Synthesis, structure, and reactivity of polymetallic C3OMe complexes of the formula (eta(5)-C5Me5)Re(NO)(PPh3)(C equivalent to CC(OMe)=)M-m(CO)(n) (M/m/n=Re/2/9, Os/3/11): A new form of coordinated carbon in which a C-3 chain links two metals and spans a third

Reaction of (eta(5)-C5Me5)Re(NO)(PPh3)(C=CLi) with Re-2(CO)(10) and then Me3O+BF4- gives the trirhenium C3OMe complex cis-(eta(5)-C5Me5)Re(NO)(PPh3)(C=CC(OMe)=)Re(CO)(4)Re(CO)(5) (3, 92%). An analogous reaction with Os-3(CO)(12) gives heterotetrametallic (eta(5)-C5Me5)Re-(NO)(PPh3)(C=CC(OMe)=)Os-3(CO)(11) (4, 87%). NMR, IR, and crystallographic data (4) show substantial contributions by Re+=C=C=C(OMe)-M- resonance forms. Reaction of 3 and excess BF3 gas in toluene precipitates [(eta(5)-C5Me5)Re(NO)(PPh3)(mu-eta(1):eta(3):eta(1)-CCC)(Re(CO)(4))-Re(CO)(5)]+BF4- (5, 64%). A crystal structure shows a slightly bent C-3 moiety (152(4)degrees) that binds a rhenium on each end and spans a third. NMR, IR, and bond length data show that 5 is best viewed as a completely metalated pi propargyl or PRe=CC=C-Re(CO)(5) adduct of Re(CO)(4). It is likely derived by initial methoxide abstraction from 3 to give a ReCCCReRe species, followed by rearrangement. Reaction of (eta(5)-C5Me5)Re(NO)(PPh3)(C=CC=CLi) with Re-2(CO)(10) and then Me3O+BF4- gives the C5OMe complex cis-(eta(5)-C5Me5)Re(NO)(PPh3)(C=CC=CC(OMe)=)Re(CO)(4)Re(CO)(5) (8, 44%). When 4 or 8 are treated with BF3 gas, C-x complexes are not detected.