Distibanes and Distibenes from Reduction of Sb(NONR )Cl by using MgI Reagents

Abstract

The bis(amidodimethyl)disiloxane antimony chlorides Sb(NON^R )Cl (NON^R =[O(SiMe₂ NR)₂ ]^2- ; R=tBu, Ph, 2,6-Me₂ C₆ H₃ =Dmp, 2,6-iPr₂ C₆ H₃ =Dipp, 2,6-(CHPh₂ )₂ -4-tBuC₆ H₂ =tBu-Bhp) are reduced to Sb^II and Sb^I species by using Mg^I reagents, [Mg(BDI^R' )]₂ (BDI=[HC{C(Me)NR'}₂ ]^- ; R'=2,4,6-Me₃ C₆ H₂ =Mes, Dipp). Stoichiometric reactions with Sb(NON^R )Cl (R=tBu, Ph) form dimeric Sb^II stibanes [Sb(NON^R )]₂ , shown crystallographically to contain Sb-Sb single bonds. The analogous distibane with R=Dmp substituents has an exceptionally long Sb-Sb interaction and exhibits spectroscopic and reactivity properties consistent with radical character in solution. When R=Dipp, reductions with Mg^I reagents directly give distibenes [Sb(μ-NON^Dipp )Mg(BDI^R' )(THF)_n ]₂ (R'=Mes, n=1; R'=Dipp, n=0). Crystallographic analysis shows a trans-substitution of the Sb=Sb double bond, with bridging NON^Dipp -ligands between the Sb^I and Mg^II centres. An attempt to access the NON^Ph -analogue using the same protocol afforded the polystibide cluster Sb₈ [μ₄ ,η^2:2:2:2 -Mg(BDI^Mes )]₄ , which co-crystallized with the ligand transfer product, [Mg(BDI^Mes )]₂ (μ-NON^Ph ).

Keywords: antimony; distibanes; distibenes; magnesium; reduction.