Structure and chemistry of a metal cluster with a four-coordinate carbide carbon atom

Abstract

Structure and chemistry of a metal cluster with a four-coordinate carbide carbon atom ( cluster, which was extremely reactive. Hydrogen addition to this iron cluster was rapid below 0C, and a C-H bond was formed in this transformation.

Polynuclear Iron Compounds with Hydrocarbon Ligands

“…The butterfly iron carbide clusters are thermally robust and their stability has been interpreted in terms of strong interactions between carbide /?-orbitals and the metal d-orbitals, (78)- (80). For (65), (66), (67) and (71), the Fe w -C-Fe w angles (0,) are essentially linear and the C-Fe w distances are substantially shorter than the C-Fe h distances (l x < / 2 ). This indicates that the rc-interaction of the carbide's p z orbital with the d-orbitals o f Fe w (78) is very strong.…”

“…Stability o f the apparent butterfly structure o f (74) and (76) with 60 CVE (see above) can also be rationalized by viewing them as a n electron precise closo tbp structure. 69 In the case o f the formation of (73) f r o m the dianion (66) where the corresponding p 7 orbital in a bent (78)-like MO is filled and projects toward the open space, nucleophilic reaction at the carbido carbon would give (73). For the conversion o f (66) to (74), a mechanism initiated by a SET process has been proposed.…”

“…I n contrast to the higher nuclearity carbido clusters, tetrairon butterfly clusters with an exposed fourcoordinate carbide ligand, structures (65), (66) and (67), exhibit greater reactivity (Scheme 7). 54 Originally, they were prepared by stepwise oxidative degradation o f (64) by way o f the pentanuclear cluster (62).…”

Controlled Expansion of a Strong‐Field Iron Nitride Cluster: Multi‐Site Ligand Substitution as a Strategy for Activating Interstitial Nitride Nucleophilicity

“…[4,[9][10] This system, however,d oes not effectively model ammonia production owing to preferential protonation at abridging position between two iron centers,rather than at the interstitial nitrogen atom, and the fact that subsequent protonations with strong acids cannot be achieved. [15][16][17][18] Thegreater nucleophilicity of [Fe 4 (m 4 -C)(CO) 12 ] 2À relative to [Fe 4 (m 4 -N)(CO) 12 ] À has been rationalized qualitatively by two main factors,namely 1) the greater charge of the carbide cluster (À2v s. À1) and 2) increased orbital energies,w hich are due to the more electropositive character of carbon compared to nitrogen. [12][13][14] In contrast, the isoelectronic and isostructural species [Fe 4 (m 4 -C)(CO) 12 ] 2À is susceptible to protonation at the interstitial carbon atom and displays chemistry pertinent to the metal cluster-surface analogy,specifically carbon monoxide activation and the cleavage of H 2 across the m 4 -carbide.…”

“…[12][13][14] In contrast, the isoelectronic and isostructural species [Fe 4 (m 4 -C)(CO) 12 ] 2À is susceptible to protonation at the interstitial carbon atom and displays chemistry pertinent to the metal cluster-surface analogy,specifically carbon monoxide activation and the cleavage of H 2 across the m 4 -carbide. [15][16][17][18] Thegreater nucleophilicity of [Fe 4 (m 4 -C)(CO) 12 ] 2À relative to [Fe 4 (m 4 -N)(CO) 12 ] À has been rationalized qualitatively by two main factors,namely 1) the greater charge of the carbide cluster (À2v s. À1) and 2) increased orbital energies,w hich are due to the more electropositive character of carbon compared to nitrogen. [11] One approach to augmenting the reactivity of [Fe 4 (m 4 -N)(CO) 12 ] À and other clusters has been to increase their electron density through the substitution of CO with more electron-donating ligands.P hosphine-substituted [Fe 4 (m 4 -N)(CO) 12Àn (L) n ] À (n = 1, 2) clusters have been reported, but they have not exhibited reactivity patterns that differ from the all-carbonyl analogue.…”