Control of the Linkage of Inorganic Fragments of VO Compounds: From Cluster Shells as Carcerands via Cluster Aggregates to Solid-State Structures
✍ Scribed by Prof. Dr. Achim Müller; Dipl.-Chem. Ralf Rohlfing; Erich Krickemeyer; Dr. Hartmut Bögge
- Publisher
- John Wiley and Sons
- Year
- 1993
- Tongue
- English
- Weight
- 554 KB
- Volume
- 32
- Category
- Article
- ISSN
- 0044-8249
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✦ Synopsis
investigated crystalline material, an X-ray powder diffractogram of 3a was recorded. The agreement between this and the diffraction pattern calculated from the single-crystal structure analysis was excellent; however, the X-ray powder diffractogram of 3 a showed large discrepancies with the one calculated for 3b.['.
Once more the uniqueness of the [tBu,P(O)NR']-(R' = iPr, qdo-C,H, 1 ) ligands is shown here: An apparently favorable combination of electronic and steric factors allows the formation of planar high-spin complexes of Nil'. This is surprising, since for the analogous thio complexes 1 the tetrahedral coordination is preferred as the bulkiness of R' increase^.'^] How great the influence of R' is on the properties of the complex is shown by the following preliminary results: According to the powder spectrum, complex 4 (R' = tBu) is planar. Its peff values vary from 1.7 (280K) to 0.6 pB @OK) (solid state) and suggest a spin-crossover between singlet and triplet state.
Experiimntal Procedure
Magnetic measurements were carried out according to Faraday (solid substance) and Evans (solution). 'IP NMR spectroscopy: Bruker AM 200 P,P-di-/c~~/-butyl-N-cyclohexylphosphinic amide: 30% aqueous H,O, (ca. 18 g) was slowly added to tBu,PNH(cyclo-C,H,,) [9] (160mmol) in toluene (100 mL) and the mixture was stirred vigorously. After the exothermic reaction had subsided the organic phase was separated and the solvent was slowly evaporated at room temperature. The amide precipitated, generally in the form of colorless needles. Yield approximately 65%. Correct elemental analysis. m.p. 175 C. ii(3'P) = 54 (toluene).
3 was prepared and handled under inert conditions. tBu,P(O)NH(cyclo-C,H,,) (19mmol) in T H F (25 mL) was treated with n-butyllithium (19mmol. 1.6M solution in hexane) and heated to reflux for a short time. The cooled solution was added to [NiCI,(PPh,),] (9.63 mmol), and the resulting solution was stirred for 2 h at i-oom temperature. Subsequently the solvent was removed under vacuum.
For the isolation o f 3 a the residue was taken up in toluene ( 5 mL). centrifuged, and the clear solution obtained was kept at 4 "C. As a result olive-green crystals of 3 a precipitated slowly from the solution. Yield > 40%. Correct elemental analysis. 1n.p. 206 'C (decomp), molecular masses (cryoscopic in benzene): 550 (0.079molal) 589 (0.085molal) For the isolation of 3 b the residue was taken up in CH,CI, ( 5 mL) and the solution was centrifuged. 3 a and 3 b precipitated from the solution as a mixture of olive-green and blue crystals, which was dissolved in the smallest amount o f dioxane by mild heating. When the solution was left to stand mainly blue crystals o f 3 b were obtained. If necessary, the latter process was repeated until the crystalline materlal was homogeneous. Yield 40%. Correct elemental analysis. 1n.p. 193 C (decomp).
Alternatibely. a saturated solution of 3 a in toluene was allowed to react with a few seed crystals of 3 b. Ink-blue crystals of 3 b precipitated at 4 C slowly in the course of several days.