Cooperative reactivity of early-late heterodinuclear transition metal complexes with polar organic substrates

A comprehensive investigation into the cooperative reactivity of two chemic ally complementary metal-complex fragments in early-late heterodinuclear co mplexes has been carried out. Reaction of the partially fluorinated tripoda l amidozirconium complexes [HC{SiMe3NR}(3)Zr(mu-Cl)(2)Li(OEt2)(2)] (R = 2-F C6H4: 2a, 2,3,4-F3C6H4: 2b) with K[CpM(CO)(2)] (M = Fe, Ru) afforded the st able metal-metal bonded heterodinuclear complexes [HC{SiMe2NR}(3)Zr-MCp(CO) (2)] (3-6). Reaction of the dinuclear complexes with methyl isonitrile as w ell as the heteroallenes CO2, CS2, RNCO and RNCS led to insertion into the polar metal-metal bond. Two of these complexes, [HC{SiMe2N(2-FC6H4)}(3)Zr(S 2C)Fe(CO)(2)Cp] (9a) and [HC{SiMe2N(2-FC2H4)}(3)Zr-(SCNPh)Fe(CO)(2)-Cp] (12 ), have been structurally characterized by a single crystal X-ray structure analysis, proving the structural situation of the inserted substrate as a bridging ligand between the early and late transition metal centre. The rea ctivity towards organic carbonyl derivatives proved to be varied. Reaction of the heterobimetallic complexes with benzyl and ethylbenzoate led to the cleavage of the ester generating the respective alkoxozirconium complexes [ HC{SiMe3N(2-FC6H4)}(3)ZrOR] (R = PhCH2: 13a, Et: 13b) along with [CpFe{C(O) Ph)(CO)2], whereas the analogous reaction with ethyl formate gave 13b along with [CpFeH(CO)(2)]; this latter complex results from the instability of t he formyliron species initially formed. Aryl aldehydes were found to react with the Zr-M complexes according to a Cannizzaro disproportionation patter n yielding the aroyliron and ruthenium complexes along with the respective benzoxyzirconium species. The transfer of the aldehyde hydrogen atom in the course of the reaction was established in a deuteriation experiment. [HC(S iMe2-N(2-FC6H4)}(3)Zr-M(CO)(2)Cp] reacted with lactones to give the ring-op ened species containing an alkoxozirconium and an acyliron or acylruthenium fragment; the latter binds to the early transition metal centre through th e acyl-oxygen atom, as evidenced from the unusuallly low-field shifted C-13 NMR resonances of the RC(O)M units. Ketones containing alpha-CH units reac t With the Zr-Fe complexes cooperatively to yield the aldol coupling produc ts coordinated to the zirconium complexes fragment along with the hydridoir on compound [CpFeH(CO)(2)], whereas 1,2-diphenylcyclopropenone underwent an oxygen transfer from the keto group to a CO ligand to give a linking CO2 u nit and a cyclopropenylidene Ligand coordinated to the iron fragment in [HC {Si(CH3)(2)N(2,3,4-F3C6H2)}(3)Zr(mu-O2C)Fe(CO){C3Ph2}Cp] (19), The atom tra nsfer was established by O-17 and C-13 labelling studies. Similar oxygen-tr ansfer processes were observed in the reactions with pyridine N-oxide, dime thylsulfoxide and methylphenylsulfoxide.