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 a nd 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-NC 5H4 (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 meth yl (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 structur e of 2 shows that the picolyl group is bonded to yttrium in an eta(3)- aza-allylic fashion. With dihydrogen, stepwise hydrogenation of the py ridyl fragment of 1 has been observed, finally yielding the 2,3-dihydr opyridyl complex [Me2Si(NCMe3)(OCMe3)](2)YNC5H8(7). Compound 1 inserts ethene to form the alpha-methylpicolyl derivative 4. Polymerization o f 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 subst ituted 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 nitrile s yielding imido-pyridine complexes. The imido-pyridine complexes that contain alpha-hydrogen readily undergo a 1,3-H shift affording the co rresponding 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).