A coordination chemistry dichotomy for icosahedral carborane-based ligands

• Published in: Nature chemistry Vol. 3; no. 8; pp. 590 - 596
• Main Authors: Spokoyny, Alexander M., Machan, Charles W., Clingerman, Daniel J., Rosen, Mari S., Wiester, Michael J., Kennedy, Robert D., Stern, Charlotte L., Sarjeant, Amy A., Mirkin, Chad A.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 22.07.2011; Nature Publishing Group
• Subjects: 639/638/263/406/911; Analytical Chemistry; Biochemistry; Boranes - chemistry; Boron; Carbon; Chemistry; Chemistry and Materials Science; Chemistry/Food Science; Inorganic Chemistry; Ligands; Organic Chemistry; Physical Chemistry; Platinum; Sulfur
• ISSN: 1755-4330; 1755-4349
• DOI: 10.1038/nchem.1088

Although the majority of ligands in modern chemistry take advantage of carbon-based substituent effects to tune the sterics and electronics of coordinating moieties, we describe here how icosahedral carboranes—boron-rich clusters—can influence metal–ligand interactions. Using a series of phosphine–thioether chelating ligands featuring meta- or ortho-carboranes grafted on the sulfur atom, we were able to tune the lability of the platinum–sulfur interaction of platinum( II )–thioether complexes. Experimental observations, supported by computational work, show that icosahedral carboranes can act either as strong electron-withdrawing ligands or electron-donating moieties (similar to aryl- or alkyl-based groups, respectively), depending on which atom of the carborane cage is attached to the thioether moiety. These and similar results with carborane-selenol derivatives suggest that, in contrast to carbon-based ligands, icosahedral carboranes exhibit a significant dichotomy in their coordination chemistry, and can be used as a versatile class of electronically tunable building blocks for various ligand platforms. Rather than tuning metal–ligand interactions using carbon-based substituents, the effect of icosahedral carborane moieties — boron-rich clusters — on the coordination chemistry of phosphine–thioether ligands has been investigated. Depending on the positional attachment of the sulfur atom, the carboranes acted as either strong electron-withdrawing or strong electron-donating substituents.