No abstract

No abstract

Reaction of [@-cymene)M(OTf)~l, with tetramethylpyrrole leads to the formation of [ @-cymene)M(NC4Mea)]OTf, 1 when M = Ru, 2 when M = Os. Complex 1 crystallized in space group P21212~ with unit cell dimensions a = 8.928(2) A, b = 13.772(4) A, c = 17.272(6) A, V = 2123.7(11) A3, and 2 = 4. The crystal structure establishes that 1 is a sandwich complex with $ + m e n e and +pyrrolyl ligands. Reaction of 1 or 2 with excess methyl triflate results in alkylation of the pyrrole nitrogen to form [(r16-p-cymene)M(q6-MeNC4Me4)l (OTf)z, 3 when M = Ru and 4 when M = Os. Reactions of 1 or 2 with LiAl(O-t-Bu)sH result in nucleophilic attack of hydride on the cymene ligand to form (r16-cymH)M(r16-NC4Me4), 5 when M = Ru, 6 when M = Os. Complexes 5 and 6 have been identified by one and two dimensional lH NMRspectroscopy. Nucleophilic attack on the cymene ligand of 1 and 2 appears to be quite general, and the products of methoxide addition, (sS-cymOMe)M(r16-NC4Mer), "when M = Ru, 8 when M = Os,have also been characterized by lH 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(0-t-Bu)sH resulted in the formation of [+ pcymene)Ru(+MeNC4Me4H)OTf, 10, which was characterized by an X-ray diffraction study.10 crystallized in space group P21/c with a = 8.153(2) A, b = 17.351(2) A, c = 16.508(2) A, p = 104.396(13)', V = 2261.9(7) A3, a n d 2 = 4. The structure established that the hydride nucleophile added to an a carbon of the pentamethylpyrrole ligand in an exo orientation. This a carbon lies out of the plane of the remaining four ring atoms with a dihedral angle of 3 8 O . The modified pentamethylpyrrole ligand coordinates to Ru in a q4-coordination mode. Further reaction of 10 with protic acid leads to further pyrrole reduction and dissociation from the metal. The reactions of the pyrrole systems are compared to those of related [(arene)Ru(thiophene)In+ derivatives.

Supplementary Material Available: Listings of additional bond lengths and angles, hydrogen atom parameters, and anisotropic thermal parameters for 5-7 (9 pages); tables of the observed and calculated structure factors (82 pages). Ordering information is given on any current masthead page.

An extensive reactivity with hydrogen and unsaturated molecules has been characterized for the /t-sulfide ligands in (CpMo)2(M-S)2S2CH2 (2). However, the bridging disulfide ligand in the heteronuclear cluster [(CpMo)2(M-S2)(M-S2FeCp)]+ (3) was not reactive toward hydrogen or olefins. Extended Huckel molecular orbital calculations have been carried out for 2 and for the hypothetical Fe-Mo cluster with bridging sulfides rather than a disulfide ligand [(CpMo)2(/t-S)2(S2FeCp)]+ (3'). The electronic structures of complexes 2 and 3' are analyzed in terms of the CP2M02S4 and methylene and the FeCp+ fragment orbitals, respectively. This approach leads to a qualitative understanding of the reasons for the structural and reactivity differences between 2 and 3.