Reactions of Secondary Amines with Bis(η⁵:η¹-pentafulvene)titanium Complexes: Formation of Titanium Amides and Titanaaziridines

Abstract

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.

From Five to Seven: Ring Expansion of Monoazadiene Titanium Complexes by Insertion of Aldehydes, Ketones and Nitriles

“…The four‐membered rings exist as azatitanacyclobutanes IVa or ‐butenes IVb, which can be generated via [2+2] cycloaddition reactions of olefins or alkynes– and titanium imido species, or by employing titanium carbenes and carbodiimides . The family of the five‐membered rings is represented by insertion products of olefins and acetylenes into titanaaziridines, leading to azatitanacylopentanes Va and −3‐pentenes Vb ,. The isomeric azatitanacyclo‐2‐pentenes Vc are formed by complexation of 1‐azabutadiene ligands .…”

Advantages of Group 4 Metallocene Bis(trimethylsilyl)acetylene Complexes as Metallocene Sources Towards Other Synthetically used Systems

“…This opens the way to a lot of other synthetically very interesting reactions. [53][54][55][56][57][58][59][60][61][62][63][64][65][66][67][68][69][70][71] The most spectacular example for unexpected results was the reaction of η 5 : η 1 -pentafulvene titanium complexes with the allylidenephosphorylide Ph 3 P=C(H)À C(H)=CH 2 , giving a titanabutatriene complex by a spontaneous double CÀ H bond activation via an intermediate Ph 3 P=C=C=CH 2 . After dimerization the titanabutatriene complex formed a binuclear zig-zag hexapentaene titanium complex (Scheme 9).…”

“…[39] Beckhaus described the weak MÀ C exo interaction in these complexes as the first examples of heteroatom free organometallic frustrated Lewis pairs in comparison to classical heteroatom containing Lewis pairs. [39,[45][46][47][48][49][50][51][52][53][54][55][56][57][58][59][60][61] Advantages of η 5 : η 1 -pentafulvene complexes in reactions with selected substrates are the high yields of products, formed at room temperature (Scheme 5-10) with a very high selectivity. This means that for selected substrates in a two step process the selective reaction of two or even more substrates is possible.…”

Molecular structures of a series of substituted bis(η5-cyclopentadienyl)titanium dihalides Cp R 2TiX 2 [X = F, Cl, Br and I; R = CHPh2, CH(p-Tol)2 and adamantyl]

“…1) show no kinetic hindrance in contrast to typical titanocene dialkyl compounds [e.g. Cp 2 Ti(CH 3 ) 2 ; Cp is cyclopentadienyl; Petasis et al, 2008] and undergo fast reactions with a large variety of electrophilic substances under mild conditions (Oswald, Gelert et al, 2017;Manssen et al, 2015Manssen et al, , 2017Oswald, Diekmann et al, 2017;Adler et al, 2014). The reaction of such bis( 5 : 1 -pentafulvene)titanium complexes with hydrogen chloride was first reported by Diekmann et al (2006).…”