Manganese (II) Coordination Complexes Involving Nitronyl Nitroxide Radicals (original) (raw)
Inorganic Chemistry, 1997
The reaction of N-n-Bu 4 MnO 4 or NaMnO 4 with appropriate reagents in ethanol-pyridine leads to the high-yield formation of new mixed-valence trinuclear oxo-centered Mn III,III,II complexes of general formulation [Mn 3 O(Xbenzoato) 6 L 3 ] (1, X ) 2-fluoro, L ) pyridine; 2, X ) 2-chloro, L ) pyridine; 3, X ) 2-bromo, L ) pyridine; 4, X ) 3-fluoro, L ) 2 pyridine + 1 H 2 O; 5, X ) 3-chloro, L ) 2 pyridine + 1 H 2 O; 6, X ) 3-bromo, L ) 2 pyridine + 1 H 2 O). The crystal structures of 1, 5, and 6 were determined. Complex 1 crystallizes in the monoclinic system, space group C2/c with a ) 15.774(2) Å, b ) 17.269(2) Å, c ) 21.411(2) Å, ) 91.11(1)°, and Z ) 4. Complex 5 crystallizes in the monoclinic system, space group P2 1 /n with a ) 15.172(2) Å, b ) 17.603(2) Å, c ) 21.996(3) Å, ) 106.300(10), and Z ) 4. Complex 6 crystallizes in the monoclinic system, space group P2 1 /n with a ) 15.533(3) Å, b ) 17.884(2) Å, c ) 21.997(4) Å, ) 106.95(1)°, and Z ) 4. The three complexes are neutral and possess an oxo-centered Mn 3 O unit with peripheral ligands provided by bridging carboxylate and terminal pyridine or H 2 O groups. Each manganese ion is distorted octahedral, and consideration of overall charge necessitates a mixed-valence Mn II Mn III 2 description. In 1, the presence of a C 2 axis through the central O atom and one of the manganese atoms (Mn II ) and the absence of imposed symmetry elements in 5 and 6 (they have the two Mn III with a terminal pyridine group and the Mn II with a H 2 O terminal molecule) suggest a trapped-valence situation in all three cases. The Mn II is assigned on the basis of its longer metal-ligand distances. Variabletemperature magnetic susceptibility studies were performed on 1-6 in the temperature range 2-300 K. Satisfactory fits to the observed susceptibility data were obtained by assuming isotropic magnetic exchange interactions and using the appropriate spin Hamiltonian and susceptibility equation. The derived J and J* exchange parameters are all relatively small in magnitude, |J| < 10 cm -1 . J characterizes the Mn II ‚‚‚Mn III interactions and J* the Mn III ‚‚‚Mn III interaction. Magnetization measurements at 2 K up to 50 kG indicate the variability of the ground state: S ) 3 / 2 for 2 and 3; S ) 1 / 2 for 1, 4, and 5; and S ) 3 / 2 , 1 / 2 for 6. X-band EPR spectra measured from 4 K to room temperature on polycrystalline samples of 1-6 show highly significant differences when the ground state is 3 / 2 or 1 / 2 . For S ) 3 / 2 complexes (2 and 3), there is a transition centered at g ≈ 4, which decreases in intensity with increasing temperature. For S ) 1 / 2 complexes, this g ≈ 4 band does not appear but instead there are broad bands centered at g ≈ 2. These results are discussed in terms of spin frustration within the Mn 3 O core, which produces different spin ground states and susceptibility values. X
Polyhedron, 2005
Four complexes of M(NO 3) 2 (4NOPy-OMe) 2 , (4NOPy-OMe = 4-(N-tert-butyloxylamino)-2-(methoxymethylenyl)pyridine, and M = Mn II , 1; Co II , 2; Ni II , 3; Cu II , 4), were prepared and fully characterized. X-ray single crystal analysis reveals that four complexes are isostructural. The molecular structures are distorted octahedral in which the methoxy oxygen atoms coordinate to the metal ion by trans-configuration while the pyridyl nitrogen atoms and the nitrate oxygen atoms coordinate by cis-configuration. The magnetic properties of all complexes were investigated by SQUID magneto/susceptometry. Temperature dependence of the molar magnetic susceptibilities in the temperature range of 2-300 K indicated that the magnetic coupling between aminoxyl radicals and metal ion was antiferromagnetic in the complex 1 and were ferromagnetic in the complexes 2-4. The quantitative analysis based on the spin Hamiltonian, H = À2J(S 1 S M + S M S 2) yielded the best fit as J/k B = À13.4 ± 0.1 K, g = 1.94 ± 0.002, and h = À0.78 ± 0.02 K for the complex 1, J/k B = 48.7 ± 2.1 K, g = 2.07 ± 0.02, and h = À2.83 ± 0.41 K for the complex 3 (the data in the temperature range 300-50 K were used), and J/k B = 57.0 ± 1.2 K, g = 2.002 ± 0.004, and h = À9.8 ± 0.1 K for the complex 4.
CrystEngComm, 2014
The reaction of M(ox)‚2H 2 O (M ) Co(II), Ni(II)) or K 2 (Cu(ox) 2 )‚2H 2 O (ox ) oxalate dianion) with n-ampy (n ) 2, 3, 4; n-ampy ) n-aminopyridine) and potassium oxalate monohydrate yields one-dimensional oxalatobridged metal(II) complexes which have been characterized by FT-IR spectroscopy, variable-temperature magnetic measurements, and X-ray diffraction methods. The complexes M(µ-ox)(2-ampy) 2 (M ) Co (1), Ni (2), Cu ) are isomorphous and crystallize in the monoclinic space group C2/c (No. 15), Z ) 4, with unit cell parameters for 1 of a ) 13.885(2) Å, b ) 11.010(2) Å, c ) 8.755(1) Å, and ) 94.21 , Ni (5), Cu ) are also isomorphous and crystallize in the orthorhombic space group Pcnn (No. 52), Z ) 8, with unit cell parameters for 6 of a ) 12.387 , b ) 12.935(3), and c ) 18.632(2) Å. Compound Co(µ-ox)(4-ampy) 2 (7) crystallizes in the space group C2/c (No. 15), Z ) 4, with unit cell parameters of a ) 16.478(3) Å, b ) 5.484(1) Å, c ) 16.592(2) Å, and ) 117.76(1)°. Complexes M(µ-ox)(4-ampy) 2 (M ) Ni (8), Cu (9)) crystallize in the orthorhombic space group Fddd (No. 70), Z ) 8, with unit cell parameters for 8 of a ) 5.342(1), b ) 17.078 , and c ) 29.469(4) Å. All compounds are comprised of one-dimensional chains in which M(n-ampy) 2 2+ units are sequentially bridged by bis-bidentate oxalato ligands with M‚‚‚M intrachain distances in the range of 5.34-5.66 Å. In all cases, the metal atoms are six-coordinated to four oxygen atoms, belonging to two bridging oxalato ligands, and the endo-cyclic nitrogen atoms, from two n-ampy ligands, building distorted octahedral surroundings. The aromatic bases are bound to the metal atom in cis (1-6) or trans (7-9) positions. Magnetic susceptibility measurements in the temperature range of 2-300 K show the occurrence of antiferromagnetic intrachain interactions except for the compound 3 in which a weak ferromagnetic coupling is observed. Compound 7 shows spontaneous magnetization below 8 K, which corresponds to the presence of spin canted antiferromagnetism.
Antiferromagnetic coupling in [Mn12O12(O2CMe)6(p-CO2-phenyl nitronyl
Transition Metal Chemistry, 2004
The synthesis of [Mn 12 O 12 (O 2 CMe) 6 (p-CO 2-phenyl nitronyl nitroxide) 10 (H 2 O) 4 ] AE 4H 2 O, (1), by direct replacement of some of the acetate groups in [Mn 12 O 12 (O 2 CMe) 16 (H 2 O) 4 ] AE 4H 2 O AE 2MeCO 2 H, (2), with the organic radical p-HO 2 Cphenyl nitronyl nitroxide, (3), is reported. E.p.r. spectra show exchange narrowing in (1) due to coupling between the manganese ions and radicals. The isotropic hyperfine splitting constant from the manganese ions is a ¼ 96 Oe at 5.5 K. The magnetic susceptibility indicates antiferromagnetic exchange interactions between the manganese ions and the radicals with the Weiss constant h ¼)25 K. The spin was determined to be S ¼ 6 from magnetization data in the 2-30 K temperature range at 50 kOe, suggesting a mixture of ground state with excited states.
Inorganic Chemistry, 1998
Aerial oxidation of Mn II /ptt 3-(ptt 3-) propane-1,2,3-trithiolate) mixtures gives [Mn 2 (pttd) 2 ] 2-, where pttd 4is the mono(disulfide) of ptt 3-. (NEt 3 Bz) 2 [Mn 2 (pttd) 2 ] (2) crystallizes in space group P2 1 /c with (at -158°C) a ) 11.540(2) Å, b ) 12.115 Å, c ) 17.478(4) Å, ) 101.78(1)°, and Z ) 2. The anion contains a doublybridged [Mn 2 S 8 ] core (Mn‚‚‚Mn ) 3.598(2) Å) with five-coordinate Mn III ions, very similar to previously reported [Mn 2 (edt) 4 ] 2-(anion of 1; edt 2-) ethane-1,2-dithiolate). Aerial oxidation of Mn II /pdt 2-(pdt 2-) propane-1,3dithiolate) mixtures gives [Mn 3 (pdt) 5 ] 2-, which is mixed valent (Mn II , 2Mn III ). (PPh 4 ) 2 [Mn 3 (pdt) 5 ] (3) crystallizes in space group P1 h with (at -161°C) a ) 14.385(6) Å, b ) 23.734(11) Å, and Z ) 2. The anion contains a near-linear Mn III Mn II Mn III unit with five-coordinate Mn III , six-coordinate Mn II , and three thiolate bridges between each Mn 2 pair; Mn‚‚‚Mn separations are 3.123(3) and 3.101(3) Å. Aerial oxidation of Mn II /edt 2-/ImH (ImH ) imidazole) mixtures gives [Mn(edt) 2 (ImH)] -. (NEt 4 )[Mn(edt) 2 (ImH)] (4) crystallizes in space group P2 1 /n with (at -72°C) a ) 13.974(5) Å, b ) 14.317(5) Å, c ) 10.564(3) Å, ) 90.13(2)°, and Z ) 4. The anion is five-coordinate and square-pyramidal. Aerial oxidation of Mn II /edt 2-/Immixtures gave [Mn 2 (Im)(edt) 4 ] 3-, which contains two Mn III ions. (NMe 4 ) 3 [Mn 2 (Im)(edt) 4 ] (5) crystallizes in space group Pna2 1 with (at -160°C) a ) 17.965(5) Å, b ) 16.094(4) Å, c ) 14.789(3) Å, and Z ) 4. The five-coordinate Mn III ions are bridged by the Imgroup across a Mn‚‚‚Mn separation of 6.487(2) Å. The anion of 4 contains high-spin Mn III (S ) 2) and exhibits inter-anion antiferromagnetic exchange interactions (J ) -0.15 cm -1 , g ) 1.91) propagated by interanion NH‚‚‚S hydrogen bonds. Complexes 1-3 and 5 all possess intraanion antiferromagnetic exchange interactions; the fitting parameters are as follows: 1, J ) -19.0 cm -1 , g ) 1.96, D ) -0.22 cm -1 ; 2, J ) -16.4 cm -1 , g ) 1.96, D ) -0.22 cm -1 ; 3, J ) -18.8 cm -1 , g ) 2.00; 5, J ) -1.75 cm -1 , g ) 1.84, D ) -0.028 cm -1 (Ĥ ) -2JS i S j convention). Complexes 1, 2, and 5 have S ) 0 ground states, while that of 3 is S ) 3 / 2 . S0020-1669(97)Supporting Information Available: Textual and tabular summaries of the structure determinations, tables of atomic coordinates, thermal parameters, and bond distances and angles, fully labeled figures for complexes 2-5 and the m Vs T equation for 3 (68 pages). Ordering information is given on any current masthead page. IC970587R Manganese(II) Dithiolate Complexes
Inorganic Chemistry, 1999
Complexes of manganese(II)-containing aminoxyl radical substituted phosphine oxide ligands are reported. The compounds [(o-nitronyl nitroxide-phenyl)diphenylphosphine oxide]bis(hexafluoroacetylacetonato)manganese(II), 3, and bis{[(p-nitronyl nitroxide-phenyl) diphenylphosphine oxide]bis(hexafluoroacetylacetonato)manganese(II)}, 4, prepared by addition of the free radical phosphine oxides to Mn(hfac) 2 , were structurally characterized. Complex 3 is mononuclear, containing an O,O-chelating ortho-substituted radical phosphine oxide ligand, while in 4 the para-substituted ligands bridge two Mn(hfac) 2 units to yield a binuclear molecular rectangle. The magnetic behavior of both systems is dominated by a strong antiferromagnetic Mn(II)-aminoxyl interaction (J ) -213 , -218 (4) cm -1 with H ) -JS Mn ‚S rad ) to give effective S ) 2 ground state units. The S ) 3 excited state is populated at high temperatures. At low temperatures a decrease in M T in both complexes is attributable primarily to interor intramolecular antiferromagnetic interactions rather than zero-field splitting (ZFS) of the S ) 2 ground state. For the bimetallic compound, the magnetic data indicate that ligand-mediated interactions between the Mn(II) spin carriers are weak. The powder EPR spectra of both systems have been recorded and successfully simulated, giving a ZFS parameter D ) 0.112 cm -1 . Crystals of 3 are triclinic, space group P1 h with a ) 10.6672 Å, b ) 13.270(6) Å, c ) 15.363(3) Å, R ) 93.84(2)°, ) 108.054(16)°, γ ) 105.69(3)°, and Z ) 2. Crystals of 4 are monoclinic, space group P2 1 /a with a ) 12.463(6) Å, b ) 19.315(3) Å, c ) 17.084(9) Å, R ) 90°, ) 98.49(2)°, γ ) 90°, and Z ) 2.
Inorganic Chemistry, 2002
Four new mononuclear complexes of formula Cd(PN) 4 (NCS) 2 (A), Cd(PNN) 4 (N 3 ) 2 (B), Zn(PNN) 4 (N 3 ) 2 (C), and Zn(PNN) 2 (NCS) 2 (D), where PNN stands for 2-(4-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide and PN for 2-(4-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl, were synthesized and structurally and magnetically characterized. The X-ray structures of compounds B and C were also determined at 90 K. Compounds A−C crystallize in the triclinic space group P1 h (No. 2), and D crystallizes in the monoclinic space group P2 1 /m (No. 11). A−C adopt a centrosymmetric distorted octahedral geometry in which the metal ions are bonded to four radical ligands through the nitrogen atom of the pyridyl rings and the azido or thiocyanato ligands occupy the apical positions. Compound D adopts a distorted tetrahedral geometry in which the zinc ion is bonded to two radicals and two thiocyanato ligands. As suggested by their magnetic behavior, the low-temperature X-ray structures of B and C show that these compounds undergo a clear structural change with respect to the room-temperature structures. The experimental magnetic behaviors were perfectly reproduced by a dimer model for A−C and an alternating chain model for D while the sudden breaks observed in the M T versus T curves for B and C were well accounted for by the highand low-temperature X-ray structures. For all these complexes the crystal structures favor significant overlap between molecular magnetic orbitals leading to rather strong intermolecular antiferromagnetic interactions. A criticism of the McConnell theory can be found in the following: Deumal, M.; Novoa, J. J.; Bearpark, M. J.; Celani, P.; Olivucci, M.; Robb, M. A.
New complexes of manganese(II) hexafluoroacetylacetonate [Mn(hfac)2] with 2-(1-R-3-pyrazol-4-yl)-4,4,5,5-tetramethyl-2-imidazoline-3-oxide-1-oxyl (R = CHF2, CH2CH2F, CH2CHF2 or CH2CF3) were synthesised and characterised structurally and magnetically. All complexes were prepared under similar conditions. Nonetheless, their crystal structures were considerably different. Depending on the structure of fluorinated alkyl substituent R, the complexation reaction led to complexes of three types: chain-polymeric complexes with the head-to-head or head-to-tail motif and complexes of molecular structure. All complexes show strong antiferromagnetic behaviour in a high-temperature region (150−300 K) and weak ferro- or antiferromagnetic exchange interactions at low temperatures. The stronger antiferromagnetic exchange, –101.7 ± 1.5 or –136 ± 10 cm–1, –82.3 ± 1.3 cm–1 and –87.4 ± 1.3 cm–1, was attributed to the magnetic interaction in three- or two-spin clusters: {>N∸O–Mn2+–O∸N<} or {>N∸...
Dalton Transactions, 2009
The reaction of H 2 phpzR (R = Me, Ph; H 2 phpzMe = 3(5)-(2-hydroxyphenyl)-5(3)-methylpyrazole and H 2 phpzPh = 3(5)-(2-hydroxyphenyl)-5(3)-phenylpyrazole) with Mn(O 2 CR¢)·nH 2 O (R¢ = Me and Ph) and ( n Bu 4 N)MnO 4 in ethanol (EtOH) affords three new manganese(III) compounds, [Mn 3 (m 3 -O)-(phpzMe) 3 (O 2 CMe)(EtOH)]·EtOH (1), ( n Bu 4 N)[Mn 3 (m 3 -O)(phpzMe) 3 (O 2 CPh) 2 ] (2) and ( n Bu 4 N)[Mn 3 (m 3 -O)(phpzPh) 3 (O 2 CPh) 2 ] (3). Their synthesis, crystal structure and magnetic properties are reported. Compounds 1-3 are m 3 -oxido-centered trinuclear manganese(III) compounds whose edges are bridged by phpzR 2with average intracluster separations of 3.25 Å . The three Mn-O-Mn angles are distorted from the equilateral triangle with values in the range of 113 • to 124 • ; 117 • to 125 • ; and 117 • to 126 • for complexes 1-3, respectively. Hydrogen bonding interactions between the trinuclear units of 1 result in a one-dimensional chain structure. Compounds 2 and 3 have isolated trinuclear units, perhaps as a result of the presence of the bulky n Bu 4 N + cation. Temperature-dependent magnetic susceptibility studies indicate the presence of both antiferromagnetic and ferromagnetic interactions in compound 1 (J 1 = -10.3 cm -1 , J 2 = +10.9 cm -1 ), while only antiferromagnetic interactions are present in compounds 2 and 3 (J 1 = -4.2 cm -1 , J 2 = -10.3 cm -1 for 2; and J 1 = -4.8 cm -1 , J 2 = -10.2 cm -1 for 3), with J 1 representing the similar Mn-O-Mn angles and J 2 representing the unique Mn-O-Mn angle (Mn(1)-O(1)-Mn(2)). of the [Mn 3 (m 3 -O)] 7+ core, where the Mn-O-Mn angle is smaller than 120 • (the value for an equilateral triangle); 15,16,19 a switch from antiferromagnetic to ferromagnetic exchange is observed at angles below approximately 120 • . 20 Recently, it has been shown that the ligand distortion, i.e. the Mn-N-O-Mn torsion angle in oximate ligands, plays an important role as well; a larger torsion angle gives rise to a stronger ferromagnetic coupling. 9,10,16,19
Journal of Coordination Chemistry
Two mononuclear complexes [(Et 3 NH)[M(hfac) 2 L] (M = Ni, 1 Zn, 2) have been synthesized using a nitronyl-nitroxide radical substituted nitrophenol, i.e., 2-(2-Hydroxy-3-methoxy-5nitrophenyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazol-3-oxide-1-oxyl, HL, as a proligand. The crystal structures of the two compounds have been solved and indicate an octahedral coordination geometry of the metal ions. The magnetic behavior for compound 1 is characterized by a strong antiferromagnetic metal-radical interaction (J =-351 ± 1 cm-1 ; H =-JS Ni S Rad). This exchange interaction was rationalized by DFT calculations. The EPR spectra recorded both in solution and solid state at 120 K confirm the S = ½ ground state for compound 1.
Inorganica Chimica Acta, 1995
The preparation of complexes M2L(NO3)4-2CH3OH-nH20 (4a-d) (M=Mn, Co, Ni, Cu; L=C18H22N604 (3); n =0.5 or 1) from pyridine-l-oxide-2,6-dialdehyde, 1,2-diaminoethane and the metal(II) nitrate is reported. The complex [Ni2L(H20)4](NO3) 4. 2H20 (5) was also prepared and its crystal structure determined. 5 is monoclinic, space group P21/n, a = 11.831(8), b = 12.168(8), c = 12.329(7)/~,/3= 114.26(5) °, Z =2. In the cyclic ligand 3, the pyridine-l-oxide rings are linked by CH(OH).NH.(CH2)2.N:CH groups, showing that partial hydrolysis of the expected Schiff-base ligand has occurred during synthesis of the complex. In the centrosymmetric complex 5, the Ni 2÷ ions are bridged in a planar Ni202 unit by the N-oxide oxygen atoms, the iigand adopting a non-planar 'stepped' conformation with pyramidal stereochemistry at the bridging O atoms. Six-fold coordination of each Ni 2÷ ion is completed by two N atoms and two c/s water molecules. The magnetic susceptibilities of 4a-d were measured between 5 and 300 K and analysed to obtain values of the parameter J in the exchange Hamiltonian-2JS~.$2: J=-1.15,-5.0,-15.5 and + 3.3 cm-~, respectively. These values are discussed in terms of the contributing orbital pathways.
Journal of the Chemical Society, Dalton Transactions, 1999
The dicyanamide anion has been observed to adopt two bridging co-ordination modes (µ and µ 3 ) in α-Mn(dca) 2 , [Mn(dca) 2 (H 2 O) 2 ]ؒH 2 O, [Mn(dca) 2 (C 2 H 5 OH) 2 ]ؒ(CH 3 ) 2 CO, [Fe(dca) 2 (CH 3 OH) 2 ] and [Mn(dca) 2 (L) 2 ] [L = py, CH 3 OH or DMF; dca = dycanamide N(CN) 2 Ϫ ], and generates weak ligand fields thus stabilising high spin configurations. The N-or O-bonded ligands L play an important role in the stabilisation of both the molecular structures and the three dimensional structure, via hydrogen bonding. The unsolvated α-Mn(dca) 2 adopts a rutile-like single network structure, based on the near orthogonal packing of 'ribbons' of . . . Mn(N᎐ ᎐ ᎐ C-N-C᎐ ᎐ ᎐ N) 2 Mn . . ., similar to that found for the isomorphous analogues of Co, Ni, Fe and Cu. Magnetisation measurements confirmed a high spin manganese d 5 system displaying antiferromagnetic coupling (θ = Ϫ25 K) above 25 K and undergoing long range magnetic ordering (T N = 16 K) to a spin-canted antiferromagnet (weak ferromagnet). Magnetisation and heat capacity measurements on some samples of α-Mn(dca) 2 indicated a possible second transition at ≈6 K, the nature of which is under investigation. From the hysteresis data at 2 K (remnant magnetisation of 29 cm 3 Oe mol Ϫ1 and coercive field of 406 Oe) a canting angle of 0.05Њ is estimated for this soft magnet. Other samples gave a higher value for the coercive field. The α-M(dca) 2 series has a diverse range of ground states; Cu II (d 9 ) is a paramagnet, Ni II (d 8 ) and Co II (d 7 ) are ferromagnets and Fe II (d 6 ) and Mn II (d 5 ) are canted antiferromagnets. Reasons for this diversity are given on the basis of the nature of exchange coupling pathways within the rutile structure and a mechanism for the long range magnetic ordering is proposed. A range of 1-D chain complexes of type [Mn(dca) 2 (L) 2 ], containing 'ribbons' of doubly bridged Mn(N᎐ ᎐ ᎐ C-N-C᎐ ᎐ ᎐ N) 2 Mn have been structurally characterised. The complex [Fe(dca) 2 (CH 3 OH) 2 ] is isostructural with the manganese analogue. 2-D Square grids are found in crystals of [Mn(dca) 2 (C 2 H 5 OH) 2 ]ؒ(CH 3 ) 2 CO and in [Mn(dca) 2 (H 2 O) 2 ]ؒH 2 O, the latter displaying, in addition, penetration of ribbons of trans-Mn(dca) 2 (H 2 O) 2 through the grids. Dehydration or desolvation results in formation of the α-Mn(dca) 2 phase. The Lewis-base adducts all display very weak antiferromagnetic coupling (J ≈ Ϫ0.12 cm Ϫ1 ) and no magnetic long-range order. Dissolution of the compounds in protic solvents leads to complete dissociation of the dicyanamide, and the axially co-ordinated ligands, L, can readily be exchanged by reaction or recrystallisation in different co-ordinating solvents.
Inorganic Chemistry, 1991
of tetraoxyphosphoranes rather than the use of P-O ring-bound oxygen atoms as studied previously.I2 In either case, chain and dimer formations resulted for the pentacoordinated spirocyclic phosphorus compounds with the rings situated axial-equatorially in trigonal-bipyramidal geometries. In contrast to the previous study12 where hydrogen bonding gave boat and chair conformations for the six-membered ring, the present study gave chair conformations exclusively. Activation energies for intramolecular exchange interpreted in terms of a pseudorotational process requiring diequatorial placement of the phosphorinane ring in a TBP exchange intermediate were similar for the two classes of hydrogen-bonded compounds and suggested that the energy required for diequatorial placement of a phosphorinane ring (11 1 kcal/mol) in the ground state exceeds the available hydrogen-bond energy.
Linear trinuclear manganese(II) complexes: crystal structures and magnetic properties
Inorganic Chemistry Communications, 2005
Two new trinuclear manganese(II) complexes, [Mn 3 (O 2 CCH(CH 3) 2) 6 (N-N) 2 ] (N-N is 1,10 0-phenanthroline (1) and 2,2 0-bipyridine (2)) have been prepared and fully characterized. Single crystal X-ray diffraction analysis confirmed a linear arrangement of three Mn(II) centers bridged by six isobutyric carboxylate groups. The magnetic measurements showed that both complexes exhibit an S T = 5/2 spin ground state induced by antiferromagnetic interactions between the Mn(II) sites: J/k B = À2.31(2) and À2.67(2) K for 1 and 2, respectively.
Thiocyanate manganese(II) complexes with pyridine and its derivatives ligands
Polyhedron, 2011
2-(Hydroxymethyl)pyridine 2,2 0 -Dipyridylamine X-ray structure UV-Vis DFT EPR Magnetic properties a b s t r a c t [Mn(SCN) 2 (L) 4/2 ] where L = py, c-pic, pyCH 2 OH, py-NH-py (dpa) complexes have been prepared and studied by IR and UV-Vis spectroscopy, and X-ray crystallography. Electronic structures of the complexes were calculated using DFT method, and the descriptions of frontier molecular orbitals and the relocation of the electron density of the compounds were determined. The differences in acceptor properties of the used pyridine derivatives ligands were shown in the values of ligand field parameters determined from electronic spectra of the complexes. The magnetic properties revealed paramagnetic behavior with a weak ferromagnetic interaction and the van Vleck contribution for [Mn(SCN) 2 (py) 4 ] (1), ideal paramagnetism for [Mn(SCN) 2 (c-pic) 4 ] (2) and a weak antiferromagnetic interaction and diamagnetic contribution for [Mn(SCN) 2 (pyCH 2 OH) 2 ] (3).
Inorganic Chemistry, 2007
Doubly bridged µ-alkoxo-µ-X (X ) pyrazolato or acetato) dinuclear Mn III complexes of 2-hydroxy-N-{2-hydroxy-3-[(2-hydroxybenzoyl)amino]propyl}benzamide) (H 5 L 1 ) and 2-hydroxy-N-{2-hydroxy-4-[(2-hydroxybenzoyl)amino]-butyl}benzamide (H 5 L 2 ), [Mn 2 (L)(pz)(MeOH) 4 ]‚xMeOH (1, L ) L 1 , x ) 0.5; 2, L ) L 2 , x ) 0; Hpz ) pyrazole) and [Mn 2 (L 1 )(OAc)(MeOH) 4 ] (3), have been prepared, and their structure and magnetic properties have been studied. The X-ray diffraction analysis of 1 (C 24.5 H 34 Å 3 , Z ) 2) revealed that all complexes consist of dinuclear units which are further extended into 1D (1 and 3) and 2D (2) supramolecular networks via hydrogen-bonding interactions. Magnetic susceptibility data evidence antiferromagnetic interactions for all three complexes: J ) −3.6 cm -1 , D ≈ 0 cm -1 , g ) 1.93 (1); J ) −2.7 cm -1 , D ) 0.8 cm -1 , g ) 1.93 (2); J ) −4.9 cm -1 , D ) 3.8 cm -1 , g ) 1.95 (3). Figure 5. Plot of [Mn2(L 1 )(OAc)(MeOH)4] (3) at the 30% probability level with atom numbering. Hydrogen atoms are omitted for clarity.