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

Abstract

Reactions of (η5-C5Me5)Re(NO)(PPh3)(C⋮CLi) with W(CO)6, Fe(CO)5, or Mn(CO)3(η5-C5H n Cl 5-n ), followed by Me3O+ BF4 -, give the heterobimetallic C3OMe complexes (η5-C5Me5)Re(NO)(PPh3)(C⋮CC(OMe))M(CO) x (η5-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 [(η5-C5Me5)Re(NO)(PPh3)(CCC)M(CO) x (η5-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 (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.

A Synthetic Breakthrough into an Unanticipated Stability Regime: A Series of Isolable Complexes in which C6, C8, C10, C12, C16, C20, C24, and C28 Polyynediyl Chains Span Two Platinum Atoms

“…Species with cumulenic bridges are much less stable. [8] Of the polyynediyl complexes, only those with {FeA C H T U N G T R E N N U N G (h 5 -C 5 Me 5 )(CO) 2 }, [9] {RuA C H T U N G T R E N N U N G (h 5 -C 5 R 5 )(L) 2 } or {Ru(L')(L) 4 } n + , [10] {ReA C H T U N G T R E N N U N G (h 5 -C 5 Me 5 )(NO)A C H T U N G T R E N N U N G (PPh 3 )}, [11] {Ru 2 (2-anilinopyridinate) 4 }, [12] {PtA C H T U N G T R E N N U N G (C 6 F 5 ){PA C H T U N G T R E N N U N G (p-tol) 3 } 2 }, [13] and {PtA C H T U N G T R E N N U N G (C 6 F 5 )A C H T U N G T R E N N U N G (RAr 2 P) 2 } [14] endgroups have been extended to long chain lengths, beyond four triple bonds (! C 10 ).…”

Facile Access to Redox‐Active C2‐Bridged Complexes with Half‐Sandwich Manganese End Groups

“…A similar behavior was observed in complexes with longer carbon chains between the metal centers. [43,44,[48][49][50][51][52][53][54][55][56][57][58][59][67][68][69][70][71][72][73][74] According to the resonance forms of Equation (3) the MnÀC bonds shorten with increasing degree of oxidation, while the internal CÀC bond elongates. This indicates that the cumulenic resonance form is transformed into the bis-carbyne type with a C À C single bond (Table 1).…”

Reactivity of 3-halopropynols: X-ray crystallographic analysis of 1,1-dihalocumulenes and 2+2 cycloaddition products

“…It is known that the reaction of polyynes such as R-(CC)n-C(OH)R2 with BF3·Et2O leads to a cationic intermediate. [23][24] Therefore we hoped that the unstable cationic cumulene can be halogenated by an external source of halogen. Higher cumulenes are highly moisture sensitive 25 and thus we focused on the development of moisture free conditions.…”