Synthesis and characterization of pyrrole-based group 4 PNP pincer complexes.

Unlabelled: The synthesis, characterization, and reactivity of several group 4 metal complexes featuring a central anionic pyrrole moiety connected via CH linkers to two phosphine donors is described. Treatment of [P(NH)P-Pr] with [MCl(THF)] (M = Zr, Hf) in the presence of base yields the dimeric complexes [M(PNP)(μ-Cl)(Cl)] featuring two bridging chloride ligands. These complexes react with sodium cyclopentadienyl and SiMeI to give the mononuclear complexes [M(PNP)(η-Cp)(Cl)] and [M(PNP)(I)], respectively. The latter react with MeMgBr to form the trialkyl complexes [M(PNP)(Me)]. Upon treatment of [Ti(NMe)] with [P(NH)P-Pr] a complex with the general formula [Ti(PNP)(NMe)] is obtained. DFT calculations revealed that the most stable species is [Ti(κ- PNP)(NMe)] featuring a κ-bound PNP ligand. When [P(NH)P-Pr] is reacted with [Ti(NMe)] in CHCl complex [Ti(PNP)(Cl)(NMe)] is formed. Treatment of a solution of [P(NH)P-Pr] and [Zr(NMe)] with SiMeBr affords the anionic seven-coordinate tetrabromo complex [Zr(PNP)(Br)][HNMe]. The corresponding hafnium complex [Hf(PNP)(Br)][HNEt] is obtained in similar fashion by utilizing [Hf(NEt)] as metal precursor. All complexes are characterized by means of NMR spectroscopy. Representative complexes were also characterized by X-ray crystallography.

Supplementary Information: The online version contains supplementary material available at 10.1007/s00706-024-03171-x.