Four-Coordinate Group-14 Elements in the Formal Oxidation State of Zero – Syntheses, Structures, and Dynamics of [{(CO)5Cr}2Sn(L2)] and Related Species
✍ Scribed by Peter Kircher; Gottfried Huttner; Katja Heinze; Berthold Schiemenz; Laszlo Zsolnai; Michael Büchner; Alexander Driess
- Publisher
- John Wiley and Sons
- Year
- 1998
- Tongue
- English
- Weight
- 879 KB
- Volume
- 1998
- Category
- Article
- ISSN
- 1434-1948
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✦ Synopsis
NMR / Salt metathesis
The sodium salts Na 2 [{(CO) 5 M} 2 EX 2 ] (M = Cr, Mo, W; E = compounds (2b, 2c) are able to rotate by a full 180°turnaround with respect to one another. This process must Ge, Sn, Pb; X = Cl, I, OOCCH 3 ) react with 2,2'-bipyridine (bipy) to form neutral compounds [{(CO) 5 M} 2 E(bipy)] (E = Sn: involve complete de-coordination of at least one of the two nitrogen donors in again at least one of the chelate cycles, 1a-1c; E = Ge: 3a; E = Pb: 4). 1,10-Phenanthroline (phen) analogues of compounds 1a-1c and 3a [{(CO) 5 M} 2 E(phen)] the activation energy for this process being around 60 kJ/ mol. By 119 Sn-NMR spectroscopy of almost all of the tin (E = Sn: 1d-1f, E = Ge: 3b) are as well accessible. The 2,2'bipyridine ligand in 1 may be formally replaced by two compounds described it is shown that equilibria between [{(CO) 5 M} 2 Sn(L 2 )] and [{(CO) 5 M} 2 Sn(L)] + L exist in all cases. pyridine (py) ligands resulting in [{(CO) 5 M} 2 Sn(py) 2 ] (1g: M = Cr, 1h: M = W). The bis-bidentate ligand 2,2'-bipyrimidine
From the temperature dependence of the δ values it is concluded that the activation barriers for this association/ (bpmd) is found to coordinate just one [{(CO) 5 M} 2 Sn] entity in [{(CO) 5 M} 2 Sn(bpmd)] (2b: M = Cr, 2c: M = W). The dissociation process is below 10 kJ/mol. The structures of all new compounds are documented by X-ray analyses and all biimidazolato (biim) ligand binds two [{(CO) 5 Cr} 2 Sn] moieties in [{(CO) 5 Cr} 2 Sn(biim)Sn{Cr(CO) 5 } 2 ] 2-, 2a. It is compounds are characterized by the usual analytical and spectroscopical techniques. shown by 1 H-NMR that the pyrimidine entities in these Na[BPh 4 ] the highly reactive sodium salts