Polyhedron Vol[ 06\ No[ 12Ð13\ pp[ 3090Ð3097\ 0887 Þ 0887 Elsevier Science Ltd  Pergamon All rights reserved[ Printed in Great Britain 9166Ð4276:87 ,08[99¦9[99 PII] S9166Ð4276"87#99104Ð9 N!bridged and H!bridged aminoalanes] Single! crystal X!ray structure determinations for the planar dimer "ð"Me 2 Si# 1 NL 1 Al"m!H## 1 and the puckered four!membered ring compound "Me 2 Si# 1 N"Me 1 N#Al"m!NMe 1 # 1 Al"H#N"SiMe 2 # 1 Jerzy F[ Janik\ a Richard L[ Wells\$ a Arnold L[ Rheingold b and Ilia A[ Guzei b a Paul M[ Gross Chemical Laboratory\ Department of Chemistry\ Duke University\ Durham\ NC 16697! 9235\ U[S[A[ b Department of Chemistry\ University of Delaware\ Newark\ DE 08605\ U[S[A[ "Received 12 March 0887^ accepted 10 May 0887# Abstract *The known bis"bis"trimethylsilyl#amino#alane "ð"Me 2 Si# 1 NŁ 1 Al"m!H## 1 "0# is obtained from dis! proportionation of the base!stabilized monomeric bis"trimethylsilyl#aminoalane ð"Me 2 Si# 1 NAlH 1 Ł = NMe 2 in re~uxing toluene[ The single!crystal X!ray structure determination for 0 provides a H!bridged planar dimer with exo!cyclic N"SiMe 2 # 1 groups[ The combination of 0 with HNMe 1 in a 0]0 ratio results in competing aminolysis at the AlÐH site and transamination at the AlÐN"SiMe 2 # 1 site of 0\ as illustrated by the molecular structure of "Me 2 Si# 1 N"Me 1 N#Al"m!NMe 1 # 1 Al"H#N"SiMe 2 # 1 "1# which is isolated from this system[ The charac! teristic structural feature of 1 is a puckered "AlÐNÐAlÐN# ring with di}erent ligands on two aluminum atoms[ Þ 0887 Elsevier Science Ltd[ All rights reserved Keywords] alanes^ trimethylsilylamines^ disproportionation^ transamination^ aminolysis^ precursors[ ——————————————————————————————————————————————— INTRODUCTION In the solid state\ some alane amine adducts show dimeric connectivities ðH 2 Al = LŁ 1 "for example\ LNMe 2 ð0Ł\ NMe 1 CH 1 Ph ð1Ł# with _ve!coordinated aluminum atoms and somewhat counterintuitive unsymmetrical AlÐHÐAl bridges while\ on the other hand\ others seem to favor a monomeric mode with four!coordinated Al in H 2 Al = L "for example\ LN"n!Bu# 2 ð2Ł\ quinuclidine ð3Ł# or _ve!coordinated Al having a NÐAl"H 2 #ÐN bond sequence as in trigonal bipyramidal H 2 Al = 1NMe 2 ð4Ł[ This span of bonding preferences in the alane adducts is generally inter! preted as a manifestation of the ligand|s steric hin! drance and is not an exclusive property of amine Lewis  On leave from the University of Mining and Metallurgy\ Krakow\ Poland[ $ Author to whom correspondence should be addressed[ 3090 bases[ The latter is illustrated by examples of the AlÐ HÐAl bridged dimer ðH 2 Al = THFŁ 1 and trigonal bipyr! amidal H 2 Al = 1THF with an OÐAl"H 2 #ÐO axis ð5Ł[ Even more complex bonding environments are enco! untered in some polymeric structures containing AlH 2 units ð6Ł[ Finally\ ionic bonding is displayed by rare species of the type "H 1 AlL# ¦ "AlH 3 # − where L is a tri! or tetradentate amine ligand ð7Ł[ The progress in the chemistry of Lewis base adducts of alane and gallane has recently been reviewed ð8Ł[ The aminoalanes\ "H n Al"NR 1 # 2−n # "n9\ 0\ 1#\ appear to exhibit similar diversity of bonding as out! lined above for alane amine adducts but relatively shorter AlÐN bond lengths in the former make the steric factor play a more obvious role[ For example\ the dimethylaminoalane\ "H 1 AlNMe 1 # 2 \ is a N! bridged trimer in solution ð09Ł and in the solid state ð00Ł but both bis"dimethylamino#alane\ ðHAl"NMe 1 # 1 Ł 1 ð01Ł\ and tris"dimethylamino#alane\ ðAl"NMe 1 # 2 Ł 1 ð02\ 03Ł\ are N!bridged dimers[ Even