Reactions of a diborylstannylene with CO₂ and N₂O: diboration of carbon dioxide by a main group bis(boryl) complex

Abstract

The reactions of the boryl-substituted stannylene Sn{B(NDippCH)2}2 (1) with carbon dioxide have been investigated and shown to proceed via pathways involving insertion into the Sn–B bond(s). In the first instance...

Ligand Assisted CO2 Activation and Catalytic Valorization by an NHI‐Stabilized Stannylene

“…In contrast to transition‐metals, a limited number of low valent main‐group metal‐initiated CO 2 activations and catalytic functionalizations have been reported [3a,4m, 7] . Pertinent to this work, insertion of CO 2 via stanna‐amination by (Sn[N(SiMe 2 R) 2 ] 2 (R=Me, Ph) I , [4g,h] stanna‐borylation by Sn[B(NDippCH) 2 ] 2 II , [4i] as well as reversible CO 2 uptake by P,P‐chelated stannylene [( i ‐Pr 2 P) 2 N] 2 Sn III , [4j] rendering Sn(II)carboxylates, could be demonstrated (Scheme 1b). Nonetheless, poor stability of these Sn(II)carboxylates leads to undesired rearrangement reactions, such as diboration of CO 2 in case of II or the 1,3‐shift of a trimethylsilyl group from the ligand to inserted CO 2 in case of I [4g–i] .…”

“…Pertinent to this work, insertion of CO 2 via stanna‐amination by (Sn[N(SiMe 2 R) 2 ] 2 (R=Me, Ph) I , [4g,h] stanna‐borylation by Sn[B(NDippCH) 2 ] 2 II , [4i] as well as reversible CO 2 uptake by P,P‐chelated stannylene [( i ‐Pr 2 P) 2 N] 2 Sn III , [4j] rendering Sn(II)carboxylates, could be demonstrated (Scheme 1b). Nonetheless, poor stability of these Sn(II)carboxylates leads to undesired rearrangement reactions, such as diboration of CO 2 in case of II or the 1,3‐shift of a trimethylsilyl group from the ligand to inserted CO 2 in case of I [4g–i] . This is attributed to the comparatively high oxophilicity of the corresponding ligand functional groups, which impede their catalytic use in CO 2 reduction [4g–j,8] …”

“…Nonetheless, poor stability of these Sn(II)carboxylates leads to undesired rearrangement reactions, such as diboration of CO 2 in case of II or the 1,3‐shift of a trimethylsilyl group from the ligand to inserted CO 2 in case of I [4g–i] . This is attributed to the comparatively high oxophilicity of the corresponding ligand functional groups, which impede their catalytic use in CO 2 reduction [4g–j,8] …”

“… a) Insertion of CO 2 by transition metal‐ligand bond cleavage. b) Recent examples of stannylenes for CO 2 activation and catalytic reduction [4g–l] . c) Two‐ coordinate stannylene‐NHI synergy (Dipp=2,6‐ i Pr 2 (C 6 H 3 ), Mes=2,4,6‐Me 3 (C 6 H 2 ), Mes Ter=2,6‐Mes 2 C 6 H 3 , pin=pinacolato, R′R′′= i Pr 2 ; R′=H, R′′=Dipp).…”

“…However, synergistic activation of CO 2 via tetrylene‐ligand cooperation and subsequent conversion to value added products is not yet reported. Based on these previous accounts, and considering the high electrophilicity of stannylenes, a Sn(II) center connected to an electron‐rich and consequently nucleophilic ligand should therefore be an excellent choice to procure CO 2 activation and conversion while bypassing the requirement for Sn(II)‐Sn(IV) redox shuttling [4h–k,8a,9] . Additionally, the reduced bond strength of Sn(II)−O in comparison to E(II)−O (E=Si, Ge) bonds renders Sn(II) an ideal metal center for CO 2 functionalization [10] …”