Structural Diversity and Rare η1 Cu-C Interactions in CuI Complexes of 1,2,3-Triazole-Functionalized Bisphosphines.

This manuscript describes the synthesis of copper complexes of 1,2,3-triazolyl-phosphines: o-Ph2P(C6H4){1,2,3-N3CC6H5)C(PPh2)} (L1), (C6H5){1,2,3-N3C(C6H4(o-PPh2))-C(PPh2)} (L2), 3-Ph2P(C5H3N){1,2,3-N3C(C6H5)C(PPh2)} (L3), o-Ph2P(C6H4){1,2,3-N3C(C5H5N)C(PPh2)} (L4), and {(3,5-Ph2PC6H4-o)21,2,3-N3CCH} (L5). The reactions of L1-L3 with CuI salts afforded dimeric complexes having the general formula [Cu2(µ -X)2L2] (L = L1, X = Cl, Br and I: 1 - 3; L= L2, X = Cl, Br and I: 4- 6; L = L3; X = Cl, Br, and I: 7-9). The reaction of L4 with CuI in a 1:2 molar ratio afforded 1D-coordination polymer [{(CuI)2{o-Ph2P(C6H4){1,2,3-N3C(C5H5N)C(PPh2)}-µ-((k1-N)(k2-P,P))}}]n (10). The reaction of L5 with cuprous halides (CuX) (X = Br, I) yielded mononuclear complexes [CuX{(3,5-Ph2PC6H4-o)21,2,3-N3CCH}-κ2P,P] (X = Br, 12; I, 13). Crystal structures of complexes 12 and 13 showed close interactions between CuI and the triazole C7 carbon. These relatively short Cu···C7 separations may be due to the η1-C interaction (dπ-pπ bond) between the triazolic carbon atom (via pz orbital) and CuI or three-centered two-electron interaction between CuI and the triazolic C-H bond. The existence of the Cu···C interaction was further evinced by the QTAIM analysis in compounds 12 and 13.

CuI-amidobis(phosphine) catalyzed C(sp3)-C(sp3) direct homo- and hetero-coupling of unactivated alkanes via C(sp3)-H activation.

Herein, we present a CuI-dimer, [CuI{Ph2PC6H4C(O)NC6H4PPh2-o}]2, which catalyzed direct C(sp3)-H homocoupling of benzyl and cycloalkane derivatives with excellent yields and regio-selectivity. The method is very simple and tolerates various functionalities. Synergistic metal-ligand cooperativity was observed in Cu-N bond cleavage and protonation of nitrogen, and facilitates a bifunctional pathway, minimising the free energy corrugation for catalytic intermediates.

CuI-Amidobis(phosphine)-Catalyzed Direct Amidation of Unactivated Alkanes via C(sp3)-H Activation.

Herein, we describe an acid-base-free, sustainable, and efficient method for direct amidation of unactivated alkanes and toluene derivatives, using the dimeric CuI complex [CuI{o-Ph2PC6H4CONC6H4PPh2-o}2] (here onward referred to as [PNP-Cu]2). Using this method, C(sp3)-N bond formation was achieved through the activation of very challenging C(sp3)-H bonds in cycloalkanes, alkenes, allyl groups, and benzyl groups, with tolerance toward ketonic groups, heterocycles, and halide functionalities. One of the precatalysts, (PNHP-Cu-Npht) was isolated and structurally characterized. Isomerization in allyl-functionalized alkanes and selective benzylic alkylation in ketones were observed. This is a novel method for C(sp3)-N bond formation via direct N-alkylation of phthalimide, sulfonamide, benzamide, and phosphamidate.

Catalytic utility of PNN-based MnI pincer complexes in the synthesis of quinolines and transfer hydrogenation of carbonyl derivatives.

This manuscript describes the synthesis of a triazolyl-pyridine-based phosphine, N-((diphenylphosphaneyl)methyl)-N-methyl-6-(1-phenyl-1H-1,2,3-triazol-4-yl)pyridin-2-amine, [2,6-{(PPh2)CH2N(Me)(C5H3N)(C2HN3C6H5)}] (1) (here onwards referred to as PNN) and its cationic and neutral MnI complexes and catalytic applications. The reaction of 1 with Mn(CO)5Br afforded a cationic complex [Mn(CO)3(PNN)]Br (2), which is highly stable in solid state, but in solution it gradually loses one of the CO groups to form a neutral complex [Mn(CO)2(PNN)Br] (3). Complex 2 on treatment with AgBF4 also yielded a cationic complex [Mn(CO)3(PNN)]BF4 (4). These complexes efficiently promoted the synthesis of quinoline derivatives via acceptor-less dehydrogenative coupling of 2-aminobenzyl alcohol and ketones, with complex 3 showing the highest activity with a very low catalyst loading (0.03 mol%) at 110 °C. Complex 3 (0.5 mol%) also showed excellent catalytic activity in the transfer hydrogenation of ketones and aldehydes to form respective secondary and primary alcohols.

Copper(I) Complexes of Amide Functionalized Bisphosphine: Proximity Enhanced Metal-Ligand Cooperativity and Its Catalytic Advantage in C(sp3)-H Bond Activation of Unactivated Cycloalkanes in Dehydrogenative Carboxylation Reactions.

The reactions of amide functionalized bisphosphine, o-Ph2PC6H4C-(O)N(H)C6H4PPh2-o (1) (BalaHariPhos), with copper salts is described. Treatment of 1 with CuX in a 1:1 molar ratio yielded chelate complexes of the type [CuX{(o-Ph2PC6H4C(O)N(H)C6H4PPh2-o)}-κ2-P,P] (X = Cl, 2; Br, 3; and I, 4), which on subsequent treatment with KOtBu resulted in a dimeric complex [Cu(o-Ph2PC6H4C(O)(N)C6H4PPh2-o)]2 (5). Interestingly, complexes 2-4 showed weak N-H···Cu interactions. These weak H-bonding interactions are studied in detail both experimentally and computationally. Also, CuI complexes 2-5 were employed in the oxidative dehydrogenative carboxylation (ODC) of unactivated cycloalkanes in the presence of carboxylic acids to form the corresponding allylic esters. Among complexes 2-5, halide-free dimeric CuI complex 5 showed excellent metal-ligand cooperativity in the oxidative dehydrogenative carboxylation (ODC) in the presence of carboxylic acids to form the corresponding allylic esters through C(sp3)-H bond activation of unactivated cycloalkanes. Mechanistic details of the catalytic process were established by isolating the precatalyst [Cu{(o-Ph2PC6H4C(O)(NH)C6H4PPh2-o)-κ2-P,P}(OOCPh)] (6) and fully characterized by mass spectrometry, NMR data, and single-crystal X-ray analysis. Density functional theory-based calculations further provided a quantitative understanding of the energetics of a series of H atom transfer steps occurring in the catalytic cycle.

Cationic and Neutral PdII and PtII Pincer Complexes of Phosphinamino-Triazolyl-Pyridine [PN(H)N]: Pincer Ligand-Stabilized Palladium Nanoparticles and Their Catalytic Annulation of Internal Alkynes to Indenones.

We describe the synthesis of a triazolyl-pyridine-based aminophosphine, N-(diphenylphosphaneyl)-6-(1-phenyl)-1H-(1,2,3-triazol-4-yl)pyridine-2-amine [2,6-{(PPh2)-N(H)(C5H3N)(C2HN3C6H5)}] [1, PN(H)N hereafter], and its palladium and platinum complexes and their catalytic application. The reaction of 1 with [M(COD)Cl2] (M = Pd or Pt) afforded the cationic complex [(MCl){PN(H)N}-κ3-P,N,N]Cl [M = Pd (2) or Pt (3)]. Alternatively, compounds 2 and 3 were also synthesized by treating [2,6-{H2N(C5H3N)(C2HN3C6H5)}] (A) with [M(COD)Cl2] (M = Pd or Pt), followed by the addition of stoichiometric amounts of PPh2Cl and Et3N. The neutral, dearomatized complexes [(MCl){PNN}-κ3-P,N,N] [M = Pd (4) or Pt (5)] were prepared by the deprotonation of the NH of 2 and 3 with 1 equiv of tBuOK. Compounds 4 and 5 were also synthesized stepwise by treating [2,6-{H2N(C5H3N)(C2HN3C6H5)}] (A) with [M(COD)Cl2] (M = Pd or Pt) to give intermediate complexes [{MCl2}2,6-{NH2(C5H3N)(C2HN3C6H5)-κ2-N,N}] [M = Pd (B) or Pt (C)], which were subsequently phosphinated. The in situ-generated PNN ligand-stabilized Pd nanoparticles from compound 2 catalyzed the annulation of o-bromobenzaldehyde with alkynes to yield indenone derivatives. Mechanistic investigations suggested that the reaction was catalyzed by Pd nanoparticles (Pd@2) generated from compound 2 and proceeded through sequential oxidative addition, alkyne insertion, and reductive elimination steps to produce indanone products.

Synthesis and characterization of the cyclodiphosphazane embedded macrocycle tetrabromo-resorcin[4]arene-tetrakis(cyclodiphosphazane) and its tetra-rhodium(I) complex.

The synthesis of a cyclodiphosphazane embedded macrocycle, tetrabromo-resorcin[4]arene-tetrakis(cyclodiphosphazane) [(µ-N(tBu)P)2{µ-(C6HBr(o-O)2-m-CHnBu)}]4 (1), and its tetra-rhodium(I) complex [(µ-N(tBu)P)2{µ-(C6HBr(o-O)2-m-CHnBu)}Rh(COD)Cl]4 (2) is described. The resorcin[4]arene backbone adopts a C4v symmetric crown conformation in 1, which transforms into a C2v symmetric boat conformation upon complexation with Rh(I) in the tetra-rhodium(I) complex 2, as evidenced by NMR spectroscopy and X-ray diffraction studies.

Synthesis and Photophysical Properties of Heavier Pnictogen Complexes.

Recent success in the synthesis of π-conjugated heavier pnictogen (As, Sb, and Bi) compounds and their transition metal complexes has led to the current surge in interest that led to significant development in the field of photophysical and optoelectronic properties of heavier pnictogens and their transition metal complexes. The presence of heavier pnictogens (As, Sb and Bi) in the molecular skeleton promotes inter-system crossing (ISC) and reverse inter-system crossing (RISC), because of the heavy atom effect, via altering the intermolecular interactions and orbital energy levels. As a result, π-conjugated heavier pnictogen compounds such as arsines, dibenzoarsepins, arsinoquinoline, heterofluorene, benzo[b]heterole (heterole=arsole, bismole, and stibole) show unique optoelectronic properties such as narrow bandgap, low-energy absorption, and long-wavelength emission than lighter pnictogen-based compounds. This review focuses on recent advances in the synthesis and photophysical properties of heavier pnictogen compounds. The synthesis and photophysical properties of heavier pnictogens are discussed and elaborated.

Novel 1,2,3-triazolyl phosphine with a pyridyl functionality: synthesis, coinage metal complexes, photophysical studies and Cu(I) catalyzed C-O coupling of phenols with aryl bromides.

This manuscript describes the synthesis and coinage metal complexes of pyridine appended 1,2,3-triazolyl-phosphine [2-{(C6H4N)(C2(PPh2)N3C6H5)}] (1), photophysical studies and their catalytic application. The reactions of 1 with copper salts afforded dimeric complexes [{Cu(µ2-X)}2{2-(C6H4N)(C2(PPh2)N3C6H5)}2] (2, X = Cl; 3, X = Br; and 4, X = I). The crystal structure indicates that the Cu⋯Cu distance in 4 (2.694 Å) is significantly shorter than that in complexes 3 (3.0387 Å) and 2 (3.104 Å), indicating strong cuprophilic interactions which is also supported by NBO calculations, signifying the involvement of 3dz2 orbitals from each Cu atom contributing to the bonding interaction. The fluorescence studies on complexes 2-4 carried out in the solid state showed broad emission bands around 560 nm on excitation at λex = 420 nm. Complex 4 on treatment with two equivalents of 1,10-phenanthroline yielded a mononuclear complex 5 which showed almost complete quenching of fluorescence in the solid state, clearly indicating that the emissive properties of 4 are mainly due to the Cu⋯Cu interaction, along with (M + X)LCT. The reactions of 1 with silver salts led to the isolation of dimeric complexes [{Ag(µ2-X)}2{2-(C6H4N)(C2(PPh2)N3C6H5)}2] (6, X = Cl; 7, X = Br; and 8, X = I) in good yield. The reaction between 1 and [AuCl(SMe2)] yielded [{AuCl}{2-(C6H4N)(C2(PPh2)N3C6H5)}] (9). The molecular structures of 2-5 and 7-9 were confirmed by single crystal X-ray analysis. The complex 4 is found to be an excellent catalyst for C-O coupling under mild conditions.

Synthesis and Characterisation of Novel Bis(diphenylphosphane oxide)methanidoytterbium(III) Complexes.

Reaction of [YbCp2(dme)] (Cp = cyclopentadienyl, dme = 1,2 dimethoxyethane) with bis(diphenylphosphano)methane dioxide (H2dppmO2) leads to deprotonation of the ligand H2dppmO2 and oxidation of ytterbium, forming an extremely air-sensitive product, [YbIII(HdppmO2)3] (1), a six-coordinate complex with three chelating (OPCHPO) HdppmO2 ligands. Complex 1 was also obtained by a redox transmetallation/protolysis synthesis from metallic ytterbium, Hg(C6F5)2, and H2dppmO2. In a further preparation, the reaction of [Yb(C6F5)2] with H2dppmO2, not only yielded compound 1, but also gave a remarkable tetranuclear cage, [Yb4(µ-HdppmO2)6(µ-F)6] (2) containing two [Yb(µ-F)]2 rhombic units linked by two fluoride ligands and the tetranuclear unit is encapsulated by six bridging HdppmO2 donors. The fluoride ligands of the cage result from C-F activation of pentafluorobenzene and concomitant formation of p-H2C6F4 and m-H2C6F4, the last being an unexpected product.

A greener approach towards the synthesis of N-heterocyclic thiones and selones using the mechanochemical technique.

This manuscript describes the synthesis of N-heterocyclic thiones and selones of a variety of imidazolium salts involving an eco-friendly and solventless ball-milling technique. The products have been isolated in almost quantitative yield, involving a minimum quantity of solvents only for the isolation of products by column chromatography, and in some cases for purification purposes. Both mono- and bisimidazolium salts afforded N-heterocyclic thiones and selones. The methodology is found to be superior in terms of reaction time, yield and energy efficiency as compared to conventional solution-state reactions.

2,2'-Bipyridine derived doubly B ← N fused bisphosphine-chalcogenides, [C5H3N(BF2){NCH2P(E)Ph2}]2 (E = O, S, Se): tuning of structural features and photophysical studies.

2,2'-Bipyridine based bisphosphine [C5H3N{N(H)CH2PPh2}]2 (1) and its bischalcogenide derivatives [C5H3N{N(H)CH2P(E)Ph2}]2 (2, E = O; 3, E = S; 4, E = Se) were synthesized, and further reacted with BF3·Et2O/Et3N to form doubly B ← N fused compounds [C5H3N(BF2){NCH2P(E)Ph2}]2 (5, E = O; 6, E = S; 7, E = Se) in excellent yields. The influence of the PE bonds on the electronic properties of the doubly B ← N fused systems and their structural features were investigated in detail, supported by extensive experimental and computational studies. Compound 6 exhibited a very high quantum yield of ϕ = 0.56 in CH2Cl2, whereas compound 7 showed a least quantum yield of ϕ = 0.003 in acetonitrile. Density functional theory (DFT) calculations demonstrated that the LUMO/HOMO of compounds 5-7 mostly delocalized over the entire π-conjugated frameworks. The involvement of PE bonds in the HOMO energy level of these compounds follows the order: PO < PS < PSe. Time-correlated single photon counting (TCSPC) experiments of compounds 5-7 revealed the singlet lifetime of 4.26 ns for 6, followed by 4.03 ns for 5 and a lowest value of 2.18 ns (τ1) and 0.47 ns (τ2) with a double decay profile for 7. Our findings provide important strategies for the design of highly effective B ← N bridged compounds and tuning their photophysical properties by oxidizing phosphorus with different chalcogens. Compounds 5 and 6 have been employed as green emitters (λem = 515 nm) in fluorescent organic light-emitting diodes (OLEDs). For compound 5, doped into the poly(9-vinylcarbazole) (PVK) matrix with 5 wt% doping concentration, nearly 90 Cd m-2 luminance with 0.022% external quantum efficiency (EQE) was achieved. The best performance was observed for compound 6 doped into PVK by 1 wt% having a maximum luminance of 350 Cd m-2 and a similar EQE value.

RuII complexes of 1,2,3-triazole appended tertiary phosphines, [P(Ph){(o-C6H4)(1,2,3-N3C(Ph)CH}2] and [P(Ph){o-C6H4(CCH)-(1,2,3-N3-Ph)}2]: highly active catalysts for transfer hydrogenation of carbonyl/nitro compounds and for α-alkylation of ketones.

The synthesis of two new 1,2,3-triazole appended monophosphines [P(Ph){(o-C6H4)(1,2,3-N3C(Ph)CH}2] (1) and [P(Ph){o-C6H4(CCH)(1,2,3-N3-Ph)}2] (2) and their RuII complexes is described. The reactions of 1 and 2 with [Ru(PPh3)3Cl2] in a 1 : 1 molar ratio produced cationic complexes 3 and 4, respectively. Both the complexes showed very high catalytic activity towards transfer hydrogenation, nitro reduction, and α-alkylation reactions and afforded the corresponding products in good to excellent yields. The free energy of ß-hydride elimination from the respective Ru-alkoxide intermediates, a key mechanistic step common to all the three catalytic pathways, was calculated to be close to ergoneutral by density functional theory-based calculations, which is posited to rationalize the catalytic activity of 3. The reduction of aromatic nitro compounds was found to be highly chemoselective and produced the corresponding amines as major products even in the presence of a carbonyl group. The triazolyl-N2 coordinated RuII-NPN complex 3 showed better catalytic activity compared to the triazolyl-N3 coordinated complex 4.

1,2,3-Triazole based ligands with phosphine and pyridine functionalities: synthesis, PdII and PtII chemistry and catalytic studies.

This manuscript describes the syntheses of pyridine appended triazole-based mono- and bisphosphines, [o-Ph2P(C6H4){1,2,3-N3C(Py)C(H)}] (2), [o-Br(C6H4){1,2,3-N3C(Py)C(PPh2)}] (3), [C6H5{1,2,3-N3C(Py)C(PPh2)}] (4), [Ph2P(C6H4){1,2,3-N3C(Py)C(PPh2)}] (5) and [3-Ph2P-2-{1,2,3-N3C(Ph)C(PPh2)}C5H3N] (6), their palladium and platinum chemistry and catalytic applications. These ligands upon treatment with [M(COD)Cl2] (M = Pd or Pt) yielded complexes with different coordination modes, depending on the reaction conditions. Both κ2-P,N and κ2-P,P coordination modes were observed in many of the complexes indicating the ambidentate nature of these ligands. Monophosphine 2 in the presence of a base afforded rare fused-5,6-membered PCN pincer complexes [MCl{o-Ph2P(C6H4){1,2,3-N3C(Py)C(H)}}-κ3-P,C,N] (7, M = Pd; 8, M = Pt), whereas the reactions of 4 with [M(COD)Cl2] (M = Pd, Pt) produced κ2-P,N chelate complexes [MCl2{C6H5{1,2,3-N3C(Py)C(PPh2)}-κ2-P,N}] (9, M = Pd; 10, M = Pt). Similar reactions of 5 and 6 resulted in κ2-P,P chelate complexes [MCl2{{3-Ph2P-2-{1,2,3-N3C(Ph)C(PPh2)}C5H3N}-κ2-P,P}] (11, M = Pd; 12, M = Pt) and [MCl2{3-Ph2P-2-{1,2,3-N3C(Ph)C(PPh2)}C5H3N}-κ2-P,P}] (13, M = Pd; 14, M = Pt), respectively. The palladium(II) complexes have shown excellent catalytic activity in the α-alkylation reaction of acetophenone derivatives.

Platinum Assisted Tandem P-C Bond Cleavage and P-N Bond Formation in Amide Functionalized Bisphosphine o-Ph2PC6H4C(O)N(H)C6H4PPh2-o: Synthesis, Mechanistic, and Catalytic Studies.

The reactions of amide functionalized bisphosphine o-Ph2PC6H4C(O)N(H)C6H4PPh2-o (1) with platinum salts are described. Treatment of 1 with [Pt(COD)Cl2] yielded a chelate complex, [PtCl2{o-Ph2PC6H4C(O)N(H)C6H4PPh2-o}κ2-P,P] (2), which on subsequent treatment with LiHMDS formed a novel 1,2-azaphospholene-phosphine complex [Pt(C6H5)Cl{o-C6H4{C(O)N(o-PPh2(C6H4))P(Ph)}}κ2-P,P] (3) involving a tandem P-C bond cleavage and P-N bond formation. The same complex 3 on passing dry HCl gas afforded the dichloro complex [PtCl2{o-C6H4{C(O)N(o-PPh2(C6H4))P(Ph)}}κ2-P,P] (5). Complex 2 upon refluxing in toluene or treatment of 1 with [Pt(COD)Cl2] in the presence of a base at room temperature resulted in the pincer complex [PtCl{o-Ph2PC6H4C(O)N(C6H4PPh2-o)}κ3-P,N,P] (4). Reaction of 1 with [Pt(COD)ClMe] at room temperature also afforded the pincer complex [PtMe{o-Ph2PC6H4C(O)N(C6H4PPh2-o)}κ3-P,N,P] (6). Mechanistic studies on 1,2-azaphospholene formation showed the reductive elimination of LiCl to form a phosphonium salt that readily adds one of the P-C bonds oxidatively to the in situ generated Pt0 species to form a chelate complex 3. The analogous palladium complex [PdCl2{o-C6H4{C(O)N(o-PPh2(C6H4))P(Ph)}}κ2-P,P] (7) showed excellent catalytic activity toward N-alkylation of amines with alcohols with a very low catalyst loading (0.05 mol %), and the methodology is very efficient toward the gram-scale synthesis of many N-alkylated amines.

Synthesis, structural, characterization and Hirshfeld analysis of a bisselenide and a zinc complex of a new hemilabile ferrocenylbisphosphane, [Fe{C5H4P(C6H4CH2NMe2-o)2}2].

The novel hemilabile ferrocenylbisphosphane 1,1'-bis(bis{2-[(dimethylamino)methyl]phenyl}phosphanyl)ferrocene, [Fe{C5H4P(C6H4CH2NMe2-o)2}2] (1), was synthesized by reacting bis(dichlorophosphanyl)ferrocene, [Fe{C5H4(PCl2)}2] with LiC6H4CH2NMe2-o. Treatment of 1 with gray selenium and anhydrous ZnCl2 yielded, respectively, the bisselenide (ferrocene-1,1'-diyl)bis(bis{2-[(dimethylamino)methyl]phenyl}phosphine selenide), [Fe(C23H28N2PSe)2] (2), and the dizinc complex [µ-1,1'-bis(bis{2-[(dimethylamino)methyl]phenyl}phosphanyl)ferrocene-κ2N,P:κ2N',P']bis[dichloridozinc(II)] dichloromethane monosolvate, [FeZn2Cl4(C23H28N2P)2]·CH2Cl2 (3), and both have been structurally characterized. Both compounds crystallized with the asymmetric unit containing half a molecule and with the Fe atom on an inversion centre. A Hirshfeld surface analysis indicated that the most significant contributions to the crystal packing of 2 are from H...H (76.7%), C...H/H...C (13.2%) and Se...H/H...Se (7.1%) contacts, while those for 3 are from H...H (62.3%), Cl...H/H...Cl (24.4%) and C...H/H...C (10.9%) contacts.

Group 11 metal complexes of the dinucleating triazole appended bisphosphine 1,4-bis(5-(diisopropylphosphaneyl)-1-phenyl-1H-1,2,3-triazol-4-yl)benzene.

The synthesis of a triazole appended dinucleating bisphosphine 1,4-bis(5-(diisopropylphosphaneyl)-1-phenyl-1H-1,2,3-triazol-4-yl)benzene (2) and its coinage metal complexes are described. The dinucleating bisphosphine 2 was obtained by the temperature-controlled lithiation of 1,4-bis(1-phenyl-1H-1,2,3-triazol-4-yl)benzene (1a) and 1,4-bis(1-(2-bromophenyl)-1H-1,2,3-triazol-4-yl)benzene (1b) followed by the reaction with iPr2PCl. The reactions of 2 with copper(I) halides in 1 : 2 molar ratios yielded the [Cu(µ2-X)]2 dimeric complexes [{Cu(µ2-X)}2(PiPr2N3PhC2)2C6H4] (3, X = Cl; 4, X = Br; and 5, X = I), whereas the reaction of 2 with AgBr resulted in the formation of hetero-cubane complex [{Ag4(µ3-Br)4}{(PiPr2N3PhC2)2C6H4}2] (7). Similar reactions of 2 with AgX in 1 : 2 molar ratios yielded disilver complexes [{Ag(µ2-X)}2{(PiPr2N3PhC2)2C6H4}] (6, X = Cl and 8, X = I). Treatment of 2 with AgOAc in a 1 : 2 molar ratio afforded a dinuclear complex [Ag2(µ2-OAc)2{(PiPr2N3PhC2)2(C6H4)}] (9) with one of the acetate ligands bridging the two metal centres in the side-on mode, whereas the other one adopting the end-on mode keeping the >CO group uncoordinated. The reaction of 2 with two equivalents of [AuCl(SMe2)] afforded the digold complex [(AuClPiPr2N3PhC2)2C6H4] (10). The molecular structures of 2-5 and 7-10 were confirmed by single crystal X-ray analysis. Non-covalent interactions between Cu and Carene were observed in the molecular structures of 3, 4 and 5. These weak interactions were also assessed by DFT calculations in terms of their non-covalent interaction plots (NCI) and QTAIM analyses.

Recent advances in organophosphorus-chalcogen and organophosphorus-pincer based macrocyclic compounds and their metal complexes.

The design and development of phosphorus based macrocycles containing one or more other heteroatoms is of crucial importance for the enhancement of modern synthetic chemistry. In recent years focus on phosphorus based macromolecules has led to intriguing and innovative structures with a variety of applications, including photophysical and host-guest properties, and in organic synthesis. This article summarizes the recent advancements in the synthesis of macrocycles that consist of organophosphorus-chalcogen (P-E, P[double bond, length as m-dash]E; E = O, S, Se) and organophosphorus-pincer based macrocyclic ligands and their transition metal complexes with emphasis given to synthetic methodologies. The reactions involve the modification of simple macrocycles with phosphorus sources or phosphorus-based chalcogenating reagents. Transition metal complexes of phosphine-based macrocyclic pincer ligands and their reactivity are also included.

Novel approach to benzo-fused 1,2-azaphospholene involving a Pd(II)-assisted tandem P-C bond cleavage and P-N bond formation reaction.

New bisphosphine o-Ph2PC6H4C(O)N(H)C6H4PPh2-o (1) (Bala-HariPhos) showed a unique reactivity towards Pd(ii) resulting in a 1,2-azaphospholene complex, involving a tandem P-C bond cleavage, P-N bond formation and cyclization process via the elimination of PhH. Mechanistic details were investigated using NMR spectroscopy, DFT calculations and kinetic data, and by SCXRD analysis. It involves the reductive elimination from a tautomerised complex to form a phosphonium salt followed by oxidative addition.

Rare Au···H Interactions in Gold(I) Complexes of Bulky Phosphines Derived from 2,6-Dibenzhydryl-4-methylphenyl Core.

Gold(I) complexes of sterically demanding phosphines derived from 2,6-dibenzhydryl-4-methylphenyl core viz: 2,6-dibenzhydryl-N,N-bis((diphenylphosphane)-methyl)-4-methylaniline (1), (2,6-dibenzhydryl-4-methylphenyl)-diphenylphosphane (2), N-(2,6-dibenzhydryl-4-methylphenyl)-1,1-diphenylphosphanamine (3), and (2,6-dibenzhydryl-4-methylphenoxy)-diphenylphosphane (4) are described. The reaction of 1 with 2 equiv of [AuCl(SMe2)] in dichloromethane yielded [{AuCl}2{Ar*N(CH2PPh2)2}] (5), which on further treatment with 2 equiv of AgSbF6 and 1 equiv of 1 produced 12-membered dimeric complex [Au2{µ-(Ar*N(CH2PPh2)2)2}][(SbF6)2] (6). A similar reaction of 5 with AgSbF6 in CH3CN afforded [{Au(NCCH3)}2{Ar*N(CH2PPh2)2}][(SbF6)2] (7). Equimolar reactions of bulky phosphines 2, 3, and 4 with [AuCl(SMe2)] resulted in [AuCl(PPh2Ar*)] (8), [AuCl(PPh2NHAr*)] (9), and [AuCl(PPh2OAr*)] (10). Complexes 9 and 10 on treatment with AgSbF6 in CH3CN produced the cationic complexes [Au(NCCH3)(PPh2NHAr*)][(SbF6)] (11) and [Au(NCCH3)(PPh2OAr*)][(SbF6)] (12), respectively. The molecular structure of complex 6 revealed the presence of a strong intramolecular aurophilic interaction with a Au···Au distance of 2.9720(4) Å. Careful analysis of molecular structure of 5 revealed the presence of rare Au···H-C (sp3) interactions between the gold(I) atom and one of the methylene protons of -NCH2PPh2 groups. The solution 1H NMR signals of the methylene protons of 5 showed a considerable downfield shift (∼1 ppm) compared to that of the free ligand indicating their interactions (Au···H) with the Au atom. Complexes 8 and 10 also showed Au···H interactions in their molecular structures. The existence of the Au···H interaction was studied by variable temperature 1H NMR data in the case of complex 5 and further evinced by the QTAIM analysis in complexes 5, 8, and 10.