Organometallic compounds of the lanthanides: Part CIXXX. Synthesis, structure and hydrolysis of ‘moderately stable’ hydrosilylation catalysts [(η5-C5H4SiMe3)2Ln(μ-Me)]2 and [(η5-C5H4SiMe2 tBu)2Ln(μ-Me)]2

Abstract The lanthanidocene chloride complexes [(η 5 -C 5 H 4 SiMe 2 R) 2 Ln(μ-Cl)] 2 (R= t Bu, Ln=Y ( 1a ), Sm ( 1b ), Lu ( 1c ); R=Me, Ln=Y ( 2a ), Sm ( 2b ), Lu ( 2c )) are prepared from the trichlorides of yttrium, samarium or lutetium and tert -butyldimethylsilylcyclopentadienylpotassium or trimethylsilylcyclopentadienylpotassium, respectively. Compounds 1 and 2 react with two equivalents of methyllithium in diethyl ether to give the new dimers [(η 5 -C 5 H 4 SiMe 2 R) 2 Ln(μ-Me)] 2 (R= t Bu, Ln=Y ( 3a ), Sm ( 3b ), Lu ( 3c ); R=Me, Ln=Y ( 4a ), Sm ( 4b ), Lu ( 4c )) which are ‘moderately stable’ in atmospheric moisture. The reactions of 2 with methyllithium in a 1:4 molar ratio in THF yield the monomeric lanthanidocene methyl complexes (η 5 -C 5 H 4 SiMe 3 ) 2 Ln(μ-Me) 2 Li(THF) 2 (Ln=Y ( 5a ), Sm ( 5b ), Lu ( 5c )). Treatment of 3 and 4 with stoichiometric amounts of H 2 O in toluene yields the dimeric lanthanidocene hydroxide complexes [(η 5 -C 5 H 4 SiMe 2 R) 2 Ln(μ-OH)] 2 (R= t Bu, Ln=Y ( 6a ), Sm ( 6b ), Lu ( 6c ); R=Me, Ln=Y ( 7a ), Sm ( 7b ), Lu ( 7c )). The molecular structures of 1c , 4a , and 7c were determined by single crystal X-ray diffraction. The lanthanidocene methyl complexes 3 and 4 are effective precatalysts for hydrosilylation of alkenes and alkynes.