Reductive Coupling of an Indenylidene with Calcium To Form Bis(indenyl) ansa-Metallocenes:  Molecular Structures of trans-Ph₂C₂H₂-rac-(η⁵-4,7-Me₂C₉H₄)₂Ca(THF)₂ and trans-Ph₂C₂H₂-rac-(η⁵-4,7-Me₂C₉H₄)₂Fe

Abstract

1-E-benzylidene-4,7-dimethylindene (1) is reductively coupled by activated calcium to form two isomers, trans-Ph2C2H2-rac-(η5-4,7-Me2−C9H4)2Ca(THF)2 (trans-rac-2) and cis-Ph2C2H2-meso-(η5-4,7-Me2−C9H4)2Ca(THF)2 (cis-meso-2) in an approximately 1:1 ratio. Reaction of the calcium species with FeCl2 produces a mixture of the corresponding trans-rac and cis-meso ferrocenophane species (3) along with another ferrocenophane isomer that is presumed to be either the trans-meso or cis-rac isomer. Thus, the relative geometry of the indenyl rings is not retained entirely during the transfer of the ligand framework from calcium to iron. A complete scrambling of the indenyl ring geometry appears to occur upon transfer of the ligand framework from calcium to zirconium. The results of X-ray crystal structure determinations of 1-E-benzylidene-4,7-dimethylindene, trans-Ph2C2H2-rac-(η5-4,7-Me2−C9H4)2Ca(THF)2, and trans-Ph2C2H2-rac-(η5-4,7-Me2−C9H4)2Fe are described.

Unusual demetalation of iron from [2]ferrocenophane skeleton of di‐nuclear ferracycle carbonyl complex

“…Whereas the distance between the rings in 1 and 2 is similar, at 3.30 Ǻ and 3.23 Ǻ respectively, demetalation causes the rings to more further apart, to 4.11 Ǻ in 3 . The tilt angles of 1 and 2 are 2.58 o and 21.84 o , respectively, the latter being comparable similar core of reported stable compounds, carba[2]‐ferrocenophane (21.6 o ), 1,1′‐(tetraphenyl‐o‐phenylene)ferrocene (23.7 o ), methylthio‐1,2‐(1,1′‐ ferrocenediyl)ethane (23.8(4) o ) 1,2‐(1,1′‐ferrocenediyl)ethane (23.62(4) o ), (η 5 ,η 5 –2,3‐bis(3‐t‐butylcyclopentadienyl)butane)‐irontetrafluoroborate (20.76o), trans‐1,2‐diphenyl‐rac‐1,2‐bis(η 5 –4,7‐dimethylindenyl) ethane)‐iron (23.08 o ), (η 5 ,η 5 –1,5(1,3)‐dicyclopentadiena‐6,6,7,7‐tetramethyl‐2,3,4‐trithiacycloheptaphane)‐iron (20.1 o ), (μ 2 ‐carbonyl)‐(μ 2 –1,2,3,4‐η 2 :η 3 ‐(ferrocene‐1,1‐diyl)‐1,4‐dimethylsilylbutane‐1,3‐diene‐1,4‐diyl)‐pentacarbonyl‐di‐ruthenium (22.85 o ) and bis(μ 2 ‐carbonyl)‐(μ 3 –1,2,3,4‐η 2 :η 3 ‐(ferrocene‐1,1′‐diyl)‐1,4‐diphenylsilylbutane‐1,3‐diene‐1,4‐diyl)‐hexacarbonyl‐tri‐ruthenium (21.82 o ) . All these tilt angles are similar to optimized structure of 2 , but higher than 1 and lesser than 3 .…”

Stereoselective Formation of C2-Symmetric ansa-Lanthanocenes by Reductive Coupling of Acenaphthylene with Activated Ytterbium or Samarium

“…According to the two different possibilities for the orientation of the two acenyl ring units of the ligand, C s ‐symmetric meso ‐ and/or C 2 ‐symmetric rac ‐ansa complexes may be expected. In contrast to the results of the reductive coupling of indenylidenes with metallic calcium2c,2e or titanium and zirconium dihalides,2d the described coupling of acene with Yb or Sm, exclusively gives the respective C 2 ‐symmetric trans‐rac ‐ansa complex as confirmed by 1 H NMR spectroscopic measurements and X‐ray diffraction analysis of 1 and 2 .…”

“…The reaction with 6‐substituted fulvenes results in the formation of mixtures of rac and meso isomers. The exclusive formation of just one isomer by fulvene‐type coupling has not yet been observed 2e. The synthesis of ansa‐metallocenes from bridged cyclopentadienyl dianions also produces only mixtures of isomers of variable rac : meso ratios 3.…”

Ultrasonic oscillations effect on rheological and processing properties of metallocene‐catalyzed linear low density polyethylene

“…Application of alkaline earth metallocenes for the synthesis of ester‐substituted ferrocene : The metathesis reaction between a heavier alkaline earth metallocene and a transition‐metal salt has been reported to be an effective means of preparing the corresponding transition‐metal metallocene 17. Thus, as shown in Scheme , in a first attempt the calcocene 10 a was treated with FeCl 2 , but no reaction was observed after heating the reaction mixture in THF at 80 °C for 24 h. To our delight, however, when the barium metallocene 10 c was used, the expected metathesis reaction proceeded smoothly, generating the ester‐substituted ferrocene derivative 12 in 82 % yield 17b,c,e. The driving force for this reaction is assumed to be the precipitation of BaCl 2 .…”