Reactions of Group 13 and 14 Hydrides and Group 1, 2, 13 and 14 Organyl Compounds with (tert‐Butylimino)(2,2,6,6‐tetramethylpiperidino)borane

Abstract ( tert‐ Butylimino)(2,2,6,6‐tetramethylpiperidino)borane ( 1 ) is a highly reactive species. Its B≡N triple bond inserts into the B−H bond of boranes, R 2 BH, generating diborylamines of the type tmp−BH−N t Bu−BR 2 (tmp = 2,2,6,6‐tetramethylpiperidino; R = H, Cl, Br, or organyl). Thexylborane reacts analogously, but only one of its two B−H bonds is used for the hydroboration of 1 . However, dihaloboranes HB(Hal) 2 −SMe 2 (Hal = Cl, Br) give B ‐haloboration products tmp−B(Hal)−N t Bu−BH(Hal), while reactions with H 2 B(Hal)−SMe 2 produce a mixture of two isomers by competing hydroboration and haloboration reactions. Tmp−BH−N t Bu−AlH 2 was obtained from 1 and AlH 3 −NMe 3 . It is a dimer in the solid state with pentacoordinate Al atoms and AlH 2 Al bridges. Hydrosilylation of 1 was achieved with Me 2 SiHCl, SiHCl 3 or Ph 2 SiH 2 to give the N ‐silyl‐substituted diaminoboranes tmp‐BH‐N t Bu−SiX 3− n R n . Me 3 SnH and Bu 3 SnH behave similarly, giving the corresponding N ‐stannylated diaminoboranes. However, when Ph 3 SnH was treated with 1 , the stannylborane tmp−B(SnPh 3 )−NH t Bu was formed showing an umpolung of the hydrostannylation. Organyllithium compounds provide access to N ‐lithiodiaminoboranes of the type tmp−BR−N t Bu−Li. The stability of these compounds depends on the substituent R. The least stable compound was the B− t Bu derivative followed by the B ‐methyl compound. However, in the presence of TMEDA tmp−BMe−N t Bu−Li is sufficiently stable to allow reactions, e.g. with B ‐chlorocatecholborane, to produce tmp−BMe−N t Bu−BO 2 C 6 H 4 . The most stable lithium compound so far is tmp−BPh−N t Bu−Li−OEt 2 , whose structure has been determined by X‐ray crystallography. MgBu 2 behaves like LiR and both of its Mg−C bonds can be used for the insertion reaction. The same is also true of ZnMe 2 . In contrast, at ambient temperature, only one of the E−C bonds of triorganylalanes, triorganylgallanes and InPh 3 is used for the insertion reaction. In the solid state, most of the new compounds show a weak to strong coordinate bond between the electrophilic centre (Li, Mg, Zn, Cd, B, Al, Ga and In) and the nitrogen atom of the tmp group which generates a four‐membered ring. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)