Varying Bonding Modes of the Zintl Ion [Ge₉]^4– in Cu^I Complexes: Syntheses and Structures of [Cu(η⁴‐Ge₉)(PR₃)]^3– (R = iPr, Cy) and [Cu(η⁴‐Ge₉)(η¹‐Ge₉)]^7–

Abstract

Three novel Cu‐capped Ge9 clusters were synthesized from K4Ge9 and phosphane‐stabilized copper(I) compounds CuCl(PR3) with R = isopropyl (iPr) or cyclohexyl (Cy). Reactions in N,N‐dimethylformamide (dmf) at ambient temperature resulted in the isolation of [Cu(η4‐Ge9)(PCy3)]3– as a [K([2.2]crypt)] salt ([2.2]crypt: 1,7,10,16‐tetraoxa‐4,13‐diazacyclooctadecane). From solutions of [Cu(η4‐Ge9)(PiPr3)]3– in liquid ammonia, the anion was isolated when the reaction mixture was stored at –70 °C. Under the same reaction conditions but at a temperature of –40 °C the cluster [Cu(η4‐Ge9)(η1‐Ge9)]7– crystallized in the presence of [2.2.2]crypt(4,7,13,16,21,24‐hexaoxa‐1,10‐diazabicyclo[8.8.8]hexacosan)or [2.2]crypt. The ligand‐free intermetalloid cluster [Cu(η4‐Ge9)(η1‐Ge9)]7– is a unique example in which two differently bonded Ge9 units are linked by a transition‐metal atom. This cluster complex remarkably demonstrates the ability of homoatomic polyanions to bind in different modes to the same transition‐metal atom. One Ge9 nido cluster binds to the copper atom by means of its open square face, whereas the second Ge9 nido cluster is coordinated through one lone pair as a two‐electron σ donor. The key role of the flexible electron‐donor properties of [Ge9]4– in the reaction path towards the formation of intermetalliod clusters is discussed.

Further studies into the reactivity and coordination chemistry of [Ge9]4− Zintl ions. The indium-containing anions [In(Ge9)2]5−, [(Ge9)2In(C6H5)]4− and [Ge9{In(C6H5)3}2]4−

“…The in-depth mechanistic studies carried out by Sevov and co-workers show that the nineatom cluster anions can act as nucleophiles or electrophiles depending on the charge associated with the cluster anions (4À and 2À, respectively), or as radical reducing agents. Finally, it is worth noting that recently a rare example of a metal complex where the metal is coordinated by two [Ge 9 ] 4e cages in different bonding modes, [Cu(h 4 -Ge 9 )(h 1 -Ge 9 )] 7e , was also reported [5].…”

Reprint of “Coordination chemistry of homoatomic ligands of bismuth, selenium and tellurium”

“…The molecular orbital (MO) scheme of the [(Bi 8 2+ )Ru 2+ (Bi 8 2+ )] cluster shows six occupied bonding orbitals with substantial contributions of the ruthenium atom and the coordinating bismuth polycations. Hence, a transfer of six electrons per polycation and thus an 18-electron situation for the ruthenium atom can be inferred, which has previously been reported for the tetrel polyanions E 9 4-(E = Si, Ge, Sn, Pb) [74][75][76]. The Bi 8 2+ polycation (as well as the E 9 4− polyanions) can be correlated to nido-carboranes ligands, such as the dicarbollide anion [77,78] The same coordination mode holds for the terminal Bi 5 + cation in the cluster [Ru 2 Bi 14 Br 4 ] 4+ = [(Bi 5 + )Ru + (Bi 4 Br 4 )Ru + (Bi 5 + )] (Fig.…”

Metal‐Centered Zintl Ions Isolated by Direct Extraction from Endohedral Intermetallic Precursor: [Co1–x@Sn9]4– (x ≈ 0.32) and [Co2@Sn17]5–

“…in the [Ag(Sn 9 -Sn 9 )] 5-cluster with an exo-bond of 2.987(1) Å between Sn atoms of different clusters. [37] The comparison of the two prisms around Sn9 is shown in Figure 4: in cluster 3a the two shortest heights are located at the same side of the antiprism adopting a "cis"-type conformation, while for cluster 2a the "trans"-type setting with one quite short and one very long height is realized. anions.…”

“…[37] Among these polyanions, it is worth to notice that all nine-membered silicon clusters were isolated from solutions of 8-. [22,35] Regarding metal-linked clusters, [(Ge 9 Cu)(Ge 9 )] 7-adopted η 4+1 connection, [36] exobonded clusters [Sn 9 AgSn 9 ] 5-, [38] [Au 3 Ge 18 ] 5-with triangular metals joint, [39] large aggregation clusters [Au 3 Ge 45 ] 9-, [40] [Pb 9 CdCdPb 9 ] 6-with double metal linkage, [41] discrete chains [Hg 3 (Ge 9 ) 4 ] 10-, [42] two infinite chains [Ge 9 Hg] 2-, [43] discrete particles [Sn 9 HgSn 9 ] 6-, [44] and a polymer [Zn(Ge 9 )] 2-adopting η 3 +η 3 connection have been reported.…”