Exchange of alkyl and tris(2-mercapto-1-t-butylimidazolyl)hydroborato ligands between zinc, cadmium and mercury

Abstract

The tris(2-mercaptoimidazolyl)hydroborato ligand, [TmBut], has been used to investigate the exchange of alkyl and sulfur donor ligands between the Group 12 metals, Zn, Cd and Hg. For example, [TmBut]2Zn reacts with Me2Zn to yield [TmBut]ZnMe, while [TmBut]CdMe is obtained readily upon reaction of [TmBut]2Cd with Me2Cd. Ligand exchange is also observed between different metal centers. For example, [TmBut]CdMe reacts with Me2Zn to afford [TmBut]ZnMe and Me2Cd. Likewise, [TmBut]HgMe reacts with Me2Zn to afford [TmBut]ZnMe and Me2Hg. However, whereas the [TmBut] ligand transfers from mercury to zinc in the methyl system, [TmBut]HgMe/Me2Zn, transfer of the [TmBut] ligand from zinc to mercury is observed upon treatment of [TmBut]2Zn with HgI2 to afford [TmBut]HgI and [TmBut]ZnI. These observations demonstrate that the phenomenological preference for the [TmBut] ligand to bind one metal rather than another is strongly influenced by the nature of the co-ligands.

Tris(2-mercaptoimidazolyl)hydroborato Cadmium Thiolate Complexes, [TmBut]CdSAr: Thiolate Exchange at Cadmium in a Sulfur-Rich Coordination Environment

“…Specifically, exchange is indicated by the observation of an off-diagonal cross peak between the 19 F NMR spectroscopic signals for [Tm Bu t ]­CdSC 6 H 4 -4-F and 4-fluorothiophenol. The observation of thiolate exchange between [Tm Bu t ]­CdSAr and ArSH (Ar = C 6 H 4 -4-F) complements the observation that exchange of thiolate ligands between zinc and cadmium centers of [Tm Bu t ]­ZnSCH 2 C­(O)­N­(H)­Ph and [Tm Bu t ]­CdSCH 2 C­(O)­N­(H)­Ph is also facile on the NMR time scale. ,, …”

“…The observation of thiolate exchange between [Tm Bu t ]CdSAr and ArSH (Ar = C 6 H 4 -4-F) complements the observation that exchange of thiolate ligands between zinc and cadmium centers of [Tm Bu t ]ZnSCH 2 C(O)N(H)Ph and [Tm Bu t ]CdSCH 2 C(O)N(H)Ph is also facile on the NMR time scale. 20b , 26 , 27 …”

“…The tris­(2-mercaptoimidazolyl)­hydroborato ligand system, [Tm R ] (Figure ), − has been shown to be effective for providing an L 2 X [S 3 ] donor array for a variety of metal centers. For example, this class of ligands has been utilized for investigating zinc enzymes that have sulfur-rich active sites. ,− Cadmium − and mercury ,,, counterparts have also been synthesized, with the latter providing a molecular model for mercury detoxification by organomercurial lyase ( MerB ) . Thiolate exchange involving the {[Tm R ]­Cd} platform, however, has received no attention, so here we report the synthesis and structures of [Tm Bu t ]­CdSAr compounds and their exchange reactions with thiols.…”

“…4-Fluorothiophenol (Aldrich), 4- tert -butylbenzenethiol (Acros), 4-methoxythiophenol (Aldrich), 3-methoxythiophenol (Aldrich), and pyridine-2-thione (Aldrich) were obtained commercially and used without further purification. [Tm Bu t ]­CdMe , and pyridine-2-selone were prepared by literature procedures.…”

Molecular structures of tris(1-tert-butyl-2-mercaptoimidazolyl)hydroborate complexes of titanium, zirconium and hafnium

“…Cyclopentadienyl (Cp R ) and tris(pyrazolyl)hydroborate [Tp R,R 0 ] are a pair of L 2 X (Green, 1995;Green & Parkin, 2014) donor ligands that have found much use as supporting ligands in the chemistry of titanium, zirconium and hafnium, especially with respect to applications involving olefin polymerization catalysis, as illustrated by compounds such as (Cp R ) 2 ZrX 2 (Kaminsky, 2001) and [Tp Me 2 ]Zr(CH 2 Ph) 3 (Nienkemper et al, 2008;Lee & Jordan, 2005). In contrast, closely related tris(1-alkyl-2-mercaptoimidazolyl)hydroborate L 2 X ligands, [Tm R ], have so far found little application to the chemistry of these elements, despite the fact that such ligands are currently used extensively in coordination chemistry (Spicer & Reglinski, 2009;Parkin, 2007;Kreider-Mueller et al, 2014). For example, the only structurally characterized [Tm R ] compounds of these elements listed in the Cambridge Structural Database (CSD, Version 5.37; Groom et al, 2016) (Buccella et al, 2006), with there being no examples of hafnium derivatives.…”