Kinetische Untersuchungen über Substitutionsreaktionen an Metallkomplexen. 9. Mitteilung [1]. Kinetik und Mechanismus der Reaktion von Hexamethylborazolchrom‐tricarbonyl mit tertiären Phosphinen und Phosphiten [2]
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Media type:
E-Article
Title:
Kinetische Untersuchungen über Substitutionsreaktionen an Metallkomplexen. 9. Mitteilung [1]. Kinetik und Mechanismus der Reaktion von Hexamethylborazolchrom‐tricarbonyl mit tertiären Phosphinen und Phosphiten [2]
Contributor:
Deckelmann, E.;
Werner, H.
Published:
Wiley, 1969
Published in:
Helvetica Chimica Acta, 52 (1969) 4, Seite 892-901
Description:
AbstractHexamethylborazolechromium tricarbonyl B3N3(CH3)6 Cr(CO)3 reacts with tertiary phosphines and phosphites under surprisingly mild conditions by cleavage of the ring‐to‐metal bond. For L = trialkylphosphines and trialkyl‐ or triaryl‐phosphites, compounds of the general composition cis‐Cr(CO)3L3 are formed, whereas for L = triphenyl‐ and tricyclohexyl‐phosphine the complexes trans‐Cr(CO)4L2 are obtained.The kinetics of the reaction of B3N3(CH3)6 Cr(CO)3 with phosphites P(OR)3 (R = CH3, C2H5, C6H5) have been studied by means of spectrophotometric methods. The second‐order rate law indicates a primary, rate‐determining attack of the phosphite to either the metal atom or the ring ligand of the borazole complex. This attack is favoured by an extremely low activation energy. The mechanism of the substitution process is discussed in detail, and the reactivity of the hexamethylborazole compound is compared with that of other half‐sandwich type complexes.