Reduction-Induced Exclusive Activation of the ansa-1,2-Bis(dimethylsilylene)ethane Chain in ansa-Permethyltitanocene Compounds
Abstract
The ansa-1,2-bis(dimethylsilylene)ethane chain is exclusively activated when the parent ansa-permethyltitanocene compounds are reduced to titanium(II) either by thermolysis of titanium-methyl bonds or by the reduction of the parent titanocene dichloride ansa-[TiCl2(eta(5)-CH2Me2-SiC5Me4)(2)] (8) with magnesium. The compound [Ti(eta(2):eta(5):eta(5)-C5Me4SiMe2CH=CHSiMe2C5Me4)] (10), with the double bond back-bonded to titanium(II), is formed by thermolysis of ansa-[TiMe2(eta(5)-CH2Me2SiC5Me4)(2)] (9) with elimination of methane or by hydrogen transfer from the ansa-chain to easily leaving ethene or 1,4-bis(trimethylsilyl)buta-1,3-diyne pi-coordinated to an ansa-titanocene moiety.
The paramagnetic compound ansa-[Ti-III{eta(1):eta(5):eta(5)-C5Me4SiMe2CHCH2SiMe2C5Me4}] (12), with the anso-chain tethered to titanium, arises from demethanation of transiently formed ansa-[(TiMe)-Me-III(eta(5)-CH2Me2SiC5Me4)(2)] or by the reduction of 8 with magnesium in tetrahydrofuran.