Abstract
fac-M(R3P)(CO)3(bdz) (R = Bu, CHMe2; M = Mo, W; dbz = 3,3'-bipyridazine, 2,2'-bipyrazine, 2,2'- and 4,4'-bipyrimidine) were obtained via electron transfer catalyzed CO substitution of M(CO)4(bdz) in good yields. The preparative procedure involves the use of substoichiometric amts. (10-20 mol\%) of K metal to generate ESR-detectable anion radical intermediates, which then undergo selective substitution of 1 cis carbonyl group by way of hyperconjugative charge transfer from the reduced bidiazine ligand to the metal fragment. A catalytic cycle results because the ESR-detectable tricarbonyl anion radical complexes can reduced M(CO)4(bdz), seen from electrochem. Ligand-centered electron transfer-catalyzed substitution is fairly slow but proceeds by $\geq$1 order of magnitude faster than the daylight-induced process which can lead to dissocn. of the partially sensitive tricarbonyls. The compds. are distinguished by long-wavelength metal-to-ligand charge transfer absorption bands resulting from transitions between the electron-rich metal and the low-lying p* orbitals of the bidiazines. Advantages and disadvantages of the anion radical ligand-induced activation of metal fragments are discussed. on SciFinder(R)
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