Reaction of the bis-isonitrile complex [Mo2Cp2(μ-SMe)3(t-BuNC)2](BF4) (1) with n-BuLi (in hexane) produced the dealkylated derivative [Mo2Cp2(μ-SMe)3(t-BuNC)(CN)] (2) in quantitative yield. However, upon treatment with either NaOH (suspension) or (Me4N)OH (in MeOH), 1 was converted into a mixture of 2 and the μ-alkylidyne species [Mo2Cp(μ-SMe)3{μ-(η5-C5H4)(t-BuN)CN(t-Bu)C}] (3), in which a deprotonated Cp and both isonitrile ligands of 1 are now linked by new carbon−carbon and carbon−nitrogen bonds.

Reaction of the bis-isonitrile complex [Mo2Cp2(μ-SMe)3(xylNC)2](BF4) (2b) with NaOH (suspension) under reflux in tetrahydrofuran produced, in quantitative yields, the μ-alkylidyne species [Mo2Cp(μ-SMe)3{μ-(η5-C5H4)(xylN)CN(xyl)C}] (4), in which a deprotonated Cp and both isonitrile ligands of 2b are now linked by new C−C and C−N bonds. Under prolonged reflux (72 h) in tetrahydrofuran 2b with either NaOH (suspension) or (Me4N)OH (in MeOH) in the presence of excess isonitrile RNC (R = xyl, But) was converted in high yields into the mixed (μ-alkylidyne)(μ-amino-oxycarbene) derivatives [Mo2Cp(μ-SMe)2{μ-(η5-C5H4)(xylN)CN(xyl)C}{μ-η1(O),η1(C)-OCNHR}] (R = xyl (5a1), R = But (5b2)) and [Mo2Cp(μ-SMe)2{μ-(η5C5H4) (xylN)CN(xyl)C}{μ-η1(O),η1(C)-OCNMeR}] (R = xyl (6a)). All these products result from hydroxide−isonitrile coupling reactions. When the mixture of 2b, (Me4N)OH (excess), and ButNC (excess) in tetrahydrofuran was heated under reflux for a short time (2 h), complex 5b1 was formed in good yields. Compounds 5b1 and 5b2 are linkage isomers, which differ only in the mode of coordination of the μ-amino-oxycarbene ligand to the Mo1−Mo2 unit; 5b1 converts into 5b2 on prolonged heating. Reaction of the secondary amino-oxycarbene derivative 5a1 with a base (NaOH) and an alkylating agent R‘ ‘4 NBr (R‘ ‘ = Et, Bun) afforded the corresponding tertiary(amino)-oxycarbene complexes [Mo2Cp(μ-SMe)2{μ-(η5-C5H4)(xylN)CN(xyl)C }{μ-η1(O),η1(C)-OCNxylR‘ ‘}] [R‘ ‘ = Et (6b), Bun (6c)]. On heating a tetrahydrofuran solution of the μ-alkylidyne compound 4 with NaOH (suspension) and an excess of either xylNC or ButNC, the mixed μ-alkylidyne and μ-amino-oxycarbene species 5a1 and 5b2 were obtained, demonstrating that 4 is an intermediate in the formation of 5a1 and 5b2 from 2b. Treatment of the mixed isonitrile−nitrile species [Mo2Cp2(μ-SMe)3(MeCN)(xylNC)](BF4) (3), containing a labile MeCN group, under reflux in tetrahydrofuran with NaOH (suspension) afforded quantitatively the μ-amino-oxycarbene compound [Mo2Cp2(μ-SMe)3{μ-η1(O),η1(C)-OCNHxyl}] (7). All new complexes have been characterized by elemental analyses and spectroscopic methods, supplemented for 5a1, 5b1, 5b2, 6a, 6b, and 7 by X-ray diffraction studies.