HIGHLY ELECTRON-DEFICIENT GROUP-3 ORGANOMETALLIC COMPLEXES BASED ON THE 1,4,7-TRIMETHYL-1,4,7-TRIAZACYCLONONANE LIGAND SYSTEM

Reaction of the neutral ligand 1,4,7-trimethyl-1,4,7-triazacyclononane (Cn) with MCl3(THF)(3) (M = Sc, Y) in acetonitrile affords the novel trihalide complexes CnMCl(3). The crystal structure of CnScCl(3) has b een determined: (CH3)(3)N-3(C2H4)(3)ScCl3; monoclinic, a = 12.477(3), b = 7.462(2), c = 15.984(4)Angstrom, beta = 90.45(3)degrees; P2(1)/c, Z = 4. Subsequent alkylation with LiCH3 in THF gives the corresponding trimethyl species CnM(CH3)(3) cleanly. Reactivity studies reveal that the metal carbon bonds of these highly coordinatively unsaturated 12e (-), d(0) complexes are remarkably unreactive toward insertion chemist ry with typical unsaturated substrates such as alkenes and alkynes. 2- Butyne does, however, react with CnY(CH3)(3) by C-H activation to give a compound that is characterized as a major allenyl isomer, Cn(CH3)(2 )Y(eta(1)-C(CH3)CCH2), in equilibrium with a minor propargyl isomer, C n(CH3)(2)Y(eta(1)-CH2CC(CH3)). In general, CnSc(CH3)(3) is observed to be significantly more stable, and also less reactive, than CnY(CH3)(3 ). CnSc(CH3)(3) can, however, be activated by reaction with either B(C 6F5)(3) or [H(CH3)(2)NPh](+)[B(C6F5)(4)](-) to give complexes which ex hibit olefin polymerization chemistry.