Synthesis and reactivity of bis(alkoxysilylamido)yttrium eta(2)-pyridyl and eta(2)-alpha-picolyl compounds

The synthesis and reactivity of bis(alkoxysilylamido)yttrium pyridyl and alpha-picolyl complexes [Me2Si(NCMe3)(OCMe3)](2) YR (R=eta(2)-(C,N)-2-NC5H4(1); R=eta(2)(C,N)-CH2-2-NC5H4 (2); R=eta(2)-(C,N)-C(H)Me-2-NC5H4 (3); R=eta(2)-(C,N)-C(H)Me-2-NC5H3-6-Me (4)) is reported 1-4 have been prepared by C-H activation of pyridine and the corresponding methyl (ethyl) and dimethyl-substituted pyridines from [Me2Si(NCMe3)(OCMe3)](2)YCH(SiMe3)(2) and by salt metathesis with the appropriate lithium salts from [Me2Si(NCMe3)(OCMe3)](2) YCl . THF. The molecular structure of 2 shows that the picolyl group is bonded to yttrium in an eta(3)-aza-allylic fashion. With dihydrogen, stepwise hydrogenation of the pyridyl fragment of 1 has been observed, finally yielding the 2,3-dihydropyridyl complex [Me2Si(NCMe3)(OCMe3)](2)YNC5H8(7). Compound 1 inserts ethene to form the alpha-methylpicolyl derivative 4. Polymerization of ethene was not observed. The pyridyl compound 1 reacts with PhC drop CH to yield the corresponding acetylide pyridine complex [Me2Si(NCMe3)(OCMe3)](2) YC drop CPh . Py (8). The complexed pyridine can be substituted by THF to give [Me2Si(NCMe3)(OCMe3)](2) YC drop CPh . THF (9), which easily loses THF and forms the base-free acetylide [Me2Si(NCMe3)(OCMe3)](2) YC drop CPh (10). Compounds 1 and 2 readily insert nitriles yielding imido-pyridine complexes. The imido-pyridine complexes that contain alpha-hydrogen readily undergo a 1,3-H shift affording the corresponding enamido-pyridine compounds. With CO, the pyridyl compound 1 gives a dipyridylketone complex {[Me2Si(NCMe3)(OCMe3)](2) Y}{mu,eta(2),eta(2)-(N,N',O)-OC(2-NC5H4)(2)} (15).