Premium
Stability of Bridged and Unbridged η 2 ‐Alkyne−titanocene and −zirconocene Complexes − Influence of Metals, Alkyne Substituents, Cp Substitution and Additional Ligands
Author(s) -
Peulecke Normen,
Baumann Wolfgang,
Kempe Rhett,
Burlakov Vladimir V.,
Rosenthal Uwe
Publication year - 1998
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/(sici)1099-0682(199803)1998:3<419::aid-ejic419>3.0.co;2-d
Subject(s) - alkyne , chemistry , medicinal chemistry , cyclopentadienyl complex , nuclear magnetic resonance spectroscopy , metallocene , stereochemistry , catalysis , organic chemistry , polymerization , polymer
The influence of metals, alkyne substituents, Cp substitution and additional ligands on the stability of bridged and unbridged η 2 ‐alkyne−titanocene and −zirconocene complexes has been investigated. The reduction of the complex [(η 5 ‐C 5 H 4 )−SiMe 2 −(η 5 ‐C 5 H 4 )]TiCl 2 with magnesium in the presence of tolan (PhC 2 Ph) does not give the expected alkyne−titanocene complex [(η 5 ‐C 5 H 4 )−SiMe 2 −(η 5 ‐C 5 H 4 )]Ti(η 2 ‐PhC 2 Ph) but by coupling of two tolan molecules the corresponding titanacyclopentadiene [(η 5 ‐C 5 H 4 )−SiMe 2 −(η 5 ‐C 5 H 4 )]TiC 4 Ph 4 ( 1 ) was obtained. In the analogous reaction with Me 3 SiC 2 SiMe 3 the stable η 2 ‐alkyne complex without additional ligands [(η 5 ‐C 5 H 4 )−SiMe 2 −(η 5 ‐C 5 H 4 )]Ti(η 2 ‐Me 3 SiC 2 SiMe 3 ) ( 2 ) was formed, due to the sterical influence of the alkyne substituents. The compounds without additional ligands (thi) 2 Ti(η 2 ‐PhC 2 Ph) ( 3 ) and (thi) 2 Ti(η 2 ‐ Me 3 SiC 2 SiMe 3 ) ( 5 ) were isolated from the unbridged titanocene complex (thi) 2 TiCl 2 (thi = tetrahydroindenyl). Two equivalents of complex 3 reacted with one equivalent of water to yield the dimeric alkylidene‐μ‐oxo complex [(thi) 2 Ti(CPh=CHPh)] 2 (μ‐O) ( 6 ). The reaction of the unbridged zirconocene compound (thi) 2 ZrCl 2 gave the alkyne complex (thi) 2 Zr(THF)(η 2 ‐Me 3 ‐ SiC 2 SiMe 3 ) ( 7 ) which is stabilized by THF. At higher temperature THF was eliminated from the orange complex 7 forming the green complex (thi) 2 Zr(η 2 ‐Me 3 SiC 2 SiMe 3 ). This behaviour was investigated in detail using NMR spectroscopy and compared to similar complexes such as Cp 2 Zr(η 2 ‐Me 3 SiC 2 SiMe 3 ) (not stable without THF), (ebthi) 2 Zr(η 2 ‐Me 3 SiC 2 SiMe 3 ) (ebthi = ethylenebistetrahydroindenyl; stable without THF) and Cp* 2 Zr(η 2 ‐Me 3 SiC 2 SiMe 3 ) (Cp* = pentamethyl‐Cp, stable without THF). All complexes were characterized by spectroscopic methods. X‐ray structural determinations were conducted for the complexes 1 , 3 and 7 . Compound 3 is the first example of a structurally characterized tolan−titanocene complex without additional ligands.