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

Abstract

A comprehensive investigation into the cooperative reactivity of two chemically complementary metal-complex fragments in early - late hetero-dinuclear complexes has been carried out. Reaction of the partially fluorinated tripodal amidozirconium complexes HC-{SiMe2NR}3ZrCμ-Cl)2Li(OEt 2)2 (R = 2-FC6H4: 2a, 2,3,4-F3C6H4: 2b) with KCpM(CO)2 (M = Fe, Ru) afforded the stable metal-metal bonded hetero-dinuclear complexes HC{SiMe2NR}3-Zr-MCp(CO)2 (3-6). Reaction of the dinuclear complexes with methyl isonitrile as well as the heteroallenes CO2, CS2, RNCO and RNCS led to insertion into the polar metal-metal bond. Two of these complexes, HC{SiMe2N(2-FC6-H4)}3Zr(S 2C)Fe(CO)2Cp (9a) and HC-{SiMe2N(2-FC2H4)} 3Zr-(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 reactivity 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{SiMe2N(2-FC6H4)}3ZrOR (R = Ph-CH2: 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 the formyliron species initially formed. Aryl aldehydes were found to react with the Zr-M complexes according to a Cannizzaro disproportionation pattern 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{SiMe2-N(2-FC6H4)}3Zr-M (CO)2Cp reacted with lactones to give the ring-opened species containing an alkoxozirconium and an acyliron or acylruthenium fragment; the latter binds to the early transition metal centre through the acyl oxygen atom, as evidenced from the unusuallly low-field shifted 13C NMR resonances of the RC(O)M units. Ketones containing α-CH units react with the Zr-Fe complexes cooperatively to yield the aldol coupling products coordinated to the zirconium complex fragment along with the hydridoiron 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 unit and a cyclopropenylidene ligand coordinated to the iron fragment in HC-{Si(CH3)2N(2,3,4-F3C6H 2)}3Zr(μ-O2C)-Fe(CO){C3Ph 2}Cp (19). The atom transfer was established by 17O and 13C labelling studies. Similar oxygen-transfer processes were observed in the reactions with pyridine N-oxide, dimethylsulfoxide and methylphenylsulfoxide