LIGAND-SUBSTRATE COMMUNICATION IN GROUP-4 AMINOPYRIDINATO COMPLEXES

Tris(aminopyridinato) zirconium and ansa-aminopyridinato titanium comp lexes have been synthesized. The reaction of (TMS-APy)(3)-Zr-Cl (4-met hyl-2-trimethysilyl-aminopyridine=TMS-Apy-H) with trimethylsilylbutadi ynyl lithium generated in situ affords (TMS-APy)(3)-Zr-CC-CC-TMS (1). (TMS-APy)(3)-Zr-Cl reacts with lithium dimethylamide and leads to (TMS -APy)(3)-Zr-NMe2 (2). Compound 2 shows and agostic interaction of the dimethylamido moiety. The reaction of Ti(NMe2)(4) with olin-2'-yl-amin o)-1,1,3,3-tetraisopropyldisiloxane = silox(APy-H)(2)] gives rise to s ilox(APy)(2)-Ti-(NMe2)(2) (3). Complex 3 reacts with epsilon-caprolact am to form a caprolactamato complex (4). X-ray crystal structure analy ses of 1, 2, 3 and 4 are reported. The complexes 1, 2, 3 and 4 may be considered to strained donor-functionalized amido(metal) complexes due to the eta(2) binding mode of the aminopyridinato ligands. An adaptat ion of the binding mode of the ligand cores, TMS-APy and silox(APy)(2) , to meet the requirements of the ancillary coordinated substrates is observed. Thus, aminopyridinato complexes seem to be valuable model co mpounds for investigations of ligand-substrate communication in early transition metal chemistry.