HETEROATOM EXCHANGE-REACTIONS IN IMIDOOSMIUM(II) SYSTEMS - CLEAVAGE OF OS-N MULTIPLE BONDS AND FORMATION OF OS-X BONDS (X = O, S, C)

The monomeric imido complex CymOsN-t-Bu (2) (Cym = eta6-p-cymene) was used as a convenient precursor in exchange reactions with a variety of H-X bonds (X = O, S, C). Complex 2 reacts with alkoxides HOCMe(CF3)2, pinacol, catechol, and 1,2-(H2N) (HO)C6H4 to give CymOs(NH-t-Bu)[OCMe (CF3)2] (4), CymOs[OC(CH3)cE(CH3)20] (5), CymOs[1,2-O2C6H4] (6), and C ymOs[1,2-0(HN)C6H4](7), respectively. CymOs(O-t-Bu)2(3) was not formed by this method but was generated by treatment of [CymOsCl2]2 (1) with KO-t-Bu. Addition of H2N-t-Bu to 3 gave 2, and reaction of 5 with cat echol gave 6. Complex 6 adds PMe3 to give CymOs[1,2-O2C6H4] (PMe3) (8) . Catechol, 1,2-(H2N)2CrH4, or H2N-p-tol hydrogen bond or coordinate t o the metal in 6 or CymOs[1,2-(NH)2C6H4] (10). Reactivity patterns gen erally correlate with the pK. of the substrate, but other factors are also involved. Several analogous thiolate complexes were also prepared . For example, imido complex 2 or bis(tert-butoxide) 3 reacted readily with t-BU-SH to give CymOs(S-t-BU)2 (13). The analogous osmium comple xes with 2,6-Me2C6H3 and 2,4,6-Me3C6H2 groups attached to the sulfur a toms (14 and 15, respectively) were obtained by treatment of imido com plex 2 with the appropriate thiols. However, reaction of 2 with p-tol- SH gave the dimeric thiolate complex [CymOs(S-p-Me-C6H4)2]2 (16). Comp lex 2 also reacts with carbon acids. The more acidic C-H bond of H2C(C OMe)2 (acacH) caused the addition of 2 mol of diketone with tert-butyl amine loss to give CymOs[CH(COMe)2][(OC(Me))2CH-O,O] (18) whereas the weaker acid (H2C(CO2Me)2) added only once across the Os-N bond to give CymOs(NH-t-Bu)[CH(CO2Me)2] (17). Treatment of dichloro dimer [CymOsCl 2]2 with K2CO3 and acacH quantitatively provided yellow CymOs(acac-0,O )Cl(19). Monoacetylacetonato complex 19 was treated with AgOAc (Ac = C OMe) to give CymOs(acac)(OAc) (21). Dimethyl malonate complex 17 was i ndependently treated with acacH and H2C(CO(Ph))2 to give CymOs[CH(CO2M e)2][(OC(Me))2CH] (22) and bright red CymOs[CH(CO2Me)2][(OC(Ph))2CH] ( 23). Carbon-proton NMR coupling data provided evidence for the presenc e of carbon-metal bound diketonate ligands in 17, 18, 22, and 23.