Oxidative Addition to Sn^II Guanidinate Complexes: Precursors to Tin(II) Chalcogenide Nanocrystals

Abstract

SnS, SnSe and SnTe are potentially important semiconductor materials. Here, we describe the application of chalcogen containing SnIV guanidinate precursors for the production of tin(II) chalcogenide nanocrystals. Reaction of the stannylene(II) guanidinate complex [{Me2NC(NCy)2}2Sn] (1) with Ph2E2 (E = S, Se, Te), and CBr4 forms the SnIV complexes [{Me2NC(NCy)2}2Sn(Ch‐Ph)2] (2–4) and [{Me2NC(NCy)2}2SnBr2] (5), respectively. Complex 5 has been subsequently used for the synthesis of the corresponding SnIV mono chalcogenide complexes, [{Me2NC(NCy)2}2Sn = E] (6–8) by the reaction of 5 with Li2E systems. Isolated tin complexes have characterized by elemental analysis, NMR spectroscopy, and the molecular structures of complexes 2–5 determined by single‐crystal X‐ray diffraction. TG analysis showed that complexes 2–4 and 6–8 all have residual masses close to those expected for the formation of the corresponding “SnE” systems. Complexes 6–8 were assessed for their utility in the formation of nanocrystalline materials. The materials obtained were characterized by powder X‐ray diffraction (XRD), field emission scanning electron microscopy (FE‐SEM) and energy dispersive X‐ray analysis (EDX). Analysis showed formation of SnSe and SnTe from complexes 7 and 8, respectively.

Atomic Layer Deposition of SnTe Thin Film Using Sn(N(CH3)2)4 and Te(Si(CH3)3)2 with Ammonia Coinjection

“…A previous study on Sn­(IV) bis-guanidinate chalcogenide complexes observed a similar conversion of Sn­(IV) to Sn­(II) and a loss of Te(0) during the thermal decomposition process around 130 °C . The process produced SnTe nanocrystals with high controllability on the +2 oxidation state of Sn . The absence of SnTe 2 phase in the phase diagram of Sn-Te solid solution further supports the deposition of SnTe instead of SnTe 2 .…”

“…The intended ligand exchange reaction for the growth of SnTe films is described below. The SnTe deposition requires the electron transfer from Te 2– to Sn­(IV) and sufficient purging of the Te(0) element. A previous study on Sn­(IV) bis-guanidinate chalcogenide complexes observed a similar conversion of Sn­(IV) to Sn­(II) and a loss of Te(0) during the thermal decomposition process around 130 °C . The process produced SnTe nanocrystals with high controllability on the +2 oxidation state of Sn .…”

Calix[4]pyrrolato Stannate(II): A Tetraamido Tin(II) Dianion and Strong Metal‐Centered σ‐Donor

“…Depending on the π‐accepting properties of stannylenes, the tin‐selenium bond can be described via two resonance forms: i) as a Sn=Se double bond (strong π‐acceptor, deshielded selenium, downfield shift) and ii) as a Sn + −Se − single bond with partial charges (weak π‐acceptor, shielded selenium, upfield shift). [Li 2 (thf) x ][2‐Se] shows a 77 Se NMR shift of −391.99 ppm, lying in a range comparable to a tetracoordinated but neutral, bis amidinato stanna(II) selenido complex—thus no notable strong upfield shift [29] . An explanation for this seemingly contrasting result with the TEP number was required.…”

Calix[4]pyrrolatostannat(II): Ein Tetraamidozinn(II)dianion als starker, metallzentrierter σ‐Donor

“…Bemerkenswerterweise liegt dieser Wert unter dem aller bisher beschriebenen Carbene (einschließlich CAACs) [2b] und der elektronenreichsten Phosphinliganden, [27] was die σ-Donor-und schwachen π-Akzeptoreigenschaften von 77 Se-NMR-Verschiebung von À 391.99 ppm, welche in einem für neutrale, tetrakoordinierte Bis(amidinato)stana(II)selenidokomplexe vergleichbaren Bereich liegt -also keine nennenswert starke Hochfeldverschiebung darstellt. [28] Eine Erklärung für dieses scheinbar widersprüchlichen Ergebnis mit dem TEP-Wert war erforderlich. Im Jahr 2020 berichteten Bertrand und Mitarbeiter über Carben-Selenid-Addukte mit unerwartet tieffeldverschobenen 77 Se-NMR-Resonanzen, welche durch nicht-klassische C(sp 3 )HÀ Se-Wasserstoffbrücken verursacht werden.…”

“…Im Jahr 2020 berichteten Bertrand und Mitarbeiter über Carben-Selenid-Addukte mit unerwartet tieffeldverschobenen 77 Se-NMR-Resonanzen, welche durch nicht-klassische C(sp 3 )HÀ Se-Wasserstoffbrücken verursacht werden. [29] [28,30] Interessanterweise wurde gezeigt, dass dianionische Calix- [4]pyrrolatokomplexe von Ni II und Cu II ausschließlich als η 5koordinierende Sechseleketronendonoren über ihre Pyrrolatoeinheiten wirken, die in ihrer zweiten Koordinationssphäre polymetallische Sandwichkomplexe bilden, während der σ-Donormodus nur für [2] 2À beobachtet wird. [13d, 31] Die oxidative Addition von Kohlenstoff-Halogen-Bindungen stellt einen üblichen Reaktivitätsmodus für niedervalente Hauptgruppenelementverbindungen, einschließlich der klassischen Stannylene, dar.…”