New Forms of Coordinated Carbon:  Wirelike Cumulenic C3 and C5 sp Carbon Chains that Span Two Different Transition Metals and Mediate Charge Transfer

Reactions of (η5-C5Me5)Re(NO)(PPh3)(C⋮CLi) with W(CO)6, Fe(CO)5, or Mn(CO)35-C5HnCl5-n), followed by Me3O+ BF4-, give the heterobimetallic C3OMe complexes (η5-C5Me5)Re(NO)(PPh3)(C⋮CC(OMe))M(CO)x5-C5HnCl5-n)y (M/x/y/n = 3, W/5/0/−; 4, Fe/4/0/−; 5, Mn/2/1/5; 6, Mn/2/1/4; 7, Mn/2/1/0). Spectroscopic and crystallographic (3) data indicate contributions by +ReCCC(OMe)−M- resonance forms. Reactions of 47 and BF3 gas give the title compounds [(η5-C5Me5)Re(NO)(PPh3)(CCC)M(CO)x5-C5HnCl5-n)y (M/x/y/n = 9, Mn/2/1/5; 10, Mn/2/1/4; 11, Mn/2/1/0; 12, Fe/4/0/−). Spectroscopic and crystallographic (9) data indicate dominant contributions by fully cumulated +ReCCCMn resonance forms. Reactions of (η5-C5Me5)Re(NO)(PPh3)(C⋮CC⋮CLi) with Mn(CO)35-C5Cl5), Mn(CO)35-C5Br5), or Fe(CO)5, followed by Me3O+ BF4-, give the C5OMe complexes (η5-C5Me5)Re(NO)(PPh3)(C⋮CC⋮CC(OMe))M(CO)x5-C5X5)y (M/x/y/X = 16, Mn/2/1/Cl; 19, Mn/2/1/Br; 20, Fe/4/0/−). However, Mn(CO)35-C5H5) does not react. Reaction of 16 and BF3 gives the C5 complex [(η5-C5Me5)Re(NO)(PPh3)(CCCCC)Mn(CO)25-C5Cl5)]+ BF4- (21) as a light-sensitive deep brown powder of >94% purity. IR and NMR data show a dominant +ReCCCCCMn resonance form. UV−visible spectra of 911 and 21 show intense absorptions at 392, 396, 414, and 480 nm (ε 55 800, 50 900, 49 100, 60 500 M-1 cm-1), respectively, and weaker longer wavelength bands. These are believed to have appreciable rhenium-to-manganese charge-transfer character.