Homo- and Heteropolynuclear Clusters of Phosphine Triphenolates

Abstract

The synthesis and structural characterization of a series of homo- and heteropolynuclear clusters constructed with a potentially tetradentate phosphine triphenolate ligand are presented. Treatment of tris(3,5-di-tert-butyl-2-hydroxyphenyl)phosphine (H3[O3P]) with 3 equiv of nBuLi in diethyl ether at -35 °C affords hexanuclear Li6[O3P]2(OEt2)2 (1) as colorless crystals. In situ lithiation of H3[O3P] with 3 equiv of nBuLi in THF at -35 °C followed by metathetical reactions with MnCl2 or NiCl2(DME) gives crystals of forest green pentanuclear MnLi4[O3P]2(THF)3 (2) or dark brown tetranuclear Ni2Li2[O3P]2(THF)2 (3), respectively. Alkane elimination of ZnR2 (R = Me, Et) with H3[O3P] in THF at 25 °C generates high yields of colorless crystalline trinuclear Zn3[O3P]2(THF)2 (4). The cluster structures of 1-4 were all determined by single crystal X-ray diffraction studies. These molecules represent the first examples of metal complexes supported by phosphine triphenolate derivatives. The cluster 2 contains a paramagnetic core of high spin Mn(II) (S = 5/2) as indicated by solution and solid state magnetic susceptibility measurements.

Facile synthesis of zwitterionic organoaluminum complexes containing formally dianionic homoscorpionate ligands

“…1 ppm. These values are significantly downfield shifted from those of H 3 [O 3 P] (−65.1 ppm) and Li 3 [O 3 P] (−57.3 ppm), consistent with their cationic nature and the lack of an Al–P bond in these complexes in view of the fact that phosphine typically gives an upfield change in 31 P chemical shift upon coordination to aluminum. The Hα atoms in ethyl 4 and 7 are chemically equivalent in their corresponding 1 H NMR spectrum, so are those in isobutyl 5 and 8 and n ‐butyl 9 .…”

“…The P‐bound methyl group reveals a doublet resonance in the 1 H NMR spectrum at 3.50 ppm with 2 J PH = 16 Hz and a doublet resonance in the 13 C{ 1 H} NMR spectrum at 16.2 ppm with 1 J CP = 61.0 Hz. In accordance with its cationic characteristics, the phosphorus atom in {H 3 [O 3 PMe]} + resonates in the 31 P{ 1 H} NMR spectrum at 26.8 ppm that is significantly downfield shifted from that of H 3 [O 3 P] at −65.1 ppm . The 19 F{ 1 H} NMR resonance of {H 3 [O 3 PMe]}OTf at −78.6 ppm is typical for a triflate anion.…”

“…Solution NMR spectra of this compound are all consistent with a C 3 ‐ or C 3v ‐symmetric structure for the cationic {H 3 [O 3 PMe]} + , as evidenced, for example, by the two sharp singlet resonances observed for arylated tert ‐butyl groups in the 1 H NMR spectrum. The hydroxy protons are observed at 7.32 ppm as a singlet resonance, contrasting with those of H 3 [O 3 P] that gives rise to a doublet resonance at 5.95 ppm with J HP = 7 Hz, a consequence clearly resulting from the lack of an OH···P coupling for the former due to quaternization of its phosphorus atom. The P‐bound methyl group reveals a doublet resonance in the 1 H NMR spectrum at 3.50 ppm with 2 J PH = 16 Hz and a doublet resonance in the 13 C{ 1 H} NMR spectrum at 16.2 ppm with 1 J CP = 61.0 Hz.…”

“…−2.2 ppm) quantitatively in 30 min. Analogous reactions conducted in diethyl ether or toluene, however, generate a mixture of products having Li 3 [O 3 P] as the major component ( 31 P NMR evidence). Organic amines such as NEt 3 and 1,4‐diazabicyclo[2.2.2]octane (DABCO) do not react with these zwitterionic complexes, suggesting a stronger basicity of {AlX[O 3 P]} − than these trialkylamines.…”

“…All solvents were reagent grade or better and purified by standard methods. Compounds tris(3,5‐di‐ tert ‐butyl‐2‐hydroxyphenyl)phosphine (H 3 [O 3 P]) and 1 were prepared following reported procedures. ε‐CL was dried over CaH 2 (1 wt %) at 80°C for 0.5 hr and distilled under reduced pressure.…”