Sb-to-P Metathesis: A Direct Route to Structurally Constrained, Cationic P Compound.

Structurally constrained, cationic P compound [LP][SbCl] with an OCO pincer-type ligand (L) having a central carbene donor was directly synthesized via an Sb-to-P metathesis reaction between PCl and LSb-Cl. [LP][SbCl] was isolated and its reactivity with small molecules (ROH and RNH) was studied, showing that [SbCl] is not an innocent counter anion, but an active participant in these reactions. When the [SbCl] was replaced with the [CBH] ([Cb]) anion, the reactions were redirected to [LP] cation only.

Hydrogen splitting at a single phosphorus centre and its use for hydrogenation.

Catalytic processes are largely dominated by transition-metal complexes. Main-group compounds that can mimic the behaviour of the transition-metal complexes are of great interest due to their potential to substitute or complement transition metals in catalysis. While a few main-group molecular centres were shown to activate dihydrogen via the oxidative addition process, catalytic hydrogenation using these species has remained challenging.

Metallomimetic Chemistry of a Cationic, Geometrically Constrained Phosphine in the Catalytic Hydrodefluorination and Amination of Ar-F Bonds.

The synthesis, isolation, and reactivity of a cationic, geometrically constrained σ-P compound in the hexaphenyl-carbodiphosphoranyl-based pincer-type ligand () are reported. reacts with electron-poor fluoroarenes via an oxidative addition-type reaction of the C-F bond to the P-center, yielding new fluorophosphorane-type species (P). This reactivity of was used in the catalytic hydrodefluorination of Ar-F bonds with PhSiH, and in a catalytic C-N bond-forming cross-coupling reactions between fluoroarenes and aminosilanes.

Intramolecular C-N bond activation by a geometrically constrained P-centre.

In this work the first examples of C-N bond activation by insertion into a geometrically constrained P-centre are shown. The mechanisms of these activation processes leading to new P species were studied both experimentally and computationally. Interestingly, in the case of insertion of the P-centre into an N-C(O)H bond, an unstable phosphoranyl-formaldehyde intermediate is probably formed, which undergoes decarbonylation in the presence of a catalytic amount of HCl producing a hydrophosphorane.

Dual Reactivity of a Geometrically Constrained Phosphenium Cation.

A geometrically constrained phosphenium cation in bis(pyrrolyl)pyridine based NNN pincer type ligand (1 ) was synthesized, isolated and its preliminary reactivity was studied with small molecules. 1 reacts with MeOH and Et NH, activating the O-H and N-H bonds via a P-center/ligand assisted path. The reaction of 1 with one equiv.

Geometrically constrained square pyramidal phosphoranide.

Geometrical constriction of main group elements leading to a change in the reactivity of these main group centers has recently become an important tool in main group chemistry. A lot of focus on using this modern method is dedicated to group 15 elements and especially to phosphorus. In this work, we present the synthesis, isolation and preliminary reactivity study of the geometrically constrained, square pyramidal (SP) phosphoranide anion (1).

Phosphorus mediated imidazolinium to oxazolium ring rearrangement.

An unexpected rearrangement occurred when an imidazolinium based OCO pincer-type ligand (1) reacted with PCl producing a chlorophosphine with a pendant oxazolium "arm" (3). The mechanism of this rearrangement was studied both experimentally and by density functional theory (DFT) computations. The deprotonation of 3 led to further unexpected results.

Facile proton-coupled electron transfer enabled by coordination-induced E-H bond weakening to boron.

We report the facile activation of aryl E-H (ArEH; E = N, O, S; Ar = Ph or C6F5) or ammonia N-H bonds via coordination-induced bond weakening to a redox-active boron center in the complex, (1-). Substantial decreases in E-H bond dissociation free energies (BDFEs) are observed upon substrate coordination, enabling subsequent facile proton-coupled electron transfer (PCET). A drop of >50 kcal mol-1 in H2N-H BDFE upon coordination was experimentally determined.

Reactions of a BICAAC with hydroboranes: propensity for Lewis adduct formation and carbene insertion into the B-H bond.

The reactivity of a bicyclic (alkyl)(amino)carbene (BICAAC) towards different boranes has been examined in the present work. The reactions with boranes BX3·SMe2 (X = H, Cl, Br), BF3·OEt2 and BCl3 yield Lewis adducts [BICAAC·BH3] (1), [BICAAC·BHCl2] (2), [BICAAC·BH2Cl] (3), [BICAAC·BF3] (4), [BICAAC·BCl3] (5) and [BICAAC·BBr3] (6) respectively, whereas more hydridic boranes, 9-borabicyclo[3.3.

Aluminum containing molecular bowls and pyridinophanes: use of pyridine modules to access different molecular topologies.

Molecular topologies varying from simple complexes to pyridinophanes (neutral and cationic) and to bicyclic pyridinophane containing organoaluminum (Al-Me) species were synthesized by varying the relative stoichiometry of bis(trimethylsilyl)-N,N'-2,6-diaminopyridine (bap) and the reactive partner (AlMe). The ultimate goal of these reactions was to systematically design cyclic structures containing group 13 elements. To highlight the reaction potential of these shapes, the bowl-shaped pyridinophane was reacted with the Lewis acid, B(CF), to generate a stable cationic derivative.

Group 13 element containing conformationally rigid "N-E-N" heteroatomic bridged [3.3](2,6)pyridinophanes (E = B, Al).

The first examples of group 13 element containing pyridinophanes have been assembled using heteroatom N-E-N bridges (E = B, Al). The presence of B and Al as acceptor atoms in the bridges and their coordination with pyridine nitrogen has a very strong influence on the conformational rigidity of the pyridinophanes.

Neutral and cationic cyclic (alkyl)(amino)carbene mercury [cAAC-Hg(ii)] complexes: scope of hydroamination of alkynes with organomercury compounds.

This study demonstrates the first synthesis of cyclic (alkyl)(amino)carbene (cAAC) adducts of Hg(ii), [cAACMe·HgBr(μ-Br)]2 (1a) and [cAACcy·HgBr(μ-Br)]2 (1b). Adduct 1b catalyzes intermolecular hydroamination of aromatic alkynes and amines under mild conditions to afford aromatic imines. The quest to prepare an electrophilic Hg(ii) complex resulted in the synthesis of cationic [(cAACcy)2Hg(H2O)]2+2[NO3]- (3) by reacting 1b with AgNO3.

Hg(ii) and Pd(ii) complexes with a new selenoether bridged biscarbene ligand: efficient mono- and bis-arylation of methyl acrylate with a pincer biscarbene Pd(ii) precatalyst.

Two equivalents of 1-benzyl-3-bromoethylbenzimidazolium bromide couple with NaSe to produce the first selenoether bridged bis-benzimidazolium salt (LH)Br. The nitrate (LH)(NO) and tetrafluoroborate (LH)(BF) salts were also synthesized from (LH)Br. The reaction of Hg(OAc) with (LH)Br gave the first pseudo pincer carbene mercury complex, [Hg(L-κC)][HgBr] (C1).

Two Different Pathways in the Reduction of [(S=)PCl(μ-NtBu)]2 with Na.

Reduction of the cyclodiphosphazane [(S=)ClP(μ-NtBu)]2 (1) with sodium metal in refluxing toluene proceeds via two different pathways. One is a Wurtz-type pathway involving elimination of NaCl from 1 followed by head-to-tail cyclization to give the hexameric macrocycle [(μ-S)P(μ-NtBu)2 P(=S)]6 (2). The other pathway involves reduction of the P=S bonds of 1 to generate colorless singlet biradicaloid dianion trans-[S-P(Cl)(μ-NtBu)]2 (2-) , which is observed in the polymeric structures of three-dimensional [{(S-)ClP(μ-NtBu)2 PCl(S)}Na(Na⋅THF2 )]n (3) and two dimensional [{(S-)ClP(μ-NtBu)2 PCl(S)} (Na⋅THF)2 ]n (4).