Synthesis and X-ray Crystal Structure Determination of New Zwitterionic Complexes of Titanocene

The reaction of (η5-iPrC5H4)2Ti(Me3SiC2SiMe3) (2) with B(C6F5)3 in toluene at room
temperature produces the zwitterionic titanium(III) complex (η5-iPrC5H4)[η5-{1,3-iPrC5H3B(C6F5)3}]Ti (3) in which the 3-hydrogen atom of one of the C5 rings is substituted by a B(C6F5)3
group. The complex is analogous in its structure to the previously described titanium(III)
zwitterion Cp[η5-C5H4B(C6F5)3]Ti (1) formed in the interaction of B(C6F5)3 with Cp2Ti(Me3SiC2SiMe3). A characteristic feature of both zwitterionic complexes is the presence of
coordinative bonds between the ortho-fluorine atoms of two C6F5 substituents and the
positively charged titanium center. Complex 1 is also obtained by the reaction of B(C6F5)3
with Cp2Ti(PhC2SiMe3). The oxidation of 1 and 3 by air oxygen affords the zwitterionic
titanoxanes {Cp[η5-C5H4B(C6F5)3]Ti}2O (4) and {(η5-iPrC5H4)[(η5-{1,3-iPrC5H3B(C6F5)3}]Ti}2O
(5), respectively, which contain two zwitterionic units in the molecule. In each of these units,
only one ortho-fluorine atom of a B(C6F5)3 group is involved in the coordination to the titanium
atom. Complex 1 readily reacts also with acetone to give the zwitterionic adduct Cp[η5-C5H4B(C6F5)3]Ti(Me2CO) (6), wherein the molecule of acetone is bonded to the Ti(III) center
through the oxygen atom. In this adduct too, only one ortho-fluorine atom of a B(C6F5)3 group
is coordinated to the metal.