Enhancing the Variability of [Ge₉] Cluster Chemistry through Phosphine Functionalization

Abstract

The synthetic approach towards molecules that contain Ge atoms with oxidations tate 0, and which are exclusively connected to other Ge atoms, is explored by using anionic clusters extracted from binary solids. Besides providing an ovel variable method for the introductiono fa lkenyl moieties to [Ge 9 ]c lusterc ompounds, this work expands the spectrum of mixed-functionalized [Ge 9 ]c luster anions, which are suitable for the straightforward synthesis of zwitterionic compounds upon coordination to metal cations. In detail, the synthesis of as eries of mixed-functionalized [Ge 9 ]c lusters is reported, including [Ge 9 {Si(TMS) 3 } 3 PRR I ]( R = tBu, R I = (CH 2 ) 3 CH=CH 2 ; 2)and [Ge 9 {Si(TMS) 3 } 2 PRR I ] À (R and R I :alkyl,alkenyl, aryl, aminoalkyl; 3a to 11 a,T MS:( trimethyl)silyl). In 2 and 3a,p entenyl functionalization of the [Ge 9 ]c lusters was achieved by reactiono ft he novel chlorophosphine tBu{(CH 2 ) 3 CH=CH 2 }PCl (1)w ith silylated [Ge 9 ]c lusters. Furthermore, the reactivity of the cluster anions 3a to 11 a towards NHC Dipp MCl (NHC Dipp = 1,3-di(2,6-diisopropylphenyl)imidazolylidine;M = Cu, Ag) showedadependency on the steric demand of the phosphine either zwitterions (3-MNHC Dipp to 7-MNHC Dipp )f eaturing P-M interactions are formed, or Ge-M coordination (8-MNHC Dipp to 11-MNHC Dipp ) occurs. For M = Ag, the formation of zwitterionic complexes was unequivocally provenb yN MR investigations showing 1 J( 31 P-107 Ag/ 109 Ag) spin-spin coupling.

FLP-type nitrile activation and cyclic ether ring-opening by halo-borane nonagermanide-cluster Lewis acid–base pairs

“…Thus, mixed substituted clusters featuring various group 14 element fragments became accessible. [36][37][38][39][40][41] However, the attachment of phosphanyl-moieties [42][43][44][45] to [Ge 9 ] showed that the clusters can be decorated with more interesting Lewis basic functional groups. Similarly of interest is the addition of a ligand comprising an electron-decient boranyl moiety by our group.…”

Boranyl‐Functionalized [Ge9] Clusters: Providing the Idea of Intramolecular Ge/B Frustrated Lewis Pairs

“…Owing to the shielding of the [Ge 9 ] core, reactions of the tris‐silylated cluster are limited to the introduction of less bulky main group element ligands, yielding uncharged cluster compounds with Ge−C, Ge−P and Ge−Sn exo ‐cluster bonds such as [Ge 9 {Si(TMS) 3 } 3 R] [R: Et, [8] (CO) t Bu, [9] t Bu, [9] {(CH 2 ) n CH=CH 2 } ( n : 1, 3) [7c] ], [Ge 9 {Si(TMS) 3 } 3 (PRR l )] (R=R l : i Pr, Cy; [5] R: t Bu, R l : {(CH 2 ) 3 CH=CH 2 } [10] ), and [Ge 9 {Si(TMS) 3 } 3 SnR 3 ] (R: n Bu, [8] Ph [11] ). Except for the Sn‐containing species, which (partially) show multicenter Ge−Sn bonds, all main group element fragments are attached to the [Ge 9 ] entity via 2‐center‐2‐electron (2c‐2e) bonds pointing radially away from the center of the cluster.…”

“…Using a rigid bis-halo-silane, a connection of two clusters to the anion [{Si(SiMe 3 ) 3 } 2 Ge 9 -SiMe 2 -(C 6 H 4 )-SiMe 2 -Ge 9 {Si(SiMe 3 ) 3 } 2 ] 2À is achieved. [17] Comparable to the reactions reported for the tris-silylated species, alkyl-, germanylor phosphanyl-decorated anions [Ge 9 {Si(TMS) 3 }Et] 2À (one Si(TMS) 3 group is cleaved upon crystallization), [18] [Ge 9 {Si-(TMS) 3 } 2 Ge(TMS) 3 ] À [19] or [Ge 9 {Si(TMS) 3 } 2 (PRR l )] À (R, R l : alkyl, aryl, aminoalkyl) [5,10,20] can be synthesized, revealing the prosperous chemistry of [Ge 9 {Si(TMS) 3 } 2 ] 2À with halomain group element compounds.…”

“…We have shown that ligands with free electron lone pairs such as phosphanyl groups (Scheme 1, A) allow for the attachment of Lewis acidic organometallic fragments, [5,10,20] and now focused on the introduction of electron acceptor functions to the sphere of the [Ge 9 ] cluster (Scheme 1, B). Scheschkewitz and co-workers recently reported on the grafting of silicoinoids of general composition Si 6 R 6 with [BH 3 ] À fragments, [21] as well as p-doping such clusters by a formal exchange of one Si vertex by a boranyl group.…”

“…Scheme 1. Different Lewis basic sites at [Ge 9 ] occurring in reported A [5,10,20] and boranyl-functionalized [Ge 9 ] cluster B with FLP character according to quantum-chemical calculations. The lone pair of only one Ge atom is shown.…”