Alkoxohydridoaluminates. I 27 Al NMR Characteristics of (C 4 H 9 ) 4 N + AlH 4-n (OR) n - in Benzene

The 27 Al NMR spectra of (C 4 H 9 ) 4 N + AlH 4-n (OR) n - prepared in the reaction of (C 4 H 9 ) 4 NAlH 4 with ROH (R = CH 3 , C 2 H 5 , i-C 3 H 7 , t-C 4 H 9 , n-C 5 H 11 , n-C 9 H 19 , cyclo-C 6 U 11 , C 6 H 5 , CH 3 OCH 2 CH 2 ) in benzene show - in contrast to the Li + and Na + salts - a distinct H-splitting, which has allowed to ascertain: 1) the presence of all members (n = 0-4) in solution, 2) the Al chemical shift and AI -H coupling constant of all individual classes, namely (n = 0): 101.6 ppm, quintet 174 Hz; (n = 1): 114-123 ppm, quartet 184-193 Hz; (n = 2): 103-112 ppm, triplet 197-219 Hz; (n = 3): 75-91 ppm, doublet 218-237 Hz; (n = 4): 51-73 ppm, singlet, 3) increased shielding in the order: CH 3 < n-R = i-R = sec-R < C 6 H 11 ⪡ C 6 H 5 < t-C 4 H 9 . The anomalous "sagging" pattern of the curve: δ 27 Al vs. number of OR groups, is interpreted on the basis of significant differences among Al and H and OR in electronegativity.