Neutral and Cationic Aluminum and Titanium Complexes Incorporating Sterically Demanding Organosilicon Ligands

New complexes of aluminum and titanium containing sterically demanding ligands and their reaction with B(C6F5)3 are reported. Treatment of [(Ph2MeSiCH2CH2)3Si]NCN[Si(CH2CH2SiMePh2)3] (1) or Si(CH2CH2SiMePh2)3OH (2) with 1 equiv of AlMe3 results in the formation of the neutral dimethylaluminum complexes {MeC[NSi(CH2CH2SiMePh2)3]2}AlMe2 (3) and [(Ph2MeSiCH2CH2)3SiOAlMe2]2 (4). Reaction of 3 with 1 equiv of B(C6F5)3 forms the neutral complex {MeC[NSi(CH2CH2SiMePh2)3]2}AlMe(C6F5) (5) and BMe(C6F5)2. In the case of 4, the analogous reaction produced the dimer [(Ph2MeSiCH2CH2)3SiOAl]2Me3(C6F5) (6). Treatment of 1 with Ti(C5Me5)Me3 fails to afford the corresponding amidinate complex. However, reaction of 2 with the same titanium half-sandwich complex cleanly gives Ti(C5Me5)[OSi(CH2CH2SiMePh2)3]Me2 (7). Reaction of 7 with 1 equiv of B(C6F5)3 leads to the formation of the ion pair {Ti(C5Me5)[OSi(CH2CH2SiMePh2)3]Me}[BMe(C6F5)3] (8), which is relatively stable at room temperature, slowly decomposing (t1/2 ≈ 48 h) to give a mixture of two neutral titanium complexes, Ti(C5Me5)[OSi(CH2CH2SiMePh2)3][CH2B(C6F5)2](C6F5) (9) and Ti(C5Me5)[OSi(CH2CH2SiMePh2)3]Me(C6F5) (10). However, when this reaction is carried out in a 1:0.5 stoichiometry, the decomposition process occurs over the course of 22 h, giving complex 10 selectively. The implications of these results with related Ziegler−Natta catalyst systems are discussed.