Hydrocarbation-formation of diiron .mu.-alkylidyne complexes from the addition of the carbon-hydrogen bond of a .mu.-methylidyne complex across alkenes

Abstract

The reaction of [(C5H5)(CO)Fe]2^-CO)^-CH)+PF6•, 1, with ethylene produced [(C5H5)(CO)Fe]2Oi-CO)Ot-CCH2CH3)+PF6", 4, in 68% yield. 4 reacted with trimethylamine to give [(C5H5)(CO)Fe]2(^-CO)(M-C=CHCH3), 5, in 84% yield. 1 reacted regioselectively with propene, 1-butene, 1-pentene, ieri-butylethylene, styrene, butadiene, allylbenzene, and isobutylene to give similar µ-alkylidyne products in 76-85% yields. The syn addition of hydrocarbation was established by the reaction of 1 with (£)-and (Z)-1,2-dideuterio-3,3-dimethyl-1 -butene, 23-E and 23-Z. The rate of the reaction of 1 with fra«s-2-butene at -50 °C followed second-order kinetics with k2 = 9.2 ± 0.7 X 10'1 23 M'1 s'1. Competition techniques were used to measure the relative reactivity of 1 toward alkenes at -50 °C, and electron-donating alkyl substituents substantially increased the reactivity of the alkene. The deuterium kinetic isotope effect for the reaction of 1 with propene and isobutylene at -50 °C was found to be 0.74 ± 0.03 and 0.80 ± 0.03. The regiochemistry, relative rates, and kinetic isotope effects are consistent with a transition state for the rate-determining step of hydrocarbation which involves only initiation of a bond from (21) Casey, C.

Syntheses and Characterization of New Vinyl‐Borylene Complexes by the Hydroboration of Alkynes with [(μ3‐BH)(Cp*RuCO)2(μ‐CO)Fe(CO)3]

“…Although, we do not have any direct experimental evidence for the formation of A , similar reactions are well recognized in hydrocarbation chemistry 25. 26 For example, Casey and co‐workers reported the isolation of diiron μ ‐ methylidyne complex, isostructural and isoelectronic to intermediate A , which undergoes hydrocarbation with alkynes 25. Therefore, we postulate that the intermediate A might involve a 1,2‐addition ( syn ) of the BH bond across the added alkynes leading to the formation of corresponding vinyl‐borylene complexes 2 – 4 through an anti‐Markovnikov addition.…”

Reactions of diiron mu-aminocarbyne complexes containing nitrile ligands

“…All the reagents were commercial products (Aldrich) of the highest purity available and used as received. [Fe 2 (CO) 4 3, 11 were prepared as described in the literature.…”

“…3 Surprisingly, none of the above nucleophilic additions involve the µ-C of the aminocarbyne ligand, which appears rather unreactive, particularly if compared with the powerful electrophilic character of the µ-methylidyne carbon in the related complex [Fe 2 (µ-CH)(µ-CO)(CO) 2 (Cp) 2 ] + . 4 Only cyanide (from NBu 4 CN) has been found to react at the carbyne carbon to yield the aminocarbene 903 Reactions of Diiron µ-Aminocarbyne Complexes Containing Nitrile Ligands Vol. 14, No.…”

New chemical and stereochemical applications of organoiron complexes

“…In a series of diiron complexes, the diiron methylidene complex is interesting in its relation to CH groups bound to metal surfaces. It is also an important intermediate in the synthesis of a wide range of hydrocarbyl-bridged diiron compounds [ 1009 ]; it adds its CH bond across the carbon-carbon double bond of simple alkenes in a hydrocarbation reaction, to produce a new series of (η-alkylidyne) diiron complexes [ 1010 ]. Because of the central importance of these diiron methylidene complexes to the new chemistry of η-alkylidene, η-acylium, and η-nitrilium complexes, the mechanism of its formation has been studied in detail [ 1011 ].…”