NDLI: Influence of the solvent and R groups on the structure of $(carboranyl)R_{2}PI_{2}$ compounds in solution. Crystal structure of the first iodophosphonium salt incorporating the anion $[7,8-nido-C_{2}B_{9}H

Content Provider	World Health Organization (WHO)-Global Index Medicus
Author	Teixidor, Francesc Viñas, Clara Sillanpää, Reijo Núñez, Rosario Kivekäs, Raikko
Description	Author Affiliation: Núñez R ( Institut de Ciència de Materials de Barcelona (CSIC), Campus de la U.A.B., E-08193, Bellaterra, Spain.)
Abstract	The influence of the electron-donor or electron-acceptor capacity of the R groups (R = $^{i}Pr,$ Ph, Et) and the solvent on the molecular geometry in solution of adducts of carboranylphosphanes $[(carboranyl)^{i}Pr_{2}P,$ $(carboranyl)Ph_{2}P$ and $(carboranyl)Et_{2}P]$ with $I_{2}$ in 1 : 1 ratios, has been studied in detail by $^{31}P\{^{1}H\}$ and $^{11}B\{^{1}H\}$ NMR spectroscopies. The more electron-accepting Ph groups make the $(carboranyl)Ph_{2}P$ less nucleophilic, thus stabilizing the $I_{2}$ encapsulated neutral biscarboranylphosphane–diiodine adducts in solution, such as $(carboranyl)Ph_{2}P⋯I–I⋯PPh_{2}(carboranyl),$ generating P⋯I–I⋯P motifs. Even in a polar solvent , such as EtOH , the arrangement is preserved. The expected basicity of these carboranylphosphanes is: $(carboranyl)^{i}Pr_{2}P$ > $(carboranyl)Et_{2}P$ > $(carboranyl)Ph_{2}P.$ Thus, the comparatively higher basicity of $(carboranyl)Et_{2}Pvs.(carboranyl)Ph_{2}P$ facilitates a higher transfer of electron density to the $I_{2}σ*,$ generating the ionic species, $[(carboranyl)Et_{2}PI]^{+}I^{−},$ even in low polar solvents , such as $CH_{2}Cl_{2}$ and toluene , with no degradation of the cluster. However, in EtOH , the formation of the anionic $[7,8-nido-C_{2}B_{9}H_{10}]^{−}cluster$ takes place by removal of one boron atom from the closocluster. The basicity of $(carboranyl)^{i}Pr_{2}P$ should be the highest, superior to $(carboranyl)Et_{2}P.$ This is observed in the reaction of these carboranylphosphanes with $I_{2}$ in EtOH . Whereas the formation of P four-coordinated molecular “spoke” charge-transfer complexes, $(carboranyl)^{i}Pr_{2}P–I–I,$ are suggested for $(carboranyl)^{i}Pr_{2}P$ in low polarity solvents , ionic species are formed in ethanolic solutions, which deboronate in a few days, faster than $(carboranyl)Et_{2}P,$ to yield the zwitterionic species. This is attributed to the higher basicity of $(carboranyl)^{i}Pr_{2}Pvs.(carboranyl)Et_{2}P.$ The X-ray crystal structure of $[7-PI^{i}Pr_{2}-8-Ph-7,8-nido-C_{2}B_{9}H_{10}],$ 2c, obtained from the reaction of $1-P^{i}Pr_{2}-2-Ph-closo-1,2-closo-C_{2}B_{10}H_{10}$ with $I_{2}$ in EtOH , confirms the formation of the zwitterion . These results prove that minor changes in the nature of the R substituents on the P atom in carboranylphosphanes, along with the solvent in which the reaction takes place, produce major alterations in the geometry of the $(carboranyl)R_{2}P–I–I$ species in solution, and in their possible further reactivity.
ISSN	14779226
Journal	Dalton Trans.
Issue Number	11
e-ISSN	13645447
Language	English
Publisher	Royal Society of Chemistry
Publisher Date	2008-03-21
Publisher Place	Great Britain (UK)
Access Restriction	Subscribed
Subject Keyword	Chemistry
Content Type	Text
Resource Type	Article
Subject	Inorganic Chemistry

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