Molecular and Electronic Structure of Platinum Bis(N‐arylamino)phosphenium Complexes including [Pt(phosphane)(phosphenium)(N‐heterocyclic carbene)]

Abstract

Dedicated to Professor M. Frederick Hawthorne on the occasion of his 75th birthdayThe application of electrophilic late-transition-metal complexes in catalysis has enjoyed widespread success in recent years. [1][2][3][4][5][6] We have been investigating electrophilic platinum complexes for catalysis and hydrocarbon CÀH bond activation [7,8] and recently reported a simple strategy for obtaining unsaturated electrophilic metal centers by addition of bulky bis(N-arylamino)phosphenium cations, easily derived from bis(N-aryl)diimines.

Metal‐Assisted, Reversible Phosphinyl Phosphination of the Carbon–Nitrogen Triple Bond in a Nitrile

“…This sequence is obviously facilitated by a higher degree of PP bond weakening in 1 a . The formation of 5 from 1 a and 4 may either involve 3 a as an intermediate or proceed by direct “nonoxidative” addition of the PP bond to the metal center; analogous insertions into PC bonds have precedence for phosphenium–carbene adducts 15…”

“…In summary, we have demonstrated the first transition‐metal‐assisted addition of diphosphines to a nitrile, which gives direct access to complexes of hybrid 1,2‐bisphosphines. Retroaddition at high temperature or direct “nonoxidative” addition15 of a diphosphine to a metal center yielded complexes featuring a combination of phospholide‐donor and phosphenium‐acceptor ligands which offer interesting prospects for further reactions. The extension of this chemistry to the synthesis of complexes of other metals and new ligands for catalysis is currently under investigation.…”

Diphosphane mit polarisierten und hoch reaktiven P‐P‐Bindungen

“…Unsymmetrische und potenziell chirale Phosphanliganden dieser Art, die interessant für Anwendungen in der Katalyse sind,21 konnten bisher ausgehend von Diphosphanen nicht hergestellt werden 22. Diese Reaktion zeigt enge Analogien zu der kürzlich beschriebenen “nichtoxidativen” Insertion eines Metallzentrums in die P‐C‐Bindung eines Phosphenium‐Carben‐Addukts 23…”

A 4,5‐Diphosphino‐Substituted Imidazolium Salt: A Building Block for the Modular Synthesis of Mixed Diphosphine–NHC Heterometallic Complexes

“…[2] A few examples of imidazolium salts substituted at the 2-position with a phosphinomethyl group have also been prepared (II) and used in the design of valuable recyclable catalysts. [3] Imidazolium salts containing a phosphino group directly bonded to a nitrogen atom (III) [4] or to the C2 atom (IV) [5] are also known, the latter is a good example of a strong p-acceptor phosphorus ligand [6] and hence better considered as an NHC-phosphenium adduct. [6b, c] To the best of our knowledge, imidazolium-4-phosphines that are unsubstituted at the 2-position are unknown.…”

“…The potential coordination capability of the imidazolium salt [5]A C H T U N G T R E N N U N G (CF 3 SO 3 ) combined with the stability and easy handling, prompted us to study their behavior as ligand in transition-metal complexes. We first checked the reaction with prototypic carbonyl complexes, such as [MnBr(CO) 5 ] and [Cr(CO) 6 ]. The treatment of these species with an equivalent amount of 5 in refluxing toluene afforded the cationic complexes 6 and 7, respectively, which contain the new imidazolium-diphosphine as a chelating ligand (Scheme 3).…”