A novel route to rhodaboratranes [Rh(CO)(PR3){B(taz)3}]+via the redox activation of scorpionate complexes [RhLL′Tt]

BLAGG, Robin J., ADAMS, Christopher J., CHARMANT, Jonathan P. H., CONNELLY, Neil G., HADDOW, Mairi F., HAMILTON, Alexander, KNIGHT, James, ORPEN, A. Guy and RIDGWAY, Benjamin M. (2009). A novel route to rhodaboratranes [Rh(CO)(PR3){B(taz)3}]+via the redox activation of scorpionate complexes [RhLL′Tt]. Dalton Transactions (40), p. 8724.

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Abstract

The reaction of a mixture of the sodium salts of dihydrobis(4-ethyl-3-methyl-5-thioxo-1,2,4-triazolyl)borate, NaBt, and hydrotris(4-ethyl-3-methyl-5-thioxo-1,2,4-triazolyl)borate, NaTt, with [{Rh(cod)(mu-Cl)}2] gave [Rh(cod)Bt] and [Rh(cod)Tt], which separately react with CO gas to give the unstable dicarbonyl [Rh(CO)2Bt] and an equilibrium mixture of two isomers of [Rh(CO)2Tt] and [(RhTt)2(mu-CO)3], respectively. Tertiary phosphorus donor ligands react with the mixture of [Rh(CO)2Tt] and [(RhTt)2(mu-CO)3] to give [Rh(CO)(PR3)Tt] (R = Cy, NMe(2), Ph or OPh) and [Rh{P(OPh)3}2Tt] in which rhodium is bound to two sulfur atoms of the scorpionate ligand; the B-H bond is directed towards the metal to give an agostic-like B-H...Rh interaction. Dinuclear [(RhTt)2(mu-CO)3] has kappa3[S3]-bound Tt ligands with a rhodium-rhodium bond bridged by three carbonyls. In solution the mononuclear Tt complexes undergo rapid dynamic interchange of the three thioxotriazolyl rings, probably via kappa3[S3]-coordinated intermediates. The monocarbonyls [Rh(CO)(PR3)Tt] (R = Cy, NMe2 or Ph) react with two equivalents of [Fe(eta-C5H5)2][PF6] in the presence of triethylamine to give the monocationic rhodaboratranes [Rh(CO)(PR3){B(taz)3}]+, with boron NMR spectroscopy providing evidence for the boron-rhodium bond. In the solid state, rhodium is bound to the three sulfur atoms and the boron of the B(taz)3 fragment, forming a tricyclo[3.3.3.0] cage. The phosphine is trans to the Rh-B bond, the long Rh-P bond indicating a pronounced trans influence for the coordinated boron. The cation [Rh(CO)(PPh3){B(taz)3}]+ reacts with [NBu(n)(4)]I to give [Rh(PPh3)I{B(taz)3}], in which the halide is trans to the Rh-B bond, and a second species, possibly [Rh(CO)I{B(taz)3}]. The dirhodaboratrane [Rh2(PCy3){B(taz)3}2][PF6]2, a minor byproduct in the synthesis of [Rh(CO)(PCy3){B(taz)3}][PF6], has a distorted square pyramidal rhodium atom with a vacant site trans to the Rh-B bond. The second metal has four coordination sites filled by the sulfur and boron atoms of a second B(taz)3 unit, the remaining octahedral sites occupied by two of the sulfur atoms of the first B(taz)3 unit which therefore bridges the two rhodium atoms.

Item Type:	Article
Research Institute, Centre or Group - Does NOT include content added after October 2018:	Biomedical Research Centre
Identification Number:	https://doi.org/10.1039/B910108J
Page Range:	p. 8724
Depositing User:	Jamie Young
Date Deposited:	29 May 2015 10:30
Last Modified:	18 Mar 2021 10:00
URI:	https://shura.shu.ac.uk/id/eprint/9921

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