[3+2] Fragmentation of an [RP₅Cl]⁺ Cage Cation Induced by an N‐Heterocyclic Carbene

Abstract

Die Käfigverbindung [DippP5Cl][GaCl4] (Dipp=2,6‐Diisopropylphenyl) reagiert mit einem N‐heterocyclischen Carben (NHC) über eine ungewöhnliche [3+2]‐Fragmentierung des P5+‐Kerns. Die Reaktion liefert eine Imidazoliumyl‐substituierte P3‐Spezies mit Triphosphaallyl‐Motiv und eine neutrale P2‐Verbindung. Der Mechanismus der Fragmentierung wurde mit experimentellen und quantenchemischen Methoden aufgeklärt.

NHC‐Mediated Synthesis of an Asymmetric, Cationic Phosphoranide, a Phosphanide, and Coinage‐Metal Phosphanido Complexes

“…[4] Furthermore, we recently reported on the reduction of cation 7 + to compound 8 + in which a dicationic diphosphane acts as a chelating Lewis acid toward a chloride anion (Scheme 1). [7] Second, they are advantageous for the stabilization of cations through delocalization of the positive charge. Haaland [6] provides a general conceptual basis to describe such bonding environments, and thus, the latter model appears to be more realistic for us and is used throughout this paper.…”

“…[5] The above-mentioned examples are either described as donor-acceptor complexes of NHC ligands and the respective P-centered moiety or as imidazoliumyl-substituted P compounds that bear a positive charge on the imidazoliumyl substituent. [7] Third, they serve to reduce the nucleophilicity of a directly bonded P III atom, thus limiting decomposition pathways and rendering the molecules interesting electron-poor ligands for transitionmetal catalysis. Independent of any such controversy, however, the imidazoliumyl substituents in the above compounds serve well for at least three purposes.…”

“…Haaland [6] provides a general conceptual basis to describe such bonding environments, and thus, the latter model appears to be more realistic for us and is used throughout this paper. [7,8] In this context, we were interested in the reactivity of cation 7 + . First, they help to stabilize low-as well as hypercoordinated P atoms.…”

Functionalization of Pentaphosphorus Cations by Complexation

“…In summary,w eh ave comprehensively studied the hitherto unknown coordination behavior of cationic poly- 24 ] À ,and the resulting mixed substituted complexes 2-X-R (X = CN and Cl) can be further modified as demonstrated by the synthesis of 2-Cy-iPr from 2-Cl-iPr.T he "functionalization by complexation" approach thus potentially enables the preparation of hitherto inaccessible and multiply substituted polyphosphorus scaffolds in the coordination sphere of transitionmetal cations.T his strategy is complementary to previously reported methods for the synthesis of functionalized polyphosphorus complexes, [9, 10c, 11, 19] and further extensions should give access to abroad range of novel P n frameworks.…”

The Highly Lewis Acidic Dicationic Phosphonium Salt: [(SIMes)PFPh2][B(C6F5)4]2

“…Oxidation of an N-heterocyclic carbene (NHC) derived cationic phosphine [10] provides a cationic difluorophosphorane, while subsequent fluoride abstraction affords a phosphonium dication salt. However, the initial systems described above, require strongly electronwithdrawing substituents, thus limiting potential structural variations.…”