Structure and bonding
The parent iminoborane, HB=NH, is produced by theSynthesis
Elimination of fluoro- or chlorosilanes provides a well-tested route. Bulky substituents such as (Me3Si)3Si stabilize the iminoborane with respect to oligomerization: :(Me3Si)3SiB(F)-N(SiMe3)2 → (Me3Si)3Si-B=N-SiMe3 + F-SiMe3 Thermal decomposition of azidoboranes induces migration of R from boron to the nascent nitrene gives iminoboranes: :R2B-N3 → RB=NR + N2Reactivity
Oligomerization
Iminoboranes tend to oligomerize, often forming cyclic derivatives. Preventing this reaction is the purpose of bulky substituents. Five types of oligomerization product are produced: cyclodimers (1,3,2,4-diazadiboretidines, Di), cyclotrimers ( borazines, Tr), bicyclotrimers ( Dewar borazines, Tr′), cyclotetramers (octahydro-1,3,5,7-tetraza-2,4,6,8-tetraborocines, Te), and polymers (polyiminoboranes, Po); which are shown below. Which product is dominant depends on the structures of reactants and the reaction conditions. Some of the products can be interconverted.Addition reactions
The addition of protic agents is fast and quantitive. Boration reaction of iminoboranes is the addition of B-X single bond to B≡N, where -X can be -Cl (chloro-boration), -N3 (azido-boration), -SR (thio-boration), -NR2 (amino-boration) and R (alkyl-boration). One of these reactions are illustrated here.Cycloaddition
The typical +3cycloaddition is the addition of B≡N and RN3 to give a BN4 ring. One of the widely investigated +2cycloadditions is the reaction of aldehydes and ketones.Coordination to transition metals
Like alkynes, iminoboranes bind transition metals.References
{{reflist Boranes Amines Boron–nitrogen compounds