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Photolytic and Reductive Activations of 2‐Arsaethynolate in a Uranium–Triamidoamine Complex: Decarbonylative Arsenic‐Group Transfer Reactions and Trapping of a Highly Bent and Reduced Form
Author(s) -
Magnall Rosie,
Balázs Gábor,
Lu Erli,
Kern Michal,
Slageren Joris,
Tuna Floriana,
Wooles Ashley J.,
Scheer Manfred,
Liddle Stephen T.
Publication year - 2019
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201903973
Subject(s) - chemistry , decarbonylation , cryptand , ligand (biochemistry) , valence (chemistry) , photodissociation , fragmentation (computing) , crystallography , stereochemistry , photochemistry , ion , organic chemistry , catalysis , biochemistry , receptor , computer science , operating system
Little is known about the chemistry of the 2‐arsaethynolate anion, but to date it has exclusively undergone fragmentation reactions when reduced. Herein, we report the synthesis of [U(Tren TIPS )(OCAs)] ( 2 , Tren TIPS =N(CH 2 CH 2 NSi i Pr 3 ) 3 ), which is the first isolable actinide‐2‐arsaethynolate linkage. UV‐photolysis of 2 results in decarbonylation, but the putative [U(Tren TIPS )(As)] product was not isolated and instead only [{U(Tren TIPS )} 2 (μ‐η 2 :η 2 ‐As 2 H 2 )] ( 3 ) was formed. In contrast, reduction of 2 with [U(Tren TIPS )] gave the mixed‐valence arsenido [{U(Tren TIPS )} 2 (μ‐As)] ( 4 ) in very low yield. Complex 4 is unstable which precluded full characterisation, but these photolytic and reductive reactions testify to the tendency of 2‐arsaethynolate to fragment with CO release and As transfer. However, addition of 2 to an electride mixture of potassium‐graphite and 2,2,2‐cryptand gives [{U(Tren TIPS )} 2 {μ‐η 2 (OAs):η 2 (CAs)‐OCAs}][K(2,2,2‐cryptand)] ( 5 ). The coordination mode of the trapped 2‐arsaethynolate in 5 is unique, and derives from a new highly reduced and bent form of this ligand with the most acute O‐C‐As angle in any complex to date (O‐C‐As ∠ ≈128°). The trapping rather than fragmentation of this highly reduced O‐C‐As unit is unprecedented, and quantum chemical calculations reveal that reduction confers donor–acceptor character to the O‐C‐As unit.