om500343w_si_003.cif (1.44 MB)
Potassium and Well-Defined Neutral and Cationic Calcium Fluoroalkoxide Complexes: Structural Features and Reactivity
dataset
posted on 2014-10-27, 00:00 authored by Sorin-Claudiu Roşca, Thierry Roisnel, Vincent Dorcet, Jean-François Carpentier, Yann SarazinThe
fluorinated aminoether alcohols (1-aza-12-crown-4)CH2C(CF3)2OH ({RO1F}H),
(MeOCH2CH2)2NCH2C(CF3)2OH ({RO2F}H), and (MeOCH2CH2)(Me)NCH2C(CF3)2OH ({RO3F}H) have been synthesized and used
to prepare the heteroleptic calcium amido complexes {ROxF}Ca(N(SiMe2R)2)
(4–7; x = 2, 3,
R = H, Me). The ability to form stable complexes varies with the chelating
and electron-donating ability of the aminoether alkoxide ligand, as
exemplified by our failure to isolate cleanly the elusive {RO1F}Ca(N(SiMe2R)2). X-ray diffraction
studies show that, in the solid state, intramolecular Ca···F
interactions help reach coordinative saturation in the dimeric [{RO2F}Ca(N(SiMe3)2)]2 ([4]2), [{RO2F}Ca(N(SiMe2H)2)]2 ([5]2), [{RO3F}Ca(N(SiMe3)2)]2 ([6]2), and [{RO3F}Ca(N(SiMe2H)2)]2 ([7]2), which crystallized free of solvent coligands. Similar stabilizing
K···F patterns were found in the polymetallic potassium
fluoroalkoxides [{RO1F}K]2 ([1]2), [{RO2F}K]4 ([2]4), and
[{RO3F}K]4 ([3]4); [2]4 and [3]4 form heterocubanes in the solid
state. Examination of the XRD data for [1]2–[7]2 shows
that metal···F interactions can be favored over binding
of Oether atoms for calcium and potassium. Pulse-gradient
spin–echo NMR spectroscopy shows that the complexes remain
aggregated in aromatic solvents. The solvent-free salts [{ROxF}Ca+]·[H2N{B(C6F5)3}2–] (x = 1 (8), 2 (9), 3
(10)) are obtained by treating 4–7 with [H(OEt2)2+]·[H2N{B(C6F5)3}2–] or by reacting Ca(N(SiMe3)2)2 with [{ROxF}HH+]·[H2N{B(C6F5)3}2–]; the solid-state structures of
[8·H2O]2 and [9·H2O]2 again showed the presence
of Ca···F contacts. Complexes 5–7 are promising catalysts for the regiospecific anti-Markovnikov
hydrophosphination of styrene with diphenylphosphine, affording TOF
values as high as 52 molsubst molCa–1 h–1 with up to 400 equiv of substrates within
1–2 h at 60 °C.
