Photoinduced Reductive C–O Couplings from Unsymmetrical Bis-Cyclometalated Pt(IV) Dicarboxylato Complexes
Year: 2024
Type: article
Abstract: High Resolution Image Download MS PowerPoint Slide Unsymmetrical bis-cyclometalated dicarboxylato complexes ( OC -6-32)-[Pt(tpy) 2 (O 2 CR) 2 ] [tpy = cyclometalated 2-( p -tolyl)pyridine, R = t -Bu ( 1 ), Me ( 2 ), Ph ( 3 ), CF 3 ( 4 )], are obtained from the reaction of cis -[Pt(tpy) 2 ] with the appropriate PhI(O 2 CR) 2 reagent. Treatment of complexes of this type with different carboxylates (R’CO 2 – ) results in the formation of mixed-carboxylato derivatives, namely ( OC -6-43)-[Pt(tpy) 2 (O 2 CMe)(O 2 CR′)] [R′ = t -Bu ( 5 ), CF 3 ( 6 ), Ph ( 7 )], ( OC -6-34)-[Pt(tpy) 2 (O 2 CCF 3 )(O 2 CR′)] [R′ = t -Bu ( 8 ), Me ( 9 ), Ph ( 10 )], and ( OC -6-34)-[Pt(tpy) 2 (O 2 C- t -Bu)(O 2 CMe)] ( 11 ). Irradiation of 1 – 3 and 5 – 11 with UV light (365 nm) in MeCN gives 5-methyl-2-(2-pyridyl)phenyl pivalate ( 12 ), 5-methyl-2-(2-pyridyl)phenyl acetate ( 13 ) or 5-methyl-2-(2-pyridyl)phenyl benzoate ( 14 ) as the major photoproduct from most complexes, resulting from a reductive C–O coupling between a tpy ligand and a carboxylato ligand. Cyclometalation of 12 – 14 at the ensuing Pt(II) species to produce cis -[Pt(tpy)(tpyO 2 CR/R′)], reduction to cis -[Pt(tpy) 2 ] and isomerization to ( OC -6-33)-[Pt(tpy) 2 (O 2 CR/R′) 2 ] are identified as secondary processes in most cases. In contrast, complex 4 exclusively photoisomerizes to ( OC -6-33)-[Pt(tpy) 2 (O 2 CCF 3 ) 2 ] ( 4′ ). The C–O couplings are favored for the most electron-rich carboxylato ligands and occur predominantly from the carboxylato trans to N. Consistent with this, a computational study reveals that the lowest singlet and triplet LMCT excited states result from electronic transitions to a dσ* orbital distributed along the N–Pt–O axis, which would trigger the observed processes.
Source: Inorganic Chemistry
Institution: Universidad de Murcia
Language: English
Subfield: Organic Chemistry
Field: Chemistry
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $4,500
OpenAlex ID: W4405837900