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Reactions of Secondary Amines with Bis(η51‑pentafulvene)titanium Complexes: Formation of Titanium Amides and Titanaaziridines

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posted on 06.02.2017, 20:50 authored by Manfred Manßen, Nicolai Lauterbach, Tim Woriescheck, Marc Schmidtmann, Rüdiger Beckhaus
The reactions of bis­(η51-pentafulvene)­titanium complexes (1) with 19 different secondary amines (Aas) have been investigated. Depending on the substitution pattern of 1 and nature of the amine used, different reaction products are formed. With use of bis­(η51-di­(p-tolyl)­pentafulvene)titanium (1b) and N-methylanilines (Aa,b), N-methylbenzylamines (Ac,d), N-methylcyclohexylamine (Ae), and dibenzylamine (Af), titanium monoamides of the type (η5-C5H4CH­(p-tolyl)2)­(η51-C5H4C­(p-tolyl)2TiNR2 (2af) have been isolated in high yields and characterized, including by single-crystal X-ray diffraction. By the reactions of bis­(η51-adamantylidene)­titanium (1a) and Af, diethylamine (Ag), and 2-methylpiperidine (Ah) similar monoamides 3fh are formed. The formation of titanium bis-amides employing different types of secondary amines (Aas) is not observed. The formation of titanaaziridines is observed exclusively by using 1a and N-methylanilines (Aa,b), N-benzylphenylamine (Ai), and N-benzyltrimethylsilylamines (Aj,k). The titanaaziridine 4i undergoes a regioselective ring enlargement reaction with 1-hexyne. By the reaction of 4i and phenylacetylene a ring opening with formation of (CpAd)2Ti­(NPh­(CH2Ph)­CCPh) (6) is observed. The acetylide 6 undergoes a thermal decomposition to give the zigzag butadiyne complex 7. In addition to the ring enlargement of 4j by ketones a ketone insertion in the titanium–Cp bond is found, as proved for 8 by single-crystal X-ray diffraction.