Use of alkane elimination in the one-step synthesis of organoscandium complexes containing a new multidentate cyclopentadienyl ligand

A new multidentate ligand, CpH(NMe)SiN(H)R (SiNR = -SiMe(2)N-tert-butyl; NMe = 3-CH2-CH(2)NMe(2); 1) was prepared in 71% yield as a mixture of 1,3 and 1,2 isomers (approximate to 7:3) in one step from CpHNMe, Me(2)SiCl(2), and tert-butylamine. The ligand was attached to scandium in an efficient alkane elimination reaction by treatment of in situ generated Sc(CH(2)SiMe(3))(3) . 2THF with diproteo 1, yielding the alkylscandium species [(Cp(NMe)SiNR)Sc(CH(2)SiMe(3))], 2, directly in 52% yield. The reaction was 100% diastereoselective for the (1S)-(RSc)/(1R)-(S-Sc) pair of enantiomers. Treatment of 2 with dihydrogen gave two of four possible diastereomeric mu-dihyrides. The C-i symmetric 1R-trans-1'S diasteriomer 3a was characterized crystallographically. Thermolysis of 2 at 70 degrees C for 3 days resulted in metalation of an N-methyl group and loss of Me(4)Si. A mixture of two dimeric compounds with bridging methylene units was formed, one of which was identified as the C-i symmetric 1R-trans-1'S diasteriomer 4a by X-ray crystallography.