Steven H. Privér

Unprecedented near-infrared (NIR) emission in diplatinum(III) (d7-d7) complexes at room temperature.

The synthesis and single-crystal X-ray structures of the first family of efficient NIR emitters with tunable emission energy based on dihalodiplatinum(III) (5d(7)-5d(7)) complexes of general formulae [Pt(2)(mu-C(6)H(3)-5-R-2-AsPh(2))(4)X(2)] (R = Me or CHMe(2); X = Cl, Br or I), together with that of their diplatinum(II) (5d(8)-5d(8)) precursors ([Pt(2)(mu-C(6)H(3)-5-R-2-AsPh(2))(4)]) and cyano counterparts (X = CN), are reported. The diplatinum(II) complexes with isopropyl groups are isolated initially as a mixture of two species, one being a half-lantern structure containing two bridging and two chelate C(6)H(3)-5-CHMe(2)-2-AsPh(2) ligands (1b) that exists in two crystalline modifications [d(Pt...Pt) = 3.4298(2) A and 4.3843(2) A]; the other is a full-lantern or paddle-wheel structure having four bridging C(6)H(3)-5-CHMe(2)-2-AsPh(2) ligands (2b) [d(Pt...Pt) = 2.94795(12) A]. Complete conversion of the isomers into 2b occurs in hot toluene. The Pt-Pt bond distances in the diplatinum(III) complexes are less than that in 2b and increase in the order X = Cl (3b) [2.6896(2) A] < Br (4b) [2.7526(3) A] < I (5b) [2.7927(7) A] approximately CN (6b) [2.7823(2), 2.7924(2) A for two independent molecules]. Comparison with the corresponding data for our previously reported series of complexes 3a-6a (R = Me) indicates that the Pt-Pt bond lengths obtained from single-crystal X-ray analysis are influenced both by the axial ligand and by intermolecular lattice effects. Like [Pt(2)(mu-pop)(4)](4-) [pop = pyrophosphite, (P(2)O(5)H(2))(2-)], the diplatinum(II) complexes [Pt(2)(mu-C(6)H(3)-5-R-2-AsPh(2))(4)] [R = Me (2a), CHMe(2) (2b)] display intense green phosphorescence, both as solids and in solution, and at room temperature and 77 K, with the emission maxima in the range 501-532 nm. In contrast to the reported dihalodiplatinum(III) complexes [Pt(2)(mu-pop)(4)X(2)](4-) that exhibit red luminescence only at 77 K in a glass or as a solid, complexes 3a-6a and 3b-6b are phosphorescent in the visible to near-infrared region at both room and low temperatures. The electronic spectra and photoemissive behavior are discussed on the basis of time-dependent density functional theory (TDDFT) calculations at the B3YLP level. The photoemissive states for the halide analogues 3a,b-5a,b involve a moderate to extensive mixing of XMMCT character and MC [d sigma-d sigma*] character, whereas the cyano complexes 6a and 6b are thought to involve relatively less mixing of the XMMCT character into the MC [d sigma-d sigma*] state.

Synthesis, X-ray structure and electrochemical oxidation of palladium(II) complexes of ferrocenyldiphenylphosphine

Four new complexes, [PdX(κ(2)-2-C(6)R(4)PPh(2))(PPh(2)Fc)] [X = Br, R = H (1), R = F (2); X = I, R = H (3), R = F (4)], containing ferrocenyldiphenylphosphine (PPh(2)Fc) have been prepared and fully characterised. The X-ray structures of complexes trans-1, cis-2 and cis-4, and that of a decomposition product of 4, [Pd(κ(2)-2-C(6)F(4)PPh(2))(μ-I)(μ-2-C(6)F(4)PPh(2))PdI(PPh(2)Fc)] (5), have been determined. These complexes show a distorted square planar geometry about the metal atom, the bite angles of the chelate ligands being about 69°, as expected. The cis/trans ratio of 1-4 in solution is strongly dependent on solvent. The new complexes and the uncoordinated PPh(2)Fc ligand were electrochemically characterised by cyclic and rotating disk voltammetry, UV-visible spectroelectrochemistry, and bulk electrolysis in dichloromethane and acetonitrile. In both cases, oxidation occurs at both the ferrocene and phosphine centres, but the complexes oxidise at more positive potentials than uncoordinated PPh(2)Fc; subsequently, the metal-phosphorus bond is cleaved, leading to free PPh(2)Fc(+), which undergoes further chemical and electrochemical reactions.

A Pyridyl‐Monoannulated Naphthalene Diimide Motif Self‐Assembles into Tuneable Nanostructures by Means of Solvophobic Control

The supramolecular self-assembly of the core-substituted naphthalene diimide bearing pyridyl motifs leads to the formation of a variety of nanostructures with pH and solvent control. The detection of HCl can be monitored by UV/Vis and fluorescence spectroscopy, as well as the naked eye, with a change in colour (blue to red, see figure). The cycle is fully reversed by the addition of triethylamine (TEA).

ortho-Metallated triphenylphosphine chalcogenide complexes of platinum and palladium: synthesis and catalytic activity.

Treatment of [PtI2(COD)] (COD = 1,5-cyclooctadiene) with 2-LiC6H4P(S)Ph2 gives the complex cis-[Pt{κ(2)-2-C6H4P(S)Ph2}2] () containing a pair of ortho-metallated triphenylphosphine sulfide rings. The selenium counterpart, [Pt{κ(2)-2-C6H4P(Se)Ph2}2] (), which exists as cis- and trans-isomers in solution, and the palladium analogues, cis-[Pd{κ(2)-2-C6H4P(X)Ph2}2] [X = S (), Se ()], are obtained by transmetallation of [MCl2(COD)] with the organotin reagent 2-Me3SnC6H4P(X)Ph2 in a 1 : 2 mol ratio. The reaction of [PdCl2(COD)] with 2-Me3SnC6H4P(X)Ph2 in a 1 : 1 mol ratio, and the reaction of with palladium(ii) acetate, give dinuclear, anion-bridged complexes [Pd2(μ-Cl)2{κ(2)-2-C6H4P(X)Ph2}2] [X = S (), Se ()] and [Pd2(μ-OAc)2{κ(2)-2-C6H4P(S)Ph2}2] (), respectively. Complexes and could not be made directly from triphenylphosphine sulfide by standard ortho-palladation procedures. The bridging framework in complexes and is cleaved by tertiary phosphines to give mononuclear derivatives [PdCl{κ(2)-2-C6H4P(X)Ph2}(PR3)] [X = S, R = Ph (); X = Se, R = Ph (); X = Se, R = 4-tolyl ()]. The selenium-containing compounds and decompose slowly in solution giving dinuclear complexes [PdCl(μ2-Se-κ(2)-P,Se-2-SeC6H4PPh2)PdCl(μ-2-C6H4PPh2)(PR3)] [R = Ph (), 4-tolyl ()]. The structure of complex establishes that the bridging 2-C6H4PPh2 group is generated by reduction of the phosphine selenide unit, not by ortho-metallation of the coordinated triphenylphosphine. The chloro-bridges of and are also cleaved by acetylacetonate (acac) and deprotonated Schiff bases forming mononuclear species [Pd{κ(2)-2-C6H4P(X)Ph2}L2] [L2 = acac, X = S (), Se (); L2 = 2-OC6H4CH[double bond, length as m-dash]NC6H4-4-R, X = S, R = OMe (), NO2 (); X = Se, R = OMe (), NO2 ()]. The ability of complexes , and the Schiff base-derivatives to catalyse Heck-Mizoroki and Suzuki-Miyaura C-C bond-forming reactions has also been investigated.

Metallophilic Contacts in 2-C6F4PPh2 Bridged Heterobinuclear Complexes: A Crystallographic and Computational Study

Treatment of the bis(chelate) complex trans-[Pd(κ(2)-2-C6F4PPh2)2] (7) with PMe3 gave trans-[Pd(κC-2-C6F4PPh2)2(PMe3)2] (13) as a mixture of syn- and anti-isomers. Reaction of 13 with CuCl, AgCl, or [AuCl(tht)] (tht = tetrahydrothiophene) gave the heterobinuclear complexes [(Me3P)2Pd(μ-2-C6F4PPh2)2MCl] [M = Cu (14), Ag (15), Au (16)], from which the corresponding salts [(Me3P)2Pd(μ-2-C6F4PPh2)2M]PF6 [M = Cu (17), Ag (18), Au (19)] could be prepared by abstraction of the chloro ligand with TlPF6; 18, as well as its triflato (20) and trifluoroacetato (21) analogues, were also prepared directly from 13 and the appropriate silver salt. Reaction of 13 with [AuCl(PMe3)] gave the zwitterionic complex [(Me3P)PdCl(μ-2-C6F4PPh2)2Au] (24) in which the 2-C6F4PPh2 ligands are in a head-to-head arrangement. In contrast, the analogous reaction with [AuCl(PPh3)] gave [(Ph3P)PdCl(μ-2-C6F4PPh2)2Au] (25) with a head-to-tail ligand arrangement. Single crystal X-ray diffraction studies of complexes 14-21 show short metal-metal separations [2.7707(11)-2.9423(3) Å] suggestive of attractive noncovalent (dispersion) interactions, a conclusion that is supported by theoretical calculations of the electron localization function and the noncovalent interactions descriptor.

Electrochemical and Chemical Oxidation of [Pt2(μ-pyrophosphite)4]4− Revisited: Characterization of a Nitrosyl Derivative, [Pt2(μ-pyrophosphite)4(NO)]3−

Electrochemical studies of the salts [cat](4)[Pt(2)(mu-pop)(4)] (cat(+) = Bu(4)N(+) or PPN(+) [Ph(3)P=N=PPh(3)](+); pop = pyrophosphite, [P(2)O(5)H(2)](2-)) have been carried out in dichloromethane. In agreement with published studies of K(4)[Pt(2)(mu-pop)(4)] in water and [Ph(4)As](4)[Pt(2)(mu-pop)(4)] in acetonitrile, the [Pt(2)(mu-pop)(4)](4-) anion is found to undergo an initial one-electron oxidation under conditions of cyclic voltammetry to a short-lived trianion, [Pt(2)(mu-pop)(4)](3-). However, in the more weakly coordinating solvent dichloromethane, [Pt(2)(mu-pop)(4)](3-) appears to undergo oligomerization instead of solvent-induced disproportionation; thus the overall process remains a one-electron reaction rather than an overall two-electron oxidative addition process, even under long time-scale, bulk electrolysis conditions. Chemical oxidation of [cat](4)[Pt(2)(mu-pop)(4)] with [NO][BF(4)] or AgBF(4) gives mainly a dark, insoluble, ill-defined solid that appears to contain Pt(III) according to X-ray photoelectron spectroscopy (XPS). In the case of [NO][BF(4)], a second reaction product, an orange solid, has been identified as a nitrosyl complex, [cat](3)[Pt(2)(mu-pop)(4)(NO)]. The X-ray structure of the PPN(+) salt shows the anion to consist of the usual lantern-shaped Pt(2)(mu-pop)(4) framework with an unusually large Pt-Pt separation [2.8375(6) A]; one of the platinum atoms carries a bent nitrosyl group [r(N-O) = 1.111(15) A; angle(Pt-N-O) = 118.1(12) degrees] occupying an axial position. The nitrosyl group migrates rapidly on the (31)P NMR time-scale between the metal atoms at room temperature but the motion is slow enough at 183 K that the expected two pairs of inequivalent phosphorus nuclei can be observed. The X-ray photoelectron (XP) spectrum of the nitrosyl-containing anion confirms the presence of two inequivalent platinum atoms whose 4f(7/2) binding energies are in the ranges expected for Pt(II) and Pt(III); an alternative interpretation is that the second platinum atom has a formal oxidation number of +4 and that its binding energy is modified by the strongly sigma-donating NO(-) ligand. Reduction of [Pt(2)(mu-pop)(4)X(2)](4-) (X = Cl, Br, I) in dichloromethane corresponds to a chemically reversible, electrochemically irreversible two-electron process involving loss of halide and formation of [Pt(2)(mu-pop)(4)](4-), as is the case in more strongly coordinating solvents.

Anti-cancer gold(I) phosphine complexes: Cyclic trimers and tetramers containing the P-Au-P moiety

We report the application of cationic tri- and tetra-nuclear gold(I) phosphine complexes [Au3(μ-dppen)3]X3 and [Au4(μ-dppa)4]X4 (X=OTf, PF6) [OTf=trifluoromethanesulfonate, dppen=trans-1,2-bis(diphenylphosphino)ethene, dppa=bis(diphenylphosphino)acetylene] for cancer treatment. The results of cytotoxicity tests on four different cancer cells [prostate (DU145), cervical (HeLa), breast (MDAMB-231) and fibro sarcoma (HT1080)] indicate these complexes possess remarkable tumor cell growth inhibitory effects and high selectivity towards cancer cells. The anti-tumor mechanism of the tri- and tetra-nuclear gold(I) complexes has also been investigated.

Synthesis of gold(I) phosphine complexes containing the 2-BrC6F4PPh2 ligand: Evaluation of anticancer activity in 2D and 3D spheroidal models of HeLa cancer cells

Newly synthesised mononuclear gold complexes containing the 2-BrC6F4PPh2 ligand have been fully characterised and their anticancer activity towards five human tumor [prostate (PC3), glioblastoma (U87MG), cervical (HeLa), fibrosarcoma (HT1080), ovarian (SKOV-3)] and normal human embryonic kidney (Hek-293T) cell lines investigated. Some of the synthesised gold complexes displayed higher cytotoxicity than cisplatin towards PC-3, HeLa and U87MG cells and inhibited the thioredoxin reductase (TrxR) enzyme, which is considered a potential target for new compounds in cancer treatment. The more physiologically relevant tumor spheroid assay demonstrated the superior potency of these gold phosphine complexes in inhibiting the growth of cervical carcinoma cell line HeLa (3D) spheroidal models. The mechanism of cell death was shown to be apoptotic cell death through cell cycle arrest, mitochondrial membrane depolarisation and increased ROS production.

Tin(IV) Compounds with 2-C6F4PPh2 Substituents and Their Reactivity toward Palladium(0): Formation of Tin–Palladium Complexes via Oxidative Addition

The tin(IV) compounds MexSn(2-C6F4PPh2)4-x (1, x = 1; 2, x = 2) and ClSn(2-C6F4PPh2)3 (3) were obtained from the reactions of 2-LiC6F4PPh2 with MeSnCl3 (3:1), Me2SnCl2 (2:1), or SnCl4 (3:1), respectively. The reactions of 2-LiC6F4PPh2 with SnCl4 in different stoichiometric ratios (4:1-1:1) gave 3 as the main product. Compound Cl2Sn(2-C6F4PPh2)2 (4) was formed in the transmetalation reaction of 3 and [AuCl(tht)] but could not be isolated. 1 and 2 react with palladium(0) sources {[Pd(PPh3)4] and [Pd(allyl)Cp]} by the oxidative addition of one of their Sn-CAryl bonds to palladium(0) with formation of the heterobimetallic complexes [MeSn(μ-2-C6F4PPh2)2Pd(κC-2-C6F4PPh2)] (5) and [Me2Sn(μ-2-C6F4PPh2)Pd(κ2-2-C6F4PPh2)] (6) featuring Sn-Pd bonds. The reaction of 3 with palladium(0) proceeds via the oxidative addition of the Sn-Cl bond to palladium(0), thus furnishing the complex [Sn(μ-2-C6F4PPh2)3PdCl] (7) featuring a Sn-Pd bond and a pentacoordinate Pd atom. Transmetalation of MexSn(2-C6F4PPh2)4-x (x = 1-3) with [Pd(allyl)Cl]2 gave MexClSn(2-C6F4PPh2)3-x and [Pd(allyl)(μ-2-C6F4PPh2)]2. For x = 1, the compound MeClSn(2-C6F4PPh2)2 (generated in situ) reacted with another 1 equiv of [Pd(allyl)Cl]2 by the oxidative addition of the Sn-Cl bond to palladium(0) and the reductive elimination of allyl chloride, thus leading to [MeSn(μ-2-C6F4PPh2)2PdCl] (8). The reductive elimination of allyl chloride was also observed in the reaction of 3 with [Pd(allyl)Cl]2, giving [Sn(μ-2-C6F4PPh2)3PdCl] (7). All compounds have been characterized by means of multinuclear NMR spectroscopy, elemental analysis, single-crystal X-ray diffraction, and selected compounds by 119Sn Mössbauer spectroscopy. Computational analyses (natural localized molecular orbital calculations) have provided insight into the Sn-Pd bonding of 5-8.

Trinuclear Mixed-valent Gold Complexes Derived from 2-C 6 F 4 PPh 2 : Phosphine Oxide Complexes of Gold(III) and an ortho-Metallated Complex of Gold(I)

Crystals of two mixed-valent gold complexes [(O2NO)AuI(μ-2-C6F4PPh2)AuIII{κ2-2-C6- F4P(O)Ph2}(μ-2-C6F4PPh2)AuI(ONO2)] (14) and [(O2NO)AuI(μ-2-C6F4PPh2)AuIII{κ3-2-C6F4- P(O)Ph(C6H4)}(μ-2-C6F4PPh2)AuI] (15) have been obtained from the reaction of the digold(I,III) complex [ClAuI(μ-2-C6F4PPh2)(κ2-2-C6F4PPh2)AuIIICl] (5) with, respectively, a small and a large excess of silver nitrate. Both complexes contain three, approximately collinear metal atoms, the central gold(III) atom being planar-coordinated by a chelate (O,C)-phosphine oxide formed by oxidation of 2-C6F4PPh2 and the carbon atoms of two bridging 2-C6F4PPh2 groups. In 14 each of the terminal gold(I) atoms is coordinated by a monodentate nitrate ion and the phosphorus atom of μ-2-C6F4PPh2, whereas in 15 the nitrate ion on one of the gold(I) atoms of 14 has been replaced by the carbon atom of a bridging C6H4 group derived by Ag+-promoted cyclometallation of a phenyl group on the neighbouring phosphine oxide Graphical Abstract Trinuclear Mixed-valent Gold Complexes Derived from 2-C6F4PPh2: Phosphine Oxide Complexes of Gold(III) and an ortho-Metallated Complex of Gold(I)