphapropene was prepared from (2-(2,4,6-tri-tert-butylphenyl)-1-(trimethylsilyl)-2-phosphaethenyl)lithium and chlorodiphenylphosphine, and the properties involving conformational aspects, coordination to metals, and sulfurization were investigated. The structure of 2-(trimethylsilyl)-1,3-diphosphapropene shows C1 symmetry with the phosphino lone pair almost perpendicular to the PC π-system, whereas the 2-chloro- and 2-me
Lithium 1,3-bis(2,6-diisopropylphenyl)-2,3-dihydro-1H-1,3,2-diazaborol-2-uide activates the C-F linkage of fluoroform (CF<sub>3</sub>H) and the Ruppert-Prakash reagent (CF<sub>3</sub>SiMe<sub>3</sub>) to provide difluoromethyl-substituted boranes as air-stable compounds.
According to a protocol for the synthesis of phosphaallenes we recently established, 3-cyclopropyl-1-(2,4,6-tri-tert-butylphenyl)-1-phosphallene was obtained from (Z)-2-bromo-3-cyclopropyl-1-(2,4,6-tri-tert-butylphenyl)-1-phosphapropene. A novel bidentate ligand, 1,2-bis(cyclopropyl)-3,4-bis(2,4,6-tri-tert-butylphenyl)-3,4-diphosphinidenecyclobutene, was prepared by oxidative homocoupling of 3-cyclopropyl-1-(2,4,6-tri-tert-butylphenyl)-1-phosphaallene in the presence of butyllithium, together wi
Reactions of sterically protected 2-bromo-3-phenyl-1-phosphapropenes with bases such as tert-butyllithium and potassium tert-butoxide successfully afforded a bulky 1,4-diphosphafulvene (Mes = 2,4,6-tBu(3)C(6)H(2)) through a novel and formal dimerization pathway of 1-phosphaallene, together with small amounts of 3-phenyl-1-phosphaallene and 3,4-diphosphanylidenecyclobutene. The structure of the 1,4-diphosphafulvene was confirmed by X-ray crystallography indicating somewhat flattened phosphorus at
(Z)-2-Chloro-3,3-diphenyl-1-(2,4,6-tri-tert -butylphenyl)-1,3- diphosphapropene was prepared from chlorodiphenylphosphine and 1-chloro-2-(2,4,6-tri-tert-butylphenyl)-2-phosphaethenyllithium and used for metal complex formation as a ligand to provide carbonyltungsten(0) complexes.
The synthesis of a remarkable cyclic bis(P-H lambda(5)-phosphorane) is reported. A stable phosphorus-heterocyclic biradical, 1,3-diphosphacyclobutane-2,4-diyl, sequentially accepts negatively and positively charged hydrogen atoms to afford 2,4-diphospha-1,3-cyclobutadiene with a diylidic structure containing two P-H bonds.
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