Synthesis of the Germanium(I) Compounds [Ge2Hal4]2– and Their Reductive Condensation to Octahedral [Ge6]2– Clusters in an Organometallic Environment

Abstract

GeI2 reacts with [M2(CO)10]2– (M = Cr, W) leading to reductive coupling of two GeI2 units to produce the [Ge2I4]2– ligands of [{(OC)5M}I2Ge–GeI2{M(CO)5}]2– (1a and 2a). The [Ph4P] salts of these anions have been characterised by X‐ray structure analyses as have the [Ph4P] salts of [{(OC)5M}Cl2Ge–GeCl2{M(CO)5}]2– (1b and 2b) obtained from the iodo derivatives 1a and 2a by halide metathesis with [Ph4P]Cl. Treatment of GeI2 with [W2(CO)10]2– in the presence of 2,2′‐bipyridine leads to [{(OC)5W}I2Ge–Ge(bipy){W(CO)5}] (3). The digermanium ligands in 1–3 contain germanium in the unconventional formal oxidation state +I. Reductive condensation of [{(OC)5Cr}I2Ge–GeI2{Cr(CO)5}]2– (1a) by addition of [Cr2(CO)10]2– leads to the octahedral cluster [{(OC)5Cr}6Ge6]2– (4) in a yield of 40%. The sequence of reactions as reported describes the first systematic approach to the synthesis of [E6]2– clusters.

Efficient Syntheses of the Complete Set of Compounds [{(OC)5M}6E6]2− (M = Cr, Mo, W; E = Ge, Sn) − Structure and Redox Behaviour of the Octahedral Clusters [Ge6]2− and [Sn6]2−

“…With THF as the eluent all by-products could be removed. [2,17,22] After elution with ethanol, the solutions of the sodium salts of 1, 2, and 3, respectively, were obtained, which were reduced to 10 mL in vacuo. Addition of solid [Ph 4 P]Cl (750 mg, [18] (518 mg, 1 mmol), solid SnCl 2 (190 mg, 1 mmol) was added in one portion.…”

“…[20] For the reaction of [Cr 2 (CO) 10 ] 2Ϫ with GeI 2 , it has been shown that [{(OC) 5 Cr}I 2 GeϪGeI 2 {Cr(CO) 5 }] 2Ϫ is obtained when the stoichiometric ratio of [Cr 2 (CO) 10 ] 2Ϫ and GeI 2 is 1:1. [17] This digermanium compound is an intermediate in the reductive pathway from GeI 2 to the [Ge 6 ] 2Ϫ core of 1: Further reduction of [{(OC) 5 Cr}I 2 GeϪGeI 2 {Cr(CO) 5 }] 2Ϫ with 2 equiv. of [Cr 2 (CO) 10 ] 2Ϫ produces 1 in fair yields (Scheme 3).…”

“…of [Cr 2 (CO) 10 ] 2Ϫ produces 1 in fair yields (Scheme 3). [17] Scheme 3. Syntheses of 1 and 3 from tetraiododigermanate(2Ϫ)-precursors in a ratio 2:1 This type of reaction has been reported for compound 1.…”

“…Syntheses of 1 and 3 from tetraiododigermanate(2Ϫ)-precursors in a ratio 2:1 This type of reaction has been reported for compound 1. [17] It has now been found that 3 can be obtained in good yields (60%) from [{(OC) 5 W}I 2 GeϪGeI 2 {W(CO) 5 }] 2Ϫ [17] and 2 equiv. of [W 2 (CO) 10 ] 2Ϫ .…”

“…It had recently been found that the digermanium derivative [{(OC) 5 Cr} 2 Ge 2 I 4 ] 2Ϫ , which is itself obtained by the reduction of GeI 2 with Na 2 [Cr 2 (CO) 10 ], is a suitable precursor from which [{(OC) 5 Cr} 6 Ge 6 ] 2Ϫ (1) is obtained in up to 40% yield by further reduction. [17] This result stimulated a more systematic screening of the reactions of [M 2 (CO) 10 ] 2Ϫ [18,19] (M ϭ Cr, Mo, W) with EHal 2 (GeI 2 , SnCl 2 ). In this way, feasible procedures for the syntheses of [{(OC) 5 M} 6 E 6 ] 2Ϫ (E ϭ Ge, Sn; M ϭ Cr, Mo, W) have been developed such that the cyclovoltammetric and spectroscopic behaviour of these compounds, as well as their solid-state and solution structures, could now be studied in detail.…”