Enantiopure -Chiral Secondary Phosphines (P*HRR') from the Catalytic Asymmetric Hydrogenation of P═C Bonds.

We report the first bottleable enantiopure -chiral secondary phosphines from the rhodium-catalyzed asymmetric hydrogenation of phosphaalkenes. Catalytic asymmetric hydrogenation, a reaction of broad academic and industrial importance for C═C, N═C, and O═C bonds, has not previously been reported for the P═C bond. The hydrogenation of ArP═CR (Ar = Mes, -Xyl and TMOP; R = Ph, 4-CHF) affords four unprecedented -stereogenic secondary phosphines in 76%-90% isolated yields with 91%-97% enantiomeric excess (ee).

Probing Radical Addition to 1-Phosphabutadienes by Employing Muonium as a "Light Isotope" of Hydrogen.

Understanding free radical addition to multiple bonds is important to elucidating the mechanistic details of addition polymerization reactions, albeit the fleeting radical intermediates are very difficult to detect by conventional methodologies. Muon spin spectroscopy (μSR) is a highly sensitive method that can detect radical species at 10 spins (cf. EPR: 10 spins, NMR: 10 spins).

Cationic Phosphinidene as a Versatile P Building Block: [L-P] Transfer from Phosphonio-Phosphanides [L-P-PR] and Subsequent L Replacement Reactions (L = N-Heterocyclic Carbene).

Cationic imidazoliumyl(phosphonio)-phosphanides [L-P-PR] (, L = 4,5-dimethyl-1,3-diisopropylimidazolium-2-yl; R = alkyl, aryl) are obtained via the nucleophilic fragmentation of tetracationic tetraphosphetane [(L-P)][OTf] ([OTf]) with tertiary phosphanes. They act as [L-P] transfer reagents in phospha-Wittig-type reactions, when converted with various thiocarbonyls, giving unprecedented cationic phosphaalkenes [L-P═CR] ([OTf]) or phosphanides [L-P-CR(NR)] ([OTf]). Theoretical calculations suggest that three-membered cyclic thiophosphiranes are crucial intermediates of this reaction.

Ambient Temperature Carbene-Mediated Depolymerization: Stoichiometric and Catalytic Reactions of -Heterocyclic- and Cyclic(Alkyl)Amino Carbenes with Poly(-Methylaminoborane) [MeNH-BH].

The reactions of the -heterocyclic carbenes (NHCs) IDipp and IBu and the cyclic(alkyl)amino carbene (CAAC) CAAC with polyaminoborane [MeNH-BH] were investigated. Stoichiometric quantities of each carbene were found to cause rapid and complete depolymerization, with the major B-N-containing product identified as the NHC-aminoborane adduct, IDipp-BHNMeH (), cyclic borazane [MeNH-BH], or borazine [MeNBH] with IDipp, IBu, and CAAC, respectively. With substoichiometric quantities of IDipp and IBu (down to 10 and 2.

Metathesis of P=C Bonds Catalyzed by N-Heterocyclic Carbenes.

The catalytic metathesis of C=C bonds is a textbook reaction that has no parallel in the widely studied area of multiple bonds involving heavier p-block elements. A high-yielding P=C bond metathesis of phosphaalkenes (ArP=CPh , Ar=Mes, o-Tol, Ph) has been discovered that is catalyzed by N-heterocyclic carbenes (NHC=Me IMe, Me I Pr). The products are cyclic oligomers formally derived from ArP=PAr [i.

A thermolytic route to a polysilyne.

We report a safe and convenient method to prepare a new class of network polysilane, or polysilyne ([RSi]). Simple thermolysis of a readily accessible linear poly(phenylsilane), [PhSiH], affords polysilyne [PhSi] with concomitant evolution of monosilanes. This new polymer shows a hyperbranched structure with unique features not observed in known polysilynes prepared via hazardous Wurtz coupling routes.

Isolable Phosphaalkenes Bearing 2,4,6-Trimethoxyphenyl and 2,6-Bis(trifluoromethyl)phenyl as P-Substituents.

The multistep synthesis and characterization of new P═C analogues of olefins from readily available starting materials is reported. Specifically, the phosphaalkenes TMOP-P═CPh (: TMOP = 2,4,6-trimethoxyphenyl) and Ar-P═CPh [: Ar = 2,6-bis(trifluoromethyl)phenyl] have been prepared, isolated, and characterized. In addition, synthetically challenging intermediates, such as the corresponding pyrophoric primary phosphines and bis(trimethylsilyl)phosphines, have been isolated and characterized.

A Smart Phosphine-Diyne Polymer Displays "Turn-On" Emission with a High Selectivity for Gold(I/III) Ions.

A polymeric phosphine sensor is reported that exhibits bright blue fluorescence in the presence of gold(I/III) ions but is nonemissive with other metal ions. Specifically, solutions of a poly(-arylenediethynylene phosphine) copolymer are 35 or 94 times more emissive when treated with solutions of (tht)AuCl or HAuCl·3HO, respectively. Model compound studies confirm phosphine coordination to metals, including gold(I/III) and rhodium(I), and the selective "turn-on" fluorescence was investigated using time-dependent density functional theory calculations.

Diels-Alder reactions of 1-phosphabutadienes: a highly selective route to P[double bond, length as m-dash]C-substituted phosphacyclohexenes.

Kinetically stabilized 1-phosphahaloprenes (2-halo-1-phosphabutadienes) as well as 1-phosphaisoprene undergo a hitherto unknown phospha-Diels-Alder dimerization of the P[double bond, length as m-dash]C-C[double bond, length as m-dash]C units upon heating. The [4+2] cyclodimerization is highly stereo- and regio-selective. The phosphaalkene-substituted phosphacyclohexene product is an unprecedented P(sp),P(sp) ligand that is of interest in polymer/materials science and catalysis.

Ammonium and Potassium Salts of a Hexacoordinate Phosphorus(V) Anion Featuring P-O and P-C Bonds.

Ammonium and potassium salts featuring the chiral mer-[P(CHCO)], mer-[1], have been isolated. Specifically, treating phosphorane P(CHCO)(CHCOH), 2, with N-containing bases [N = PhNMe, PhNH, pyridine (py), isoquinoline, (-)-brucine, N( n-CH)] afforded ammonium salts [NH]- mer-[1]. Each compound was fully characterized spectroscopically, and four were subjected to X-ray crystallographic analysis.

Unconventional ionic ring-deconstruction pathways of a three-membered heterocycle.

Two different ionic deconstructions of a three-membered COP ring have been discovered. The first involves displacement of the C[double bond, length as m-dash]O unit (aldehyde elimination) induced by base whilst the second involves acid-initiated extrusion of the ring-carbon (2-methyl-2-butene). Insight into the latter deconstruction was obtained by quantum chemical calculations.

Free Radical Reactivity of a Phosphaalkene Explored Through Studies of Radical Isotopologues.

Muonium (Mu), an H atom analogue, is employed to probe the addition of free radicals to the P=C bond of a phosphaalkene. Specifically, two unprecedented muoniated free radicals, MesP -CMu(Me) (1 a, minor product) and MesPMu-C Me (1 b, major product), were detected by muon spin spectroscopy (μSR) when a solution of MesP=CMe (1: Mes=2,4,6-trimethylphenyl) was exposed to a beam of positive muons (μ ). The μ serves as a source of Mu (that is, Mu=μ +e ).

Phosphorus-Containing Block Copolymers from the Sequential Living Anionic Copolymerization of a Phosphaalkene with Methyl Methacrylate.

Although living polymerization methods are widely applicable to organic monomers, their application to inorganic monomers is rare. For the first time, we show that the living poly(methylenephosphine) (PMP ) anion can function as a macroinitiator for olefins. Specifically, the phosphaalkene, MesP=CPh (PA), and methyl methacrylate (MMA) can be sequentially copolymerized using the BnLi-TMEDA initiator system in toluene.

2-Aminophenolate ligands for phosphorus(v): a lithium salt featuring the chiral [P(OCHNR)] anion.

Phosphoranes P(OC6H4NR)2(OC6H4NHR) [R = Me (2a), Ph (2b), C6F5 (2c)] were synthesized by treating PCl5 with the respective 2-aminophenol derivative (1a-c, 3.1 equiv.).

Exploring the chemistry of backbone amino(chloro)phosphanyl-substituted imidazole-2-thiones.

Backbone (R'N)P-substituted imidazole-2-thiones 2a-c [(R'N)P-IMS; IMS = 1,3-dialkylimidazole-2-thione-4-yl, a: R = Pr, R' = Et; b: R = Mes, R' = Et, c: R = Me, R' = Pr] were treated with PCl to synthesize R'N(Cl)P-substituted imidazole-2-thiones 3a-c [R'N(Cl)P-IMS]. The P-chloro compounds 3a,b were used to explore the chemistry further, i.e.

[HL][P(1,2-OCCl)] (L = THF, DMF): Brønsted acid initiators for the polymerization of n-butyl vinyl ether and p-methoxystyrene.

The development of solid, weighable Brønsted acids featuring the hexacoordinated phosphorous(v) anion [TRISPHAT] are reported. H(DMF)[1] and H(THF)[1] {[1] = [P(1,2-OCCl)]} were synthesized and fully characterized by H, P, C and 2D-NOESY NMR spectroscopy, X-ray crystallography, mass spectrometry and elemental analysis. Both, H(DMF)[1] and H(THF)[1] are found to be suitable initiators for the polymerization of n-butyl vinyl ether and p-methoxystyrene.

Strong Evidence of a Phosphanoxyl Complex: Formation, Bonding, and Reactivity of Ligated Phosphorus Analogues of Nitroxides.

Facile access to [W(CO) (Ph P-OTEMP)] is used to initiate a study on the generation, properties, and reactions of transient phosphanoxyl complexes [ML (R PO)], the first example of which could be trapped via heterocoupling with the trityl radical. It is also demonstrated that the phosphorus nitroxyl complex acts as radical initiator in the polymerization of styrene. The quest for P-O versus O-N bond homolysis, as well as the initial steps of the polymerization were studied by DFT methods.

Copper(I) Complexes of Pyridine-Bridged Phosphaalkene-Oxazoline Pincer Ligands.

The synthesis of enantiomerically pure pyridine-bridged phosphaalkene-oxazolines ArP═C(Ph)(2,6-C5H3NOx) (1, Ar = Mes/Mes*, Ox = CNOCH(i-Pr)CH2/CNOCH(CH2Ph)CH2) is reported. This new ligand forms a κ(P), κ(2)(NN) dimeric complex with copper(I) (7) that dissociates into a cationic κ(3)(PNN) monomeric complex upon addition of a neutral ligand {[1a·CuL]OTf (8a-e): L = PPh3 (a), P(OPh)3 (b), 2,6-lutidine (c), 4-DMAP (d), 1-methylimidazole (e)}. The P-Cu bond lengths in 8 are influenced by the π-accepting/σ-donating properties of L, and this can be observed by changes in the δ(31)PP═C NMR shift.

Homo- and Heteropolynuclear Complexes Containing Bidentate Bridging 4-Phosphino-N-Heterocyclic Carbene Ligands.

The abnormal reaction of phosphaalkenes with N-heterocyclic carbenes (NHC) offers a convenient method to introduce new functionality at the backbone of an NHC. The 4-phosphino-substituted NHC (1a) derived from 1,3-dimesitylimidazol-2-ylidene (IMes) and MesP═CPh2 is shown to be an effective bifunctional ligand for Au(I) and Pd(II). Several new complexes are reported: 2a: 1a·AuCCl, 3a: 1a·(AuCl)2, 4a: [(1a)2AuC]Cl, 5a: [(1a·AuPCl)2AuC]Cl], and 6a: 1a·(PdC) (AuPCl).

Even the normal is abnormal: N-heterocyclic carbene C(2) binding to a phosphaalkene without breaking the P=C π-bond.

The reaction of MesP=CPh2 with the least sterically demanding N-heterocyclic carbene (NHC = IMe) results in formation of the 'abnormal' (C(4)-substituted) 4-phosphino-NHC (1). In contrast, reaction with Me2IMe gives the unprecedented 'normal' C(2) adduct, Me2IMe → P(Mes)=CPh2 (2). Particularly striking is the asymmetric and weak bonding of the NHC to the P=C moiety in 2.

Polymers and the p-block elements.

A survey of the state-of-the-art in the development of synthetic methods to incorporate p-block elements into polymers is given. The incorporation of main group elements (groups 13-16) into long chains provides access to materials with fascinating chemical and physical properties imparted by the presence of inorganic groups. Perhaps the greatest impedance to the widespread academic and commercial use of p-block element-containing macromolecules is the synthetic challenge associated with linking inorganic elements into long chains.

Poly(p-phenylenediethynylene phosphane): A Phosphorus-Containing Macromolecule that Displays Blue Fluorescence Upon Oxidation.

Despite the challenges associated with their synthesis, hybrid inorganic-organic polymers featuring heavier main-group elements spaced by π-conjugated organic functionalities have garnered considerable recent attention due to their chemical functionality and novel photophysical properties. We have succeeded in the preparation of an unprecedented organophosphorus polymer possessing functional phosphane-di-yne moieties in the main chain. Namely, poly(p-phenylenediethynylene phosphane) (PPYP) is prepared using a nickel(II)-catalyzed P-C bond-forming reaction.

Synthesis of an imidazolium phosphanide zwitterion and its conversion into anionic imidazol-2-ylidene derivatives.

Matter of opinion: The novel zwitterion 1 has been synthesized and studied theoretically and also converted into anionic NHCs 2. The former can also be described as a phosphinidene adduct of an abnormal N-heterocyclic carbene (1') and, in the same vein, the latter represents a phosphinidene adduct of an anionic N-heterocyclic dicarbene (2').