Fluoro-Germanium (IV) Cations with Neutral Co-Ligands—Synthesis, Properties and Comparison with Neutral GeF4 Adducts

Abstract

The reaction of [GeF4L2], L = dmso (Me2SO), dmf (Me2NCHO), py (pyridine), pyNO (pyridine-N-oxide), OPPh3, OPMe3, with Me3SiO3SCF3 (TMSOTf) and monodentate ligands, L, in a 1:1:1 molar ratio in anhydrous CH2Cl2 formed the monocations [GeF3L3][OTf]. These rare trifluoro-germanium (IV) cations were characterised by microanalysis, IR, 1H, 19F{1H} and, where appropriate, 31P{1H} NMR spectroscopy. The 19F{1H} NMR data show that in CH3NO2 solution the complexes exist as a mixture of mer and fac isomers, with the mer isomer invariably having the higher abundance. The X-ray structure of mer-[GeF3(OPPh3)3][OTf] is also reported. The attempts to remove a second fluoride using a further equivalent of TMSOTf and L were mostly unsuccessful, although a mixture of [GeF2(OAsPh3)4][OTf]2 and [GeF3(OAsPh3)3][OTf] was obtained using excess TMSOTf and OAsPh3. The reaction of [GeF4(MeCN)2] with TMSOTf in CH2Cl2 solution, followed by the addition of 2,2′:6′,2”-terpyridine (terpy) formed mer-[GeF3(terpy)][OTf], whilst a similar reaction with 1,4,7-trimethyl-1,4,7-triazacyclononane (Me3-tacn) in MeCN solution produced fac-[GeF3(Me3-tacn)][OTf]. Dicationic complexes bearing the GeF22+ fragment were isolated using the tetra-aza macrocycles, 1,4,7,10-tetramethyl-1,4,7,10-tetra-azacyclododecane (Me4-cyclen) and 1,4,8,11-tetramethyl-1,4,8,11-tetra-azacyclotetradecane (Me4-cyclam), which reacted with [GeF4(MeCN)2] and two equivalents of TMSOTf to cleanly form the dicationic difluoride salts, cis-[GeF2(Me4-cyclen)][OTf]2 and trans-[GeF2(Me4-cyclam)][OTf]2. The 19F{1H} NMR spectroscopy shows that in CH3NO2 solution there are four stereoisomers present for trans-[GeF2(Me4-cyclam)][OTf]2, whereas the smaller ring-size of Me4-cyclen accounts for the formation of only cis-[GeF2(Me4-cyclen)][OTf], and is confirmed crystallographically. New spectroscopic data are also reported for [GeF4(L)2] (L = dmso, dmf and pyNO). Density functional theory calculations were used to probe the effect on the bonding as fluoride ligands were sequentially removed from the germanium centre in the OPMe3 complexes.

Neutral and Cationic Complexes of Silicon(IV) Halides with Phosphine Ligands

“…The reaction of [SiCl 4 (PMe 3 ) 2 ] with one or two equivalents of TMSOTf in CH 2 Cl 2 generated the six-coordinate complexes with coordinated triflate rather than lower coordinate cations, [SiCl 3 (PMe 3 ) 2 (OTf)] and [SiCl 2 (PMe 3 ) 2 (OTf) 2 ], respectively. The same result was also found in many germanium and tin systems . Crystals of [SiCl 2 (PMe 3 ) 2 (OTf) 2 ] were grown by layering a CH 2 Cl 2 solution with n -hexane, and the structure revealed the “all trans ” six-coordinate complex shown in Figure .…”

“…Since phosphine-substituted cations of silicon(IV) chloride or bromide do not form spontaneously, the use of halide abstraction reagents, AlX 3 , TMSOTf (Me 3 SiO 3 SCF 3 ), and Na[BAr F ], which have been used successfully to generate tin(IV) and germanium(IV) cations, 17 was explored. The reactions of AlX 3 with the neutral silicon phosphine complexes caused loss of phosphine to the aluminum and were not pursued.…”

“…The same result was also found in many germanium and tin systems. 17 Crystals of [SiCl 2 (PMe 3 ) 2 (OTf) 2 ] were grown by layering a CH 2 Cl 2 solution with n -hexane, and the structure revealed the “all trans ” six-coordinate complex shown in Figure 5 . This is in contrast to the [GeF 2 (PMe 3 ) 2 (OTf) 2 ] analog, in which the triflates only interact weakly with the metal center and are mutually cis.…”

The chemistry of the s- and p-block elements with 2,2′:6′,2′′-terpyridine ligands

“…Very recently, Reid et al prepared [Ge(tpy)F 3 ](OTf ), which exhibited an increased solubility in organic solvents. 230 Thus, 19 F NMR spectroscopic analysis was performed and corroborated the existence of the mer-configured [Ge(tpy)F 3 ] + cation.…”

Synthesis, Structure, and Biological Activity of the Germanium Dioxide Complex Compound with 2-Amino-3-Hydroxybutanoic Acid

“…We used hydrated germanium dioxide as a precursor. It should be noted that germanium dioxide itself is used in some dietary supplements [18][19][20][21].…”