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The “Hidden” Reductive [2+2+1]‐Cycloaddition Chemistry of 2‐Phosphaethynolate Revealed by Reduction of a Th‐OCP Linkage
Author(s) -
Du Jingzhen,
Balázs Gábor,
Wooles Ashley J.,
Scheer Manfred,
Liddle Stephen T.
Publication year - 2021
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.202012506
Subject(s) - cycloaddition , chemistry , context (archaeology) , stereochemistry , ligand (biochemistry) , reactivity (psychology) , reductive elimination , medicinal chemistry , organic chemistry , catalysis , medicine , paleontology , biochemistry , receptor , alternative medicine , pathology , biology
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(CH 2 CH 2 NSiPr i 3 )] 3− ), with RbC 8 via [2+2+1] cycloaddition, produces an unprecedented hexathorium complex [{Th(Tren TIPS )} 6 (μ‐OC 2 P 3 ) 2 (μ‐OC 2 P 3 H) 2 Rb 4 ] ( 5 ) featuring four five‐membered [C 2 P 3 ] phosphorus heterocycles, which can be converted to a rare oxo complex [{Th(Tren TIPS )(μ‐ORb)} 2 ] ( 6 ) and the known cyclometallated complex [Th{N(CH 2 CH 2 NSiPr i 3 ) 2 (CH 2 CH 2 SiPr i 2 CHMeCH 2 )}] ( 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 KC 8 or CsC 8 were used the phosphinidiide C−H bond activation product [{Th(Tren TIPS )}Th{N(CH 2 CH 2 NSiPr i 3 ) 2 [CH 2 CH 2 SiPr i 2 CH(Me)CH 2 C(O)μ‐P]}] ( 3 ) and the oxo complex [{Th(Tren TIPS )(μ‐OCs)} 2 ] ( 7 ) were isolated.