Cyclopentadienylmolybdenum(II) and -(III) Complexes Containing Diene and Allyl Ligands. 3. Reactivity Studies of the Bis(butadiene) Complex [CpMo(s-cis-supine-η-C4H6)(s-trans-η-C4H6)][BF4

Abstract

The compound [CpMo(s-cis-supine-C4H6)(s-trans-C4H6)]BF4 (2) reacts with a variety of nucleophilic reagents to afford either substitution of the s-trans-butadiene ligand or regioselective nucleophilic addition to the endo terminal carbon of the s-trans butadiene ligand. The reaction with tBuNC affords the substitution product [CpMo(s-cis-supine-C4H6)(tBuNC)2]BF4 (3). Nucleophilic addition of PMe3 leads to [CpMo(s-cis-supine-C4H6)(syn-prone-C3H4-1-CH2PMe3)]BF4 (4), which has been characterized also by X-ray crystallography. Nucleophilic addition of methyllithium or allylmagnesium bromide affords [CpMo(s-cis-supine-C4H6)(syn-prone-C3H4-1-CH2R)]BF4 (R = Me, (5), CH2CHCH2 (6)). The Grignard reaction, however, also affords the substitution product CpMo(s-cis-supine-C4H6)(prone-C3H5). Compound 5 is oxidized by ferrocenium to [5]+, which rapidly and extensively isomerizes to [CpMo(s-cis-supine-C4H6)(syn-supine-C3H4-1-Et)]+ ([7]+). Reduction of the latter by cobaltocene affords CpMo(s-cis-supine-C4H6)(syn-supine-C...