Pentadienyl-metal-phosphine chemistry. 24. Thiapentadienyl-iridium-phosphine chemistry. Synthesis of sulfur-containing iridacycles via carbon-hydrogen bond activation

Aromatic Iridacycles

“…Gradually, all of the six-membered ring converts to the five-membered ring, and compound 24 can be isolated cleanly. 30 It is interesting that in the sulfur system, unlike the analogous oxygen system described earlier, C-H bond activation does not occur at the C4-H4 bond to produce a five-membered ring with an exocyclic CdS bond, a result that reflects the relative weakness of C-S double bonds as compared to C-O double bonds. However, in both systems, fivemembered rings are thermodynamically preferred over six-membered rings for the reasons outlined earlier.…”

Chemistry of Iridium(I) Cyclooctadiene Compounds with Thiapentadienyl, Sulfinylpentadienyl, and Butadienesulfonyl Ligands

“…In particular, this ring-opening reaction of thiophene with iridium has been observed when Ir(H) 2 (triphos)(Et) produces, by reductive elimination of ethane, the reactive 16-electron fragment (triphos)IrH [triphos = MeC(CH 2 PPh 2 ) 3 ], which affords the thiapentadienyl ligand coordinated through the terminal double bond and the sulfur to iridium in Ir(1-2,5-η-CH 2 CHCHCHS)(triphos) (C). 11 Reactions of aqueous base with the dicationic iridium thiophene complex [Cp*Ir(2,5-dimethyl-η 5 4 -SC(Me)CHCHC(O)Me)] 3 (BF 4 ) 2 (G). 12 The mononuclear acylthiolate complex [Cp*Ir(η 4 -SC(Me)-CHCHC(O)Me)] (D) was also reported from the reaction of [Cp*Ir(2,5-dimethyl-η 5 -thiophene)][BF 4 ] 2 with PhLi in THF or (n-Bu) 4 N + OH − in MeCN, 13 and the dicationic thiophene complex readily adds secondary amines to afford [Cp*Ir(η 4 -SC(Me)CHCHC(Me)(N(CH 2 ) n )](BF 4 ) (n = 4, 5) (H).…”

“…11 Reactions of aqueous base with the dicationic iridium thiophene complex [Cp*Ir(2,5-dimethyl-η 5 4 -SC(Me)CHCHC(O)Me)] 3 (BF 4 ) 2 (G). 12 The mononuclear acylthiolate complex [Cp*Ir(η 4 -SC(Me)-CHCHC(O)Me)] (D) was also reported from the reaction of [Cp*Ir(2,5-dimethyl-η 5 -thiophene)][BF 4 ] 2 with PhLi in THF or (n-Bu) 4 N + OH − in MeCN, 13 and the dicationic thiophene complex readily adds secondary amines to afford [Cp*Ir(η 4 -SC(Me)CHCHC(Me)(N(CH 2 ) n )](BF 4 ) (n = 4, 5) (H). 14 Alternative methods for the synthesis of the corresponding oxidative derivatives of the thiapentadienyl ligand, such as the 5-oxothiapentadienyl or sulfinylpentadienyl, and 5,5-dioxothia-pentadienyl or butadienesulfonyl, have been developed in the past decade, and, consequently, their capability as ligands in organometallic transition compounds is still unknown.…”

“…16 The butadienesulfonyl ligand has shown different coordination modes, chemical versatility, and stability, as observed by its isomerization 16−18 and inter-and intramolecular hydrogen interactions. 18,19 The chemistry of iridium with the cyclooctadiene ligand is now explored; the first examples of dimeric structures [(η 4 -COD)Ir(μ 2 -1-2,5-η-CH 2 CHCHCHE)] 2 17,20 (E = S, SO), which include bridging thia-and sulfinyl-pentadienyl ligands, 19 were obtained after treatment of [(η 4 -COD)Ir(μ-Cl)] 2 with sodium thiapentadienide and potassium sulfinyl-pentadienide. The reaction of lithium and potassium butadienesulfinates with [(η 4 -COD)Ir(μ-Cl)] 2 produced the corresponding ion-pair complexes (η 4 -COD)IrCl(dioxo-thiapentadienide).…”

Organometallic Complexes as Models for the Adsorption of Thiophenes on Hydrodesulfurization (HDS) Catalysts

“…As noted in the previous section, thiophene forms an q' (S) complex of the type Cp*(C0)2Re(q1 (S)-T), where Cp* = q5-CsMes. The analogous selenophene complex, Cp*(C0)2Re(q2-Sel), however, contains an q2-coordinated selenophene 5) with the metal situated above the selenophene plane as determined from a partially successful X-ray diffraction study.20121 Also, the 'H and 13C NMR chemical shifts of the q2-coordinated carbon and associated hydrogen atoms are substantially upfield (2.5-3.5 ppm in the 'H and [75][76][77][78][79][80][81][82][83][84][85] ppm in the 13C NMR spectra) of those of the uncoordinated CH groups; these upfield shifts are characte-* I Re ristic of n-bonded carbons and their associated hydrogen(s) It is surprising that T and Sel coordinate differently in the Cp*(C0)2Re system since their organic chemistry Is so It appears that the olefin in Sel Is a better II accepting ligand than in thiophene. Another surprise was the observation that 2,5-Me2Sei in the analogous Cp* (CO)nRe(q' (Se)-2,5-Me2Sel) complex is q' (Se)-coordinated (FIG.…”