SYNTHESIS, STRUCTURE, AND REACTIVITY OF FUNCTIONALIZED GERMYL COMPLEXES OF THE FORMULA (ETA-5-C5H5)RE(NO)(PPH3)(GEPH2X) - EQUILIBRIA INVOLVING THE GERMYLENE COMPLEX [(ETA-5-C5H5)RE(NO)(PPH3)(=GEPH2)]+TFO-
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Reactions of Li+[(5-C5H5)Re(NO)(PPh3)] with Ph3GeCl and Ph2GeCl2 (THF, 78 C) give germyl complexes (5-C5H5)Re(NOHPPh3HGePh3) (3, 84%) and (5-CsHs)Re(NO)(PPh3)(GePh2Cl) (4, 82%). Reactions of 4 with LiAlH and Me3SiOTf give (5-C5H6)Re(NO)(PPh3)(GePh2H) (5, 88%) and (5-C5Hs)Re(NO)(PPh3)(GePh2OTf) (6, 82%). The triflate substituent in 6 is very labile, as evidenced by rapid reactions with halide ion sources to give (5-C5H5)Re(NO)(PPh3)(GePh2X) (X = F, Br, I; 9294%) and with pyridine and 4-methylpyridine to give [(5-C5H5) Re(NO) (PPh3) (GePh2(4-NC5H4R))]TfO (8376%). The , 3C NMR resonances of the diastereotopic germanium phenyl groups in 6 coalesce at low temperatures (G*(268 K, CD2Cl2) = 12.6 kcal mol1). The most likely mechanisms for this dynamic behavior entail initial triflate dissociation to give the germylene complex [(5-C5H5)Re(NO)(PPh3)(=GePh2)]+TfO (12). The crystal structure of 6 (monocliic, P21/n (No. 14); = 16.908 (3) , b = 20.160 (3) , c = 10.437 (2) , = 93.82 (2), Z = 4) exhibits features suggestive of a substantial resonance contribution by 12. Addition of HBF4OEt2 to 3 gives the hydride complex [(5-C5H5)Re(NO)(PPh3)(GePh.i)(H)]+BF4 (43%), and reaction of 5 with n-BuLi and then HBF4OEt2 gives the germylcyclopentadienyl complex (5-C5H4GePh2H)Re(NO)(PPh3)(H) (46%). 1991, American Chemical Society. All rights reserved.
