Elaborate Network of Hydrolysis and Methanolysis Reactions Involving the 2,5-Dimethylthiophene Ligand in Cp*Ir(η⁵-2,5-Me₂T)²⁺

Abstract

Reactions of aqueous base with the dicationic iridium and rhodium thiophene complexes [Cp*Ir(η5-2,5-Me2T)](X)2 (X = BF4, 1(BF 4 ); X = OSO2CF3, 1(OTf)) and [Cp*Rh(η5-2,5-Me2T)](BF4)2 (8(BF 4 )) and the acid/base reactivity of these products are discussed. The reaction of 1(BF 4 ) with 1 equiv of aqueous KOH (0.01 M) affords the following mixture of mono-, di-, and tetranuclear compounds: [Cp*Ir(η4-SC(Me)CHCHC(O)Me)] (3), (Cp*Ir)[Cp*Ir(η4-SC(Me)CHCHC(O)Me)]3(BF4)2 (4(BF 4 )), [(Cp*Ir)2(μ2,η4-SC(Me)CHCC(O)Me)](BF4) (5(BF 4 )), and [Cp*Ir(μ2,η3-SC(Me)CHCH2C(O)Me)]2(BF4)2 (6(BF 4 )). The 1H and 13C NMR data are consistent with the single-crystal X-ray diffraction structures of the cationic complexes 4(BF 4 ), 5(OTf), and 6(BF 4 ). These products are formed by a complex series of reactions that begin with the displacement of the 2,5-dimethylthiophene (2,5-Me2T) ligand from 1 and reaction of the resulting “[Cp*Ir]2+” fragment with 3. In the synthesis of 8(BF 4 ), the new complex [(Cp*Rh)2(μ2,η4-SC(Me)CHCC(O)Me)](BF4) (9(BF 4 )), analogous to 5(BF 4 ), is produced. Studies of the reactions of [Cp*Rh(η5-2,5-Me2T)](BF4)2 (8(BF 4 )) with OH- and MeO- show a type of reactivity quite different from that observed for 1(BF 4 ) and 1(OTf). The solvolysis of 8(BF 4 ) in acetone affords the mononuclear complex [Cp*Rh(OCMe2)2(OH)](BF4) (10(BF 4 )), whose crystal structure is described. Detailed NMR studies establish the pathways by which [Cp*Ir(η5-2,5-Me2T)]2+ (1) and [Cp*Rh(η5-2,5-Me2T)]2+ (8) react with H2O/OH- and MeOH/MeO- to give the variety of observed products.

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

“…Compound 12 is formed by a half-molecule of the dimer 4 , which bridges, through the chloro atom, to a (η 4 -COD)Ir(1-2,5-η-CH 2 CHCHCHSO 2 ); one oxygen of the butadienesulfonyl ligand also bridges the corresponding (η 4 -COD)IrCl fragment. The bond length of S1–Ir1 is particularly short [2.2738(14) Å] compared to that in 14 , 15 , 17 – 20 [average 2.31 Å, Table ] and Cp*IrCl(1-2,5-η-CH 2 CHCHCHSO 2 ) [2.3091(18) Å] and is even shorter than that in the dimeric structures [Cp*Ir(Cl) 2 {(5-η-CHRCHCRCHSO 2 )}(Li)(THF)] 2 [average 2.2948 Å]. As expected, S1–O2 [1.507(5) Å] is significantly longer, due to the O2 to Ir2 bridging bond.…”

“…Reactions of aqueous base with the dicationic iridium thiophene complex [Cp*Ir(2,5-dimethyl-η 5 -thiophene)][X] 2 (X = BF 4 , OTf) afford a mixture of mono-, di-, and tetranuclear compounds [Cp*Ir(η 4 -SC(Me)CHCHC(O)Me)] (D), [(Cp*Ir) 2 (μ 2 ,η 4 -SC(Me)CHCHC(O)Me)](BF 4 ) (E), [Cp*Ir(μ 2 ,η 3 -SC(Me)CHCH 2 C(O)Me)] 2 (BF 4 ) 2 (F), and (Cp*Ir)[Cp*Ir(η 4 -SC(Me)CHCHC(O)Me)] 3 (BF 4 ) 2 (G) . 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, 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) …”

Synthesis of a Sulfido- and Thiolato-Bridged Trinuclear Bimetallic Cluster [{(η5-C5Me5)Ir}2{(η5-C5H5)Ru}Cl(μ3-S)(μ2-SCH2CH2CN)2] and Its Reactions with CO, Isocyanide, and Alkyne

“…For the Ru−C(35)C(34)−S(1) linkage, the C(34)−C(35) bond length at 1.401(8) Å is intermediate between the typical C−C single and double-bond distances and comparable to those in the π-bonded alkenethiolato ligands in, for example, [Cp*Ir{μ,η 3 -SC(Me)CHCH 2 COMe}] 2 [BF 4 ] 2 (1.392(9) Å) and [(Cp*Ru) 2 (CpTi) 2 Pd 2 (PPh 3 )(μ 3 -S) 3 (μ 2 -O){μ 3 -SC(COOMe)CCOOMe}] ( 7 ; 1.401(9) Å) . The Ru−C(35) and S(1)−C(34) distances of 2.082(9) and 1.78(1) Å in 6 are not exceptional; neither are those for the Ru−C and S−C single bonds.…”

Competitive Carbon−Sulfur vs Carbon−Carbon Bond Activation of 2-Cyanothiophene with [Ni(dippe)H]2

“…Many homogeneous organometallic systems have also been studied in an attempt to better understand the mechanism(s) of HDS, including model studies of C−S cleavage at Mo, Co, Rh, Ir, and Pt . The complex [Ni(dippe)H] 2 ( 1 ) has also been found to insert into the C−S bonds of a wide range of thiophenes, including the challenging dibenzothiophene, 4-methyldibenzothiophene, and 4,6-dimethyldibenzothiophene substrates .…”