Inductive effects of 10 and 12-vertex closo-carborane anions: cluster size and charge make a difference

Abstract

A phosphine containing a 10-vertex carborane anion substituent and its subsequent ligation to a Rh(I) carbonyl complex is reported. The complex is characterized by NMR spectroscopy and a single crystal X-ray diffraction study. In addition, the inductive effects of both 10 and 12 vertex C-functionalized closo-carborane anions are elucidated via I.R. analysis of the CO stretching frequencies of two Rh carbonyl complexes. Unlike C-functionalized neutral o-carborane the 10 and 12-vertex carborane anions are both strong electron donor substituents.

1,12-Diiodo-Ortho-Carborane: A Classic Textbook Example of the Dihalogen Bond

“…However, in the case of anionic carboranes, it is rather difficult to find a cation that, on the one hand, will not form additional non-covalent bonds with the anion and, on the other hand, will be small enough not to hinder the formation of intermolecular dihalogen bonds between the anions. In addition, unlike the C-substituted ortho-carborane, the C-substituted carba-closo-dodecaborate anion has no or negligible electron-withdrawing effects [55].…”

Silver(I) Clusters with Carba‐closo‐dodecaboranylethynyl Ligands: Synthesis, Structure, and Phosphorescence

“…Thus, the specific structural features of the clustera ppeared to be responsible for the phosphorescence efficiency:p entagonal bipyramidal cluster 4 showed aq uantum yield of 0.76, which is unprecedented for silver(I) clusters. [25] Besidesc omplexes and clusters with the ] 2À anion, only af ew coordination compounds with {closo-1-CB 11 }-based ligands bound to am etal center have been described [26] (e.g.,c arbene, [27] phosphane, [28] and metal-C cluster complexes). [17] Af urtherc lass of compounds stabilized by this boron-based ligand are Au I clusters of the type [{12-(R 3 PAu) 2 CC-closo-1-CB 11 H 11 } 2 ]( R = Me, Et), which are unprecedented with respect to their structure and the strengtho ft he stabilizinga urophilic interactions.…”

“…A further class of compounds stabilized by this boron‐based ligand are Au I clusters of the type [{12‐(R 3 PAu) 2 C≡C‐ closo ‐1‐CB 11 H 11 } 2 ] (R=Me, Et), which are unprecedented with respect to their structure and the strength of the stabilizing aurophilic interactions . Besides complexes and clusters with the [12‐C≡C‐ closo ‐1‐CB 11 H 11 ] 2− anion, only a few coordination compounds with { closo ‐1‐CB 11 }‐based ligands bound to a metal center have been described (e.g., carbene, phosphane, and metal–C cluster complexes) …”

Electrostatic vs. inductive effects in phosphine ligand donor properties and reactivity

“…65,66 The efficacy of both methods in rationalizing reactivity trends supports that both electrostatic and inductive interactions are active, and methods to distinguish between them are still being pursued to this day. [67][68][69] A more thorough understanding of the ARTICLE Journal Name 2 | J. Name., 2012, 00, [1][2][3] This journal is © The Royal Society of Chemistry 20xx…”

“…However, the origin of this increase (electrostatic or inductive) has remained elusive, and has largely been considered inductive by default. 68,69,[94][95][96][98][99][100][101] The ambiguity regarding through space effects of covalently bound distal anions limits the rational design of ligand scaffolds that leverage electric fields to enhance reactivity. For instance, a recent computational study predicts accelerated oxidative addition (OA) reactivity at a PMe3 supported Pd complex in the presence of either an externally applied electric field or a correctly positioned chloride ion.…”