1083427-27-3Relevant articles and documents
New cationic and zwitterionic Cp*M(κ2-P,S) complexes (M = Rh, Ir): Divergent reactivity pathways arising from alternative modes of ancillary ligand participation in substrate activation
Hesp, Kevin D.,McDonald, Robert,Ferguson, Michael J.,Stradiotto, Mark
, p. 16394 - 16406 (2008)
Treatment of 0.5 equiv of [Cp*IrCl2]2 with 1/3-PiPr2-2-StBu-indene afforded Cp*Ir(Cl)(κ2-3-PiPr2-2-S-indene) (1) in 95% yield (Cp* = η5-C5Me5). Addition of AgOTf or LiB(C6F5)4·2. 5OEt2 to 1 gave [Cp*Ir(κ2-3-P iPr2-2-S-indene)]+X- ([2] +X-; X = OTf, 78%; X = B(C6F5) 4, 82%), which represent the first examples of isolable coordinatively unsaturated [Cp′Ir(κ2-P, S)] +X- complexes. Exposure of [2]+OTf- to CO afforded [2·CO]+OTf- in 91% yield, while treatment of [2]+B(CeF5)4 - with PMe3 generated [2·PMe3] +B(C6F5)4- in 94% yield. Treatment of 1 with K2CO3 in CH3CN allowed for the isolation of the unusual adduct 3·CH3CN (41% isolated yield), in which the CH3CN bridges the Lewis acidic Cp*Ir and Lewis basic indenide fragments of the targeted coordinatively unsaturated zwitterion Cp*Ir(κ2-3-PiPr2-2-S- indenide) (3). In contrast to the formation of [2·CO]+OTf -, exposure of 3·CH3CN to CO did not afford 3·CO; instead, a clean 1:1 mixture of (κ2-3-P iPr2-2-S-indene)lr(CO)2 (4) and 1,2,3,4-tetramethylfulvene was generated. Treatment of [2]+OTf - with Ph2SiH2 resulted in the net loss of Ph2Si(OTf)H to give Cp*Ir(H)(κ2-3-P iPr2-2-S-indene) (5) in 44% yield. In contrast, treatment of [2]+B(C6F5)4- with Ph2SiH2 or Ph2SiH3 proceeded via H-Si addition across Ir-S to give the corresponding [Cp*Ir(H) (κ2-3-PiPr2-2-S(SiHPhX)-indene)] +B(C6F5)4- complexes 6a (X = Ph, 68%) or 6b (X = H, 77%), which feature a newly established S-Si linkage. Compound 6a was observed to effect net C-O bond cleavage in diethyl ether with net loss of Ph2Si(OEt)H, affording [Cp*Ir(H) (κ2-3-PiPr2-2-SEt-indene)] +B(C6F5)4- (7) in 77% yield. Furthermore, 6a proved capable of transferring Ph2SiH 2 to acetophenone, with concomitant regeneration of [2] +B(C6F5)4-; however, [2]+X- did not prove to be effective ketone hydrosilylation catalysts. Treatment of 1/3-PiPr2-2-S tBu-indene with 0.5 equiv of [Cp*RhCl2]2 gave Cp*Rh(Cl)(κ2-3-PiPr2-2-S- indene) (8) in 94% yield. Combination of 8 and LiB(C6F 5)4-2.5Et2O produced the coordinatively unsaturated cation [Cp*Rh(κ2-3-PiPr 2-2-S-indene)]+B(C6F5) 4- ([9]+B(C6F5) 4-), which was transformed into [Cp*Rh(H) (κ2-3-PiPr2-2-S(SiHPh2)- indene)]+B(C6F5)4- (10) via net H-Si addition of Ph2SiH2 to Rh-S. Unlike [2] +X-, complex [9]+B(C6F 5)4- was shown to be an effective catalyst for ketone hydrosilylation. Treatment of 3·CH3CN with Ph 2SiH2 resulted in the loss of CH3CN, along with the formation of Cp*Ir(H)(κ2-3-PiPr 2-2-S-(1-diphenylsilylindene)) (11) (64% isolated yield) as a mixture of diastereomers. The formation of 11 corresponds to heterolytic H-Si bond activation, involving net addition of H- and Ph2HSi + fragments to Ir and indenide in the unobserved zwitterion 3. Crystallographic data are provided for 1, [2·CO]+OTf -, 3·CH3CN, 7, and 11. Collectively, these results demonstrate the versatility of donor-functionalized indene ancillary ligands in allowing for the selection of divergent metal-ligand cooperativity pathways (simply by ancillary ligand deprotonation) in the activation of small molecule substrates.
