New forms of coordinated carbon: Wirelike cumulenic C-3 and C-5 sp carbon chains that span two different transition metals and mediate charge transfer
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abstract
Reactions of (5-C5Me5)Re(NO)(PPh3)(CCLi) with W(CO)6, Fe(CO)5, or Mn(CO)3(5-C5H(n)Cl(5-n)), followed by Me3O+ BF4-, give the heterobimetallic C3OMe complexes (5- C5Me5)Re(NO)(PPh3)(CCC(OMe)=)M(CO)(x)(5-C5H(n)Cl(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 [(5-C5Me5)Re(NO)-(PPh3)(CCC)M(CO)(x)(5-C5H(n)Cl(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 (5- C5Me5)Re(NO)(PPh3)(CCCCLi) with Mn(CO)3(5-C5Cl5), Mn(CO)3(5C5Br5), or Fe(CO)5, followed by Me3O+ BF4-, give the C5OMe complexes (5-C5Me5)Re(NO)(PPh3)(CCCCC(OMe)=)M(CO)(x)(5- C5X5)(y)(M/x/y/X = 16, Mn/2/1/Cl; 19, Mn/2/1/Br; 20, Fe/4/0/-). However, Mn(CO)3(5-C5H5) does not react. Reaction of 16 and BF3 gives the C5 complex [(5-C5Me5)Re(NO)(PPh3)(CCCCC)Mn(CO)2(5-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 ( 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.
