By means of 27Al, 'H, "0 and 13C NMR spectroscopy the structure of the methylaluminoxane (MAO) cocatalyst of Kaminsky-Sinn catalysts was investigated. We have found that the 27Al NMR resonance line of MA0 is extremely broad at room temperature (6 = 60, Amll2 50 f 10 kHz). At elevated temperatures (40-120°C) MA0 exhibits an 27Al resonance at 6 110 f 10, 15 -10 kHz, that is, within the range reported for the aluminoxane clusters [(t-Bu)A1(p3-0)I6 and [t-Bu)A1(p3-0)l9 with cage structures. The "Al resonance at 6 149-153, usually attributed to MAO, belongs to A1Me3 present in MA0 samples. The 1 7 0 NMR resonance of MA0 at 50 "C (6 67, Awl,, 1.7 kHz) is within the range typical for three-coordinate 0x0 ligands, but it can be attributed only to a minor part of MA0 oligomers. It was shown that the intensity of 27Al and 1 7 0 NMR resonances of MA0 increases with increasing temperature, whereas the width of both resonances is almost constant. The results obtained lead to the conclusion that at ambient conditions MA0 forms oligomers (MeAlO), with cage structure and MeA103 environment. Upon increasing the temperature these oligomers reversibly break into smaller MA0 units. Based on the 27Al NMR data the average radius (R) of MA0 oligomers is approximately 5.1 + 0.3 A at 120°C. This radius corresponds to (MeAlO), species with 9 < n < 14. +t ambient conditions the predominant part of MA0 forms oligomers with R = 7 f 0.5 A and 20 < n < 30.

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Structure of Mo(VI), V(V), and Ti(IV) Alkylperoxy and Peroxy Complexes Deduced from NMR Data and Their Reactivity -[36 refs.]. -(TALZI, E. P.; SHALYAEV, K. V.; BABUSHKIN, D. E.; SOBOLEV, A. P.; ZAMARAEV, K. I.; Kinet.

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