Bioinspired Tungsten Complexes Employing a Thioether Scorpionate Ligand

Abstract

The synthesis and characterization of a series of novel tungsten complexes employing the bioinspired, sulfur-rich scorpionate ligand [PhTt] (phenyltris­((methylthio)­methyl)­borate) are reported. Starting from the previously published tungsten precursor [WBr2(CO)3(NCMe)2], a salt metathesis reaction with 1 equiv of Cs­[PhTt] led to the desired complex [WBr­(CO)3(PhTt)] (1), making it the first tungsten complex employing a poly­(thioether)­borate ligand. Surprisingly, the reaction of [WBr2(CO)3(NCMe)2] with an excess of the ligand gave complex [W­(CO)2(η2-CH2SMe)­(PhTt)] (2) with a bidentate (methylthio)­methanide ligand as the major product. Thereby, phenyldi­((methylthio)­methyl)­borane is formed, which was isolated and characterized by NMR spectroscopy. The bromido ligand in [WBr­(CO)3(PhTt)] was further substituted by the S,N-bidentate methimazole in order to make the first coordination sphere more sulfur-rich forming [W­(CO)2(mt)­(PhTt)] (3). Alkyne tungsten complexes employing the sulfur-rich scorpionate ligand were accessible by reaction of [WBr2(CO)­(C2R2)2(NCMe)] (R = Me, Ph) with Cs­[PhTt] forming [WBr­(CO)­(C2R2)2(PhTt-S,S′)] (R = Me 4, Ph 5), with the potentially tridentate ligand coordinated only via two sulfur atoms. In the case of 4, the higher flexibility of the bidentate coordination leads to the formation of two isomers with respect to the six-membered ring formed by the tungsten center and the two coordinated sulfur atoms of the ligand. All complexes 1–5 were characterized by single-crystal X-ray diffraction analysis.

Soft Scorpionate Hydridotris(2‐mercapto‐1‐methylimidazolyl) borate) Tungsten‐Oxido and ‐Sulfido Complexes as Acetylene Hydratase Models

“…Also the precursors with substituted alkynes reacted selectively to the mono‐alkyne products under elimination of the second alkyne. This is in contrast to our previously investigated soft scorpionate system phenyltris((methylthio)methyl)borate (PhTt) which only allowed isolation of bis ‐alkyne complexes of the type [W(CO)(C 2 R 2 ) 2 (PhTt‐S,S′)Br] (R=Me, Ph) . Thus, complexes 1 – 3 were synthesized by stirring the respective precursor and NaTm Me for 1–12 h at room temperature.…”

“…This is in contrastt oo ur previously investigateds oft scorpionate system phenyltris((methylthio)methyl)borate (PhTt)w hich only allowed isolation of bis-alkyne complexes of the type [W(CO)(C 2 R 2 ) 2 (PhTt-S,S')Br] (R = Me, Ph). [23] Thus, complexes 1-3 were synthesized by stirring the respective precursor and NaTm Me for 1-12 ha tr oom temperature. After work-up asd escribed in the experimental section they were isolated in high yields.…”

Probing Intermediates of Ion/Molecule Reactions by their Independent Gas‐Phase Synthesis and Fragmentation – The Thiomethoxymethyl Complexes [(bipy)M(CH2SCH3)]+ (M=Pt, Pd, Ni)

“…This time is usually sufficient to fully redistribute the internal energy over all internal degrees of freedom. [52,133] The m/z values are generally given based on the isotopologues, which contain 1 H, 12 C, 14 N, 16 O, 32 S, 58 Ni, 108 Pd, and 194 Pt only. Note that this is not necessarily the highest signal of the corresponding isotope pattern.…”

“…An independent gas‐phase synthesis of the cations [(bipy)M(CH 2 SCH 3 )] + (M=Pt ( 3 ), Pd ( 6 ), and Ni ( 7 )) followed by CID experiments might provide insights into the subtle differences, which the three metals nickel, palladium, and platinum exhibit within these fragmentation reactions. Moreover, thiomethoxymethyl complexes are generally rather rare, and only few crystallographically characterized transition‐metal complexes with CH 2 SCH 3 moieties have been described so far [101–111] . Studies, however, which highlight the general reactivity features of the transition‐metal‐bound thiomethoxymethyl group, are lacking as far as we can judge.…”

“…graphically characterized transition-metal complexes with CH 2 SCH 3 moieties have been described so far. [101][102][103][104][105][106][107][108][109][110][111] Studies, however, which highlight the general reactivity features of the transition-metal-bound thiomethoxymethyl group, are lacking as far as we can judge. The gas-phase synthesis of [(bipy)M(CH 2 SCH 3 )] + (M = Pt (3), Pd (6), Ni (7)), followed by collision-induced dissociation (CID) should thus provide insights into the chemistry of this quite underrepresented chemical moiety.…”