Reduction of [Cp*Sb]₄with Subvalent Main‐Group Metal Reductants: Syntheses and Structures of [(L¹Mg)₄(Sb₄)] and [(L²Ga)₂(Sb₄)] Containing Edge‐Missing Sb₄Units

Abstract

[Cp*Sb] (Cp*=C Me ) reacts with [L Mg] and L Ga with formation of [(L Mg) (μ ,η -Sb )] (L =iPr NC[N(2,6-iPr C H )] , 1) and [(L Ga) (μ,η -Sb )] (L =HC[C(Me)N(2,6-iPr C H )] , 2). The cleavage of the Sb-Sb and Sb-C bonds in [Cp*Sb] are the crucial steps in both reactions. The formation of 1 occurred by elimination of the Cp* anion and formation of Cp*MgL , while 2 was formed by reductive elimination of Cp* and oxidative addition of L Ga to the Sb unit. 1 and 2 were characterized by heteronuclear NMR spectroscopy and single-crystal X-ray diffraction, and their bonding situation was studied by quantum chemical calculations.

Synthesis, Structure, and Reactivity of Ga‐Substituted Distibenes and Sb‐Analogues of Bicyclo[1.1.0]butane

“…All calculated bond lengths within the Ga 2 Sb 2 ( 1 , 2 ) and Ga 2 Sb 4 ( 3 ) cores (BP86‐D3/def2‐SVP level of theory, Tables S2–S4 in the Supporting Information) agree well with the corresponding experimental values (Δ r =0.02–0.08 Å). As predicted by atoms in molecules (AIM), electron localization function (ELF), and natural bond orbital (NBO) analyses, all Sb−Sb bonds in 1 , 2 , and 3 are covalent in nature (Tables S2–S4, Figures –), in accordance with recently reported computational data for these types of complexes …”

“…The Ga atoms in 3 adopt distorted tetrahedral geometries. The Sb−Ga bonds are comparable to those of 1 , 3 , 5 , and [(LGa) 2 (μ,η 2:2 ‐Sb 4 )] [2.6637(11)‐2.6779(11) Å], but slightly shorter than the sum of the covalent radii. The offsets from the best plane of the C 3 N 2 units of the ligands are 0.60(2) Å (Ga1) and 0.51(2) Å (Ga2).…”

“…The bonding situations in 1 , 2 , and 3 were analyzed by using a number of quantum chemical techniques to gain further insight into the chemical bonding within the Ga 2 Sb 2 and Ga 2 Sb 4 skeletons and the results were also compared to those observed in [(LGaNMe 2 ) 2 (μ,η 1:1 ‐Sb 4 )] 5 and [(LGa) 2 (μ,η 2:2 ‐Sb 4 )], respectively. All calculated bond lengths within the Ga 2 Sb 2 ( 1 , 2 ) and Ga 2 Sb 4 ( 3 ) cores (BP86‐D3/def2‐SVP level of theory, Tables S2–S4 in the Supporting Information) agree well with the corresponding experimental values (Δ r =0.02–0.08 Å).…”

“…In addition, reduction reactions of distibines R 4 Sb 2 (R=Me, Et) with LM (M=Al, Ga) proceeded with insertion of LM into the weak Sb−Sb bond and subsequent formation of LM(SbEt 2 ) 2 , whereas analogous reactions with stronger reducing Mg I reagents formed the Zintl‐type [Sb 8 ] 4− anions [(LMg) 4 (μ 4 ,η 2:2:2:2 ‐Sb 8 )] and [(L′Mg) 4 (μ 4 ,η 2:2:2:2 ‐Sb 8 )] {L′=HC[C(Me)N(2,4,6‐Me 3 C 6 H 2 )] 2 } . Very recently, we showed that reduction reactions of cyclo‐tetrastibine [Cp*Sb] 4 , in which the central Sb atoms adopt the formal oxidation state +I, with LGa and [L′′Mg] 2 (L′′= i Pr 2 NC[N(2,6‐ i Pr 2 C 6 H 3 )] 2 ), yielded [(LGa) 2 (μ,η 2:2 ‐Sb 4 )] and [(L′′Mg) 4 (μ 4 ,η 1:2:2:2 ‐Sb 4 )] . Although both compounds formally contain [Sb 4 ] 4− tetraanions as the central structural motifs, their connectivities and bonding natures strongly differ.…”

A General Route to Metal‐Substituted Dipnictenes of the Type [L(X)M]2E2

“…Moreover, reactions of LM (M=Al, Ga, In) with distibine Et 4 Sb 2 occurred with insertion of LM into the Sb−Sb bond and formation of LM(SbEt 2 ) 2 . Comparable findings were reported for reactions of LAl with diphosphines, whereas the reaction of LGa with [Cp*Sb] 4 (Cp*= C 5 Me 5 ), in which the Sb atoms adopt the formal oxidation state +I, yielded [(LGa) 2 (μ,η 2:2 ‐Sb 4 )] . Interestingly, analogous reactions with the stronger reducing Mg I reagents occurred with formation of [(LMg) 4 (μ 4 ,η 2:2:2:2 ‐Sb 8 )] and [(L′Mg) 4 (μ 4 ,η 2:2:2:2 ‐Sb 8 )] (L′=HC[C(Me)N(2,4,6‐Me 3 C 6 H 2 )] 2 ), containing the Zintl‐type [Sb 8 ] 4− anion, as well as [(L′′Mg) 4 (μ 4 ,η 1:2:2:2 ‐Sb 4 )] (L′′= i Pr 2 NC[N(2,6‐ i Pr 2 C 6 H 3 )] 2 ) containing a [Sb 4 ] 4− tetraanion, respectively …”