New CO-releasing molecules, CO-RMs, based on indenyl iron carbonyls have been identified. Half-lives for carbon monoxide (CO) release, (1)H NMR, (13)C NMR, IR, mass spectra, elemental analysis and biological data have been determined for the compounds. Limited correlations have been made between half-lives and ΔG(‡) for CO release and spectroscopic parameters, ν(CO) and δ((13)CO). X-ray structures have been determined for [Fe(η(5)-C(9)H(7))(CO)(2)L][BF(4)] where L is CO, NCMe, PPh(3), P(OPh)(3), NC(5)H(5) or 1-methylimidazole. Improved preparations of [Fe(η(5)-C(9)H(7))(CO)(2)](2) and [Fe(η(5)-C(9)H(7))(CO)(3)][BF(4)] are reported.
New CO-releasing molecules, [Fe(CO)3X(S2CNR2)] and [Fe(CO)3I(S2COEt)],
are reported.
[Fe(CO)3X(S2CNR2)] releases the first
two carbonyls rapidly to myoglobin (t
1/2 < 1 min) and the third carbonyl more slowly. In the case of [Fe(CO)3I(S2COEt)], only 0.4 mol of CO are lost. [Fe(CO)3Br(S2CNEt2)] has low toxicity. CO loss
is much slower from [Fe(CO)2(S2CNR2)2] (R2 = Me2, Et2, (CH2CH2)2O, (CH2CH2)2, (CH2CH2OH)2; t
1/2 >24 h) and is not observed from [Fe(CO)2(S2COEt)2]. The mechanism of CO loss
was investigated using Gaussian 09 calculations for [Fe(CO)3Br(S2CNMe2)] and [Fe(CO)2(S2CNMe2)2]. The X-ray structures of [Fe(CO)3Br(S2CNMe2)] and [Fe(CO)3I(S2CNEt2)]2I2 were determined.
[Fe(L-cysteinate)(2)(CO)(2)](2-) is a CO releasing molecule which has low cytotoxicity to RAW264.7 macrophages. It provides an example of CO binding using ligands available to ion channels which use CO as a signalling molecule in the absence of heme. Previous work has shown that this compound consists of five isomers and it was proposed that the two isomers with trans-dicarbonyls are dominant. In this work the isomers are re-assigned and shown to be capable of releasing CO, albeit too slowly to act as a signalling receptor. It is shown that by linking the two L-cysteines together to form [Fe(SCH(2)CH{CO(2)H}NHCH(2))(2)(CO)(2)], only one isomer is isolated.
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