PREPARATION AND STRUCTURES OF SOME NEW PYRROLIDINIDO-ALANES AND PIPERIDINIDO-ALANES AND PYRROLIDINIDO-ALUMINATES AND PIPERIDINIDO-ALUMINATES

Alane and lithium tetrahydroaluminated each reacted with an excess of pyrrolidine or piperidine in tetrahydrofuran (thf) to give the new din uclear compounds {Al[N(CH2)(n)CH2](3)}(2) [n = 3 (from pyrrolidine) 1 or 4 (from piperidine) 2] and L(2)Li[mu-N(Ch(2))(n)CH2]Al-2[N(CH2)(n)C H2](2) [ n = 3, L = thf 3 or HN(CH2)(3)CH2 4; n = 4, L = thf 5]. The c ompounds were characterised by elemental analysis, multinuclear NMR sp ectroscopy, mass spectrometry and 1, 4 and 5, X-ray crystallography. I n 1, which contains an Al2N2 ring, average distances are Al-N(terminal ) 1.797(2) and Al-N(bridging) 1.963(2) Angstrom. Exocyclic N-Al-N angl es are in the range 112.6-114.4 degrees, the endocyclic N-Al-N angle i s 86.69(9)degrees and Al-N-Al is 93.31(9)degrees. The sums of the angl es at the terminal nitrogens are close to 360 degrees. In 4, which con tains an LiN2Al ring, distances are Al-N(terminal) 1.824(8), Al-N(brid ging) 1.880(7), Li-N(terminal) 2.035(20) and Li-N(bridging) 2.149(20) Angstrom. The sums of the angles at terminal nitorgens are 349.1 and 3 55.4 degrees. Ring angles are N-Al-N 100.0(3), Al-N-Li 82.0(4) and N-L i-N 84.2(5)degrees. In 5 average distances are Al-N(terminal) 1.828(3) , Al-N(bridging) 1.895(3), Li-O 1.987(6) Angstrom and Li-N(bridging) 2 .135(6) Angstrom. The sums of the angles at terminal nitrogens are 358 .1 and 357.4 degrees. Ring angles are N-Al-N 100.69(13), Al-N-Li 84.0( 2) and N-Li-N 86.2(2)degrees. Exchange between bridging and terminal a mido groups is slow on the NMR time-scale at 250 MHz in 1 and 2 but fa st in 2-5. Separate signals for axial and equatorial protons are obser ved from cooled samples of 2 and 5.