Multi-electron redox processes at a Zr(iv) center facilitated by an appended redox-active cobalt-containing metalloligand

Jeremy P Krogman; Mark W Bezpalko; Bruce M Foxman; Christine M Thomas

doi:10.1039/c6dt01498d

Multi-electron redox processes at a Zr(iv) center facilitated by an appended redox-active cobalt-containing metalloligand

Dalton Trans. 2016 Jul 5;45(27):11182-90. doi: 10.1039/c6dt01498d.

Authors

Jeremy P Krogman¹, Mark W Bezpalko¹, Bruce M Foxman¹, Christine M Thomas¹

Affiliation

¹ Department of Chemistry, Brandeis University, 415 South Street MS 015, Waltham, MA 02451, USA. [email protected].

PMID: 27326824
DOI: 10.1039/c6dt01498d

Abstract

The reactivity of a reduced heterobimetallic Co(-I)/Zr(IV) complex, ((t)BuNC)Co((i)Pr2PNMes)3Zr(THF) (), with a series of azido and diazo reagents is explored to demonstrate the feasibility of facilitating two-electron redox processes at a formally d(0) Zr(iv) center using the appended Co fragment exclusively as an electron-reservoir. Addition of mesityl or adamantyl azide to affords the terminal ((t)BuNC)Co((i)Pr2PNMes)3Zr[triple bond, length as m-dash]NMes () and bridging ((t)BuNC)Co((i)Pr2PNMes)2(μ-NAd)Zr((i)Pr2PNMes) () Co(I)/Zr(IV) imido products, respectively. Similarly, diphenyldiazomethane reacts with to afford the terminal Ph2CN2(2-)-bound product ((t)BuNC)Co((i)Pr2PNMes)3Zr[triple bond, length as m-dash]N-N[double bond, length as m-dash]CPh2 () via a two-electron oxidation of the Co center. Thermolysis of results in a structural rearrangement to the diazomethane-bridged isomer ((t)BuNC)Co((i)Pr2PNMes)2(μ-N2CPh2)Zr((i)Pr2PNMes) (). In contrast, treatment of with 0.5 equivalents of the conjugated diazo reagent ethyl diazoacetate affords a tetranuclear Zr(IV)/Co(0) complex, ((t)BuNC)Co((i)Pr2PNMes)3Zr(μ2-κ(1)-O-η(2)-N,N-OC(OEt)CHN2)Zr(MesNP(i)Pr2)3Co(CN(t)Bu) (), bridged through enolate and η(2)-bound diazo functionalities.