Novel Synthesis of Zirconocene Difluoride and Alkyl Monofluoride Complexes

Abstract

Starting from zirconocene bis(trimethylsilyl)acetylene complexes Cp‘2Zr(L)(η2-btmsa) via the 2-vinylpyridine complexes Cp‘2Zr(2-vipy) a novel synthetic method for zirconocene difluoride and alkyl monofluoride complexes was elaborated. Examples with selected different ligand systems Cp‘2 [Cp2 = bis(η5-cyclopentadienyl); ebthi = 1,2-ethylene-1,1‘-bis(η5-tetrahydroindenyl); (thi)2 = bis(η5-tetrahydroindenyl); Me2Si(η5-C5H4)2 = dimethylsilylbis(η5-cyclopentadienyl); (i)2 = bis(η5-indenyl); ebi = 1,2-ethylene-1,1‘-bis(η5-indenyl); and Me2Si(η5-C9H10)2 = dimethylsilyl-1,1‘-bis(η5-tetrahydroindenyl)] were synthesized. In the series of these investigations new complexes (i)2Zr(THF)(η2-btmsa) (1), rac-(ebi)Zr(THF)(η2-btmsa) (2), (thi)2Zr(2-vipy) (3), Me2Si(η5-C5H4)2Zr(2-vipy) (4), (i)2Zr(2-vipy) (5), and rac-(ebthi)Zr(2-Ph-vipy) (6) were prepared as starting materials. Different methods for preparation of the zirconocene difluorides rac-(ebthi)ZrF2 (7), (thi)2ZrF2 (8), Me4C2(η5-C5H4)2ZrF2 (9), and Me2Si(η5-C9H10)2ZrF2 (10) and the monofluorides Cp2Zr(F)(CH2CH2-2-Py) (11), rac-(ebthi)Zr(F)(CH2CH2-2-py) (12), (thi)2Zr(F)(CH2CH2-2-py) (13), Me2Si(η5-C5H4)2Zr(F)(CH2CH2-2-py) (14), and Me2Si(η5-C9H10)2ZrF(Me) (15) are reported and compared. The molecular structures of the bis-η5-tetrahydroindenyl complexes 3, 8, and 13 were confirmed by X-ray crystal structure analysis.

Reactions of 2‐Substituted Pyridines with Titanocenes and Zirconocenes: Coupling versus Dearomatisation

“…Furthermore, we investigated reactions of zirconocene‐( η 2 ‐Me 3 SiC 2 SiMe 3 ) complexes with 2‐vinylpyridine ( vipy ) and obtained the neutral complexes [Cp 2 Zr(vipy)] ( B ), [(ebthi)Zr(vipy)] ( C ), and [(thi) 2 Zr(vipy)] ( D ) (ebthi=1,2‐ethylene‐1,1′bis( η 5 ‐tetrahydroindenyl); thi= η 5 ‐tetrahydroindenyl). It is interesting to note that all these compounds have dearomatised pyridine rings, and therefore they can be best described as 1‐zircona‐2‐azacyclopent‐3‐enes with a formally reduced vipy .…”

Reactions of Zirconocene Bis(trimethylsilyl)acetylene Complexes with Fluorinated Pyridines: C–H vs. C–F Bond Activation

“…[25] The monofluoride [(η 5 -tetrahydroindenyl) 2 Zr(F)(CH 2 CH 2 -2-Py)] [Zr-C = 2.377(3) Å] and the difluoride [(η 5 -tetrahydroindenyl) 2 ZrF 2 ] [Zr-F = 1.946(2) and 1.974(2) Å] exhibit comparable bond lengths. [52] In the molecular structure of complex 7 (Figure 4), the bond length for Zr1-C11 [2.353(5) Å] is the same as that found for complex 6. The observed Zr1-Cl1 bond length of 2.422(1) Å corresponds well with that found in other complexes of this type, e.g.…”

“…20-30 ppm). [52] The increased steric demand of the rac-ebthi ligand system is responsible for restricted rotation of the pyridyl group about the Zr-C bond. For the Cp complex 3 only two 19 F resonances were found whereas the ebthi complex 4 exhibits four (an exchange between the otherwise equivalent ortho or meta fluoro substituents by pyridyl rotation does not occur).…”

“…Using the monomeric imidozirconocene complex [rac-(ebthi)-Zr=NtBu], they observed activation of the ortho C-F bond and the formation of an amininopyridinato complex rac-(ebthi)ZrF(-NtBu-2-C 5 NF 4 ). [33] In the light of the surprising results concerning zirconocene difluorides and alkyl monofluorides in the catalytic polymerisation of olefins, [34][35][36][37] we began to question whether the above mentioned alkyne complexes could activate C-F bonds to form the zirconocene fluoro complexes by C-F bond cleavage. These investigations were also extended to cover the question of whether hydride complexes (Zr-H systems, formed by reactions of systems containing Zr-F and Al-H bonds) could cleave the C-F bonds of B(C 6 F 5 ) 3 .…”

Activation of Metallacyclopropenes, five‐membered Metallacyclocumulenes and Metallacyclopentynes of Zirconium with iBu2AlH

“…These results were compared with results in which the complexes Cp 2 Zr(h 4 -1,2,3,4-H 2 C 4 H 2 ) (8), rac-(EBTHI)ZrF 2 (9), [13] rac-(EBTHI)ZrCl 2 (10), [14] [rac-(EBTHI)-Zr(H)(m-H)] 2 (11) [15] and rac-(EBTHI)-Zr(F)CH 2 -CH 2 (2-Py) (12) [16] were activated by the addition of i-Bu 2 AlH together with water, too. Additionally, the complexes rac-(EBTHI)ZrF 2 (9), rac-(EBTHI) ZrCl 2 (10) and rac-(EBTHI)ZrMe 2 (13) [17] were activated by MAO to understand the importance of alkylation for the formation of these active catalysts.…”