Dipyrromethene and β‑Diketiminate ZincHydride Complexes: Resemblances and Differences

A new dipyrromethene (DPM) ligand with bulky DIPP-substituents is introduced (DIPP = 2,6-diisopropylphenyl). The ligand, abbreviated as DIPPDPM, was deprotonated with ZnEt2 to give (DIPPDPM)ZnEt, which reacted with I2 to form (DIPPDPM)ZnI. Reaction of the latter with K[N(iPr)HBH3] afforded a labile Zn amidoborane complex which, after β-hydride elimination, formed (DIPPDPM)ZnH. Crystal structures of (DIPPDPM)ZnX (X = Et, I, H) revealed their monomeric nature. The Zn–N bond distances are somewhat longer than those in the corresponding monomeric β-diketiminate complexes (DIPPBDI)ZnX (DIPPBDI = CH[C(Me)N-DIPP]2). This is in agreement with calculated NPA charges, which are lower on the N atoms of DPM compared to those on BDI. Reaction of (DIPPDPM)ZnH with CO2 gave (DIPPDPM)Zn(O2CH), which crystallized as a monomer with a symmetrically bound η2-formate ligand. In contrast, the β-diketiminate complex crystallizes as a dimer [(DIPPBDI)Zn(O2CH)]2 with bridging formate ligands. Reaction of (DIPPDPM)Zn(O2CH) with va...