The "Hidden" Reductive [2+2+1]-Cycloaddition Chemistry of 2-Phosphaethynolate Revealed by Reduction of a Th-OCP Linkage.

ABSTRACT: The reduction chemistry of the newly emerging 2-phosphaethynolate (OCP)^- is not well explored, and many unanswered questions remain about this ligand in this context. We report that reduction of [Th(Tren^TIPS )(OCP)] (2, Tren^TIPS =[N(CH₂ CH₂ NSiPrⁱ ₃ )]^3- ), with RbC₈ via [2+2+1] cycloaddition, produces an unprecedented hexathorium complex [{Th(Tren^TIPS )}₆ (?-OC₂ P₃ )₂ (?-OC₂ P₃ H)₂ Rb₄ ] (5) featuring four five-membered [C₂ P₃ ] phosphorus heterocycles, which can be converted to a rare oxo complex [{Th(Tren^TIPS )(?-ORb)}₂ ] (6) and the known cyclometallated complex [Th{N(CH₂ CH₂ NSiPrⁱ ₃ )₂ (CH₂ CH₂ SiPrⁱ ₂ CHMeCH₂ )}] (4) by thermolysis; thereby, providing an unprecedented example of reductive cycloaddition reactivity in the chemistry of 2-phosphaethynolate. This has permitted us to isolate intermediates that might normally remain unseen. We have debunked an erroneous assumption of a concerted fragmentation process for (OCP)^- , rather than cycloaddition products that then decompose with [Th(Tren^TIPS )O]^- essentially acting as a protecting then leaving group. In contrast, when KC₈ or CsC₈ were used the phosphinidiide C-H bond activation product [{Th(Tren^TIPS )}Th{N(CH₂ CH₂ NSiPrⁱ ₃ )₂ [CH₂ CH₂ SiPrⁱ ₂ CH(Me)CH₂ C(O)?-P]}] (3) and the oxo complex [{Th(Tren^TIPS )(?-OCs)}₂ ] (7) were isolated.

SUBMITTER: Du J 

PROVIDER: S-EPMC7839465 | biostudies-literature | 2021 Jan

REPOSITORIES: biostudies-literature