Carbene-Dichlorosilylene Stabilized Phosphinidenes Exhibiting Strong Intramolecular Charge Transfer Transition

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Chalcogen‐bonded silicon phosphinidenes LSi(E)−P−MecAAC (E=S (1); Se (2); Te (3); L=PhC(NtBu)2; MecAAC=C(CH2)(CMe2)2N‐2,6‐iPr2C6H3)) were synthesized from the reactions of silylene–phosphinidene LSi−P−MecAAC (A) with elemental chalcogens. All the compounds reported herein have been characterized by multinuclear NMR, elemental analyses, LIFDI‐MS, and single‐crystal X‐ray diffraction techniques. Furthermore, the regeneration of silylene–phosphinidene (A) was achieved from the reactions of 2–3 with L′Al (L′=HC{(CMe)(2,6‐iPr2C6H3N)}2). Theoretical studies on chalcogen‐bonded silicon phosphinidenes indicate that the Si−E (E=S, Se, Te) bond can be best represented as charge‐separated electron‐sharing σ‐bonding interaction between [LSi−P−MecAAC]+ and E−. The partial double‐bond character of Si−E is attributed to significant hyperconjugative donation from the lone pair on E− to the Si−N and Si−P σ*‐molecular orbitals.

Section: Methodsmentioning

confidence: 99%

Treatment of Silylene–Phosphinidene with Chalcogens Resulted Exclusively in the Formation of Silicon‐Bonded Chalcogens

Sinhababu¹,

Siddiqui²,

Sarkar³

et al. 2019

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“…Notably, the C cAAC −Si bond lengths of (Cy‐cAAC) 2 Si 2 are significantly different. The dark blue colored cAAC‐dichlorosilylene stabilized phosphinidene (P‐Tip) [(cAAC)→SiCl 2 →P‐Tip, Tip=triisopropylphenyl] displays a strong intramolecular charge transfer (ICT) transition due to the electronic transition from the π P=Si type orbital to the low lying LUMO (π* C−N ) of cAAC . The above‐mentioned examples have in common that they exhibit unusual electronic properties due to the presence of cAACs as ligands.…”

Section: Methodsmentioning

confidence: 99%

Two Structurally Characterized Conformational Isomers with Different C−P Bonds

Roy

Mondal

Kundu

et al. 2017

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The cyclic alkyl(amino) carbene (cAAC) bonded chlorophosphinidene (cAAC)PÀCl (2/2')w as isolated from the direct reaction between cAAC and phosphorus trichloride (PCl 3 ). Compound 2/2' has been characterizedb y NMR spectroscopy and mass spectrometry. 31 PNMR investigations [d % 160 ppm (major) and d % 130 ppm (minor)] reveal that there are two different Pe nvironments of the PÀCl unit. X-ray single-crystal determinations uggests ac o-crystallization of two conformational isomers of (cAAC)PÀCl (2/2'); the major compound possessing ac AACÀPCl unit with C cAAC ÀP1 .75 .T his CÀPb ond length is very close to that of (NHC) 2 P 2 [NHC = N-heterocyclic carbene].T he residual density can be interpreted as ac onformational isomer with as horter C cAAC ÀPb ond similar to an on-conjugated phosphaalkene [RÀP=CR 2 ]. Our study shows an unprecedented example of two conformational isomersw ith different C carbene Àelementb onds. Additionally,B r( 3c/3c'), I( 4c/4c'), and H( 5c/5c')a nalogues [(Me 2 -cAAC)PÀX; X= Br (3), I( 4), H( 5)] of 2c/2c'[(Me 2 -cAAC)PÀCl] were also synthesized and characterized by NMR spectroscopy suggesting similare quilibrium in solution. The unique property of cAAC and the required electronegativity of the X( X= Cl, Br,I ,a nd H) atom play ac rucial role for the existence of the two isomersw hichw ere further studied by theoretical calculations.Since the synthetic reports of stable and isolable singlet Nheterocyclic carbenes (NHCs) in 1988 by Bertrand et al. [1] and in 1991 by Arduengo et al., [2] syntheses and characterization of severals table carbenes have been reported. [3] The use of carbenes has brought numerousb reakthroughs in the field of homogenous catalysis [4] and NHCs have been utilized as strong s-donors in different fields of chemistry. [5] The carbene carbon atom of an NHC is bound to two s-withdrawing and p-donating nitrogen atoms. [5] Consequently,t he accumulationo fe lectron density in the p z -orbital of the carbenec arbon atom is reasonably high leading to the weak p-accepting property of NHC. [6] Theoretical studies as well as experimental evidence have shown that non-negligible p-back-donation occurs in the bondingb etween NHCs and transition metals. [7] The syntheses of cyclic alkyl(amino)c arbenes (cAACs) [8] were reported in 2005 by Bertrande tal. One s-withdrawing and p-donating nitrogen atom of an NHC is replaced by a s-donating quaternary carbon atom in cAAC leading to al ower lying LUMO. cAACs are superior ligands for the stabilization of various unstable chemicals pecies, [9] radicals, [10] and elements in their different oxidation states [11] due to their stronger p-accepting properties. This is energetically advantageous for acceptance of pback donation from the element bound to the carbene carbon atom (C cAAC )o fc AAC (see the Supporting Information). [3b, 12, 13] The electronic properties of C cAAC and the accumulation of electron densities on the elements (E) are very important since they control the chemical behavior of the cAAC-containing compo...

“…2‐Chloro‐ and 2,2‐dichlorophosphasilenes can be obtained as stable NHC complexes 44 – 46 (Figure ) . These complexes possess shorter Si−P bond lengths, compared to 40 – 43 , decreasing from 2.1319(11) Å in 44 to 2.1129(10) Å in 46 . The cyclic (alkyl)(amino) carbene (CAAC) and imidazole‐2‐ylidene NHC complexes 45 and 46 display similar structural features.…”

Section: Structure and Synthesismentioning

confidence: 99%

“…These complexes possess shorter Si−P bond lengths, compared to 40 – 43 , decreasing from 2.1319(11) Å in 44 to 2.1129(10) Å in 46 . The cyclic (alkyl)(amino) carbene (CAAC) and imidazole‐2‐ylidene NHC complexes 45 and 46 display similar structural features. These molecules exhibit trans ‐bent geometry (C CAAC ‐Si‐P‐C Tip torsion angle 169.24°, 45 a ).…”

Section: Structure and Synthesismentioning

confidence: 99%

Advances in Phosphasilene Chemistry

Nesterov

Breit

Inoue

2017

Heavier alkene analogues possess unique electronic properties and reactivity,e ncouraging multidisciplinary research groups to utilize them in the rational designo fn ovel classes of compounds and materials.P hosphasilenes are heavier imine analogues,c ontaining highly reactiveS i =P double bonds. Recent achievements in this field are closely related to the progress in the chemistry of stable low-coordinate silicon compounds. In this Review,w eh avea ttempted to summarize in ac omprehensive way the availabled ata on the structures, syntheses, electronic andc hemical properties of these compounds, with an emphasis on recent achievements.