Synthesis and reactivity of dinitrogen, oxo, and nitrido complexes of first row transition metals supported by hydrotris(pyrazolyl)borate ligands

Abstract

Following previous work done by members of the Theopold Lab, which was limited by the propensity for C-H bond activation on the hydrotris(3-tert-butyl-5-methylpyrazolyl)borate ligand, this work is a continuation of efforts to produce oxo complexes with the more robust hydrotris(3-ferrocenyl-5-methylpyrazolyl)borate ligand. TpFc,MeFeX (X = Cl (1), Br (2), I (3)) and TpFc,MeCoBr (4) have been synthesized and used to produce [TpFc,MeFeI]2(µ2-η1:η1-N2) (9) and [TpFc,MeCoI]2(µ2-η1:η1-N2) (10) to act as synthons for activation of oxygen. In a similar effort, alkyl complexes TpFc,MeFeBn (5) and TpFc,MeFeEt (6) were synthesized and reacted with carbon monoxide to produce a formally univalent TpFc,MeFe(CO) (7), to act as a synthon. ☐ When 9 is reacted with single oxygen atom transfer reagents the novel bridging oxo complex in the form of [TpFc,MeFe]2(µ2-η1:η1-O) (16) is produced. 16 is only the second instance of such a FeII-O-FeII compound to have been isolated and structurally characterized. In the effort to produce additional chalcogenide compounds the complexes TpFc,MeFeOCPh3 (13) and TpFc,MeFeSCPh3 (14) were produced by salt metathesis with 3. The reaction of 14 with KH in the presence of 18-crown-6 to produce a bridging sulfide, [TpFc,MeFe]2(µ2-η1:η1-S) (15). Attempts to produce imide compounds to act as isoelectronic models for terminal oxo compounds by reacting organic azides with 9 and 10 resulted in the production of tetrazene complex TpFc,MeCoN4Bn2 (17), as well as metallated azides TpFc,MeFeN3 (20) and TpFc,MeCoN3 (21). ☐ Reactions of 3 and 4 with the lithiated nitride transfer reagent 2,3:5,6-Dibenzo-7-azabicyclo[2.2.1]hepta-2,5-diene (dbabh) resulted only in transmetallation of production of TpFc,MeLi. Reactions of TptBu,MeFeI and TptBu,MeCoI with Li-dbabh resulted in TptBu,MeFe-dbabh (22) and TptBu,MeCo-dbabh (23), which do not decompose under heating to produce terminal nitrides. TptBu,MeCrEt reacts with H-dbabh to produce the first example of a first row transition metal nitride compound supported by a Tp ligand, TptBu,MeCrN (24), which reacts with MeI to produce a rare example of a methyl imide, TptBu,MeCrNMe (26).