Zirconium and hafnium (1-pyridinio)imido complexes: functionalized terminal hydrazinediido analogues

Abstract

Reaction of the diamidozirconium complex [Zr(N₂^TBSN_py)(NMe₂)₂] (1) (N₂^TBSN_py = CH₃C(C₅H₄N)(CH₂NSiMe₂tBu)₂) or the diamidohafnium complex [Hf(N₂^TBSN_py)(NMe₂)₂] (2) with one molar equiv. of 1-aminopyridinium triflate in the presence of one equiv. of pyridine gave the corresponding (1-pyridinio)imido complexes [Zr(N₂^TBSN_py)(N–NC₅H₅)(OTf)(py)] (3) and [Hf(N₂^TBSN_py)(N–NC₅H₅)(OTf)(py)] (4). These were converted to the acetylide complexes [Zr(N₂^TBSN_py)(N–NC₅H₅)(CCPh)(py)] (5) and [Hf(N₂^TBSN_py)(N–NC₅H₅)(CCPh)(py)] (6) by reaction with lithium phenylacetylide and substitution of the triflato ligand. Upon reaction of 3 and 4 with one molar equivalent of R-NC (R = tBu, Cy, 2,6-xyl), N–N bond cleavage in the (1-pyridinio)imido unit took place and the respective carbodiimido complexes [M(N₂^TBSN_py](NCNR)(OTf)(py)] (7–12) were formed instantaneously. A similar type of reaction with CO gave the isocyanato complex [Zr(N₂^TBSN_py](NCO)(OTf)(py)] (13). Finally, the abstraction of the pyridine ligand in compounds 3 and 4 with B(C₆F₅)₃ led to the formation of the triflato-bridged dinuclear complexes [Zr(N₂^TBSN_py)(N–NC₅H₅)(OTf)]₂ (14) and [Hf(N₂^TBSN_py)(N–NC₅H₅)(OTf)]₂ (15).