Spontaneous vs. Base‐Induced Dehydrochlorination of Group 14 ortho‐Carboranylamidinates

Synthesis and Structural Characterization of Two New Main Group Element Carboranylamidinates

“…In the IR spectrum of 3, typical bands of the amidine moiety were observed at 3403 cm −1 (νN-H), 1577 cm −1 (νC=N), and 1260 cm −1 (νC-N). A medium strong band at 2584 cm −1 can be assigned to the carborane cage (νB-H) [22]. The antimony derivative 4 was fully characterized in the same manner.…”

“…In both cases, the complex having a [HL] − -type ligand is the only identified product, and no evidence for the formation of products with [L] 2− ligands has been observed. Consequently, the divalent germanium precursor turned out to react with Li[HL] in a similar manner as GeCl 4 [22], while the reaction of SbCl 3 took a different course than that of PhPCl 2 [20].…”

“…In the resulting lithium ortho-carboranylamidinates Li[(o-C 2 B 10 H 10 )C(NR)(NHR)] (= Li[HL]; 2a: R = i Pr, 2b: R = Cy (cyclohexyl)), a proton is formally shifted from a carboranyl carbon atom to the amidinate unit, resulting in an amidine moiety acting as a monodentate N-donor functionality (Scheme 1a). The lithium derivatives were further treated with various metal and non-metal chloride precursors to yield carboranylamidinates of e.g., Sn(II) and Cr(II) [8], Rh(I) and Ir(I) [13][14][15][16], Fe(II) and Fe(III) [17,18], Mo(II), Mn(II), Co(II), Ni(II), Cu(II) [18,19], Ti(IV), Zr(IV), Si(IV), Ge(IV), Sn(IV), Pb(IV), and P [20][21][22]. In the case of reactions with Cp 2 TiCl 2 , Cp 2 ZrCl 2 , PhPCl 2 , and various dichlorosilanes R 2 SiCl 2 , formal dehydrochlorination led to complexes with dianionic [(o-C 2 B 10 H 10 )C(NR) 2 ] 2− (= [L] 2− ) ligands having a deprotonated amidine group [20,22].…”

“…The lithium derivatives were further treated with various metal and non-metal chloride precursors to yield carboranylamidinates of e.g., Sn(II) and Cr(II) [8], Rh(I) and Ir(I) [13][14][15][16], Fe(II) and Fe(III) [17,18], Mo(II), Mn(II), Co(II), Ni(II), Cu(II) [18,19], Ti(IV), Zr(IV), Si(IV), Ge(IV), Sn(IV), Pb(IV), and P [20][21][22]. In the case of reactions with Cp 2 TiCl 2 , Cp 2 ZrCl 2 , PhPCl 2 , and various dichlorosilanes R 2 SiCl 2 , formal dehydrochlorination led to complexes with dianionic [(o-C 2 B 10 H 10 )C(NR) 2 ] 2− (= [L] 2− ) ligands having a deprotonated amidine group [20,22]. In a recent study, we have shown that the formation of this product class is preferred for highly Lewis-acidic centers, while "soft" metal centers form stable complexes with the original [(o-C 2 B 10 H 10 )C(NR)(NHR)] − (= [HL] − ) ligand [22].…”

“…In the case of reactions with Cp 2 TiCl 2 , Cp 2 ZrCl 2 , PhPCl 2 , and various dichlorosilanes R 2 SiCl 2 , formal dehydrochlorination led to complexes with dianionic [(o-C 2 B 10 H 10 )C(NR) 2 ] 2− (= [L] 2− ) ligands having a deprotonated amidine group [20,22]. In a recent study, we have shown that the formation of this product class is preferred for highly Lewis-acidic centers, while "soft" metal centers form stable complexes with the original [(o-C 2 B 10 H 10 )C(NR)(NHR)] − (= [HL] − ) ligand [22]. In all cases (i.e., for both [HL] − -and [L] 2− -type ligands, and independent from the choice of the central atom), the ligand adopts a characteristic κC,κN-chelating coordination mode instead of the "normal" κN,κN -chelating mode of coordinated amidinate anions [23,24].…”