We present the high-temperature synthesis of intermetallic precursors K4Ge9, their dissolution in ethylenediamine to form Ge94- deltahedral Zintl ions, and the reaction of the clusters with alkynes to form organo-Zintl ions. The latter are characterized by electrospray mass spectrometry in solutions and by single-crystal X-ray diffraction in the solid state.
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Method Article
Synthesis of Nine-atom Deltahedral Zintl Ions of Germanium and their Functionalization with Organic Groups
In This Article
Summary
Abstract
Although the first studies of Zintl ions date between the late 1890's and early 1930's they were not structurally characterized until many years later.1,2 Their redox chemistry is even younger, just about ten years old, but despite this short history these deltahedral clusters ions E9n- (E = Si, Ge, Sn, Pb; n = 2, 3, 4) have already shown interesting and diverse reactivity and have been at the forefront of rapidly developing and exciting new chemistry.3-6 Notable milestones are the oxidative coupling of Ge94- clusters to oligomers and infinite chains,7-19 their metallation,14-16,20-25 capping by transition-metal organometallic fragments,26-34 insertion of a transition-metal atom at the center of the cluster which is sometimes combined with capping and oligomerization,35-47 addition of main-group organometallic fragments as exo-bonded substituents,48-50 and functionalization with various organic residues by reactions with organic halides and alkynes.51-58
This latter development of attaching organic fragments directly to the clusters has opened up a new field, namely organo-Zintl chemistry, that is potentially fertile for further synthetic explorations, and it is the step-by-step procedure for the synthesis of germanium-divinyl clusters described herein. The initial steps outline the synthesis of an intermetallic precursor of K4Ge9 from which the Ge94- clusters are extracted later in solution. This involves fused-silica glass blowing, arc-welding of niobium containers, and handling of highly air-sensitive materials in a glove box. The air-sensitive K4Ge9 is then dissolved in ethylenediamine in the box and then alkenylated by a reaction with Me3SiC≡CSiMe3. The reaction is followed by electrospray mass spectrometry while the resulting solution is used for obtaining single crystals containing the functionalized clusters [H2C=CH-Ge9-CH=CH2]2-. For this purpose the solution is centrifuged, filtered, and carefully layered with a toluene solution of 18-crown-6. Left undisturbed for a few days, the so-layered solutions produced orange crystalline blocks of [K(18-crown-6)]2[Ge9(HCCH2)2]•en which were characterized by single-crystal X-ray diffraction.
The process highlights standard reaction techniques, work-up, and analysis towards functionalized deltahedral Zintl clusters. It is hoped that it will help towards further development and understanding of these compounds in the community at large.
Protocol
1. Preparing Niobium Tubes
- Before cutting the niobium (Nb) tubes, prepare Nb-cleaning solution. In a 500 ml plastic bottle, measure out and add via a 100 ml measuring cylinder the following stock solutions as received: 110 ml H2SO4, followed by 50 ml HNO3, followed by 40 ml HF. Mix well and allow reaching room temperature before using.
- Measure the Nb tube, 4.5 cm in length, and cut with a pipe cutter. Avoid kinking the tubing. Repeat 3 more times.
- In a well-ventilated fume-hood, place the four Nb tubes, length-wise, in a 100 ml plastic beaker. Pour the Nb-cleaning solution into the beaker until tubes are....
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Discussion
It is important to clean well the partially oxidized Nb tubes. However, if the tubes are left too long in the Nb cleaning solution, this will severely compromise the thickness of the tube. Thus, 10 – 15 seconds are imperative and the tubes should be very lustrous at the end (Fig 3). After the tubes are sealed inside the fused silica jacket they should be cleaned again with a dilute Nb acid solution. This should result in mild effervescence, cleaning any oxidized areas on Nb tubes that occurred during welding o.......
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Disclosures
No conflicts of interest declared.
Acknowledgements
The authors would like to thank the National Science Foundation for the continuous financial support (CHE-0742365) and for the purchase of a Bruker APEX II diffractometer (CHE-0443233) and a Bruker Microtof-II mass spectrometer (CHE-0741793). The authors would also like to thank CEST facility for their use of the Micromass Quattro-LC mass spectrometer.
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Materials
| Name | Company | Catalog Number | Comments |
|---|---|---|---|
| D8-Xray diffractometer | Bruker Corporation | Bruker APEX II | |
| Electrospray mass spectrometer | Bruker Corporation | Microtof-II | |
| Electrospray mass spectrometer | Micromass | Quattro-LC | triple -quadropole |
| Drybox | Innovative Technology | S-1-M-DL | IT-Sys1 model |
| Inert Gas/Vacuum Shielded Arc Welding Arrangement |  LDS Vacuum Products | Special Order | |
| Arc Welder Power Source | Miller | Maxstar-91 | |
| Welding Rubber Gloves | Home Depot | KH643 | |
| Electric Engraver | Burgess Products | 74 | Vibro-Graver |
| Circular Glass Saw | Pistorius Machine Co. Inc | GC-12-B | |
| Tube Furnace | Lindberg/Blue M | TF55035 | Minimite Laboratory Tube Furnace, Moldatherm (1100 °C) |
| Glass Drying Oven | Fisher Scientific | 13-247-650G | |
| High Vacuum Hg Schlenk-Line | Special Order | Univ Of Notre Dame | Alternative: Edwards E050/60; VWR International; Cat. No. EVB302-07-110 |
| Large Torch | Victor Technologies | JT100C | Welding torch, tip: Victor 5-W-J |
| Small Torch | Veriflo Co. | 3A | Blow-pipe |
| Tesla Coil | VWR international | KT691550-0000 | Leak detector |
| Stirrer/Hot -Plate | VWR international | 12620-970 | VWR HOT PLATE STR DY-DUAL120V |
| Balance | Denver Instrument | 100A | XE Series |
| Centrifuge | LW Scientific, Inc. | E8C-08AV-1501 | Variable speed |
| Graphite Reamer, (flaring) | ABR Imagery, Inc. | 850-523 B01 | Open holes in Glass Blowing and flaring edges |
| Striker | Fisher Scientific | 12-007 | |
| Vise-Grips | Home Depot | 0902L3SM | |
| Pipe-Cutter | Home Depot | 32820 | |
| Cutting Pliers | Home Depot | 437 | |
| Plastic Beaker | VWR international | 13890-046 | |
| Measuring Cylinder | VWR international | 65000-006 | Careful, HF etches glass (if using a glass one) |
| Large Plastic Bottle | VWR international | 16128-542 | |
| 13 x 100 Test-Tubes | VWR international | 47729-572 | CULTURE TUBE 13X100 CS1000 |
| Laboratory (Rubber) Stoppers | Sigma-Aldrich | Z164437-100EA | Size 00 |
| Test-Tube Rack | VWR international | 60196-702 | 10-13 mm tube OD |
| Stir-Bars | StirBars.com/Big Science Inc. | SBM-0803-MIC | PTFE 8x3 mm Micro |
| Glass Pipettes | VWR international | 14673-043 | VWR PIPET PASTEUR 9IN CS1000 |
| Rubber Bulbs | VWR international | 56311-062 | Latex, thin walled |
| Glass Wool | Unifrax I LLC | 6048 | Fiberfrax Bulk Fiber Insulation, Ceramic fiber |
| Glass Slides | VWR international | 16004-422 | 75x25x1mm, Microscope Slides |
| Paratone-N oil | Hampton Research | Parabar 10312 | Known as: Paratone-N, Paratone-8277, Infineum V8512 |
| High Vacuum Silicone Grease | VWR international | 59344-055 | Dow Corning |
| Liquid Nitrogen | University of Notre Dame | ||
| Argon Gas Cylinder | Praxair, Inc. | TARGHP | |
| Nitrogen Gas Cylinder | Praxair, Inc. | QNITPP | |
| Oxygen Gas Cylinder | Praxair, Inc. | OT | 337 cf CYL |
| Hydrogen Gas Cylinder | Praxair, Inc. | HK | 195 cf CYL |
| Propane Gas Cylinder/source | University of Notre Dame | UND | |
| Quartz tubing, Lg | Quartz Scientific Inc. | 100020B | 20 mm id x 22mm od x 48" clear fused quart tubing |
| Quartz tubing, Md | Quartz Scientific Inc. | 100007B | Clear Fused Quartz Tubing,7mm id x 9mm od x 48" |
| Round Bottom Quartz Joint | Quartz Scientific Inc. | 6160189B | Ball joint |
| Quartz Safety Glasses | Wale Apparatus | 11-1127 | waleapparatus.com |
| Pyrex Safety Glasses | Wale Apparatus | 11-2125-B3 | For clear and color borosilicate glass |
| Blow Hose Kit | Glass House | BH020 | glasshousesupply.com |
| Niobium Tubes | Shaanxi Tony Metals Co., Ltd | Niobium Tube, 50 ft | Seamless Niobium Tube Outside diameter: 0.375 (±0.005) inches. Wall thickness: 0.02(±0.003) Inches Niobium should be annealed. |
| PEEK Starter Kit for Mass Spect | Waters | PSL613321 | PEEK (PolyEtherEtherKetone) tubing, nuts, ferrule, fits |
| Mass Spect Needle Set | VWR international | 60373-992 | Hamilton Manufacturer (81165) |
| H2SO4 | VWR international | BDH3072-2.5LG | ACS Grade |
| HNO3 | VWR international | BDH3046-2.5LPC | ACS Grade |
| HF | VWR international | BDH3040-500MLP | ACS Grade |
| Distilled Water | University of Notre Dame | UND | |
| Acetone | VWR international | BDH1101-4LP | |
| Ethylenediamine | VWR international | AAA12132-0F | 99% 2.5 L |
| Toluene | VWR international | 200004-418 | 99.8 %, anhydrous |
| Mercury | Strem Chemicals, Inc. | 93-8046 | |
| Potassium (K) metal | Strem Chemicals, Inc. | 19-1989 | Sealed in glass ampoule under Ar |
| Germanium (Ge) powder | VWR international | AA10190-18 | GERM PWR -100 MESH 99.999% 50G |
| Bistrimetylsilylacetylene, (Me3SiC≡CCSiMe3) | Fisher Scientific | AC182010100 | |
| 18-crown-6 (1,4,7,10,13,16-Hexaoxacyclooctadecane) | VWR international | 200001-954 | 99%, 25 gm |
| 2,2,2-crypt (4,7,13,16,21,24-Hexaoxa-1,10 diazabicyclo[8.8.8]hexacosane) | Sigma-Aldrich | 291110-1G | 98% |
References
- Corbett, J. D. Polyatomic Zintl Anions of the Post-Transition Elements. Chem. Rev. 85, 383-397 (1985).
- Fässler, T. F. The renaissance of homoatomic nine-atom polyhedral of the heavier carbon-group elements Si-Pb. Coord. Chem. Rev. 215, 34....
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