GoldGold Interaction—Stannaborate [SnB₁₁H₁₁]²⁻ Coordination Chemistry

Abstract

We are currently investigating the coordination chemistry and ligand properties of the dianionic stanna-closo-dodecaborate cluster [SnB 11 H 11 ] 2À (1). So far, in a variety of transition-metal complexes, the ligand was found to coordinate exclusively as a terminal ligand with the formation of a tin-metal bond.[1]Here we present the surprising results of preliminary investigations on the stannaborate chemistry with gold electrophiles. 2À :[(Ph 3 P)AuCl]). Interestingly, 50 % of the starting material [(Ph 3 P)AuCl] is still present in the mixture. The other signals in the 31 P NMR spectrum exhibit tin satellites, which provides direct spectroscopic evidence for the formation of a covalent Au À Sn bond. In this solution the anion of 3 is the major Au-Sn component (35 %) and exhibits a characteristic signal in the 31 P NMR spectrum at d = 54.4 ppm with a 2 J(Sn,P) coupling constant of 109.4 Hz. The anion of 2 was identified in solution by a small signal (3 %) at d = 62.9 ppm ( 2 J(Sn,P) = 186.9 Hz). A bis(triphenylphosphane) substitution product ([(Ph 3 P) 2 Au(SnB 11 H 11 )] À ) is also present in solution (5 %) and displays a signal in the 31 P NMR spectrum at d = 44.5 ppm ( 2 J(P, 117 Sn) = 984.2 Hz, 2 J(P, 119 Sn) = 1027.5 Hz). This compound was synthesized in a separate experiment from nucleophile 1, PPh 3 , and [(Ph 3 P)AuCl] in reasonable yield and details will be published later. Treatment of the [(Ph 3 P)AuCl] with 1.5 equivalents of heteroborate 1, led to an increase in the amount of Au 2 Sn 3 cluster 3 formed (68.6 % yield).The geometry of the metal core in the anions of 2 (Figure 1) and 3 (Figure 2)

Stannaborate Chemistry: Nucleophilic Substitution at the Cluster Sphere

“…[3] The investigation of the ligand abilities of this cluster with respect to its cocatalytic properties and use in metal cluster formation are of interest to us. [4,5] Furthermore, we are studying organic transformation reactions at the cluster sphere. So far it is well established that the dianion [SnB 11 H 11 ] 2Ϫ acts as a nucleophile with alkyl iodides or reactive alkyl bromides like propargyl bromide.…”

Anionic Gold(I) Complexes—Twelve‐ and Ten‐Vertex Monocarba‐closo‐borate Anions with Carbon–Gold σ Bonds

“…, with transition metals has been described in detail [9] and unusual gold-tin clusters have been reported, [10,11] for example, [(Ph 3 P) 2 Au 2 (closo-1-SnB 11 H 11 ) 3 ] 4À . [10] Transition-metal complexes with a metal-C cluster 2c-2e s bond of derivatives of the two isomeric anions, [closo-1-CB 9 H 10 ]…”

“…[10] Transition-metal complexes with a metal-C cluster 2c-2e s bond of derivatives of the two isomeric anions, [closo-1-CB 9 H 10 ]…”

Germa‐closo‐dodecaborate: An Ambident and Flexible Coordinating Ligand

“…Examples for μ 2 coordination in the dimeric complex [Au 2 4-[dppm = 1,1-bis(diphenylphosphanyl)methane] have been described earlier. [9] Another interesting feature of the stannaborate cluster is its ability to coordinate through η 3 (B-H) towards transition-metal fragments. [10] [11,12] In this paper we report transition-metal complexes that contain the germanium nucleophile that coordinates tive 3 is high enough to react with [Mo(CO) 5 (thf)] to give the bimetallic complex [(triphos)Fe(GeB 11 H 11 )(MoCO) 5 ] (5), which contains an ambident coordinating germaborate moiety.…”