Divalent Titanium via Reductive N-C Coupling of a TiIV Nitrido with π-Acids

Angew Chem Int Ed Engl. 2024 Apr 15:e202404601. doi: 10.1002/anie.202404601. Online ahead of print.ABSTRACTThe nitrido-ate complex [(PN)2Ti(N){μ2-K(OEt2)}]2 (1) reductively couples CO and isocyanides in the presence of DME or cryptand, to form rare, five-coordinate TiII complexes having a linear cumulene motif, [K(L)][(PN)2Ti(NCE)] (E = O, L = Kryptofix222, (2); E = NAd, L = 3 DME, (3); E = NtBu, L = 3 DME, (4); E = NAd, L = Kryptofix222, (5)). Oxidation of 2-5 with [Fc][OTf] afforded an isostructural TiIII center containing a neutral cumulene [(PN)2Ti(NCE)] (E = O, (6); E = NAd (7), NtBu (8)). Moreover, 1e- reduction of 6 and 7 in the presence of cryptand cleanly reformed corresponding discrete TiII complexes 2 and 5, which were further characterized by solution magnetization measurements and high- frequency and -field EPR (HFEPR) spectroscopy. Furthermore, oxidation of 7 with [Fc*][B(C6F5)4] resulted in a ligand disproportionated TiIV complex having transoid carbodiimides, [(PN)2Ti(NCNAd)2] (9). Comparison of spectroscopic, structural, and computational data for the divalent, trivalent, and tetravalent systems, including their 15N enriched isotopomers demonstrate these cumulenes to decrease in order of backbonding as TiII→TiIII→TiIV and increasing order of p-donation as TiII→TiIII→TiIV, thus displaying more covalency in TiIII species. Lastly, we show a synthetic cycle whereby complex 1 can deliver an N-atom to π-acids.PMID:38619509 | DOI:10.1002/anie.202404601

Source: Angewandte Chemie - April 15, 2024 Category: Chemistry Authors: Mrinal Bhunia Christian Sandoval-Pauker Dominik Fehn Lauren Grant Shuruthi Senthil Michael Gau Andrew Ozarowski Jurek Krzystek Joshua Telser Balazs Pinter Karsten Meyer Daniel J Mindiola Source Type: research