On the electronic structure of MPS3 phases

Polyhedron, 2003

The reactions of the aromatic nitrogen donor ligands pyridine (py) and 4,4?-bipyridyl (4,4?-bipy) with the transition metal silylamides M{N(SiMe 3 ) 2 } 2 (M 0/Mn, Fe or Co) were investigated. Treatment of the metal amides with pyridine afforded the bispyridine complexes M{N(SiMe 3 ) 2 }(py) 2 (M 0/Mn, 1a; Fe, 2a; Co, 3a). Distillation or sublimation of 2a or 3a afforded the monopyridine complexes M{N(SiMe 3 ) 2 } 2 (py) (M 0/Fe, 2b; Co, 3b). The addition of pyrazine (prz) to Mn{N(SiMe 3 ) 2 } 2 also yielded the bispyrazine adduct Mn{N(SiMe 3 ) 2 } 2 (prz) 2 , 1b. However, the reaction of 4,4?-bipyridyl with Fe{N(SiMe 3 ) 2 } 2 or Co{N(SiMe 3 ) 2 } 2 afforded the polymeric chain-like complexes {M{N(SiMe 3 ) 2 } 2 (4,4?-bipy)} (M 0/Fe, 4; Co, 5). With the exception of 2b, all complexes were characterized by X-ray crystallography. The complexes 1a, 1b, 2a and 3a displayed monomeric structures and metal geometries that are based on a tetrahedron with interligand angles that deviate markedly from idealized values. Complex 3b was found to have a distorted trigonal planar geometry. In contrast, complexes 4 and 5 displayed polymeric zig-zag chain structures which have four coordinate metal centers connected by 4,4?-bipyridyl ligands. Magnetic studies indicated that complexes 1 Á/3b have high-spin electron configurations and that the paramagnetic centers in 4 and 5 did not interact with each other through the 4,4?bipyridyl ligands. #

Journal of the American Chemical Society, 1986

solvent removal under high vacuum gave a crude product that was chromatographed on silica gel (elution with pentane) to provide hydrocarbon 22d (6.4 mg, 62%): mp 116-1 17 "c; 'H NMR (CDC131 300 MHz) 6 1.11-1.32 (m, 1.1 H), 1.54-1.91 (m, 15 H); "c NMR (CDCl3, m l z 242 (91%, M' ).

Journal of the American Chemical Society, 1999

Compounds Cp*MH 3 (dppe) (M ) Mo, 1; W, 2) are oxidized chemically and electrochemically to the corresponding 17-electron cations 1 + and 2 + . Analogous oxidations of 1-d 3 and 2-d 3 provide 1 + -d 3 and 2 + -d 3 , respectively. Complex 2 + is stable in CH 2 Cl 2 , THF, and MeCN at room temperature. A single-crystal X-ray analysis of the PF 6salt of 2 + shows a geometry for the cation which is intermediate between octahedral and trigonal prismatic, which is reproduced by geometry optimization of the [CpWH 3 (PH 2 CH 2 CH 2 PH 2 )] + model at the B3LYP/LANL2DZ level. Identical calculations on the neutral analogue also reproduce the previously reported trigonal prismatic structure for 1. A blue shift in the M-H stretching vibrations upon oxidation for both Mo and W compounds indicates that a M-H bond strengthening accompanies the oxidation process. The DFT calculations (M-H bond lengths, BDE, and stretching frequencies) are in good agreement with the experimental results. Complex 1 + decomposes in solution at room temperature by one or more of three different mechanisms depending on conditions: H 2 reductive elimination, solvent-assisted disproportionation, or deprotonation. In THF or CH 2 Cl 2 , a reductive elimination of H 2 affords the stable paramagnetic monohydride Cp*MoH(dppe)PF 6 (3), which adds a molecule of solvent in CH 2 Cl 2 , THF, and MeCN. EPR studies show that the CH 2 Cl 2 molecule coordinates in a bidentate mode to afford a 19-electron configuration. A solvent dependence of the decomposition rate [k(CH 2 Cl 2 ) ≈ 7.8k(THF) at 0°C] and an inverse isotope effect [k H /k D ) 0.50(3) in CH 2 Cl 2 at 0°C] indicate the nature of 1 + as a classical trihydride and suggest a decomposition mechanism which involves equilibrium conversion to a nonclassical intermediate followed by a rate-determining associative exchange of H 2 with a solvent molecule. In MeCN at 20°C, a solvent-assisted disproportionation (rate ) k disp [1 + ] 2 , k disp ) 3.98(9) × 10 3 s -1 M -1 ) and a deprotonation by residual unoxidized 1 (rate ) k deprot [1 + ][1], k deprot ) 2.8(2) × 10 2 s -1 M -1 ) take place competitively, as shown by detailed cyclic voltammetric and thin-layer cyclic voltammetric studies. The stoichiometric chemical oxidation of 1 in MeCN leads to a mixture of [Cp*MoH 2 (dppe)(MeCN)] + and [Cp*MoH(dppe)(MeCN) 2 ] 2+ by the disproportionation mechanism.

J Am Chem Soc, 1999

Compounds Cp*MH 3 (dppe) (M ) Mo, 1; W, 2) are oxidized chemically and electrochemically to the corresponding 17-electron cations 1 + and 2 + . Analogous oxidations of 1-d 3 and 2-d 3 provide 1 + -d 3 and 2 + -d 3 , respectively. Complex 2 + is stable in CH 2 Cl 2 , THF, and MeCN at room temperature. A single-crystal X-ray analysis of the PF 6salt of 2 + shows a geometry for the cation which is intermediate between octahedral and trigonal prismatic, which is reproduced by geometry optimization of the [CpWH 3 (PH 2 CH 2 CH 2 PH 2 )] + model at the B3LYP/LANL2DZ level. Identical calculations on the neutral analogue also reproduce the previously reported trigonal prismatic structure for 1. A blue shift in the M-H stretching vibrations upon oxidation for both Mo and W compounds indicates that a M-H bond strengthening accompanies the oxidation process. The DFT calculations (M-H bond lengths, BDE, and stretching frequencies) are in good agreement with the experimental results. Complex 1 + decomposes in solution at room temperature by one or more of three different mechanisms depending on conditions: H 2 reductive elimination, solvent-assisted disproportionation, or deprotonation. In THF or CH 2 Cl 2 , a reductive elimination of H 2 affords the stable paramagnetic monohydride Cp*MoH(dppe)PF 6 (3), which adds a molecule of solvent in CH 2 Cl 2 , THF, and MeCN. EPR studies show that the CH 2 Cl 2 molecule coordinates in a bidentate mode to afford a 19-electron configuration. A solvent dependence of the decomposition rate [k(CH 2 Cl 2 ) ≈ 7.8k(THF) at 0°C] and an inverse isotope effect [k H /k D ) 0.50(3) in CH 2 Cl 2 at 0°C] indicate the nature of 1 + as a classical trihydride and suggest a decomposition mechanism which involves equilibrium conversion to a nonclassical intermediate followed by a rate-determining associative exchange of H 2 with a solvent molecule. In MeCN at 20°C, a solvent-assisted disproportionation (rate ) k disp [1 + ] 2 , k disp ) 3.98(9) × 10 3 s -1 M -1 ) and a deprotonation by residual unoxidized 1 (rate ) k deprot [1 + ][1], k deprot ) 2.8(2) × 10 2 s -1 M -1 ) take place competitively, as shown by detailed cyclic voltammetric and thin-layer cyclic voltammetric studies. The stoichiometric chemical oxidation of 1 in MeCN leads to a mixture of [Cp*MoH 2 (dppe)(MeCN)] + and [Cp*MoH(dppe)(MeCN) 2 ] 2+ by the disproportionation mechanism.

Inorganic Chemistry, 2001

The reaction of [Mn 3 O(2-X-benzoato) 6 L 3 ] (X ) Cl, Br; L ) pyridine) with 2,2′-bipyridine in CH 2 Cl 2 leads to the high-yield formation of new mixed-valence tetranuclear Mn II Mn 3 III complexes of general formulation [Mn 4 O 2 -(X-benzoato) 7 (bpy) 2 ] (1, X ) 2-chloro; 2, X ) 2-bromo). The crystal structure of 1 was determined. Complex 1 crystallizes in the monoclinic system, space group P2 1 /n with a ) 19.849(8) Å, b ) 13.908(5) Å, c ) 30.722(19) Å, ) 107.35(2)°, Z ) 4. Complex 1 is neutral, and consideration of overall charge necessitates a mixed-valence Mn II Mn III 3 description. Each manganese ion is distorted octahedral, especially the three Mn III ions, owing to a first-order Jahn-Teller effect. The Mn II is assigned on the basis of the longer metal-ligand distances. Variable temperature magnetic susceptibility studies were performed on 1 and 2 in the temperature range 2-300 K. The topology of the molecule requires three J values, J bb between the two-body Mn III ions and two J wb ("wing-body") between the Mn III ions of the "body" of the butterfly and the Mn II or Mn III of the "wing" of the butterfly. Without any simplifying assumptions, a full diagonalization matrix method is necessary to solve the problem, but assuming that both J wb are identical, it is then possible to solve the problem numerically by applying the Kambe method. With both methods, the derived J bb and J wb exchange parameters are very similar for the 2-Cl and 2-Br complexes. The best R factors [∑ i ( Mcalc -Mobs ) 2 /∑ i ( Mobs ) 2 ] (∼10 -6 ) were obtained from 300 to 40 K. The J values are, thus, as follows. For 1, J bb ) -23.2 cm -1 , J wb ) -4.9 and -4.8 cm -1 , and g ) 1.93. For 2, J bb ) -22.8 cm -1 , J wb ) -4.8 and -4.7 cm -1 , and g ) 1.92. With these values, the expected ground-state spin must be 7 / 2 , very close in energy to low-lying spin states of 9 / 2 , 5 / 2 , 3 / 2 , and 1 / 2 . They are all almost degenerate. By application of Kambe's method (with only one J wb ), the results are completely similar. Magnetization measurements at 2-30 K from 2 to 50 kG confirm that the ground state is S ) 7 / 2 for 1, with the D parameter equal to -0.60 cm -1 .

Room-temperature crystal structure of the transition-metal coordination polymers MCl2(bpy) (M = Fe, Co, Ni, bpy = 4, 4'-bipyridine) belongs to the orthorhombic crystal system, space group Cmmm (#65). Magnetic susceptibility M(T)/H and isothermal magnetization M(H) have been measured. Spontaneous antiferromagnetic ordering was observed in M(T)/H of all compounds, with transition temperatures 10.0 K, 5.0 K, and 8.5 K, for M = Fe, Co, and Ni, respectively. A metamagnetic transition was found in M(H) of each compound. The metamagnetic-transition critical fields for Fe, Co, and Ni compounds are 3.5 kG, 2.5 kG, and 12 kG, respectively. High temperature M(T)/H data of all compounds were fit to a modified Curie-Weiss law. The values of effective moment yielded from the fitting indicate the high spin states for all M ions. The magnetic behaviors exhibited in this system are attributed to the ferromagnetic intra-chain M-M exchange interaction through the Cl2 bridges along the c axis and t...

Dalton Transactions, 2012

Two new coordination polymers have been synthesized with Mn 2+ and Dy 3+ ions using a new bent etherbridged tricarboxylic acid ligand, o-cpiaH 3 (5-(2-carboxy-phenoxy)-isophthalic acid). The ligand readily reacts with a Mn 2+ salt in presence of pyridine ( py) under hydrothermal condition to afford a 3D coordination polymer {[Mn 9 (o-cpia) 6 ( py) 3 (3H 2 O)]·H 2 O} n (1), that contains two types of polymeric chains. One of them is merely carboxylate bridged Mn 2+ where each metal ion shows both penta-and hexa-coordination. The other chain consists of carboxylate-bridging along with terminally bound pyridines providing both penta-and hexa-coordination to each metal ion. When o-cpiaH 3 is treated with Dy(NO 3 ) 3 .xH 2 O under solvothermal condition, it gives rise to an unusual double layer (6,6) connected 2D coordination polymer {[Dy(o-cpia)]} n (2), where each metal ion is hexacoordinated. The double layer 2D sheets are stacked to each other in AA⋯ fashion through strong C-H⋯π interactions to generate an overall 3D supramolecular architecture. Both the complexes have been characterized by single crystal X-ray diffraction, IR spectroscopy, thermogravimetry and elemental analysis. Variable temperature magnetic susceptibility measurements indicate that 1 exhibits metamagnetic behavior while 2 shows weak antiferromagnetic behavior. † Electronic supplementary information (ESI) available: selected bonds and distances for 1 and 2, figures, IR, TGA analysis, ESI-MS, and NMR. CCDC reference numbers 841423 and 841424. For ESI and crystallographic data in CIF or other electronic format see

Organometallics, 2014

The binuclear complexes Cp*(dppe)FeC CCCCCM(dppe)Cp* (6, M = Fe; 8, M = Ru) were obtained in good yield by treatment of the iron chloro complex Cp*(dppe)Fe−Cl (5) in the presence of KF with the bis(silylated) hexatriyne Me 3 SiCCCCCCSiMe 3 and the ruthenium complex Cp*(dppe)RuCCCCC CSiMe 3 (7), respectively. The oxidized species 6(PF 6) n (n = 1, 2) and 8(PF 6) were obtained in ca. 80% yield by treatment of the parent neutral compounds with 1 or 2 equiv of [Cp 2 Fe](PF 6) in THF or dichloromethane at −78°C. The CV of these compounds show three reversible waves with a separation larger than 0.5 V. The salts 6(PF 6) n (n = 1, 2), and 8(PF 6) were characterized by XRD. Quantum chemistry calculations performed at the DFT level on the oxidized species show a strong contribution of the −C 6 − spacer to the delocalization of the spin density. IR spectra analyzed with the support of TD-DFT calculations are consistent with the delocalization of the odd electron on the fast IR time scale for the two mixed-valence complexes 6(PF 6) and 8(PF 6). Combined ESR measurements on rigid glass and on single crystal samples clearly establish that the electronic properties of MV species and particularly their magnetic anisotropies depend on the conformation of the molecules. In the case of the doubly oxidized species 6(PF 6) 2 , which carries two unpaired electrons, it is shown that the singlet vs triplet ground states can be inverted by the rotation of one metal end with respect to the other around the all-carbon chain axis. Very strong NIR bands are found for the symmetric 6(PF 6) and nonsymmetric 8(PF 6) MV (mixed-valence) derivatives allowing the determination of very large electronic couplings (H ab = 3070 and 4025 cm −1 , respectively).

Inorganica Chimica Acta, 2005

The study of the magnetic properties and EPR spectra of the one-dimensional bis(l-chloro) Mn(II) polymer [Mn(l-Cl) 2 (bpy)] n (1) (bpy = 2,2 0 -bipyridine) is reported. Magnetic susceptibility measurements reveal a weak ferromagnetic interaction between the Mn(II) ions (J = +0.19 cm À1 ). This is the first polymer of six-coordinated Mn(II) ions with a [Mn 2 (l-Cl) 2 ] 2+ magnetic repeating unit, showing a ferromagnetic interaction. The coordination octahedra are elongated in the ClÁ Á ÁCl direction and the elongation axes are parallel along the chain. Extended Hü ckel calculations show that the octahedra share an equatorial-apical edge, with the equatorial plane being parallel, and perpendicular to the Mn 2 (l-Cl) 2 . Due to this disposition, the overlap through the chloride bridges is small, so the antiferromagnetic contribution must also be small and, therefore, a ferromagnetic behaviour is observed. The EPR spectra of a polycrystalline sample of 1 at different temperatures are also reported. A variation of the bandwidth with temperature is observed, which could be because this ferromagnetic interaction is weak: above 150 K the dipolar interaction is the predominant effect, while below 150 K the magnetic exchange interaction dominates.

Inorganic Chemistry, 1991

Oxidative-addition reactions of Y? (Y = CI, Br, 1) to the quadruply bonded complexes Mo2X4(dppm), (X = CI, Br, I) produce the corresponding edge-sharing bioctahedral molecules Mo2X4Y2(dppm), in high yield. All nine of these compounds are now available and have been investigated by infrared and UV-visible spectroscopy as well as by electrochemical methods. Structural determinations of three of them, M~&I,I~(dppm)~ (2), MqBr6(dppm), (4), and M~,I,(dppm)~ (8), have been carried out, although in the case of 4 refinement is incomplete. Pertinent crystal data are as follows: for 2, PI, a = 9.922 (3) A, b = 13.013 (5) A, c = 12.152 (5) A, a = 93.31 (3)', 6 = 107.06 (2)O, y = 108.63 (2)O, V = 1402 (1) A', Z = 1; for 4, Pi, a = 16.069 (6) A, b = 20.994 (6) A, c = 10.756 (6) A, a = 102.43 (3)', fl = 106.99 (4)', y = 77.52 (3)', V = 3343 (3) A), Z = 2; for 8, R 1 [ n , a = 16.194 (8) A, 6 = 11.090 (2) A, c = 20.574 (7) A, fl = 108.72 (4) ', V = 3499 (6) A3, Z = 2. Compound 2 has bridging CI atoms, and each terminal position is occupied by a 1:l mixture of CI and I. The Mo-Mo distances in 2,4,8, and Mo,Cb(dppm), are respectively 2.827 (I), 2.879 (2), 3.061 (I), and 2.789 (I) A. Magnetic susceptibility data over a temperature range 5-300 K have been fitted to an expression that allows evaluation of the gap between a ground singlet state and a low triplet state. For 2 the gap is >1750 cm-l, while for the other three compounds whose structures are known, MozX6(dppm),, X = CI, Br, and I, the S-T gap is 1100-1400 cm-I, indicating that both direct MM coupling and indirect coupling across the r-X atoms play a part. ' equiv, 17 pL). The solution was stirred at room temperatuie for 12 h and filtered to yield a bright green solid (0.310 g) and a red-green dichroic filtrate. Addition of diethyl ether to the filtrate produced 0.10 g of additional solid. The combined solids were dried in vacuo. Yield: 0.41 g (91%).