group P2,,,; a =14.828(2). h = 11.513(1), c =16.637(2)A. 0 =112.735(4). V = 2619.5(5) A', 2 = 4 , pidlid =1.373 gem-,; p = 4.25 m m -' ; max. absorption correction factor l.60:20max =115,24';Cu,,radiation; T = 298K:O-28scan;reflectionscollectedjunique!used, 3767/3579 (R,,, = 0.0219)/3577; parameters refined, 352; Rl!xR2 [2794 reflections with I > 2a/], 0.0576/0.1579; GOF = 1.029; [ A / GI,,, = 0.003; [A&JAp]*," 0.373/ -0.308 eA-3, structure solution and refinement with the programs SHELXS-86 and SHELXL-93: H atoms of 1.10phenanthroline were located by difference maps and refined isotropically, the rest were introduced at calculated positions as riding on bonded atoms; all non-H atoms refined anisotropically (except atoms of the solvent methanol which refined isotropically with occupancy fixed at 10.5. Crystallographic data (excluding structure factors) for the structure reported in this paper have been deposited with the Cambridge Crystallographic Data Centre as supplementary publication no. CCDC-179-98. Copies of the data can be obtained free of charge on application to The Director, CCDC, 12 Union Road.

No abstract

Several diorganoscandium complexes stabilized by the β-diketiminato ligands (Ar)NC(R)-CHC(R)N(Ar) (Ar ) 2,6-iPr-C 6 H 3 ; R ) CH 3 (ligand a), R ) tBu (ligand b)) have been synthesized. Reaction of the lithium salts of the ligands with ScCl 3 ‚3THF leads to the complexes LScCl 2 (THF) n , which may be readily alkylated to form the dialkyl derivatives. Most are isolated as base-free, four-coordinate complexes. Several have been characterized via X-ray crystallography, and a detailed discussion of their structures is presented. Steric interactions between Ar and the Sc-alkyl groups force the scandium to adopt an out-ofplane bonding mode. In solution, this is manifested via a fluxional process which equilibrates the two diastereotopic alkyl groups and ligand groups as well. The barriers to this process roughly correlate with the steric bulk of the alkyl substituents. At elevated temperatures, the dialkyl derivatives LScR 2 undergo a metalation process whereby one of the alkyl groups is eliminated as RH, and a ligand iPr group is metalated in the methyl position. These reactions are first order in scandium complex, and activation parameters of ∆H q ) 19.7(6) kcal mol -1 and ∆S q ) -17(2) cal mol -1 K -1 were measured for the loss of Me 4 Si from (Ligb)-Sc(CH 2 SiMe 3 ) 2 .

No abstract

No abstract