A remarkably stable acyclic phosphamethine cyanine dye.

While cyanine dyes enjoy a multitude of uses in science and technology, their phosphorus analogues, phosphamethine cyanine dyes, have not yet found benchtop applications primarily because of their sensitivity to air and moisture. We are excited to report full characterization of an extraordinarily stable acyclic phosphamethine cyanine dye. Nitrile substituents on the N-heterocyclic framework afford air and water stability as well as resistance to methylation and sulfuration even under forcing conditions.

Triphosphenium salts: air-stable precursors for phosphorus(I) chemistry.

The chemistry of low-coordinate phosphorus-containing species is an area of intense interest in modern main group chemistry. While typical routes for accessing such species include pyrophoric phosphorus-centered precursors or harsh reducing agents, triphosphenium cations represent a more convenient and safer alternative. This Perspective summarizes the use of air- and moisture-stable triphosphenium salts of [dppeP]+ as a source of P+ ions for the generation of a variety of new and/or useful low-coordinate phosphorus-containing species.

The phosphinoboration of acyl chlorides.

This investigation examines the reactivity of phosphinoboronate esters Ph2PBpin (pin = 1,2-O2C2Me4) and Ph2PBcat (cat = 1,2-O2C6H4), as well as other phosphinoboron species, with various aryl and aliphatic acyl chlorides. These reactions proceed smoothly to give acyl phosphines of the type RC(O)PR'2 along with loss of a boron-chloride compound. In some cases, a second equivalent of the phosphinoboron species can add to the C[double bond, length as m-dash]O double bond at elevated temperatures to give the corresponding diphosphines RC(OBR''2)(PR'2)2.

Phosphonium-Templated Iodoplumbates.

A new family of iodoplumbates based on phosphonium cations have been synthesized and characterized via X-ray crystallography. Thermogravimetric analysis demonstrates that these materials have a remarkably high thermal stability and show potential for applications as organic-inorganic hybrid semiconductors. We also present the synthesis of three novel phosphonium salts and the crystallographic elucidation of these compounds.

2,6-Bis(benzimidazol-2-yl)pyridine complexes of group 14 elements.

Treatment of MCl (M = Ge or Sn) with 2,6-bis(benzimidazol-2-yl)pyridine (G-BZIMPY, G = NBn, N(3,5-CF)Bn, NAllyl and O) yielded the self-ionization products [G-BZIMPYMCl][MCl] (1-6) in high yields (75-98%). Reduction reactions are examined and the nickel complexes 8 and 9 ([(NBn-BZIMPY)Ni][MCl]) are isolated from the reaction of Ni(COD) with 1 and 2 respectively. [NBn-BZIMPYSnCl][SnCl] shows a significantly stronger MLCT band in the UV-vis absorption spectrum than its germanium counterparts, with germanium complexes exhibiting negative solvatochromism that is not observed in tin complexes.

2,6-Bis(benzimidazol-2-yl)pyridines as more electron-rich and sterically accessible alternatives to 2,6-bis(imino)pyridine for group 13 coordination chemistry.

Treatment of GaCl3 with 2,6-bis(benzimidazol-2-yl)pyridine (G-BZIMPY, G = NBz, N(3,5-CF3)Bz, N-allyl and O) yielded the autoionization products [G-BZIMPYGaCl2][GaCl4] (1-4) in great yields. The Ga(iii) complex 1 was reduced to Ga(i) using K2[Fe(CO)4], resulting in the complex [(NBzBZIMPY)(Cl)Ga-Fe(CO)4] (7). GaCl3 and AlCl3 were complexed by the structurally similar bis(imino)pyridine (DIMPY) and the resulting complexes are compared to those of G-BZIMPY.

Diphosphoniodiphosphene Formation by Transition Metal Insertion into a Triphosphenium Zwitterion.

Treatment of two equivalents of the triphosphenium zwitterion L with sources of Ni and Pd form the mononuclear η -diphosphoniodiphosphene complexes 1 and 2. The reaction between L and [FeCp(CO) ] results in the binuclear μ-η :η -diphosphoniodiphosphene iron complex 3, which features an alternative bonding motif of the diphosphoniodiphosphene unit. The formation of these species has been confirmed by spectroscopic methods and single-crystal X-ray diffraction analysis, and their electronic structures have been elucidated using computational methods.

Synthesis of Heteroleptic Phosphorus(I) Cations by P Transfer.

Reported are general synthetic approaches for the syntheses of asymmetrically substituted phosphorus(I) cations by P transfer from [dppeP] (dppe = 1,2-bis(diphenylphosphino)ethane). The first method grants access to acyclic derivatives and is accomplished by the sequential substitution of dppe using first a sterically encumbered ligand which cannot form a stable homoleptic complex, followed by a second equivalent of a less sterically demanding ligand. The second method grants access to cyclic derivatives and utilizes asymmetric hybrid phosphine/N-heterocyclic carbene ligands.

Synthesis of Heavy Dicyanamide Homologues from Air-Stable Precursors.

A convenient synthesis of dicyanophosphide and dicyanoarsenide anions is reported. These heavy homologues of the long-known and fundamentally important dicyanamide anion were formed through the nucleophilic displacement of bis(diphenylphosphino)ethane (dppe) from the pnictogen transfer agents [dppePn][BPh ] (Pn=P, As) by exposure to cyanide salts. The protocol requires three synthetic steps from commercially available materials and the [dppePn][BPh ] salts are remarkably temperature, air, and moisture stable.

Accessing multimetallic complexes with a phosphorus(i) zwitterion.

We present the synthesis of a zwitterionic triphosphenium molecule, Bu(CH)(PPh)P (L), which can act as a single- or multidentate ligand with group 6, 7, 8 and 9 metal carbonyl complexes. Group 6, [M(CO)L] complexes are formed under photolytic conditions, where the metal is bound at the P(i) center. In the case of Mo(CO), the bimetallic complex [M(CO)LMo(CO)] is generated, which features bonds to both the phosphorus(i) center and the cyclopentadienyl moiety of the molecule.

Assessing the Ligand Properties of NHC-Stabilised Phosphorus(I) Cations.

The isolation and full characterisation of a series of cationic metal-carbonyl complexes bearing an N-heterocyclic carbene stabilised phosphorus(I) ligand are reported. Specifically, the mononuclear coordination complexes [LM(CO) ][BPh ] (M=Cr, Mo, W), [LFe(CO) ][BPh ] and the dinuclear complexes [LMn (CO) ][BPh ] and [LCo (CO) ][BPh ], in which L=[bis(1,3,4,5-tetramethylimidazol-2-ylidene)phosphanide] , have all been isolated in the solid state and structurally confirmed by single-crystal X-ray diffraction. The dicationic platinum complex trans-[L PtCl ][BPh ] is also reported and fully characterised.

Preparation and Reactivity of a Triphosphenium Bromide Salt: A Convenient and Stable Source of Phosphorus(I).

We present herein the optimized synthesis of a triphosphenium bromide salt. Apart from being a versatile metathesis reagent, this unusually stable low-valent-phosphorus-containing compound acts as a useful P transfer agent. Unlike traditional methods employed to access low-coordinate phosphorus species which usually require pyrophoric phosphorus-containing precursors (white phosphorus, Tris(trimethylsilyl)phosphine, etc.

Convenient Preparation and Detailed Analysis of a Series of NHC-Stabilized Phosphorus(I) Dyes and Their Derivatives.

A safe, convenient, and P-atom-efficient synthesis of N-heterocyclic-carbene- (NHC-) stabilized phosphorus(I) bromide salts is reported that involves P(+) transfer from an easily prepared triphosphenium precursor. The resulting family of phosphamethine cyanine dyes featuring N,N'-dialkyl-substituted 4,5-dimethylimidazole-2-ylidenes ((R)NHC(Me)) and benzimidazole-2-ylidenes ((R)NHC(B)) (R = Me, Et, iPr) have been fully characterized. We found that increasing N-alkyl group size causes increased twisting of the carbene fragments from the C-P-C plane, which decreases the magnitude of hyperconjugation between the π-type lone pair on phosphorus and the carbene fragments.

A simple route to phosphamethine cyanines from S,N-heterocyclic carbenes.

Although salts of thiazolium cations are known, many readily prepared iodide salts have eluded spectroscopic and structural characterization; herein, data for a variety of such salts are reported. It has been demonstrated that thiazolium cations can be deprotonated to generate S,N-heterocyclic carbenes and their "electron rich olefin" dimers, but use of the former has been largely overshadowed by that of the more common N-heterocyclic carbenes. We report herein that the deprotonation of thiazolium iodides and their subsequent reaction with a conveniently prepared triphosphenium precursor grants phosphamethine cyanine cations with solid-state geometry and electronic structure unlike those of NHC-stabilized cations.

Remarkably stable chelating bis-N-heterocyclic carbene adducts of phosphorus(i) cations.

A convenient one-pot synthesis of chelating bis-N-heterocyclic carbene-ligated P(I) salts is described. The solid state structures of these remarkably stable phosphamethine cyanine dyes with various N-alkyl groups and counter-anions are reported, and initial reactivity results are discussed.