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Convenient syntheses for Cp, Cp*, and related cyclopentadienyl derivatives ( 4 Cp = C 5 HiPr 4 ; CpЈЈЈ = C 5 H 2 tBu 3 -1,2,4) of formula [(Ring) 2 Mo 2 O 5 ] are described. Compound [Cp 2 Mo 2 O 5 ] was produced in good yields by the rapid oxidation of red [CpMoO 2 ] 4 with PhIO in CH 2 Cl 2 . [Cp* 2 Mo 2 O 5 ] was obtained by CH 3 COOH acidification of aqueous solutions of [Cp*MoO 3 ] − Na + , the latter being generated in a single step from [Cp*MoCl 4 ] and more than 5 equiv. of aqueous NaOH in air. Minor quantities of [Cp*MoO 2 ] 2 were also isolated from this reaction, although the formation of this by-

The reduction of MoCl5 with metallic tin in diethyl ether provides a rapid and convenient entry to [MoCl4(OEt2)2] This compound can be transformed easily and in high yields into a variety of other useful synthons. The loss of ether in the solid state affords a new and reactive form of MoCl4. Treatment with THF, PMe3 or LiOtBu affords [MoCl4(THF)2], [MoCl4(PMe3)3] or [Mo(OtBu)4] in high isolated yields. Treatment with metallic tin in THF affords [MoCl3(THF)3] All of these reactions can be carried out under simple experimental conditions and represent significant improvements relative to previously reported syntheses of the same compounds.

The dinuclear dichalcogenides [{(C 5 HR 4 )NiE} 2 ] (R ) CHMe 2 ; E ) S (2), Se (3), Te (4)) have been synthesized from [{(C 5 HR 4 )NiBr} 2 ] (1) (R ) CHMe 2 ) and the corresponding disodium dichalcogenides. Crystal structure analyses show four-membered Ni 2 E 2 rings with weak, but significant E‚‚‚E interaction. 1-4 were characterized electrochemically and reveal nickel-centered oxidations, bridging ligand-centered reductions, and the formation of mixedvalent Ni(II)/Ni(III) species.