Metal–Ligand Cooperative C–H Bond Formation by Cyclopentadienone Platinum Complexes

Abstract

C–H bond cleavage and formation is one of the most essential elementary reactions in organic chemistry. Herein, a heterolytic sp3 C–H bond reductive elimination from hydroxyCp dimethylplatinum­(IV) B is reported. Protonation of cyclopentadienone dimethylplatinum­(II) A afforded B via the protonation of the ligand. Successive C–H bond formation from the C anion of the methyl group and the H cation of the hydroxyCp group was observed in the presence of carboxylic acids or hydrogen chloride. The reaction was accompanied by the concurrent reduction of Pt­(IV) to Pt­(II). Experimental and theoretical investigations suggested that the mechanism for the C–H bond formation was acid-mediated metal–ligand cooperative outer-sphere reductive elimination.

Umpolung of B−H Bonds by Metal–Ligand Cooperation with Cyclopentadienone Iridium Complexes

“…This difference in the DG°values eventually resulted in the exclusive progress of deprotonation of Ir À H from the kinetically favored cis isomer Int-II(cis). Other possibilities for the BÀ H bond cleavage via direct addition with or without mediator from Int-I, which is similar to the classical metal-ligand cooperative bond cleavage/formation of HÀH and CÀH bonds, [19,20] were located at high in energy, 30.3 kcal mol À1 or 53.5 kcal mol À1 relative to 4 c' ( Figure S88). In sharp contrast to the energy profile with 4 c', when the phenyl-substituted cyclopentadienone iridium complex 4 a' was employed, DG°v alue of deprotonation transition state from the cis intermediate (TS II-III (Ph-cis-H)) is higher to be inaccessible (Figure 3 b, 28.0 kcal mol À1 relative to 4 a').…”

Synthesis and Reactivity of PtII Methyl Complexes Supported by Pyrazolate Pincer Ligands

“…We were interested in exploring the potential of pyrazolate groups to aid in C–H bond cleavage/formation reactions. Protonation of Pt II –CH 3 complexes has previously been reported to result in methane release. , Recently, Nozaki and co-workers reported acid addition to a Shvo-type Pt II –CH 3 complex . Experimental and theoretical evidence suggested the ligand was the initial site of protonation before methane liberation.…”

“…14,15 Recently, Nozaki and co-workers reported acid addition to a Shvo-type Pt II −CH 3 complex. 16 Experimental and theoretical evidence suggested the ligand was the initial site of protonation before methane liberation. Similarly, addition of a pyrazolate site on the ligand has the potential to promote this reactivity by providing a kinetic site for protonation.…”

Reversible PtII–CH3 deuteration without methane loss: metal–ligand cooperation vs. ligand-assisted PtII-protonation

“…Although widely explored in other areas of organometallic chemistry, 37 examples of metal–ligand cooperation in the context of C–H activation/reductive elimination at Pt are scarce. 38 …”