| Abstract
| - The reaction of 2 equiv of the new pyrrole-substituted cyclopentadienyl ligand cyclo-C4H4NSiMe2C5H5 (2a, CppyH) with Zn[N(SiMe3)2]2 gives the bis(cyclopentadienyl)zinc complexZn(Cppy)2 (3a). The reaction of 2a and the related derivatives cyclo-2,5-Me2C4H2NSiMe2C5H5(2b, CppymeH) and 3,5-Me2C6H3CH2CMe2C5H5 (2c, CpmesH) with dibutylmagnesium givesthe corresponding magnesocenes MgCpR2 (3a−c). Prolonged heating of the appropriatecyclopentadiene with zinc dialkyls in toluene, or alternatively stirring with [XZnN(SiMe3)2]2in toluene at 40 °C for 1 h, gives the monocyclopentadienyl zinc alkyl complexes CpRZnX(6a, CpR = Cppy, X = Me; 6c, CpR = Cpmes, X = Me; 7a, CpR = Cppy, X = Et; 7c, CpR = Cpmes,X = Et), which provide spectroscopic evidence for a Zn···(hetero)arene interaction. Additionof tetramethylethylenediamine (TMEDA) gives CpRZnX(TMEDA) (8a, b, X = Me; 9a−c, X= Et). The crystal structures of 8b and 9c show η2-bound cyclopentadienyl ligands, withone long and one short Zn−C interaction. The reaction of 7c with B(C6F5)3 in toluene proceedswith alkyl/C6F5 exchange to give CpmesZn(C6F5) (10). Treatment of 9c with B(C6F5)3 in tolueneresults in an ionic product, [CpmesZn(TMEDA)]+[EtB(C6F5)3]- (11). On the other hand, thereaction of 9a with B(C6F5)3 in toluene or dichloromethane proceeds with β-H abstraction,with concomitant loss of ethene, as well as both ethyl and cyclopentadienyl abstraction.Both 11 and 9a/B(C6F5)3 mixtures catalyze the polymerization of cyclohexene oxide andε-caprolactone.
- The syntheses and structures of zinc cyclopentadienyl complexes of the type CpRZnX and CpRZnX(TMEDA) are described [X = Me, Et; CpR = CpSiMe2NC4H4, CpSiMe2NC4Me2H2-2,5, CpCMe2CH2C6H3Me2-2,5). Treatment with B(C6F5)3 generates ionic products, e.g., [CpmesZn(TMEDA)+[EtB(C6F5)3]-, which catalyze the polymerization of cyclohexene oxide and ε-caprolactone.
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