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The first long-term air- and moisture-stable phosphamethine cyanine salt is obtained through the use of 4,5-dicyanoimidazolium ligands.

This study reports on the exploration of the phosphinoboration reaction with several thiosemicarbazones (R5R4NC(S)NR3N=CR1R2). Reactions between either Ph2PBpin (pin = 1,2-O2C2Me4) or Ph2PBcat (cat = 1,2-O2C6H4) with thiosemicarbazones containing a terminal primary or secondary amine afforded boron-containing heterocyclic 1,3,4-thiadiazoline products in excellent yield. The addition of Ph2PBpin to thiosemicarbazones containing an NMe2 group in the terminal position generated novel five-membered heterocycles in moderate yield, which included boron, sulfur, and nitrogen atoms. Heterocyclization of the thiosemicarbazones occurs preferentially in the presence of functional groups such as acetyl and pyridyl groups.

The uncatalyzed addition of catecholborane to α-diimines has been examined. Reactions proceed smoothly at room temperature in the absence of a catalyst or additive, providing bis-hydroboration products with 3-coordinate boron centres or mono-hydroboration products with 4-coordinate boron centres, depending on the nature of the diimine reagent.

Catenation is common for the light main-group elements whereas it is rare for the heavy elements. Herein, we report the first example of a neutral molecule containing a Bi4 chain. It is prepared in a one-step reaction between bismuth trichloride and bis(diisopropylphosphino)amine in methanol suspension. The same reaction carried out in dichloromethane gives quite different products. All products have been characterized spectroscopically and using single-crystal X-ray analysis.

The preparation of a series of 4,4',5,5'-substituted benzo-fused 1,2,5,6-tetrathiocins X2C6H2S4C6H2X2 (1a-1g) were prepared from the reaction of S2Cl2 with 1,2-C6H4X2 (X = OMe, OEt; X2 = OCH2O, OCH2CH2O, OCH2CH2CH2O, MeNC([double bond, length as m-dash]O)NMe, O(CH2CH2O)4). The oxidative addition of 1a-1g to zero-valent Pd2dba3 or Pt2dba3 (dba = dibenzylideneacetone) in the presence of bis (diphenylphosphino)ethane (dppe) resulted in formation of the substituted mononuclear benzenedithiolate complexes M(L)(dppe) [L = dithiolate ligand; 2a-2g (M = Pd) and 3a-3g (M = Pt)] in 37-89% yield based on recrystallized material. Representative examples of M(L)(dppf) [dppf = bis-diphenylphosphinoferrocene; 4a, 4g (M = Pd) and 5g (M = Pt)] were prepared in a similar fashion. The structures of all derivatives were determined by X-ray diffraction, multinuclear NMR and elemental analysis. The reactivity of the two crown ether dithiolate complexes, 2g and 4g, with 1 equivalent of NaBPh4 led to isolation of the 1 : 1 complexes in which the Na+ cation is bound in the macrocyclic crown, [Na(2g)(MeOH)2][BPh4] and [Na(4g)][BPh4] whose structures were determined by X-ray diffraction. Electrochemical studies supported through DFT calculations on the crown ether derivatives revealed a series of ligand-based oxidation waves corresponding to the dithiolate ligand (and dppf for 4g and 5g) whose redox potentials were shifted by ca. +0.1 V on binding to Na+.

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. These ambiphilic diphosphines behave like substituted (1,1-bis(diphenylphosphino)methane) derivatives in a reaction of PhC(OBpin)(PPh2)2 (2a) with (η5-C9H7)Rh(η2-coe)2 (coe = cis-cyclooctene) affording the indenyl rhodium complex (η5-C9H7)Rh(PhC(OBpin)(PPh2)2) (3a) where the phosphines are bound to the metal centre in a κ2-P,P bidentate manner.

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. These range from phosphorus-rich oligomers to phosphamethine cyanine dyes. Special emphasis is placed on the electronic structure of the newly generated species as well as their subsequent reactivity.

The reductive dehalogenation of a zwitterionic GeII species to make a zwitterionic GeI dimer with a 1,2-dicationic core is reported herein. To the root of the stability of this compound, the molecular and electronic structures were comprehensively characterized and investigated using crystallographic, spectroscopic, and computational methods. It was determined that the Ge centers are attracted because they are both electron-rich and positively charged. A comparison to the electronic structure in triphosphenium cations revealed varying degrees of covalent bonding and that this difference can be distinguished spectroscopically.

We have investigated the addition of a simple phosphinoboronate ester, Ph2PBpin (pin = 1,2-O2C2Me4), to 2-diphenylphosphinobenzaldehyde (2-Ph2PC6H4C(O)H) and related aldimine derivatives (2-Ph2PC6H4C(NR)H) as a simple and effective strategy for generating unique diphosphine ligands bearing a pendant Lewis-acid Bpin group. These reactions proceed selectively to give one new product where the phosphide fragment has added to the aldehyde (or imine) carbon atom and the electron-deficient boron group has added to the electron-rich heteroatom. Preliminary studies show these new compounds can ligate to Pd(II) and Pt(II) metal centres. These novel metal complexes, as well as the organic soluble [MCl2(coe)]2 (M = Pd, Pt, coe = cis-cyclooctene) compounds, have been shown to be effective precatalysts in the cyclisation of alkynoic acids to give the corresponding exo-dig cyclic lactones. Reactions employing these metal complexes also generated unusual endo-dig cyclic lactones not traditionally observed in these cyclisation reactions. For instance, reactions of 4-pentynoic acid also afforded significant amounts of α-angelica lactone, a biologically-important compound traditionally prepared via the catalytic dehydration and cyclisation of levulinic acid.

Treatment of MCl2 (M = Ge or Sn) with 2,6-bis(benzimidazol-2-yl)pyridine (G-BZIMPY, G = NBn, N(3,5-CF3)Bn, NAllyl and O) yielded the self-ionization products [G-BZIMPYMCl][MCl3] (1-6) in high yields (75-98%). Reduction reactions are examined and the nickel complexes 8 and 9 ([(NBn-BZIMPY)2Ni][MCl3]2) are isolated from the reaction of Ni(COD)2 with 1 and 2 respectively. [NBn-BZIMPYSnCl][SnCl3] 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.

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.

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.

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. Interplay between the different ligand types and their stoichiometries relative to those of [dppeP]+ also allows for the isolation of symmetrical derivatives with pendant phosphines.

A series of germanium(II) and tin(II) bromide polyether complexes have been synthesized. Specifically, [GeBr([15]crown-5)][GeBr3], [GeBr([18]crown-6)][GeBr3], [GeBr(triglyme)][GeBr3], [GeBr(tetraglyme)][GeBr3], [SnBr([18]crown-6)][SnBr3], [Sn([15]crown-5)2][SnBr3]2, [SnBr(triglyme)][SnBr3], and [SnBr(tetraglyme)][SnBr3] have been fully characterized including by single crystal X-ray diffraction. The synthesis of [GeBr(dibenzo[24]crown-8)][GeBr3] and [GeCl(dibenzo[24]crown-8)][GeCl3] are also reported, along with the crystal structure of the latter’s water adduct, which features a water molecule adjacent to the GeCl+ ion within the cavity of the crown ether.

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)5 ][BPh4 ] (M=Cr, Mo, W), [LFe(CO)4 ][BPh4 ] and the dinuclear complexes [LMn2 (CO)8 ][BPh4 ] and [LCo2 (CO)6 ][BPh4 ], 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-[L2 PtCl2 ][BPh4 ]2 is also reported and fully characterised. The donor ability of [L]+ has been assessed by IR spectroscopy of its metal-carbonyl complexes and by using DFT calculations. The results suggest that [L]+ is a weak π-acceptor with moderate donor strength and thus it bridges the gap that exists between phosphines and amines in terms of ligand properties. Collectively, these molecules represent the first crystallographically characterised cationic metal-carbonyl derivatives of a PI -centred ligand and are a rare collection of cationic metal-carbonyl complexes.

A series of cationic complexes involving a pnictogen(III) (Pn = P, As, Sb) centre and the tetradentate ligand tris((1-ethyl-benzoimidazol-2-yl)methyl)amine (BIMEt3) have been synthesized and comprehensively characterized. Oxidation of [P(BIMEt3)]3+ with XeF2 provides access to [PF2(BIMEt3)]3+ representing the first structurally characterized example of a phosphorus(V) centred trication.

A series of complexes with the formulae [(BIMEt3)SnF4-x][OTf]x with x = 1-4 has been synthesized by successive fluoride abstraction from SnF4 with TMSOTf in the presence of the tetradentate nitrogen donor BIMEt3 (tris ((1-ethyl-benzoimidazol-2-yl)methyl)amine). Single crystal X-ray diffraction and heteronuclear NMR spectroscopic analysis provided insight into these new main group cations. Electrospray ionization mass spectrometric analysis on solutions containing the different salts allowed for successful detection of the cations [(BIMEt3)SnF]3+, [(BIMEt3)SnF2]2+ and [(BIMEt3)SnF3]+.

Conformationally flexible cores that generate large free volume when stacked and have an insufficient number of side-chains for filling the lateral space around each core have been proposed as desi...

The manipulation of white phosphorus (P4) has been a long-standing challenge for chemists. While the holy grail remains at finding a method to catalytically activate and functionalize P4 to yield new organophosphorus compounds, fundamental research lies in developing procedures to control the reactivity of elemental phosphorus. In this work, Lewis acidic transition metal moieties M(CO)5 (M = Cr, Mo, W) and AuCl react with P4 derivatized with a low valent germanium compound. For both M(CO)5 and AuCl, bis-functionalized products can be formed; however the monosubstituted derivatives are found to be more stable, and the decomposition can be monitored by 31P{1H} NMR spectroscopy. The selective reactivity of white phosphorus, once a P–P bond has been activated, is a key step in yielding new organophosphorus compounds.

The transition metal-free addition of phosphinoboronate ester Ph2PBpin (pin = 1,2-O2C2Me4) to heterocumulenes including carbodiimides, isocyanates, isothiocyanates and carbon dioxide has been investigated. The corresponding 1,2-addition products were readily prepared at room temperature without the need of a catalyst or added base. Addition of methanol to the compounds derived from addition of Ph2PBpin to carbodiimides, isocyanates, and isothiocyanates resulted in traditional hydrophosphination products. The methodology developed in this study provides a simple and elegant route for the generation of a wide range of functionalized phosphines. The phosphinoboronate ester Ph2PBpin also selectively and reversibly adds to CO2 at room temperature in a 1,2-manner.

The reductive dehalogenation of a zwitterionic Ge

Herein we present the oxidation of base-stabilized tetrelII dications [LM][OTf]2 [L = BIMEt3 = tris(1-ethyl-benzoimidazol-2-ylmethyl)amine and M = Ge, Sn] with PCl5, SeCl4, Br2, and I2 to access di...

Treatment of two equivalents of the triphosphenium zwitterion L with sources of Ni0 and Pd0 form the mononuclear η2 -diphosphoniodiphosphene complexes 1 and 2. The reaction between L and [FeCp(CO)2 ]2 results in the binuclear μ-η1 :η1 -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.

A series of complexes with the formulae [(BIMEt3)SnF4-x][OTf]x with x = 1-4 has been synthesized by successive fluoride abstraction from SnF4 with TMSOTf in the presence of the tetradentate nitrogen donor BIMEt3 (tris ((1-ethyl-benzoimidazol-2-yl)methyl)amine). Single crystal X-ray diffraction and heteronuclear NMR spectroscopic analysis provided insight into these new main group cations. Electrospray ionization mass spectrometric analysis on solutions containing the different salts allowed for successful detection of the cations [(BIMEt3)SnF]3+, [(BIMEt3)SnF2]2+ and [(BIMEt3)SnF3]+.

The synthesis and characterization of a series of 1,4-dialkyl-1,2,4-triazolium iodide and tetraphenylborate salts featuring methyl, ethyl, and isopropyl substituents and their use as precursors, in conjunction with triphosphenium reagents, to generate 1,4-dialkyl-1,2,4-triazol-5-ylidene-stabilized phosphorus(I) ions is described. The use of tetraphenyl borate salts of both reagents produces the most pure products. The structural and spectroscopic features of the products are compared to those of analogous ions featuring 1,3-imidazol-2-ylidene ligands.

Notable aspects of the chemistry of complexes of polyether ligands including crown ethers, cryptands, glycols, glymes, and related polyether ligands with heavier group 13 and 14 elements are reviewed with a focus on results from 2005 to the present. The majority of reported polyether complexes contain lead(ii) and thallium(i) but recent breakthroughs in regard to the preparation of low oxidation state reagents of the lighter congeners have allowed for the generation of complexes containing indium(i), gallium(i), germanium(ii), and even silicon(ii). The important roles of ligand size, donor types, and counter anions in regard to the chemical properties of the polyether complexes is highlighted. A particular focus on the structural aspects of the numerous coordination complexes provides a rationale for some of the spectacular contributions that such compounds have made to Modern Main Group Chemistry.

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][BPh4 ] (Pn=P, As) by exposure to cyanide salts. The protocol requires three synthetic steps from commercially available materials and the [dppePn][BPh4 ] salts are remarkably temperature, air, and moisture stable. All products have been fully characterized by spectroscopic methods and by single-crystal X-ray diffraction, and the electronic structures of the DCPn anions have been assessed computationally.

A tris((1-ethyl-benzoimidazol-2-yl)methyl)amine (BIMEt3) complex of P3+ is oxidized with XeF2 to access [PF2(BIMEt3)]3+ representing the first structurally characterized example of a phosphorus(v)3+ cation., A series of cationic complexes involving a pnictogen(iii) (Pn = P, As, Sb) centre and the tetradentate ligand tris((1-ethyl-benzoimidazol-2-yl)methyl)amine (BIMEt3) have been synthesized and comprehensively characterized. Oxidation of [P(BIMEt3)]3+ with XeF2 provides access to [PF2(BIMEt3)]3+ representing the first structurally characterized example of a phosphorus(v) centred trication.

The synthesis and characterization of the tris(1-ethyl-benzoimidazol-2-ylmethyl)amine (BIMEt3 = L) complex of Ge(ii)2+ is described. Oxidation of [LGe]2+ with Selectfluor gives [LGeF2]2+, in a process that is envisaged to involve a tricationic complex [LGeF]3+ as an intermediate, which has been isolated by fluoride ion abstraction from [LGeF2]2+.

We present the synthesis of a zwitterionic triphosphenium molecule, tBu(C5H2)(PPh2)2PI (L), which can act as a single- or multidentate ligand with group 6, 7, 8 and 9 metal carbonyl complexes. Group 6, [M(CO)5L] complexes are formed under photolytic conditions, where the metal is bound at the P(I) center. In the case of Mo(CO)6, the bimetallic complex [M(CO)5LMo(CO)3] is generated, which features bonds to both the phosphorus(I) center and the cyclopentadienyl moiety of the molecule. Interestingly, group 7 and 9 metal carbonyl dimers generate bimetallic complexes in the form [M2(CO)nL], where both metal centers are bound at the phosphorus(I) center. A detailed analysis of these molecules is provided, including X-ray diffraction, multinuclear NMR, infrared spectroscopy and computational investigations.

The phosphorus-sulfur heterocycles 1,2-thiaphosphetenes and phosphirene sulfides have been prepared, and represent the first structurally characterized derivatives for either class of compound. These strained P-S ring systems are formed by the reaction of a phosphinidene sulfide and alkyne. Using an internal alkyne, only the 3-membered PV , phosphirene sulfide was produced, whereas a terminal alkyne yielded a mixture of phosphirene sulfide and 1,2-thiaphosphetene (PIII ). Detailed computational analysis revealed that for numerous derivatives of alkynes, the corresponding 4-membered rings are always more stable than the 3-membered isomers. The electronic nature of "free" phosphinidene sulfides (R-P=S) is discussed based on computational results.

The manipulation of white phosphorus (P

The synthesis of novel bis(trithio)phosphines is achieved by oxidative addition of tetrathiocins to the phosphorus(I) reagent [PIdppe][Br] in good yields under ambient conditions. These bis(trithio)phosphines and the related intermediate diphosphine species are characterized by X-ray diffraction and multinuclear NMR and a mechanism is proposed for the formation of these molecules. In contrast, the related reaction with diphenyldisulfide produces a mononuclear tris(phenylthio)phosphine.

Two unique systems based on low-coordinate main group elements that activate P4 are shown to quantitatively release the phosphorus cage upon short exposure to UV light. This reactivity marks the first reversible reactivity of P4, and the germanium system can be cycled 5 times without appreciable loss in activity. Theoretical calculations reveal that the LUMO is antibonding with respect to the main group element-phosphorus bonds and bonding with respect to reforming the P4 tetrahedron, providing a rationale for this unprecedented activity, and suggesting that the process is tunable based on the substituents.

115In solid-state NMR (SSNMR) spectroscopy is applied to characterise a variety of low oxidation-state indium(i) compounds. 115In static wideline SSNMR spectra of several In(i) complexes were acquired with moderate and ultra-high field NMR spectrometers (9.4 and 21.1 T, respectively). 115In MAS NMR spectra were obtained with moderate and ultra-fast (>60 kHz) spinning speeds at 21.1 T. In certain cases, variable-temperature (VT) 115In SSNMR experiments were performed to study dynamic behaviour and phase transitions. The indium electric field gradient (EFG) and chemical shift (CS) tensor parameters were determined from the experimental spectra. With the aid of first principles calculations, the tensor parameters and orientations are correlated to the structure and symmetry of the local indium environments. In addition, calculations aid in proposing structural models for samples where single crystal X-ray structures could not be obtained. The rapidity with which high quality 115In SSNMR spectra can be acquired at 21.1 T and the sensitivity of the 115In NMR parameters to the indium environment suggest that 115In SSNMR is a powerful probe of the local chemical environments of indium sites. This work demonstrates that 115In NMR can be applied to a wide range of important materials for the purpose of increasing our understanding of structures and dynamics at the molecular/atomic level, especially for the characterisation of disordered, microcrystalline and/or multi-valence solids for which crystal structures are unavailable. This journal is © The Royal Society of Chemistry 2014.

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.), or harsh reducing agents (alkali metals, potassium graphite, etc.), the current approach does not involve pyrophoric or explosive reagents and can be done on large scales (>20 g) in excellent yields by undergraduates with basic air-free synthetic training. The bromide counter ion is readily exchanged with other anions such as tetraphenyl borate (described herein) using typical salt metathesis reagents to obtain materials with desired properties and reactivities. The versatility of this P+ transfer approach is exemplified by the reactions of these triphosphenium precursors with an N-heterocyclic carbene and an anionic bisphosphine, each of which readily displace the neutral bisphosphine to give an NHC-stabilized phosphorus(I) cation and a phosphorus(I) containing zwitterion, respectively.

We report the formation and characterization of new self-assembled monolayers (SAMs) formed from dihexadecyldithiophosphate (C16) 2DDP and compare their properties with those of SAMs formed from the structurally similar adsorbate dihexadecyldithiophosphinic acid (C 16)2DTPA. The new (C16)2DDP SAMs were characterized using X-ray photoelectron spectroscopy, reflection-absorption infrared spectroscopy, contact angle measurements, and electrochemical impedance spectroscopy. The data indicate that (C16)2DDP forms SAMs on gold films formed by e-beam evaporation in which all adsorbates chelate to gold, in contrast to (C16)2DTPA SAMs, in which 40% of the adsorbates are monodentate. The alkyl chains of the (C 16)2DDP SAM are also less densely packed and ordered than those of the (C16)2DTPA SAM. To understand these differences, we present density functional theory calculations that show that there are only minimal differences between the geometric and electronic structures of the two adsorbates and that the energetic difference between monodentate and bidentate binding of a gold(I) ion are surprisingly small for both adsorbates. This study leads to the conclusion that differences in intermolecular interactions within the SAM are the driving force for the difference in chelation between the two adsorbates. © 2013 American Chemical Society.

A collection of zwitterionic phosphanide metal carbonyl coordination complexes has been synthesized and fully characterized, representing the first isolated series of metal complexes for the triphosphenium family of compounds. The dicoordinate phosphorus atom of the zwitterion is formally in the +1 oxidation state and can coordinate to one metal, 2M (M = Cr, Mo, W) and 2Fe, or two metals, a Co2(CO)6 fragment 4, depending on the starting reagents. All complexes have been isolated in greater than 80% yield, and structures were confirmed crystallographically. Metrical parameters are consistent with 1 being a weak donor and results in long metal-phosphorus bonds being observed in all cases. Unique bimetallic structures, 3M (M = Cr, Mo, W), consisting of a M(CO)5 fragment on phosphorus and a piano-stool M(CO)3 fragment on a boron phenyl group have been identified in the (31)P{(1)H} NMR spectra and confirmed using X-ray diffraction studies. Use of the borate backbone in 1, which renders the molecule zwitterionic, proves to be a determining factor in whether these metal complexes will form; the halide salt of a cationic triphosphenium ion, 6[Br], shows no evidence for formation of the analogous metal complexes by (31)P{(1)H} NMR spectroscopy, and tetraphenylborate salts, 6[BPh4] and 7[BPh4], produce complexes that are unstable.

Attempts to coordinate neutral ligands to low oxidation state indium centers are often hindered by disproportionation pathways that produce elemental indium and higher oxidation state species. In contrast, we find that reactions of the salt, InOTf (OTf=trifluoromethanesulfonate), with α-diimine ligands yielded intensely colored compounds with no evidence of decomposition. X-ray structural analysis of InOTf⋅(Mes) DAB(Me) ((Mes) DAB(Me) =N,N-dimesityl-2,3-dimethyl-diazabutadiene; 1) reveals a discrete molecular compound with a pyramidal coordination environment at the indium center, consistent with the presence of a stereochemically active lone pair of electrons on indium and a neutral diazabutadiene chelate ligand. The use of the less-electron-rich (Mes) DAB(H) ligand ((Mes) DAB(H) =N,N-dimesityl-diazabutadiene) engenders dramatically different reactivity and produces a metallopolymer (InOTf⋅(Mes) DAB(H) )∞ (2) linked via CC and InIn bonds. The difference in reactivity is rationalized by cyclic voltammetry and DFT studies that suggest more facile electron transfer from In(I) to the (Mes) DAB(H) and bis(aryl)acenaphthenequinonediimine (BIAN) ligands. Solution EPR spectroscopy indicates the presence of non-interacting ligand-based radicals in solution, whereas solid-state EPR studies reflect the presence of a thermally accessible spin triplet consistent with reversible CC bond cleavage.

Comparison of experimental and theoretical parameters pertaining to structural and spectral properties of two nickel(II) complexes containing triphenylphosphine and 5-methyl-N-(2-mercaptophenyl)salicylideneimine (1) or 5-chloro-N-(2-mercaptophenyl)salicylideneimine (2) are presented. The calculated structural results of these complexes show that the DFT can well reproduce the structure of title compounds. The UV, IR and NMR spectra of the title compounds are determined using both experimental and theoretical methods. The optical absorption properties of the title compounds are calculated using time-dependent density functional theory method (TD-DFT). The IR spectra are calculated from the harmonic vibrational frequencies at the ground-state geometry of the title-compounds. The NMR spectra are calculated using the gauge-independent atomic orbital (GIAO) method. The results calculated using theoretical methods coincide well with the experimental results.

Square planar palladium(II) complexes of the type [Pd(L)(PPh3)] (1–6) (where L is the dianion of N-(2-mercaptophenyl)salicylideneimine or 5-substituted-N-(2-mercaptophenyl)salicylideneimine or N-(2-mercaptophenyl)naphthylideneimine) have been synthesised from the reactions between [Pd(PPh3)4] and H2L in dichloromethane–ethanol mixture. The new complexes have been characterized by analytical and spectral (electronic, IR, 1H, 13C{1H} and 31P{1H} NMR spectroscopy) techniques. The structures of three complexes (1, 2 and 6) have been solved by single-crystal X-ray diffraction experiments which indicate square planar coordination geometries around palladium(II) by O, N, S and P donor atoms. The palladium(II) complexes (1–6) exhibited good catalytic activity in Suzuki–Miyaura cross-coupling reaction between phenylboronic acid and 4-bromotoluene in N,N-dimethylacetamide at 100 °C. Complex 3 (1 mol%) was found to be the most active and hence was used for probing the scope of possible substrates. Heterocyclic boronic acid and heterocyclic aryl bromides have also been used as substrates to provide heterocyclic biaryls.

Go for the gold! Incorporating a borate anion into the backbone of a triphosphenium cation produces a unique zwitterionic phosphanide that can coordinate to one or two {AuCl} fragments depending on the steric bulk of the ligand (see picture; Au yellow, P purple, Cl green). Computational investigations show that in this μ-type ligand, the phosphorus atom behaves only as a σ,π donor.

Notable aspects of the chemistry of complexes of polyether ligands including crown ethers, cryptands, glycols, glymes, and related polyether ligands with heavier group 13 and 14 elements are reviewed with a focus on results from 2005 to the present. The majority of reported polyether complexes contain lead(II) and thallium(I) but recent breakthroughs in regard to the preparation of low oxidation state reagents of the lighter congeners have allowed for the generation of complexes containing indium(I), gallium(I), germanium(II), and even silicon(II). The important roles of ligand size, donor types, and counter anions in regard to the chemical properties of the polyether complexes is highlighted. A particular focus on the structural aspects of the numerous coordination complexes provides a rationale for some of the spectacular contributions that such compounds have made to Modern Main Group Chemistry.