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Comparing the Acidity of (R3P)2BH-Based Donor Groups in Iridium Pincer Complexes

Department of Chemistry, Philipps-Universität Marburg, Hans-Meerwein-Str. 4, 35032 Marburg, Germany
Author to whom correspondence should be addressed.
Inorganics 2019, 7(5), 61;
Received: 31 March 2019 / Revised: 28 April 2019 / Accepted: 29 April 2019 / Published: 7 May 2019
(This article belongs to the Special Issue Metal Complexes Containing Boron Based Ligands)
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In the current manuscript, we describe the reactivity of a series of iridium(III) pincer complexes with the general formulae [(PEP)IrCl(CO)(H)]n (n = +1, +2) towards base, where PEP is a pincer-type ligand with different central donor groups, and E is the ligating atom of this group (E = B, C, N). The donor groups encompass a secondary amine, a phosphine-stabilised borylene and a protonated carbodiphosphorane. As all ligating atoms E exhibit an E–H bond, we addressed the question of wether the coordinated donor group can be deprotonated in competition to the reductive elimination of HCl from the iridium(III) centre. Based on experimental and quantum chemical investigations, it is shown that the ability for deprotonation of the coordinated ligand decreases in the order of (R3P)2CH+ > R2NH > (R3P)2BH. The initial product of the reductive elimination of HCl from [(PBP)IrCl(CO)(H)]n (1c), the square planar iridium(I) complex, [(PBP)Ir(CO)]+ (3c), was found to be unstable and further reacts to [(PBP)Ir(CO)2]+ (5c). Comparing the C–O stretching vibrations of the latter with those of related complexes, it is demonstrated that neutral ligands based on tricoordinate boron are very strong donors. View Full-Text
Keywords: boron; iridium; pincer; carbodiphosphorane boron; iridium; pincer; carbodiphosphorane

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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

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Maser, L.; Schneider, C.; Alig, L.; Langer, R. Comparing the Acidity of (R3P)2BH-Based Donor Groups in Iridium Pincer Complexes. Inorganics 2019, 7, 61.

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