Generation of functionally substituted cyclopentadienyl ligands in osmium(IV) chemistry

Abstract

Several types of substituted cyclopentadienyl osmium(IV) complexes can be obtained by reaction of OsH(η5-C5H5)Cl(EPh3)(PiPr3) (E = Ge (1), Si (2)) with LiNu reagents. Both 1 and 2 react with LiCH2CN. The reactions give OsH2(η5-C5H4EPh3)(CH2CN)(PiPr3) (E = Ge (3), Si (4)). The reaction of the perdeuterated cyclopentadienyl complex OsH(η5-C5D5)Cl(SiPh3)(PiPr3) (2-d5) with LiCH2CN affords Os(H)(D)(η5-C5D4SiPh3)(CH2CN)(PiPr3) (4-d5). Complex 4 reacts with CD3OD to give OsH2(η5-C5H4SiPh3)(CD2CN)(PiPr3) (4-d2), which can be also obtained by addition of LiCD2CN to 2. The treatment of 1 with RLi leads to OsH2(η5-C5H4R)(GePh3)(PiPr3) (R = CH3 (5), nBu (6), secBu (7)). Under the same conditions, the addition of nBuLi to OsH(η5-C5D5)Cl(GePh3)(PiPr3) (1-d5) affords Os(H)(D)(η5-C5D4nBu)(GePh3)(PiPr3) (6-d5). Complex 2 also reacts with CH3Li and nBuLi. In both cases, complex (8) is obtained. The structure of 8 has been determined by X-ray diffraction analysis. The distribution of ligands around the metallic center can be described as a four-legged piano stool geometry with the phosphine and the metalated phenyl group mutually transoid. The treatment at room temperature of 2-d5 with nBuLi leads to a mixture of (8-d4) and Os(H)(D)(η5-C5D4nBu)(SiPh3)(PiPr3) (9-d5) in a 2:1 molar ratio. The reaction of 2 with secBuLi also gives a mixture. In this case, it is formed by OsH2(η5-C5H4secBu)(SiPh3)(PiPr3) (10) and 8 in a 1:4 molar ratio. The addition of LiCH2C(O)CH3 to 2 leads to (11). The reactions of 1 with LiNR2 afford OsH2(η5-C5H4NR2)(GePh3)(PiPr3) (R = Et (12), allyl (13)), while under the same conditions 2 gives mixtures of 8 and OsH2(η5-C5H4NR2)(SiPh3)(PiPr3) (R = Et (14), allyl (15)). The structure of 13 has been also determined by X-ray diffraction analysis. The distribution of ligands around the metallic center is also a four-legged piano stool geometry, but in this case, the phosphine is transoid to GePh3. Both 1 and 2 react with LiPPh2. The reactions give the cyclopentadienyl phosphine derivatives OsH2(η5-C5H4PPh2)(EPh3)(PiPr3) (E = Ge (16), Si (17)).