Metallabicyclo[3.1.0]hexene und deren Umlagerung zu Vinylmetallacyclobutenen (M=Ti, Zr)

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Abstract
Metallabicyclo[3.1.0]hexenes and Their Rearrangement to Vinylmetallacyclobutenes (M=Ti, Zr)Alkyne‐metallocene complexes, e.g. the alkynetitanocenes 1a, b, the alkyne(trimethylphosphane)titanocenes 2a, b and the alkyne(trimethylphosphane)zirconocenes 5a–d react readily with 3,3‐dimethylcyclopropene (3a) and 3,3‐diphenylcyclopropene (3b) to give the corresponding bis(η5‐cyclopentadienyl)‐metallabicyclo[3.1.0]hexene derivatives 4a–e, (M=Ti) and 6a–g (M=Zr) in high yields. In an analogous manner, metallabicyclo[3.1.0]hexene derivatives of Ti or Zr can be prepared from 1,2‐diphenylcyclopropene(trimethylphosphane)metallocenes 9 and 10 and 2‐butyne to yield 11 and 12 and from benzyne 3a or 3b to yield 8a and 8b. Some of these metallabicyclo[3.1.0]hexene derivatives rearrange quantitatively to the corresponding 4‐(dimethylvinyl)‐1‐metalla‐2‐cyclobutene derivates 16 and 17a and 4‐(diphenylvinyl)‐1‐metalla‐2‐cyclobutenes 15c and 17a–c when they are heated to 60–80°C for several hours. The 4‐(diphenylvinyl)‐1‐titana‐2‐cyclobutene derivatives 15a–c can also be obtained by reaction of [(2,2‐diphenylvinyl)carbene](trimethylphosphane)‐titanocen (13) with disubstituted alkynes such as tolane, phenyltrimethylsilylacetylene and bis(trimethylsily)acetylene. With other alkynes, e.g. 2‐butyne, 1‐butyne, 1‐propyne or acetylene, 13 reacts by polymerization of these alkynes; the corresponding 4‐vinyl‐1‐titanacyclobutene derivatives could not be detected in the reaction mixture. All new metallacycles are fully characterized by spectroscopic methods, extensive 1H‐ and 13C‐NMR studies provide unambiguous proof of their structures.