Kinetics and Mechanism of Cyclopropanation of Cyclooctene by [Fe(η⁵-C₅H₅)(CO)₂CH₂SPh₂]BF₄

Abstract

The kinetics of reaction of [Fe(η 5 -C 5 H 5 )(CO) 2 CH 2 SPh 2 ]BF 4 with cyclooctene in CH 2 Cl 2 solution have been studied under pseudo-first-order conditions at room temperature. The variation of k obs is nonlinear in both cyclooctene and added Ph 2 S. The results are interpreted in terms of a two-step reaction in which the cation [Fe(η 5 -C 5 H 5 )(CO) 2 CH 2 SPh 2 ] + undergoes reversible, dissociative loss of Ph 2 S followed by competitive capture of the methyleneiron complex by cyclooctene to produce bicyclo[6.1.0]nonane. The methyleneiron intermediate is 4-5 times more reactive toward diphenylsulfide than cyclooctene. In the absence of added Ph 2 S, millimolar solutions of the iron complex react with cyclooctene at room temperature with a half-life of about 36 min to give >85% yields of bicyclo[6.1.0]nonane after 3 h, and it is thus more reactive than the dimethyl-and methylphenylsulfonium salt analogues.

Manganese(I) and Rhenium(I) Tricarbonyl (Alkylthio)methyl and Alkylidenesulfonium Complexes

“…In the structure of both cationic complexes, the three M−CO distances are virtually identical; thus, in contrast with akylthioalkyl groups (see above), the alkylidenesulfonium ligand has a trans influence indistinguishable from that of the bipyridyl chelate. The geometries around the sulfur atoms of 5b and 6b are pyramidal, and the sums of the three C−S−C angles, 312.4 and 313.6°, respectively, and the C−S distances are similar to the values previously found for other alkylidenesulfonium complexes 4c2 Selected Bond Distances and Angles for Complexes 5b and 6b 5b 6b M(1)−C(4) 2.122(6) 2.243(6) M(1)−C(1) 1.804(6) 1.921(7) M(1)−C(2) 1.792(6) 1.919(7) M(1)−C(3) 1.803(7) 1.912(8) M(1)−N(1) 2.055(5) 2.187(5) M(1)−N(2) 2.040(5) 2.173(5) C(4)−S(1) 1.755(6) 1.744(7) S(1)−C(5) 1.806(7) 1.787(7) S(1)−C(21) 1.787(6) 1.786(7) C(1)−O(1) 1.130(7) 1.140(7) C(2)−O(2) 1.148(7) 1.145(8) C(3)−O(3) 1.143(8) 1.152(8) C(1)−M(1)−C(4) 173.9(3) 173.6(3) C(2)−M(1)−C(4) 96.1(3) 96.9(3) C(3)−M(1)−C(4) 92.4(3) 94.4(3) N(1)−M(1)−C(4) 82.3(2) 81.2(2) N(2)−M(1)−C(4) 86.7(2) 83.7(2) C(3)−M(1)−C(1) 87.4(3) 87.0(3) C(3)−M(1)−C(2) 88.7(3) 88.3(3) C(2)−M(1)−C(1) 90.0(3) 89.4(3) C(3)−M(1)−N(1) 97.0(2) 99.6(2) C(2)−M(1)−N(1) 174.2(2) 172.0(2) C(1)−M(1)−N(1) 91.7(2) 92.4(2) C(3)−M(1)−N(2) 175.9(2) 174.1(2) C(2)−M(1)−N(2) 95.5(2) 97.6(3) C(1)−M(1)−N(2) 93.0(2) 94.2(2) N(1)−M(1)−N(2) 78.90(19) 74.6(2) S(1)−C(4)−M(1) 118.3(3) 116.8(3) C(21)−S(1)−C(5) 101.1(3) 102.0(3) C(4)−S(1)−C(21) 105.7(3) 105.8(3) C(4)−S(1)−C(5) 105.6(4) 105.8(3)<...…”

“…A comparison between the neutral and cationic complex for each metal reveals, as the most salient feature, virtually identical M−CH 2 distances. This is somewhat unexpected; thus, some shortening of the M−C bond would be anticipated to occur upon methylation, given that the methylidenesulfonium complex can be considered the adduct of a dialkyl sulfide and a methylidene complex and, therefore, should have some incipient carbene character 4c. In the structure of both cationic complexes, the three M−CO distances are virtually identical; thus, in contrast with akylthioalkyl groups (see above), the alkylidenesulfonium ligand has a trans influence indistinguishable from that of the bipyridyl chelate.…”

“…Thus, [CpRe(NO)(PPh 3 )(CH 2 SMe 2 )] + reversibly loses dimethyl sulfide (to give the methylidene complex [CpRe(CH 2 )(NO)(PPh 3 )] + ), which can also be displaced by neutral nucleophiles such as PPh 3 and pyridine . On the other hand, the complex [Cp(CO) 2 Fe(CH 2 SMe 2 )] + exchanged dimethyl sulfide with other dialkyl sulfides, yielding new alkylidenesulfonium complexes 4e. The geometry of our [M(CH 2 S(Me)R)(CO) 3 (bipy)] + complexes is octahedral, and, considering that the alkylidenesulfonium group occupies an axial position, the planar ring of the bipy chelate and the two carbonyl groups lie in a equatorial plane.…”

“…Owing to their limited stability, these highly electrophilic species are often generated in situ. The corresponding sulfide−alkylidene adducts, i.e., salts of the cationic alkylidenesulfonium complexes [Cp(CO) 2 FeCH 2 SR 2 ] + , have been found to be stable yet active in olefin cyclopropanation . Reagents of this kind have been prepared with several other metal fragments .…”

Gold Sulfonium Benzylide Complexes Undergo Efficient Benzylidene Transfer to Alkenes

“…Inspired by the facile alkylidene transfer reactions of iron sulfoniumy lide complexes, [27] and the generation of well-defined Rh, Os, and Ru benzylidene complexes from sulfonium benzylides, [28] we targeted gold sulfonium benzylide complexes of the form [(L)AuCHPh(SR 1 R 2 )] + as potential carbene transfer reagents. [29][30][31][32] Initial efforts to synthesize gold sulfonium benzy- lide complexes by S-alkylation of gold a-thiobenzyl complexes [26,27] or throughl igand displacementw ith sulfonium benzylides [28] proved unsuccessful. However,athird approach involving nucleophilic substitution of ag old a-chlorobenzyl carbenoid complex with sulfide, whichw as modelled after similar transformations reported by Steinborn [26] and Echavarren, [24] provede ffective.…”