Selective tin-carbon bond cleavage reactions of trimethylstannylzirconocene dichloride with electrophiles

The reaction of 5,5-bis(trimethylstannyl)cyclopentadiene with CpZrCl3 (C-p = eta (5)-C3H5) affords the monostannylated metallocene complex (eta (5)-Me3SnC5H4)CpZrCl2 (1), accompanied by variable amounts of (eta (5)-ClMe2SnC5H4)CpZrCl2 (2). The complex (1) reacts with BCl3 or with ICl to afford 2 (Sn-CH3 cleavage), but with HCl, CpzZrCl(2) is obtained instead (Sn-Cp cleavage). Depending on the reaction conditions, treatment of either 1 or 2 with BBr3 affords (eta (5)-BrMe2SnC5H4)CpZrBr2 (3) or (eta (5)-Br2MeSnC5H4)CpZrBr2 4). The reaction of 1 with excess I-2 affords the iodostannylated complex (eta (5)-IMe2SnC5H4)CpZrCl2 (5). Two of the complexes (2(.)2C(6)H(5)CH(3) and 4(.)THF) are crystallographically characterized. The adduct 4(.)THF has a distorted trigonal bipyramidal geometry about tin with a long O-Sn distance of 2.655 Angstrom. We find overall that Me3Sn substituents undergo electrophilic halodemethylation much more readily than corresponding Me3Si substituents, whereas the reactivities of the halostannylated complexes toward nucleophiles such as airborne moisture are much lower than those of their halosilylated counterparts.