Synthesis and properties of 1,3-Bis(2,6-diisopropylphenyl)-2-(trimethylstannyl)- 2,3-dihydro-1H-1,3,2-diazaborole

Abstract

The diazaborole Me3Sn–B{N(Dipp)CH}2 (1; B{N(Dipp)CH}2=N,N′-bis(2,6-diisopropylphenyl)-2,3-dihydro-1H-1,3,2-diazaborolyl) was prepared by the reaction of Me3SnCl with one equivalent of Li[B{N(Dipp)CH}2]. Single crystals of 1 were obtained from hexane (triclinic space group P1̅). The diazaborole 1 was mono-deprotonated at the heterocycle upon treatment with Li[Me] to give product 2. In contrast to Li[B{N(Dipp)CH}2] which reacted with P4 to give the tetraphosphenediide Li2[{HC(Dipp)N}2B–P(1)P(2)P(3)P(4)–B{N(Dipp)CH}2] (3; δP=364.5, –29.4; 1JP(2),P(3)=–509.8 Hz, 1JP(1),P(2)=–434.3 Hz, 2JP(1),P(3)=–3.7 Hz, 3JP(1),P(4)=178.9 Hz) and the triphosphenide Li[{HC(Dipp)N}2B–PPP–B{N(Dipp)CH}2] (δP=665.1, 175.4; 1JP,P=500 Hz), the stannyl derivative 1 did not activate white phosphorus. The reaction of 1 with GaCl3 yielded either Me2ClSn–B{N(Dipp)CH}2 (4) or MeCl2Sn–B{N(Dipp)CH}2 (5) depending on the molar ratio of the reactants. The monochlorinated diazaborole Me2ClSn–B{N(Dipp)CH}2 was also obtained by the reaction of 1 with AsCl3.

Authentic Sn═B-Double Bonds in Polar Stannaborene Derivatives

“…The magnesium salt 3 exhibits a short Sn–B bond with an interatomic distance of 2.079(9) or 2.086(9) Å and a short B–Mg interaction of 2.190(9), 2.211(9) Å (Figure , Table , two independent dimers were found in the asymmetric unit). Typical bond lengths for single bonds between boron and tin lie in the range of [2.168(4) – 2.311(3) Å]. ,− To rationalize the short interatomic Sn–B distance found in 3 , DFT calculations were performed with the anionic bromide fragment of 3 [ o -C 6 H 4 (Ar*SnB­{PPh 2 }­MgBr 2 {thf})] − and the dimer ( 3′ ) 2 (Table , 3 and 3′ are used to designate a monomeric fragment of ( 3 ) 2 and ( 3′ ) 2 ; ( 3′ ) 2 : exchange of i Pr groups for H-atoms in ( 3 ) 2 ). The HOMO exhibiting a Sn–B π-bond orbital and the HOMO–1 representing a lone pair at boron which coordinates to the magnesium atom are shown in Figure .…”