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(eta5-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(trimethylphosphane)zirconocene (7) and the cyclopropenes 3a or 3b to yield 8a and Bb. Some of these metallabicyclo[3.1.0]hexene derivatives rearrange quantitatively to the corresponding 4-(dimethylvinyl)-1-metalla-2-cyclobutene derivatives 16 and 17a and 4-(diphenylvinyl)-1-metalla-2-cyclobutenes 15c and 17a-c when they are heated to 60-80-degrees-C for several hours. The 4-(diphenylvinyl)-1-titana-2-cyclobutene derivatives l5a-c can also be obtained by reaction of [(2,2-diphenylvinyl)carbene](trimethylphosphane)titanocen (13) with disubstituted alkynes such as tolane, phenyltrimethylsilylacetylene and bis(trimethylsilyl)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 H-1- and C-13-NMR studies provide unambiguous proof of their structures.