Reactions of Secondary Amines with Bis(η⁵:η¹‑pentafulvene)titanium Complexes:\nFormation of Titanium Amides and Titanaaziridines

Abstract

The reactions of\nbis­(η⁵:η¹-pentafulvene)­titanium\ncomplexes (<b>1</b>) with 19 different secondary amines (<b>Aa</b>–<b>s</b>) have been investigated. Depending\non the substitution pattern of <b>1</b> and nature of the amine\nused, different reaction products are formed. With use of bis­(η⁵:η¹-di­(<i>p</i>-tolyl)­pentafulvene)titanium (<b>1b</b>) and <i>N</i>-methylanilines (<b>Aa</b>,<b>b</b>), <i>N</i>-methylbenzylamines (<b>Ac</b>,<b>d</b>), <i>N</i>-methylcyclohexylamine (<b>Ae</b>), and\ndibenzylamine (<b>Af</b>), titanium monoamides of the type (η⁵-C₅H₄CH­(<i>p</i>-tolyl)₂)­(η⁵:η¹-C₅H₄C­(<i>p</i>-tolyl)₂TiNR₂ (<b>2a</b>–<b>f</b>) have been isolated in high\nyields and characterized, including by single-crystal X-ray diffraction.\nBy the reactions of bis­(η⁵:η¹-adamantylidene)­titanium\n(<b>1a</b>) and <b>Af</b>, diethylamine (<b>Ag</b>), and 2-methylpiperidine (<b>Ah</b>) similar monoamides <b>3f</b>–<b>h</b> are formed. The formation of titanium\nbis-amides employing different types of secondary amines (<b>Aa</b>–<b>s</b>) is not observed. The formation of titanaaziridines\nis observed exclusively by using <b>1a</b> and <i>N</i>-methylanilines (<b>Aa</b>,<b>b</b>), <i>N</i>-benzylphenylamine (<b>Ai</b>), and <i>N</i>-benzyltrimethylsilylamines\n(<b>Aj</b>,<b>k</b>). The titanaaziridine <b>4i</b> undergoes a regioselective ring enlargement reaction with 1-hexyne.\nBy the reaction of <b>4i</b> and phenylacetylene a ring opening\nwith formation of (Cp^Ad)₂Ti­(NPh­(CH₂Ph)­CCPh) (<b>6</b>) is observed. The acetylide <b>6</b> undergoes a thermal decomposition to give the zigzag butadiyne complex <b>7</b>. In addition to the ring enlargement of <b>4j</b> by\nketones a ketone insertion in the titanium–Cp bond is found,\nas proved for <b>8</b> by single-crystal X-ray diffraction.