TY - JOUR
T1 - Niobium isocyanide complexes, Nb(CNAr)6, with Ar = 2,6-dimethylphenyl (Xyl), a diamagnetic dimer containing four reductively coupled isocyanides, and Ar = 2,6-diisopropylphenyl (Dipp), a paramagnetic monomer analogous to the highly unstable hexacarbonylniobium(0)
AU - Kucera, Benjamin E.
AU - Roberts, Christopher J.
AU - Young, Victor G.
AU - Brennessel, William W.
AU - Ellis, John E
N1 - Funding Information:
The authors thank the US National Science Foundation and the donors of the Petroleum Research Fund, administered by the American Chemical Society, for support of this research.
Publisher Copyright:
© 2019.
PY - 2019/9/1
Y1 - 2019/9/1
N2 - Treatment of bis(mesitylene)niobium(0) with 6-7 equivalents of 2,6-dimethylphenyl isocyanide (CNXyl) affords two products with the empirical formula Nb(CNXyl) n (n = 7 or 6), which have been shown to be the diamagnetic dimers bis[μ-N,N′,N′′,N′′′-tetrakis(2,6-dimethylphenyl)squaramidinato(2-)]bis[pentakis(2,6-dimethylphenyl isocyanide)niobium(I)], [Nb2(C9H9N)10(C36H36N4)] or [Nb(CNXyl)5]2[μ-C4(NXyl)4]·xSolvent, 1, and bis[μ-N,N′,N′′,N′′′-tetrakis(2,6-dimethylphenyl)squaramidinato(2-)]bis[tetrakis(2,6-dimethylphenyl isocyanide)niobium(I)] tetrahydrofuran trisolvate, [Nb2(C9H9N)8(C36H36N4)]·3C4H8O or [Nb(CNXyl)4]2[μ-C4(NXyl)4]·3THF (THF = tetrahydrofuran), 2. Each contains NbI bound to either five or four terminal isocyanides, respectively, and to an unprecedented bridging tetraarylsquaramidinate(2-) unit, coordinated as a bidentate ligand to each niobium center, symmetrically due to the crystallographic inversion center that coincides with the centroid of the central C4 unit. Thus, in the presence of CNXyl, the bis(mesitylene)niobium(0) is oxidized to niobium(I), resulting in the facile loss of both mesitylene groups and the reductive coupling of two CNXyl groups per niobium to provide the first examples of tetraarylsquaramidinate(2-) ligands, [cyclo-C4N4Ar4]2-, coordinated to metals. In contrast, bis(mesitylene)niobium(0) reacts with the more crowded 2,6-diisopropylphenyl isocyanide (CNDipp) to afford the paramagnetic monomer hexakis(2,6-diisopropylphenyl isocyanide)niobium(0), [Nb(C13H17N)6] or Nb(CNDipp)6, 3, the first zero-valent niobium isocyanide analog of the highly unstable Nb(CO)6, which is presently only known to exist in an argon matrix at 4.2K.
AB - Treatment of bis(mesitylene)niobium(0) with 6-7 equivalents of 2,6-dimethylphenyl isocyanide (CNXyl) affords two products with the empirical formula Nb(CNXyl) n (n = 7 or 6), which have been shown to be the diamagnetic dimers bis[μ-N,N′,N′′,N′′′-tetrakis(2,6-dimethylphenyl)squaramidinato(2-)]bis[pentakis(2,6-dimethylphenyl isocyanide)niobium(I)], [Nb2(C9H9N)10(C36H36N4)] or [Nb(CNXyl)5]2[μ-C4(NXyl)4]·xSolvent, 1, and bis[μ-N,N′,N′′,N′′′-tetrakis(2,6-dimethylphenyl)squaramidinato(2-)]bis[tetrakis(2,6-dimethylphenyl isocyanide)niobium(I)] tetrahydrofuran trisolvate, [Nb2(C9H9N)8(C36H36N4)]·3C4H8O or [Nb(CNXyl)4]2[μ-C4(NXyl)4]·3THF (THF = tetrahydrofuran), 2. Each contains NbI bound to either five or four terminal isocyanides, respectively, and to an unprecedented bridging tetraarylsquaramidinate(2-) unit, coordinated as a bidentate ligand to each niobium center, symmetrically due to the crystallographic inversion center that coincides with the centroid of the central C4 unit. Thus, in the presence of CNXyl, the bis(mesitylene)niobium(0) is oxidized to niobium(I), resulting in the facile loss of both mesitylene groups and the reductive coupling of two CNXyl groups per niobium to provide the first examples of tetraarylsquaramidinate(2-) ligands, [cyclo-C4N4Ar4]2-, coordinated to metals. In contrast, bis(mesitylene)niobium(0) reacts with the more crowded 2,6-diisopropylphenyl isocyanide (CNDipp) to afford the paramagnetic monomer hexakis(2,6-diisopropylphenyl isocyanide)niobium(0), [Nb(C13H17N)6] or Nb(CNDipp)6, 3, the first zero-valent niobium isocyanide analog of the highly unstable Nb(CO)6, which is presently only known to exist in an argon matrix at 4.2K.
KW - 2,6,diisopropylphenyl isocyanide
KW - 2,6,dimethylphenyl isocyanide
KW - crystal structure
KW - isocyanide
KW - low
KW - niobium
KW - squaramidinate
KW - squarate
KW - valent
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U2 - 10.1107/S205322961901101X
DO - 10.1107/S205322961901101X
M3 - Article
C2 - 31484814
AN - SCOPUS:85071772168
SN - 2053-2296
VL - 75
SP - 1259
EP - 1265
JO - Acta Crystallographica Section C: Structural Chemistry
JF - Acta Crystallographica Section C: Structural Chemistry
ER -