Coordination Chemistry of Cyclic Disilylated Stannylenes and Plumbylenes to Group 4 Metallocenes

Reduction of group 4 metallocene dichlorides with magnesium
in
the presence of cyclic disilylated stannylene or plumbylene phosphine
adducts yielded the respective metallocene tetrylene phosphine complexes.
Under the same conditions the use of the respective dimerized stannylene
or plumbylene gave metallocene ditetrylene complexes. A computational
analysis of these reactions revealed for all investigated compounds
multiple-bonded character for the M–E­(II) linkage, which can
be rationalized in the case of the monotetrylene complex with the
classical σ-donor/π-acceptor interaction. The strength
of the M–E­(II) bond increases descending group 4 and decreases
going from Sn to its heavier congener Pb. The weakness of the Ti–E­(II)
bonds is caused by the significantly reduced ability of the titanium
atom for d–p π-back-bonding.