Facile rotation around a silicon-phosphorus double bond enabled through coordination to tungsten

Correction: Citation missing unintentionally. Missing intention is included in the additional file. To cite the Correction refer to DOI:10.1039/c5cc04247

Transition Metal Complexes with the Cyclic Polyene Ligands of the Heavy Group 14 Elements

科学研究費助成事業(科学研究費補助金)研究成果報告書：基盤研究(C)2009-2011課題番号：2155003

Free Radical Chemistry of Phosphasilenes

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Free Radical Chemistry of Phosphasilenes

Understanding the characteristics of radicals formed from silicon‐containing heavy analogues of alkenes is of great importance for their application in radical polymerization. Steric and electronic substituent effects in compounds such as phosphasilenes not only stabilize the Si=P double bond, but also influence the structure and species of the formed radicals. Herein we report our first investigations of radicals derived from phosphasilenes with Mes, Tip, Dur, and NMe2 substituents on the P atom, using muon spin spectroscopy and DFT calculations. Adding muonium (a light isotope of hydrogen) to phosphasilenes reveals that: a) the electron‐donor NMe2 and the bulkiest Tip‐substituted phosphasilenes form several muoniated radicals with different rotamer conformations; b) bulky Dur‐substituted phosphasilene forms two radicals (Si‐ and P‐centred); and c) Mes‐substituted phosphasilene mainly forms one species of radical, at the P centre. These significant differences result from intramolecular substituent effects

Spectroscopic Identification of Trifluorosilylphosphinidene and Isomeric Phosphasilene and Silicon Trifluorophosphine Complex

The perfluorinated silylphosphinidene, F3SiP, in the triplet ground state is generated by the reaction of laser-ablated silicon atoms with PF3 in solid neon and argon matrices. The reactions proceed with the initial formation of a silicon trifluorophosphine complex, F3PSi, in the triplet ground state, and a more stable inserted phosphasilene, FPSiF2, in the singlet ground state upon deposition. The trifluorosilylphosphinidene was formed through F-migration reactions of FPSiF2 and F3PSi following a two-state mechanism under irradiation with visible light (λ = 470 nm) and full arc light (λ > 220 nm), respectively. High-level quantum-chemical methods support the identification of F3PSi, FPSiF2, and F3SiP by matrix-isolation IR spectroscopy

Systematic manipulation of siliconoid clusters : from peripheral functionalization to heteroatom doping

Unsaturated silicon clusters (siliconoids) arise as transient intermediates during the industrial preparation of bulk silicon by chemical vapor deposition of silane precursors. Stable representatives reiterate surface features of silicon materials. The present thesis deals with the systematic manipulation of the ligand periphery and the cluster core of Si6 siliconoids. The attachment of representative electrophiles at that particular silicon scaffold is now possible at two distinct vertices and their influence on the electronic structure is rationalized. The isolation of boron- and phosphorus-substituted derivatives prompted investigations on the incorporation of the dopant atoms in the cluster core itself. An NHC-stabilized, cyclic Si2P phosphasilene is shown to dimerize upon Lewis-acid induced abstraction of the donating NHC-ligand. The resulting Si4P2 species exhibit cluster structures reminiscent of the corresponding Si6 siliconoids despite their apparent saturated nature. Access to unsaturated ESi5 heterosiliconoids (E = B, P) was finally gained via a novel dianionic Si5 cluster, which is obtained by the formal reductive cleavage of a SiTip2 moiety from the Si6 siliconoid. The successful incorporation of dopant atoms in siliconoids extends the siliconoid/silicon surfaces analogy to the technological process of silicon doping.Ungesättigte Siliciumcluster (Silicoide) treten als kurzlebige Zwischenprodukte bei der industriellen Herstellung von Bulk-Silicium durch chemische Gasphasenabscheidung von Silan-Vorstufen auf. Stabile Vertreter weisen Oberflächenmerkmale von Siliciummaterialien auf. Die vorliegende Arbeit befasst sich mit der systematischen Manipulation der Ligandenperipherie und des Clusterkerns von Si6-Silicoiden. Die Bindung repräsentativer Elektrophile an diesem bestimmten Siliciumgerüst ist nun an zwei verschiedenen Positionen möglich und ihr Einfluss auf die elektronische Struktur wird rationalisiert. Die Isolierung von Bor- und Phosphor-substituierten Derivaten veranlasste Untersuchungen zum Einbau der Dotierelemente in den Clusterkern selbst. Es wurde gezeigt, dass ein NHC-stabilisiertes, cyclisches Si2P-Phosphasilen bei Lewis-Säure-induzierter Abstraktion des Donor-NHC-Liganden dimerisiert. Die resultierenden Si4P2-Spezies weisen trotz ihrer augenscheinlich gesättigten Natur Clusterstrukturen auf, die an die entsprechenden Si6-Silicoide erinnern. Ungesättigte ESi5-Heterosilicoide (E = B, P) wurden schließlich über einen neuen dianionischen Si5-Cluster zugänglich, der durch die formale reduktive Abspaltung einer SiTip2-Einheit vom Si6-Silicoid erhalten wird. Der erfolgreiche Einbau von Dotierelementen in Silicoide erweitert die Silicoid/Silicium-Oberflächen Analogie um den technologischen Prozess der Siliciumdotierung

Chemie freier Radikale von Phosphasilenen

Das Verständnis der Eigenschaften von Radikalen, die ausgehend von Si-haltigen, schweren Analoga von Alkenen gebildet werden, ist wichtig für ihre Anwendung in der radikalischen Polymerisation. Sterische und elektronische Substituenteneffekte in Phosphasilenen stabilisieren nicht nur die Si=P-Doppelbindung, sondern beeinflussen auch die Struktur und Natur der gebildeten Radikale. Wir berichten hier über Untersuchungen an Phosphasilen-abgeleiteten Radikalen mit Mes-, Tip-, Dur- und NMe2-Substituenten am P-Atom mithilfe von Myonenspinspektroskopie und DFT-Rechnungen. Die Addition von Myonium (einem leichten Isotop von Wasserstoff) an Phosphasilene zeigt, dass a) das Elektronendonor-NMe2- und das sperrigste Tip-substituierte Phosphasilen mehrere myonierte Radikale mit unterschiedlichen Rotamer-Konformationen bilden; b) das sperrige Dur-substituierte Phosphasilen zwei Radikale (Si- und P-zentriert) bildet; und c) Mes-substituiertes Phosphasilen hauptsächlich eine Radikalspezies am P-Zentrum bildet. Diese signifikanten Unterschiede rühren von einem intramolekularen Substituenteneffekt her

Forging a Cage into a Chain: Stepwise Transformation of P4_4 by Silylenes to a Si3_3P4_4 Motif

We have discovered a route to access the longest low-valent molecular silaphospha-chain, a seven-membered chain structure that incorporates three silicon and four phosphorus atoms by stepwise activation of white phosphorus (P$_4$) using two different silylene precursors. The chain species was formed via a highly reactive polyphosphide intermediate. The isolation of a stable analogue of this reaction intermediate was achieved by stepwise reaction with mono and bis(silylenes). Due to the rigidity of the ferrocenediyl framework of the bis(silylene), the isomerization process of the chain structure was hampered. Theoretical studies such as natural bond orbital and atoms in molecules analyses of the seven-membered chain species indicated some degree of delocalization of the double bond system

Phosphorus-Based Substituents in Two-Coordinate Silicon Chemistry: Diphosphanosilylenes and [1.1.1]Propellanes

Low oxidation-state silicon compounds are fundamentally interesting for both academic research and industry. Phosphorus-substituted, two-coordinate congeners thereof are especially appealing, mostly for electronic reasons. However, they remain rare, with only the NHC-stabilized phosphasilenylidene (Im-Dipp2)Si=PMes* (1) reported in 2015 (Im-Dipp2 = 1,3-Dipp2-imidazol-2-ylidene, Dipp = 2,6-i-Pr2C6H3, Mes* = 2,4,6-t-Bu3C6H2). As a hybrid of the seminal NHC-stabilized disilicon(0) (Im-Dipp2)Si=Si(Im-Dipp2) and diphosphene Mes*P=PMes*, compound 1 is a promising starting material in low-valent main group element chemistry. Results of prior reactivity studies on compound 1 include the formation of the η1 transition metal complexes [Fe(CO)4(1)] and [CuCl(1)] as well as the NHC-stabilized 2-silaheteroallenes (Im-Dipp2)(X)SiPMes* (1-X; X = O, NMes; Mes = 2,4,6-Me3C6H2). These inspiring findings prompted the additional reactivity studies on 1 featured in this work. For instance, [Ni(CO)3(1)] was afforded by reaction of [Ni(CO)4] with 1 and served to determine its Tolman electronic parameter. In terms of NHC-stabilized 2-silaheteroallenes, chalcogenation of 1 with SePCy3 and TePCy3 (Cy = cyclohexyl) gave 1-Se and 1-Te, while 1-NTripp was obtained by treatment of 1 with the organic azide N3Tripp (Tripp = 2,4,6-i-Pr3C6H2). Unexpectedly, reaction of 1 with the phosphinidene transfer reagent Mes*PPMe3 afforded the disilatriphospha[1.1.1]propellane Si2(PMes*)3 (2-Si). It constitutes the lighter congener of Ge2(PMes*)3 (2-Ge), which has been previously isolated in our laboratory. Protonation of 2-Si and 2-Ge with [H(OEt2)2][BRF4] (RF = 3,5-(CF3)2C6H3) yielded the respective phosphonium salts [H(2-Si,Ge)][BRF4] under conservation of the [1.1.1]propellane functionalities. Furthermore, reaction of 1 with the NHC Im-i-Pr2-Me2 (Im-i-Pr2Me2 = 1,3-i-Pr2-4,5-Me2-imidazol-2-ylidene) afforded Si2(Si(Im-i-Pr2-Me2)PMes*)(PMes*)2 (3), which may be described as an NHC-stabilized trimer of a phosphasilenylidene, an NHC-stabilized phosphasilene, and a [1.1.1]propellane. Although stable diphosphanosilylenes are highly desired compounds, they remain elusive despite several literature-reported synthetic attempts. In this work, a novel synthetic approach is followed featuring a Hückel-aromatic cyclic tetrylene design, similar to Arduengo carbenes, and a key late-stage salt metathesis at the oxidation state of Si(II). Thus, the first stable P-heterocyclic silylenes (PHSis) Si(PR(CH))2 (R = Mes* (4a-Si), Eind (4b-Si, Eind = 1,1,3,3,5,5,7,7-octaethyl-s-hydrindacen-4-yl)) could be isolated. Both PHSis were afforded from the corresponding 1,4-bisphosphanides Li2(PR(CH))2 (R = Mes* (7a), Eind (7b)) by reaction with suitable NHC-stabilized silicon dihalogenides, respectively. The precursors 7a,b were obtained from the respective 1,4-diphospha-1,3-butadienes RP(CH)2PR (6a,b) via direct lithiation reactions. Initial reactivity studies on the PHSi 4a-Si towards Im-Me4 (Im-Me4 = 1,3-i-Pr2-4,5-Me2-imidazol-2-ylidene), B(C6F5)3, TePCy3, and HCl yielded the corresponding NHC and borane adducts, a 1,3-ditelluradisiletane, and a chlorosilane. Remarkably, 4a,b-Si underwent unprecedented transmetalation reactions to the respective germylenes Ge(PR(CH))2 (4a,b-Ge) upon reaction with GeCl2(1,4-dioxane). The PHSis 4a,b-Si reacted with transition metal reagents to predominantly form complexes of the type [LnM(4a,b-Si)] (LnM = 16 valence electron transition metal fragment). Also, complex [Cp2Ti(PMe3)(4a-Si)] decomposed in a stepwise, partially selective manner to the s-trans-1,4-diphospha-1,3-butadiene complex [Cp2Ti(6a)]. This work also features the synthesis of the ß-phosphaenone TerMesPC(Me)C(Me)O (TerMes = 2,6-Mes2C6H3) starting from diacetyl using the phospha-Wittig reagent TerMesPPMe3. Moreover, the 1,4-diphospha-1,3-butadiene 6a was shown to rearrange to the 1,3-diphospha-1,4-pentadiene (Im-Me4)C(H)PMes*C(H)PMes* upon reaction with the NHC Im-Me4. Lastly, the synthesis of the 16 valence electron titanocene NHC complex [Cp2Ti(Im-Me4)] was revisited

Generation and Identification of the Trifluorosilylarsinidene F3SiAs and Isomeric Perfluorinated Arsasilene FAsSiF2

The trifluorosilylarsinidene F3SiAs in the triplet ground state has been generated through the reaction of laser-ablated silicon atoms with AsF3 in cryogenic Ne- and Ar-matrices. The reactions proceed with the initial formation perfluorinated arsasilene FAsSiF2 in the singlet ground state by two As‒F bonds insertion reaction on annealing. The trifluorosilylarsinidene F3SiAs was formed via F-migration reactions of FAsSiF2 under irradiation at UV light (λ = 275 nm). The characterization of FAsSiF2 and F3SiAs by IR matrix-isolation spectroscopy is supported by computations at CCSD(T)-F12/aug-cc-pVTZ and B3LYP/aug-cc-pVTZ levels of theory