[(TMEDA)Co(NO)2][BPh4]: A versatile synthetic entry point to four and five coordinate {Co(NO)2}10 complexes

[(TMEDA)Co(NO)2][BPh4] reacts with Group 1 salts of various monoanionic ligands to yield four and five coordinate {Co(NO)2}10 complexes. The synthesis of the four coordinate complex of the form [{LX}Co(NO)2] via salt-metathesis reactions of [(TMEDA)Co(NO)2][BPh4] with [{ArNC(Me)CHC(Me)NAr}Li(OEt2)] (Ar = 2,6-di-iso-propylphenyl) is reported. In addition [(TMEDA)Co(NO)2][BPh4] reacts with either KTp∗ or a suite of cyclopentadienyllithium and cyclopentadienylsodium reagents, to generate the corresponding five coordinate [{L2X}Co(NO)2] complexes ({L2X = C5H5, MeC5H4, Cp∗, tBuC5H4, Ph2CHC5H4, Me3SiC5H4, tBuMe2SiC5H4, iPr3SiC5H4, 1,3-(iPr3Si)2C5H3 and Tp∗). In support of existing precedent, the four coordinate complex is a thermally robust and readily isolable species while five coordinate complexes are thermally unstable transient intermediates that may either undergo dissociation of an NO ligand or be trapped by alkenes to form the corresponding metal dinitrosoalkane complexes. These reactions demonstrate that [(TMEDA)Co(NO)2][BPh4] provides a versatile synthetic entry point to cobalt dinitrosyl complexes and obviates the need for the repeated use of nitric oxide in the preparation of dinitrosoalkane complexes of cobalt.

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► [(TMEDA)Co(NO)2][BPh4] as a precursor for various {Co(NO)2}10 complexes.
► Reaction with β-diketiminate ligand generates the 4-coordinate complex (BDI)Co(NO)2.
► Reaction with MTp∗ and MCp generates the 5-coordinate complexes {L2X}Co(NO)2.
► 4-coordinate complexes are isolable; 5-coordinate complexes readily lose 1 equiv NO.
► Alkene trapping of 5-coordinate transients yields isolable dinitrosoalkane complexes.