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-

Reactions of Li+[(eta-5-C5H5)Re(NO)(PPh3)]- with Ph3GeCl and Ph2GeCl2 (THF, -78-degrees-C) give germyl complexes (eta-5-C5H5)Re(NO)(PPh3)(GePh3) (3, 84%) and (eta-5-C5H5)Re(NO)(PPh3)(GePh2Cl) (4, 82%). Reactions of 4 with LiAlH4 and Me3SiOTf give (eta-5-C5H5)Re(NO)(PPh3)(GePh2H) (5, 88%) and (eta-5-C5H5)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 (eta-5-C5H5)Re(NO)(PPh3)(GePh2X) (X = F, Br, I; 92-94%) and with pyridine and 4-methylpyridine to give [(eta-5-C5H5)Re(NO)(PPh3)(GePh2(4-NC5H4R))]+TfO- (83-76%). The C-13 NMR resonances of the diastereotopic germanium phenyl groups in 6 coalesce at low temperatures (DELTA-G double-ended-dagger (268 K, CD2Cl2) = 12.6 kcal mol-1). The most likely mechanisms for this dynamic behavior entail initial triflate dissociation to give the germylene complex [(eta-5-C5H5)Re(NO)(PPh3)(= GePh2)]+TfO- (12). The crystal structure of 6 (monoclinic, P2(1)/n (No. 14); a = 16.908 (3) angstrom, b = 20.160 (3) angstrom, c = 10.437 (2) angstrom, beta = 93.82 (2)-degrees, Z = 4) exhibits features suggestive of a substantial resonance contribution by 12. Addition of HBF4.OEt2 to 3 gives the hydride complex [(eta-5-C5H5)Re(NO)(PPh3)(GePh3)(H)]+BF4- (43%), and reaction of 5 with n-BuLi and then HBF4.OEt2 gives the germylcyclopentadienyl complex (eta-5-C5H4GePh2H)Re(NO)(PPh3)(H) (46%).