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)₃(η⁵-C₅H_nCl_5-n), followed by Me₃O⁺ BF₄^-, give the heterobimetallic C₃OMe complexes (η⁵-C₅Me₅)Re(NO)(PPh₃)(C⋮CC(OMe))M(CO)_x(η⁵-C₅H_nCl_5-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 4−7 and BF₃ gas give the title compounds [(η⁵-C₅Me₅)Re(NO)(PPh₃)(CCC)M(CO)_x(η⁵-C₅H_nCl_5-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)₃(η⁵-C₅Cl₅), Mn(CO)₃(η⁵-C₅Br₅), or Fe(CO)₅, followed by Me₃O⁺ BF₄^-, give the C₅OMe complexes (η⁵-C₅Me₅)Re(NO)(PPh₃)(C⋮CC⋮CC(OMe))M(CO)_x(η⁵-C₅X₅)_y (M/x/y/X = 16, Mn/2/1/Cl; 19, Mn/2/1/Br; 20, Fe/4/0/−). However, Mn(CO)₃(η⁵-C₅H₅) does not react. Reaction of 16 and BF₃ gives the C₅ complex [(η⁵-C₅Me₅)Re(NO)(PPh₃)(CCCCC)Mn(CO)₂(η⁵-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 9−11 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.