Abstract
The neutral complexes trans-[GeF4(PiPr3)2] and [GeF4(κ2-L)] (L = CH3C(CH2PPh2)3 or P(CH2CH2PPh2)3) are obtained from [GeF4(MeCN)2] and the ligand in CH2Cl2. Treatment of [GeF4(PMe3)2] with n equivalents of TMSOTf (Me3SiO3SCF3) leads to formation of the series [GeF4-n(PMe3)2(OTf)n] (n = 1, 2, 3), each of which contains six-coordinate Ge(IV) with trans PMe3 ligands and X-ray structural data confirm that the OTf groups interact with Ge(IV) to varying degrees. Unexpectedly, [GeF3(PMe3)2(OTf)] undergoes reductive defluorination in solution, forming the Ge(II) complex, [Ge(PMe3)3][OTf]2 (and [FPMe3]+). The bulkier PiPr3 leads to formation of the ionic [GeF3(iPr3P)2][OTf], containing a [GeF3(iPr3P)2]+ cation. [GeF4{o-C6H4(PMe2)2}], containing the cis-chelating diphosphine, also reacts with n equivalents of TMSOTf to generate [GeF4-n{o-C6H4(PMe2)2}(OTf)n] (n = 1, 2, 3). As for the PMe3 system, the trifluoride, [GeF3{o-C6H4(PMe2)2}(OTf)], is unstable to reductive defluorination in solution, producing the pyramidal Ge(II) complex [Ge{(o-C6H4(PMe2)2}(OTf)][OTf], whose crystal structure has been determined. The [GeF3{Ph2P(CH2)2PPh2}(OTf)] and [GeF2{Ph2P(CH2)2PPh2}(OTf)2], obtained similarly from the parent tetrafluoride complex, are poorly soluble, however their structures were confirmed crystallographically. The complexes in this work have been characterised via variable temperature 1H, 19F{1H} and 31P{1H} NMR studies in solution, IR spectroscopy and microanalysis and through single crystal X-ray analysis of representative examples across each series. Trends in the NMR and structural parameters are also discussed.
Highlights
P-block coordination and organometallic chemistry has seen a surge in research activity over recent years
Germanium tetrafluoride is a molecular monomer with boiling point = −36.5 °C, which has been shown to form a range of six-coordinate complexes either by the direct reaction of GeF4 with the neutral ligands, or by using an appropriate adduct, typically [GeF4(MeCN)2]
We describe here the coordination chemistry of GeF4 with neutral mono, bi, tri- and tetra-phosphine ligands, together with the reactions of [GeF4(PR3)2] (R = Me or iPr), [GeF4{oC6H4(PMe2)2}], and [GeF4{Ph2P(CH2)2PPh2}] with TMSOTf (Me3SiO3SCF3), revealing that fluoride ligands can be readily abstracted, in some cases sequentially, generating a range species with OTf − anions, which interact with the Ge(IV) centres to varying degrees
Summary
P-block coordination and organometallic chemistry has seen a surge in research activity over recent years. The complex is unstable in solution and a CH2Cl2 solution of the compound left to evaporate overnight led to the deposition of crystals of the Ge(II) complex, [Ge(PMe3)3][OTf ]2, containing a Ge(II) dication, the direct synthesis (from GeCl2(dioxane), PMe3 and TMSOTf ) and crystal structure of which we have reported recently.[18] This indicates that the [GeF3(PMe3)2(OTf )] is susceptible to redox chemistry and further analysis of its 19F{1H} NMR spectrum over time shows the appearance of a doublet at −135.7 ppm ( JPF = 936 Hz) (Fig. S3.2.5†), consistent with the formation of [FPMe3]+,19 indicating that the Ge(II) dication is a result of reductive defluorination in solution.
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