PUB - Publikationen an der Universität Bielefeld

The reaction of 1,3,5-trimethyl-1,3,5-triazacyclohexane (TMTAC) with [La{Al(CH3)(4)}(3)] resulted in C-H activation, leading to the formation of [(TMTAC) La{Al(CH3)(4)}{(mu(3)-CH2)[Al(CH3)(2)(mu(2)-CH3)](2)}] (1) containing a bis(aluminate) dianion and subsequent extrusion of methane. A similar reaction with [Y{Al(CH3)(4)}(3)] led to the formation of CH4, [TMTAC{Al(CH3)(3)}(2)] (2) and {[(TMTAC) Y][Y-2(mu(2)-CH3)][{( mu(6)-C)[Al(mu(2)-CH3)(2)(CH3)](3)}{(mu(3)-CH2)(mu(2)-CH3)Al(CH3)(2)}(2) ](3), containing a six-coordinate carbide ion and two [CH2Al(CH3)(3)](2)(-) anions. Compound 3 is a product of multiple C-H activation. This reaction was monitored by in situ H-1 NMR spectroscopy. The analogous reaction with [Sm{Al(CH3)(4)}(3)] led to the formation of 2, of [(TMTAC) Sm{(mu(2)-CH3)(CH3)(2)Al}(2){(mu(3)-CH2) Al-2(CH3)(2)}(2)](4), which contains a tris(aluminate) trianion, and [{(TMTAC) Sm}{Sm-2(mu(2)-CH3)}{( mu(6)-C)[Al(mu(2)-CH3)(2)(CH3)](3)}{(mu(3)-CH2)(mu(2)-CH3)Al(CH3)(2)}(2) ] (5), which is isostructural to 3. The products were characterised by elemental analyses (except 4, 5), 1 by multinuclear NMR spectroscopy and compounds 1, 2, 3, 4 and 5 by X-ray crystallography. Quantumchemical calculations were undertaken to support the crystallographic data analysis and confirm the structure of 3 and to compare it with an analogous compound where the central six-coordinate carbon has been replaced by oxygen. The investigations point to a mechanism of sterically induced condensation of [Al(CH3)(4)](-) groups in close proximity in the coordination spheres of the rare-earth metal atoms, which is dependent on the size of these metal atoms.