Imido complexes of titanium bearing eta(2)-pyrazolato ancillary ligand sets

Treatment of dichlorobis(3,5-di-tert-butylpyrazolato)titanium(IV) with Grig nard (CH3MgCl, C6H5CH2MgCl) or organolithium (LiCH2Si(CH3)(3)) reagents (2 equiv) afforded the dialkyl derivatives dimethylbis(3,5-di-tert-butylpyrazo lato)titanium(IV) (93%); dibenzylbis(3,5-di-tert-butylpyrazolato)titanium(I V) (43%), and bis(methyltrimethylsilyl)bis(3,5-di-tert-butylpyrazolato)tita nium(IV) (49%). Analogous methylation of chlorotris(3,5-di-tert-butylpyrazo lato)titanium(IV) with CH3MgCl afforded methyltris(3,5-di-tert-butylpyrazol ato)titanium(IV) (52%). Attempted alkylation of trichloro(3,5-di-tert-butyl pyrazolato)titanium(IV) with CH3MgCl (3 equiv) afforded dimethylbis(3,5-di- tert-butylpyrazolato)titanium(IV) (35%), along with extensive decomposition . This experiment indicates that trimethyl(3,5-di-tert-butylpyrazolato)tita nium(IV) is unstable at ambient temperature. The reactivity of dichlorobis( 3,5-di-tert-butylpyrazolato)titanium(IV) and dimethylbis(3,5-di-tert-butylp yrazolato)titanium(IV) toward primary amines was studied. Treatment of dich lorobis(3,5-di-tert-butylpyrazolato) titanium(IV) with excess tert-butylami ne afforded tert-butylimido(chloro)(3,5-di-tert-butyl pyrazolato)titanium(I V) dimer (10%), chlorotris(3,5-di-tert-butylpyrazolato)titanium(IV)(56%), a nd tert-butylammonium chloride (85%). Analogous treatment of dimethylbis(3, 5-di-tert-butylpyrazolato)titanium(IV) with tert-butylamine gave the monome ric imido complex tert-butylimidobis(3,5-di-tert-butylpyrazolato)(tert-buty lamine)titanium(IV) (33%). Addition of pyridine to the reaction between dim ethylbis(3,5-di-tert-butylpyrazolato)titanium(IV) and tert-butylamine or is opropylamine afforded the pyridine adducts tert-butylimidobis(3,5-di-tert-b utylpyrazolato)(pyridine)titanium(IV) (80%) and isopropylimidobis (3,5-di-t ert-butylpyrazolato)(tert-butylamine)titanium(IV) (46%), respectively. Trea tment of dimethylbis(3,5-di-tert-butylpyrazolato)titanium(IV) with 1-amino- 4-methylpiperazine led to the hydrazide(1-) complex 1-amido-4-methylpiperaz ine(methyl)bis(3,5-di-tert-butylpyrazolato)titanium(IV) (64%), which contai ns both a titanium-methyl bond and a primary hydrazide(1-) ligand. It is pr oposed that the thermal stability of this compound arises from bidentate co ordination of the hydrazide(1-) ligand, which places the reactive nitrogen- hydrogen bond distal to the titanium-methyl bond. The reactivity of tert-bu tylimidobis(3,5-di-tert-butylpyrazolato)(tert-butylamine)titanium(IV) towar d acetylenes, nitriles, and ketones is discussed. The X-ray crystal structu res of bis(methyltrimethylsilyl)bis(3,5-di-tert-butyl-pyrazolato)titanium(I V), tert-butylimido(chloro)(3,5-di-tert-butylpyrazolato)titanium(IV) dimer, and isopropylimidobis(3,5-di-tert-butylpyrazolato)(tert-butylamine)titaniu m(IV) were determined.