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Four‐Coordinate Group‐14 Elements in the Formal Oxidation State of Zero – Syntheses, Structures, and Dynamics of [{(CO) 5 Cr} 2 Sn(L 2 )] and Related Species
Author(s) -
Kircher Peter,
Huttner Gottfried,
Heinze Katja,
Schiemenz Berthold,
Zsolnai Laszlo,
Büchner Michael,
Driess Alexander
Publication year - 1998
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/(sici)1099-0682(199806)1998:6<703::aid-ejic703>3.0.co;2-h
Subject(s) - chemistry , denticity , pyridine , ligand (biochemistry) , tin , crystallography , oxidation state , stereochemistry , medicinal chemistry , crystal structure , metal , organic chemistry , biochemistry , receptor
The sodium salts Na 2 [{(CO) 5 M} 2 EX 2 ] (M = Cr, Mo, W; E = 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: 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)] (E = Sn: 1d – 1f , E = Ge: 3b ) are as well accessible. The 2,2′‐bipyridine ligand in 1 may be formally replaced by two 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 (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 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 shown by 1 H‐NMR that the pyrimidine entities in these compounds ( 2b , 2c ) are able to rotate by a full 180° turn‐around with respect to one another. This process must involve complete de‐coordination of at least one of the two nitrogen donors in again at least one of the chelate cycles, the activation energy for this process being around 60 kJ/mol. By 119 Sn‐NMR spectroscopy of almost all of the tin 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. From the temperature dependence of the δ values it is concluded that the activation barriers for this association/dissociation process is below 10 kJ/mol. The structures of all new compounds are documented by X‐ray analyses and all compounds are characterized by the usual analytical and spectroscopical techniques.