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Synthesis and Structural Characterization of Azatitanacyclobutane Derivatives

✍ Scribed by Rüdiger Beckhaus; Martin Wagner; Ruimin Wang


Publisher
John Wiley and Sons
Year
1998
Tongue
English
Weight
475 KB
Volume
1998
Category
Article
ISSN
1434-1948

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✦ Synopsis


The titanocene vinylidene intermediate [Cp* 2 Ti=C=CH 2 ] (9) The azatitanacyclobutane [Cp* 2 Ti{ϪNPhϪC(Ph)(H)Ϫ(C= CH 2 )Ϫ}] (22) was formed from the reaction between 9 and reacted with the carbodiimides RϪN=C=NϪR [R = p-CH 3 C 6 H 4 (19a), C 6 H 11 (19b)] to give the N=C-cycloaddition benzylidene aniline [PhN=C(Ph)H (21)]. Reactivity studies showed that azatitanacyclobutanes are unreactive upon typi-products [Cp* 2 Ti{ϪNRϪC(=NR)Ϫ(C=CH 2 )Ϫ}] [(R = p-CH 3 C 6 H 4 (20a), C 6 H 11 (20b)]. The X-ray structure of 20a in cal ring-enlargement reactions as observed for other fourmembered titanacycles. form of a surprisingly stable n-hexane clathrate is presented.

Results and Discussion

Oxatitanacyclobutanes (1) and azatitanacyclobutenes (3) are under discussion as intermediates in reactions of Tiϭ

The vinylmethyl derivative 8 reacts with one equivalent CR 2 with carbonyl compounds or nitriles. The high electroof the carbodiimide RNϭCϭNR (R ϭ p-CH 3 C 6 H 5 19a, philicity of the metal centre has generally prevented the iso-R ϭ C 6 H 11 19b) at room temperature in n-hexane as solvent lation and characterization of oxa-and azatitanacyclowith evolution of methane to give a dark green solution, butenes: spontaneous ring opening reactions afford carfrom which the azatitanacyclobutane complexes 20 are obbonyl olefination (1Ǟ2), or products of vinylimido intertained as green crystals (20a) or as a green oil (20b). These mediates (3Ǟ4). [1] The present paper deals with the compounds are formed nearly quantitatively (NMR) and formation of azatitanacyclobutane complexes (5) prepared can be isolated in 92% (20a) and 88% (20b) yield. The mass by [2ϩ2] cycloaddition of a TiϭC and NϭC units.

spectra show the expected molecular peaks. For 20b, a cycloreversion with formation of 9 can be detected from the fragmentation pattern, whereas for 20a, the liberation of a C 5 Me 5 ligand is the main fragmentation step, indicating a higher stability of the azatitanacyclobutane unit.

From the thermally generated titana-allene intermediate Cp* 2 TiϭCϭCH 2 (9), formed by ethane or methane elimination from Cp* 2 Ti[ϪCH 2 CH 2 (CϭCH 2 )Ϫ] (10) or Cp* 2 Ti(CHϭCH 2 )(CH 3 ) (8), a wide range of four-membered titanacycles (11Ϫ18) can be produced.


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