Reactivity of tetramethylpyrrole complexes of ruthenium and osmium

Abstract

Reaction of [(p-cymene)M(OTf)[sub 2]][sub x] with tetramethylpyrrole leads to the formation of [(p-cymene)M(NC[sub 4]Me[sub 4])]OTf, 1 when M = Ru, 2 when M = Os. Complex 1 crystallized in space group P2[sub 1]2[sub 1]2[sub 1] with unit cell dimensions a = 8.928(2) A, b = 13.772(4) A, c = 17.272(6) A, V = 2123.7(11) A[sup 3], and Z = 4. The crystal structure establishes that 1 is a sandwich complex with [eta][sup 6]-cymene and [eta][sup 5]-pyrrolyl ligands. Reaction of 1 or 2 with excess methyl triflate results in alkylation of the pyrrole nitrogen to form ([eta][sup 6]-p-cymene)M([eta][sup 5]-MeNC[sub 4]Me[sub 4])(OTf)[sub 2], 3 when M = Ru and 4 when M = Os. Reactions of 1 or 2 with LiAl(O-t-Bu)[sub 3]H result in nucleophilic attack of hydride on the cymene ligand to form ([eta][sup 6]-cymH)M([eta][sup 5]-NC[sub 4]Me[sub 4]), 5 when M = Ru, 6 when M = Os. Complexes 5 and 6 have been identified by one and two dimensional [sup 1]H NMR spectroscopy. Nucleophilic attack on the cymene ligand of 1 and 2 appears to be quite general, and the products of methoxide addition, ([eta][sup 5]-cymOMe)M([eta][sup 5]-NC[sub 4]Me[sub 4]) 7 when M = Ru, 8 when M = Os havemore » also been characterized by [sup 1]H NMR data. In contrast, reactions of the pentamethylpyrrole complexes 3 and 4 with nucleophiles lead to nucleophilic addition to the pentamethylpyrrole ligand. For example, the reaction of 3 with LiAl(O-t-Bu)[sub 3]H resulted in the formation of ([eta][sup 6]-p-cymene)Ru([eta][sup 4]-MeNC[sub 4]Me[sub 4]H)OTf, 10, which was characterized by an X-ray diffraction study. 10 crystallized in space group P2[sub 1]c with a = 8.153(2) [degrees], b = 17.351 (2) [angstrom], c = 16.508(2) [angstrom], beta = 104.396(13)[degrees], V = 2261.9(7) [angstrom][sup 3], and Z = 4. 28 refs., 5 figs., 3 tabs.« less