[As₃M(As₃Pb₃)]³⁻ (M = Nb, Ta): Ternary Heterometallic Clusters with Early Transition Metal Atoms and Aromatic [Pb₃]²⁻

Abstract

Main observation and conclusion Two ternary clusters, [As3Nb(As3Pb3)]3− 1 and [As3Ta(As3Pb3)]3− 2, were directly extracted from “K8NbPbAs5” and “K8TaPbAs5” intermetallic solid in the presence of ethylenediamine and 2.2.2‐crypt, respectively. Both 1 and 2, comprising an electron‐poor early transition metal‐atom Nb or Ta coordinated to a As3 triangle and a bowl‐like As3Pb3, were characterized by single crystal X‐ray diffraction, energy dispersive X‐ray (EDX) and electrospray ionization mass‐spectrometry (ESI‐MS). They also represent the first examples of the Pb‐As hybrid in solution‐based Zintl anion chemistry and DFT calculations revealed a σ‐aromaticity of the [Pb3]2− unit.

Synthesis and Characterization of Homoleptic Zintl Anions [(Pn7)M(Pn7)]4− (M/Pn=Pb/As, Zn/Bi)

“…The range is a bit wider than that observed for [(As 7 )Pb(As 7 )] 4− , but the average value of the Pb−As bond lengths in [PbAs 15 ] 3− (2.818 Å) and [(As 7 )Pb(As 7 )] 4− (2.912 Å) agree well. They are a longer on average than reported for [As 3 M(As 3 Pb 3 )] 3− (2.7836 Å for M=Nb; 2.7826 Å for M=Ta) [26] . Both the bond lengths and the coordination environments of the atoms suggest that all bonds within the two anions in 1 are (polar) covalent in nature, with a slight polarization of the electron density of the Pb−As bonds towards the more electronegative As atom (cf.…”

“…They are a longer on average than reported for [As 3 M(As 3 Pb 3 )] 3À (2.7836 Å for M = Nb; 2.7826 Å for M = Ta). [26] Both the bond lengths and the coordination environments of the atoms suggest that all bonds within the two anions in 1 are (polar) covalent in nature, with a slight polarization of the electron density of the PbÀ As bonds towards the more electronegative As atom (cf. EN(Pb): 1.55 and EN(As): 2.20 according to the Allred-Rochow scale).…”

Synthesis and characterisation of the ternary intermetalloid clusters {M@[As8(ZnMes)4]}3− (M = Nb, Ta) from binary [M@As8]3− precursors

“…1–3 The majority of known clusters in this class are synthesised either by extraction of the corresponding quaternary intermetallic phases or by the reaction of binary Tt/Pn or Tr/Pn Zintl anions with sources of low-valent transition metals, lanthanides or actinides. 4–6 Scheme 1a illustrates the extraction of the quaternary solid-state Zintl phase K/Ge/As/M (M = V, Nb, Ta) in ethylenediamine (en) in the presence of the sequestering agent, [2.2.2]crypt, which allows for the crystallization of cluster anions including 12-vertex [M@Ge 8 As 4 ] 3− (M = V, Ta), and 14-vertex [M@Ge 8 As 6 ] 3− (M = Nb, Ta). 7,8 Clusters such as [Zn@Zn 5 Sn 3 Bi 3 @Bi 5 ] 4− , 9 [Ni 2 @Sn 7 Bi 5 ] 3− , 10 [Pd 3 @Sn 8 Bi 6 ] 4− , 11 [Pd@Pd 2 Pb 10 Bi 6 ] 4− , 12 and [Eu@Sn 6 Bi 8 ] 4− , 13 have, in contrast, been accessed by reacting a salt of a binary mixed main group Zintl compound, [K([2.2.2]crypt)] 2 [TrBi 3 ]·en (Tr = Ga, In, Tl) or [K([2.2.2]crypt)] 2 [Tt 2 Pn 2 ]·en (Tt/Pn = Sn/Sb, Sn/Bi, Pb/Bi) 14,15 with various organometallic compounds.…”