Bis(η5:η1-pentafulvene)titanium Complexes: Catalysts for Intramolecular Alkene Hydroamination and Reagents for Selective Reactions with N-H Acidic Substrates

Intramolecular catalytic hydroamination reactions of geminally disubstituted amino alkenes employing the bulky substituted bis(eta(5):eta(1)-pentafulvene)titanium complexes 1a and 1b and the corresponding benzannelated derivative 2 as catalysts are presented. While all three complexes are competent hydroamination catalysts, best results are achieved with the bis(benzofulvene) derivative 2. In addition, a series of Ti-N-containing compounds became available by stoichiometric reactions of 1 with N-H acidic substrates. In such a way, using aniline derivates (H2N-Ar, Ar: p-tolyl, 1-naphthyl) the bisamides (eta(5)-C5H4-CHR2)(2)Ti(NHAr)(2) (CHR2: adamantyl, Ar: p-tolyl 5a; R: p-tolyl, Ar: p-tolyl 5b; R: p-tolyl, Ar: 1-naphthyl 5c; CHR2: adamantyl, Ar: 1-naphthyl 5d) are prepared in high yields under mild conditions. In contrast to this, the employment of the catalytically relevant amine H2NCH2C(Ph)(2)CH2CH=CH2 (3a) in a reaction with (eta(5):eta(1)-C5H4=CR2)(2)Ti (CR2: adamantylidene, 1a) leads to the titanium monoamide (eta(5):eta(1)-C5H4=CR2)(eta(5)-C5H4-CHR2)Ti(NHCH2-C(Ph)(2)CH2CH=CH2) (6), characterized by X-ray diffraction. In reaction of 1a and 1b with benzophenone imine the titanocene bis(enamides) (eta(5)-C5H4-CHR2)(2)Ti(N=CPR2)(2) 7a and 7b are formed. Titanium nitrogen double bonds are formed by treatment of 1a with 1,1-diphenylhydrazine. In that manner the hydrazido titanocene (eta(5)-C5H4-CHR2)(2)Ti=N-N(Ph)2(CHR2:adamantyl) was structurally characterized as the pyridine adduct 9. Three different Ti-N bonds are formed in one step by reaction of (eta(5):eta(1)-C5H4=CR2)(2)Ti (R: p-tolyl, 1b) with 1,1-diphenylhydrazine and pyridine (py), leading to (eta(5)-C5H4-CHR2)Ti(=N-NPh2)(-N-NPh2)py 10b (dative Ti-N bond: Ti-py 2.211(2) angstrom', single Ti-N bond: Ti-NNPh2- 1.968(2) angstrom', double Ti-N bond: Ti-NNPh22- 1.738(1) angstrom'). The formation of 10b is accompanied by the liberation of one C5H5CHR2 ligand. Generally, the bis(eta(5):eta(1)-pentafulvene)titanium complexes 1 and 2 are valuable catalysts in hydroamination reactions and reagents in order to prepare Ti-N-containing metallocene-type derivatives.