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Phosphane, PH3—a highly pyrophoric and toxic gas—is frequently contaminated with H2 and P2H4, which makes its handling even more dangerous. The inexpensive metal–organic framework (MOF) magnesium formate, α-[Mg(O2CH)2], can adsorb up to 10 wt % of PH3. The PH3-loaded MOF, PH3@α-[Mg(O2CH)2], is a non-pyrophoric, recoverable material that even allows brief handling in air, thereby minimizing the hazards associated with the handling and transport of phosphane. α-[Mg(O2CH)2] further plays a critical role in purifying PH3 from H2 and P2H4: at 25 °C, H2 passes through the MOF channels without adsorption, whereas PH3 adsorbs readily and only slowly desorbs under a flow of inert gas (complete desorption time≈6 h). Diphosphane, P2H4, is strongly adsorbed and trapped within the MOF for at least 4 months. P2H4@α-[Mg(O2CH)2] itself is not pyrophoric and is air- and light-stable at room temperature., Angewandte Chemie. International Edition, 62 (13), ISSN:1433-7851, ISSN:1521-3773, ISSN:0570-0833

The chiral tetrachelating amino−olefins (R,R)-N,N‘-bis(5H-dibenzo[a,d]cyclohepten-5-yl)-1,2-diaminocyclohexane ((R,R)-trop2dach) and (S,S)-N,N‘-bis(5H-dibenzo[a,d]cyclohepten-5-yl)-1,2-diphenyl-1,2-ethylenediamine ((S,S)-trop2dpen) were prepared and used as ligands in the complexes (R,R)-[Rh(trop2dach)]OTf and (S,S)-[Rh(trop2dpen)]OTf (OTf- = CF3SO3-). Quasi-reversible reductions, d8-[RhI(trop2diamine)]+ + e- → d9-[Rh0(trop2diamine)] and d9-[Rh0(trop2diamine)] + e- → d10-[Rh-I(trop2diamine)]-, at rather negative potentials (trop2diamine = trop2dach, E1/21 = −1.83 V, E1/22 = −2.27 V; trop2diamine = trop2dpen, E1/21 = −1.78 V, E1/22 = −2.24 V; vs Fc+/Fc) indicate the donor capacity of the amine functions. One NH group in (R,R)-[Rh(trop2dach)]OTf (pKa = 15.7(2), NH bond dissociation energy (BDE) 317(2) kJ mol-1) is easily deprotonated to give the neutral amide (R,R)-[Rh(trop2dach-H)], which is quasi-reversibly oxidized at E° = −0.34 V (vs Fc/Fc+) to the radical cation (R,R)-[Rh(trop2dach-H)]•+. The pKa and B...

The new tetrachelating diphosphanes 1,2-[(5H-dibenzo[a,d]cyclohepten-5-yl)phenylphosphano]ethane, R,S-11 [R,S-bis(troppPh)], and the corresponding enantiomers R,R-bis(troppPh), R,R-12, and S,S-bis(troppPh), S,S-12, were synthesised from 1,2-bis(phenylphosphano)ethane (9), and 5-chloro-5H-dibenzo[a,d]cycloheptene (10). With the meso form R,S-11, the rhodium(I) complex [Rh{R,S-bis(troppPh)}]PF6 (15), and the iridium(I) complex [Ir(cod){R,S-bis(troppPh)}]O3SCF3 (16), were prepared. The cation of the 16-electron rhodium complex 15 has a square planar structure, which is markedly distorted towards a square pyramid with the rhodium centre in the apex. The structure of the cation of the 18-electron complex of 16 is trigonal bipyramidal and unprecedented a phosphorus and an olefin unit occupy the axial positions. Cyclic voltammetry data of 15 indicate, that considerable strain energy (ca. 30 kJ mol−1) is build up when the [Rh{R,S-bis(troppPh)}]+ cation is reversibly reduced in THF by one electron to the paramagnetic neutral complex [Rh{R,S-bis(troppPh)}]0.

The intact deposition of a complex into carbon powder allows the construction of an organometallic fuel cell (OMFC) that efficiently converts alcohols into carboxylic acids. This method may provide a way for the synthesis of fine chemicals from renewable resources under waste-free conditions.

The chlorido-bridged dimeric complex [Rh 2 (μ-Cl) 2 (trop 2 -NH) 2 ] [trop 2 NH =bis(benzo[a,d]cycloheptenyl)amine] or the acetonitrile complexes [Rh(trop 2 NH)(MeCN) 2 ] + (CF 3 SO 3 - ) and [IrCl(MeCN)(trop2NH)] are well-suited precursor complexes for phenanthroline-type complexes [M(trop2NH)(R,R-phen)] + A - (M = Rh, Ir; R = H, Me, Ph substituents in the 4,7-or 5,6-positions of the phen ligand, A - = CF 3 SΟ 3 - , PF 6 - ). These complexes contain 18-valence-electron configured metal centers in a trigonal-bipyramidal coordination sphere with the amino (NH) group in an axial position and each of the olefinic C=C trop units is in an equatorial position. The cationic amino complexes [M(trop 2 NH)(R,R-phen)] + are sufficiently acidic (pK a in dmso: 18.2-19.0) to be quantitatively deprotonated by one equivalent of KOtBu to give neutral amido complexes [M(trop2N)(R,R-phen)] (M = Rh, Ir). These can be easily oxidized to give aminyl radical complexes [M(trop 2 N - )(R,R-phen)] + A - , which for M = Rh can be isolated as green crystals. The iridium complex [Ir(trop 2 N . )(phen)] + is unstable. High-resolution pulse EPR spectroscopy was used to gain insight into the electronic structure of the aminyl radical complexes. Remarkably, the rhodium and iridium complexes have a very similar electronic structure, as revealed by their EPR parameters ([Rh(trop 2 N . ](phen)] + : g 1,2,3 = 2.084(2), 2.049(2), 2.027(2); lA iso l = 45.4 (N1), 10.4 (N 2 ), 3.1 (N3) 27.0 (Rh) MHz; [Ir(trop 2 N . )(phen)] + : g 1,2,3 = 2.140(2), 2.107(2), 2.015(2); lA iso l = 47 (N1), 7.9 (N2), 3.5 (N3), 26.8 (Ir) MHz} and these show that about 60 % of the spin population is localized on the nitrogen center (N1) of the trop 2 N ligand. In reactions with stannanes (R 3 SnH) and thiols (RSH), H-atom transfer to the trop 2 N nitrogen atom is observed, [M(trop 2 N . ](phen)] + + EH→ [M(trop 2 NH)(phen)] + + 1/2HE-EH.

(Chemical Equation Presented) A little goes a long way: An iridium-nitrogen-radical complex is a highly active and selective catalyst for the dehydrogenation (oxidation) of primary alcohols to aldehydes in the presence of the oxidant benzoquinone (see simplified scheme). With only 0.01 mol% of the complex, turnover frequencies of up to 150 000 s-1 are reached. © 2007 Wiley-VCH Verlag GmbH and Co. KGaA.

The reaction of phenyldichlorophosphane, PhPCl2, a commercially important precursor for organophosphorus compounds, with lithium and sodium as reducing metals was re-investigated with the aim to well-characterize the resulting oligophosphandiides, [M2(PnPhn)(solv)x] (M = Li, Na). Experimental conditions for the optimal formation of these compounds were found for both series with M = Li and M = Na and several of these were crystallized and characterized by X-ray diffraction studies. As a result, we find that sodium strongly prefers ion triple structures [M2(PnPhn)(solv)x] over solvent-separated ion pairs, [M(solv)m]+[MPnPhn(solv)n]?, which have a higher tendency to form with M = Li. Also, while [Na2(P4Ph4)(solv)x] retains its structure in thf solution, [Li2(P4Ph4)(solv)x] partially dissociates into the radical anion (Ph2P2).? which is detected by EPR spectroscopy. The knowledge about the structures and the behavior of the alkali metal diphosphandiides allows us to propose a reaction mechanism for their formation., Chimia, 59 (3), ISSN:0009-4293

Metal-stabilized phenoxyl radicals appear to be important intermediates in a variety of enzymatic oxidations. We report that transition metal coordination also supports an aminyl radical, resulting in a stable crystalline complex: [Rh(I)(trop 2 N . )(bipy)] + OTf – (where trop is 5-H-dibenzo[a,d]cycloheptene-5-yl, bipy is 2,2′-bipyridyl, OTf – is trifluorosulfonate). It is accessible under mild conditions by one-electron oxidation of the amide complex [Rh(I)(trop 2 N)(bipy)], at a potential of –0.55 volt versus ferrocene/ferrocenium. Both electron paramagnetic resonance spectroscopy and density functional theory support 57% localization of the unpaired spin at N. In reactions with H-atom donors, the Rh-coordinated aminyl behaves as a nucleophilic radical.

The 17-electron complexes [M(tropp(ph))2] (M=Co0, Rh0, Ir0) were prepared and isolated (tropp = tropylidene phosphane). A structural analysis of [Co(tropp(ph))2] revealed this complex to be almost tetrahedral, while the heavier homologues have more planar structures. Partially deuterated tropp complexes [D6][M(tropp(ph))2] were synthesised for M = Rh and Ir in order to enhance the resolution in the EPR spectra. This synthesis involves a four-fold intramolecular C-H activation reaction, whereby alkyl groups are transformed into olefins. Dihydrides were observed as intermediates for M = Ir. The electronic and geometric structures of all complexes [M(tropp(ph))2] (M = Co, Rh, Ir) and [D6][M(tropp(ph))2] (M = Rh, Ir) were investigated by continuous wave (CW) and echo-detected EPR in combination with pulse ENDOR and ESEEM techniques. In accord with their planar structures, cis and trans isomers were detected for [M(tropp(ph))2] (M = Rh0, Ir0) for which a dynamic equilibrium was established. The thermodynamic data show that the cis isomer is slightly preferred by deltaH(o) = -4.7 +/- 0.3 kJ mol(-1) (M = Rh) and delta H(o) = -5.1 +/- 0.5 kJ mol(-1); (M = Ir). The entropies for the process trans-[M(tropp(ph))2] cis-[M(tropp(ph))2] are also negative [deltaS(o) = -5 +/- 1.5 J mol(-1) (M = Rh); deltaS(o) = -17 +/- 3.7 J mol(-1) (M = Rh)], indicating higher steric congestion in the cis isomers. The cobalt(0) and irdium(0) complexes show rather large g anisotropies, while that of the rhodium(0) complex is small (Co: g(parallel) = 2.320, g(perpendicular) = 2.080; cis-Rh: g(parallel) = 2.030, g(perpendicular) = 2.0135; trans-Rh: g(parallel) = 2.050, g(perpendicular) = 2.030; cis-Ir: g(parallel) = 2.030, g(perpendicular) = 2.060; trans-Ir: g(parallel) = 1.980, g(perpendicular) = 2.150). The g matrices of [M(tropp(ph))2] (M = Co, Rh) are axially symmetric with g(parallel) > g(perpendicular), indicating either a distorted square planar structure (SOMO essentially d(x2 - y2) or a compressed tetrahedron (SOMO essentially d(xy)). Interestingly, for [Ir(tropp(ph))2] the inverse ordering, g(perpendicular) > g(parallel) is found; this cannot be explained by simple ligand field arguments and must await a more sophisticated analysis. The hyperfine interactions of the unpaired electron with the metal nuclei, phosphorus nuclei, protons, deuterons and carbon nuclei were determined. By comparison with atomic constants, the spin densities on these centres were estimated and found to be small. However, the good agreement of the distance between the olefinic protons and the metal centres determined from the dipolar coupling parameter indicates that the unpaired electron is primarily located at the metal centre.

CO 2 reacts with hexyne(−3) in a catalytic reaction under formation of tetraethyl-2-pyrone, when the catalytic system alkyl 3 P/acetonitrile/nickel(0) is used. The selectivity of this homogeneous-catalytic reaction can be increased to values of 96% when phosphanes of high basicity and small cone angle are used. The investigation of the system Ni(COD) 2 /tricyclohexylphosphane/acetonitrile shows that acetonitrile can act as ligand in complexes of nickel(0). A yellow-brown tetranuclear complex was isolated, the structure of which was determined by X-ray diffraction studies. Acetonitrile acts as bridging ligand and is coordinated alkyne-analogously to one nickel center with its triple bond. The free electron pair of the nitrogen atom is bonded to a second nickel atom. Some reaction steps of this selective catalytic reaction are discussed. This reaction represents the first example of a selective homogeneous-catalytic co-oligomerization between CO 2 and an unsaturated substrate which takes place under CC linkage with a 3 d -transition metal.