The new tripod ligands bis(pyrazolyl)(3-tert-butyl-2-thioimidazol-1-yl)hydroborate (L(1)) and bis(pyrazolyl)(3-isopropyl-2-thioimidazol-1-yl)hydroborate (L(2)), together with zinc nitrate or zinc chloride and the corresponding thiolates, have yielded a total of 17 zinc-thiolate complexes. These comprise aliphatic as well as aromatic thiolates and a cysteine derivative. Structure determinations have confirmed the tetrahedral ZnN(2)S(2) coordination in the complexes. Upon reaction with methyl iodide, the species L(1).Zn-SR are slowly converted to L(1).Zn-I and the free thioethers CH(3)SR. A kinetic analysis has shown these alkylations to be about 1 order of magnitude slower than those of the tris(pyrazolyl)borate complexes Tp(Ph,Me)Zn-SR. Alkylations with trimethyl phosphate were found to proceed very slowly even in DMSO at 80 degrees C.

The biologically relevant alkylations of the thiolate ligands in tripod zinc thiolates by methyl iodide were studied kinetically. Five tripod ligands of the pyrazolyl/thioimidazolyl borate type were employed, offering N3, N2S, NS2, and S3 donor sets. For each of them, the ethyl-, benzyl-, phenyl-, and p-nitrophenylthiolate zinc complexes were investigated, yielding a total of 20 second-order rate constants. The comparison of these rate constants shows three effects: (1) the electronic effect among the thiolates, i.e., the ethanethiolates react about 3 orders of magnitude faster than the p-nitrophenylthiolates; (2) the steric effect among the pyrazolylborates, i.e., the phenyl-substituted ones react about 2 orders of magnitude faster than the tert-butyl-substituted ones; and (3) the strong acceleration by the sulfur donors in the tripods, reaching 4 orders of magnitude between the reaction times of the (N3)Zn-SR and (S3)Zn-SR complexes.

The NS 2 ZnX coordination in thiolate-alkylating zinc enzymes is reproduced in (tripod)ZnX complexes with substituted pyrazolylbis(thioimidazolyl)borate tripod ligands. Intermediate (tripod)Zn nitrates and perchlorates are converted into (tripod)Zn thiolates, including the biologically relevant homocysteinate. Methylation with CH 3 I converts these to (tripod)ZnI and the corresponding thioethers CH 3 SR, including methionine. A kinetic investigation has shown the alky-

The anionic bis(pyrazolyl)(thioimidazolyl)borate ligands BpMt(R) with R = tert-butyl and isopropyl were obtained as their potassium salts by reacting potassium tris(pyrazolyl)borate with the corresponding thioimidazoles in the melt at 150 degrees C. They were applied to form some tetrahedral zinc complexes and identified by the crystal structures of (BpMt(t-Bu))ZnCl and (BpMt(i-Pr))Zn-SC(6)H(4)-p-Cl.

To answer the question as to whether gallium in its oxidation state +1 favors a σ‐ or a π‐coordination of aromatic nitrogen bases, we reacted [Ga(C6H5F)2]+[Al(ORF)4]– {RF = C(CF3)} with pyrazine and 2,6‐di‐tert‐butyl‐4‐methylpyridine (DTBMP). In doing so, we obtained the first tricoordinate, nonchelated, homoleptic N‐donor complex of gallium(I): [Ga(pyrazine)3]+[Al(ORF)4]–, in which each gallium(I) cation is coordinated in a trigonal‐pyramidal fashion by three η1‐donating pyrazine ligands. Hence, the gallium(I) cations favor σ‐ over π‐coordination. Depending on the reaction conditions, and due to the bifunctionality of pyrazine, 1D coordination polymers of {[Ga(μ‐pyrazine)2(η1‐pyrazine)]+[Al(ORF)4]–}∞ were also obtained. With the sterically demanding DTBMP, which is conventionally used as a proton scavenger, the mixed complex [Ga(C6H5F)2(DTBMP)]+[Al(ORF)4]– was isolated, thus proving incorrect the perception of DTBMP being “non‐nucleophilic”. The structural findings were confirmed by multinuclear NMR investigations and density functional performed at the RI‐BP86/SV(P) level.

The crystal structures of nine organic salts of which seven are ionic liquids (ILs), comprising imidazolium, ammonium, piperidinium, and sulfonium cations, were determined. The occurrence of short contacts in the compounds' crystal structures was quantified with Hirshfeld surface analyses. Temperature dependent crystal structure data for several organic salts were recorded systematically in the temperature range from 100 K to room temperature. The thermal behavior of the cell constants was linear and anisotropic for almost all compounds. The accuracy of the molecular volume (Vm) – the key quantity in volume based thermodynamics (VBT) – was investigated in terms of its temperature dependency and the statistical error of the constituent ion volumes (Vm+/–). The former effect turned out to be at most on the same order of magnitude as the errors of Vm+/–. The same analysis was applied to the recently proposed new internally consistent molecular ion volumes (Vm, new+/–). For this purpose, a set of overall 40 Vm, new+/– values of typical polyatomic ions constituting ILs was established. In general, it is recommended to use as many salts as possible and as many temperature dependent data as available for the derivation of new Vm+/– and Vm, new+/– values.

The synthesis, spectroscopic and structural characterisation of a series of [M(hfip)6]– (M = Nb, Ta; hfip = O–C(H)(CF3)2) salts that are the typical starting materials to introduce these weakly coordinating anions by metathesis reactions into a given system is described. The salts Li[Nb(hfip)6] and Li[Ta(hfip)6] formed in 65 to 77 % yield from freshly sublimed MCl5 and Li[hfip]. By contrast, several attempts to synthesize Li[Sb(hfip)6] on the similar route (replace NbCl5 by SbCl5) failed to yield a pure product. Upon metathesis of the Li‐niobate with AgF in CH2Cl2, the pure Ag[Nb(hfip)6] formed. Mixing Li[Nb(hfip)6] with an equimolar amount of Cl–CPh3 in CH2Cl2 gave the yellow [CPh3][Nb(hfip)6]. Several of the compounds were characterized by X‐ray analysis. Thus, the crystal structures of the Li+‐ and Ag+‐solvates 1, 2‐C6H4F2{LiNb(hfip)6}2, [Li(H2O)][Ta(hfip)6], and [Ag(C6H5F)][Nb(hfip)6] as well as that of [CPh3][Nb(hfip)6] were solved and are described in this work.