Titanaaziridines or η(2)-imine titanium complexes are considered key intermediates of the titanium-catalyzed hydroaminoalkylation of alkenes. Herein, we present an efficient synthetic route to this class of compounds, starting from N-methylanilines and a bis(η(5):η(1)-pentafulvene)titanium complex. Consecutive reactions on the η(2)-methyleneaniline complexes, characterized for the first time, prove a high chemical versatility. In particular, hydroaminoalkylation products were found in reactions of the three-membered titanacycles with alkenes. For the first time, all the intermediates of the hydroaminoalkylation of alkenes were isolated and characterized.

The reactions of bis­(η5:η1-pentafulvene)­titanium complexes (1) with 19 different secondary amines (Aa–s) 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(η5:η1-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)­(η5:η1-C5H4C­(p-tolyl)2TiNR2 (2a–f) have been isolated in high yields and characterized, including by single-crystal X-ray diffraction. By the reactions of bis­(η5:η1-adamantylidene)­titanium (1a) and Af, diethylamine (Ag), and 2-methylpiperidine (Ah) similar monoamides 3f–h are formed. The formation of titanium bis-amides employing different types of secondary amines (Aa–s) 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.

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Metallocene dihalides and derivatives thereof are of great interest as precursors for catalysts in polymerization reactions, as antitumor agents and, due to their increased stability, as suitable starting materials in salt metathesis reactions and the generation of metallocene fragments. We report the synthesis and structural characterization of a series of eleven substituted bis(η-cyclopentadienyl)titanium dihalides, namely bis[η-1-(diphenylmethyl)cyclopentadienyl]difluoridotitanium(IV), [Ti(CH)F], bis{η-1-[bis(4-methylphenyl)methyl]cyclopentadienyl}difluoridotitanium(IV), [Ti(CH)F], and bis{η-1-[bis(adamantan-2-yl)methyl]cyclopentadienyl}difluoridotitanium(IV), [Ti(CH)F], together with the bromide and iodide analogues, and the chloride analogues of the diphenylmethyl and adamantyl complexes. These eleven complexes were prepared by the reaction of the corresponding bis(η:η-pentafulvene)titanium complexes with different hydrogen halides (Cl, Br and I). The titanocene fluorides become available via chloride-fluoride exchange reactions.

Zwei auf einen StreichN‐Methylaniline werden in Gegenwart eines Bis(η5,η1‐pentafulventitan)komplexes durch zweifache Bindungsaktivierung direkt in Titanaaziridine überführt. Basierend auf dieser Umsetzung berichten S. Doye, R. Beckhaus et al. in ihrer Zuschrift auf über die Isolierung und Untersuchung sämtlicher Schlüsselintermediate der titankatalysierten Hydroaminoalkylierung von Alkenen. Damit wird erstmals ein experimenteller Beleg für den bisher nur vorgeschlagenen Reaktionsmechanismus dieser auch industriell relevanten Reaktion erbracht.