Single-molecule magnets constructed from cyanometalates: {[Tp*Fe(III)(CN)3M(II)(DMF)4]2[OTf]2} x 2DMF (M(II) = Co, Ni)

Treatment of several divalent transition-metal trifluoromethanesulfonates [M(II)(OTf)2; M(II) = Mn, Co, Ni] with [NEt4][Tp*Fe(III)(CN)3] [Tp* = hydridotris(3,5-dimethylpyrazol-1-yl)borate] in DMF affords three isostructural rectangular clusters of {[Tp*Fe(III)(CN)3M(II)(DMF)4]2[OTf]2} x 2DMF (M(II) = Mn, 3; Co, 4; Ni, 5) stoichiometry. Magnetic studies of 3-5 indicate that the Tp*Fe(CN)3(-) centers are highly anisotropic and exhibit antiferromagnetic (3 and 4) and ferromagnetic (5) exchange to afford S = 4, 2, and 3 spin ground states, respectively. ac susceptibility measurements suggest that 4 and 5 exhibit incipient single-molecule magnetic behavior below 2 K.     

Hybrid molecular magnets obtained by insertion of decamethyl-metallocenium cations into layered, bimetallic oxalate complexes:

A new series of hybrid organometallic - inorganic layered magnets with the formula [Z(III)Cp*2][M(II)M(III)(ox)3] (Z(III) = Co, Fe; M(III) = Cr, Fe; M(II) = Mn, Fe, Co, Cu, Zn; ox = oxalate; Cp* = pentamethylcyclopentadienyl) has been prepared. All of these compounds are isostructural and crystallize in the monoclinic space group C2/m, as found by X-ray structure analysis. Their structure consists of an eclipsed stacking of the bimetallic oxalate-based extended layers separated by layers of organometallic cations. These salts show spontaneous magnetization below To, which corresponds to the presence of ferro-, ferri-, or canted antiferromagnetism. Compounds in which the paramagnetic deca-methylferrocenium is used instead of the diamagnetic decamethylcobaltocenium are good examples of chemically constructed magnetic multilayers with alternating ferromagnetic and paramagnetic layers. The physical properties of this series have been thoroughly studied by means of magnetic measurements and ESR and Mossbauer spectroscopy. We have found that the two layers are electronically quasiindependent. As a consequence, the bulk properties of these magnets have not been significantly affected by the insertion of a paramagnetic layer of S = 1/2 spins in between the extended layers. In fact, the critical temperatures remain unchanged even when comparing [MCp*2]+ derivatives with [XR4]+ compounds (X = N, P; R = Ph, nPr, nBu). Nevertheless, the presence of the paramagnetic layer has been shown to have some influence on the hysteresis loops of these compounds. In the same context, the spin polarization of the paramagnetic units (which arises from the internal magnetic field created by the bimetallic layers in the ordered state) has been observed by Mossbauer and ESR spectroscopy.     

Structure of the decamethyl titanocene cation,a metallocene with two agostic C-h bonds,and its interaction with fluorocarbons

The tetraphenylborate salt of the decamethyl titanocene cation, [Cp*2Ti][BPh4] (1, Cp* = C5Me5), was prepared by reaction of Cp*2TiH with [Cp2Fe][BPh4] and by reaction of Cp*2TiMe with [PhNMe2H][BPh4]. The crystal structure of 1 shows that the Cp*2Ti cation has a bent metallocene structure with agostic interactions with the metal center of two adjacent methyl groups on one of the Cp* ligands. Compound 1 reacts readily with THF to give the adduct [Cp*2Ti(THF)][BPh4] (2). In fluorobenzene, 1 forms the eta1-fluorobenzene adduct [Cp*2Ti(eta1-FC6H5)][BPh4] (3), which was structurally characterized. In contrast to the thermal stability of 3, addition of alpha,alpha,alpha-trifluorotoluene to either 1 or 2 results in C-F activation to give Cp*2TiF2 and PhCF2CF2Ph as the main products. This reactivity toward benzylic C-F bonds is also reflected in the reactivity toward the fluorinated borate anions [B(C6F5)4]- and {B(3,5-(CF3)2C6H3]4}-: reaction of Cp*2TiMe with their [PhNMe2H]+ salts results in a stable complex for the former anion, whereas rapid C-F activation is observed for the latter.     

M(mu-CN)Fe(mu-CN)M' chains with phthalocyanine iron centers: preparation, structures, and isomerization

The molecular building blocks Fe(II)Pc (Pc = phthalocyaninato2-), Fe(III)Pc, ZnPc, Cp(dppe)Fe, and Cp(PPh3)2Ru were combined in the cyanide-bridged dinuclear reference compounds with M-CN-ZnPc and M-CN-FePc-CN arrays containing Fe(II)Pc and Fe(III)Pc. The linear trinuclear species with the M(mu-CN)Fe(mu-CN)M' backbone were prepared for both Fe(II)Pc and Fe(III)Pc centers, for terminal Fe/Fe, Fe/Ru, and Ru/Ru combinations and for all three possible cyanide orientations (M-CN-Fe-NC-M', M-CN-Fe-CN-M', and M-NC-Fe-CN-M'). The 15 complexes obtained were identified from their IR spectra and six structure determinations. The preferred orientation of the cyanide bridges could be established starting from the [Fe-NC-Fe(III)Pc-CN-Fe]+ complex, which is labile in solution and isomerizes to the corresponding [Fe-CN-Fe(III)Pc-NC-Fe]+ complex. A kinetic analysis of this isomerization has yielded an activation barrier of roughly 110 kJ/mol.     

Tuning of inter- versus intrachain magnetic interactions in cyano-bridged Ni(II)/M(III) (M = Cr, Fe, Co) chain complexes

The reaction of [M(CN)6]3- (M = Cr3+, Fe3+, Co3+) with the nickel(II) complex of 2,4-diamino-1,3,5-triazin-6-yl-{3-(1,3,5,8,12-pentaazacyclotetradecane)} ([NiL]2+) in excess of ANO3 or ACl (A = Li+, Na+, K+, Rb+, Cs+, NH4+) leads to the cyano-bridged dinuclear assemblies A{[NiL][M(CN)6]}.xH2O (x = 2-5). X-ray structures of Li{[NiL][Cr(CN)6]}.5H2O, NH4{[NiL][Cr(CN)6]}.3.5H2O, K{[NiL][Cr(CN)6]}.4H2O, K{[NiL][Fe(CN)6]}.4H2O, Rb{[NiL][Fe(CN)6]}.3.5H2O, and Cs{[NiL][Fe(CN)6]}.3.5H2O, as well as the powder diffractometry of the entire Fe(III) series, are reported. The magnetic properties of the assemblies are dependent on the monocation A and discussed in detail. New efficient pathways for ferromagnetic exchange between Ni(II) and Fe(III) or Cr(III) are demonstrated. Field dependencies of the magnetization for the Fe(III) samples at low temperature and low magnetic field indicate a weak interchain antiferromagnetic coupling, which is switched to ferromagnetic coupling at increasing magnetic field (metamagnetic behavior). The interchain magnetic coupling can be tuned by the size of the A cations.     

Electronic structure of mononuclear bis(1,2-diaryl-1,2-ethylenedithiolato)iron complexes containing a fifth cyanide or phosphite ligand: a combined experimental and computational study

A series of mononuclear square-based pyramidal complexes of iron containing two 1,2-diaryl-ethylene-1,2-dithiolate ligands in various oxidation levels has been synthesized. The reaction of the dinuclear species [Fe(III)2(1L*)2(1L)2]0, where (1L)2- is the closed shell di-(4-tert-butylphenyl)-1,2-ethylenedithiolate dianion and (1L*)1- is its one-electron-oxidized pi-radical monoanion, with [N(n-Bu)4]CN in toluene yields dark green crystals of mononuclear [N(n-Bu)4][Fe(II)(1L*)2(CN)] (1). The oxidation of 1 with ferrocenium hexafluorophosphate yields blue [Fe(III)(1L*)2(CN)] (1ox), and analogously, a reduction with [Cp2Co] yields [Cp2Co][N(n-Bu)4][Fe(II)(1L*)(1L)(CN)] (1red); oxidation of the neutral dimer with iodine gives [Fe(III)(1L*)2I] (2). The dimer reacts with the phosphite P(OCH3)3 to yield [Fe(II)(1L*)2{P(OCH3)3}] (3), and [Fe(III)2(3L*)2(3L)2] reacts with P(OC6H5)3 to give [Fe(II)(3L*)2{P(OC6H5)3}] (4), where (3L)2- represents 1,2-diphenyl-1,2-ethylenedithiolate(2-). Both 3 and 4 were electrochemically one-electron oxidized to the monocations 3ox and 4ox and reduced to the monoanions 3red and 4red. The structures of 1 and 4 have been determined by X-ray crystallography. All compounds have been studied by magnetic susceptibility measurements, X-band EPR, UV-vis, IR, and M?ssbauer spectroscopies. The following five-coordinate chromophores have been identified: (a) [Fe(III)(L*)2X]n, X = CN-, I- (n = 0) (1ox, 2); X = P(OR)3 (n = 1+) )3ox, 4ox) with St = 1/2, SFe = 3/2; (b) [Fe(II)(L*)2X]n, X = CN-, (n = 1-) (1); X = P(OR)3 (n = 0) (3, 4) with St = SFe = 0; (c) [Fe(II)(L*)(L)X]n <--> [Fe(II)(L)(L*)X]n, X = CN- (n = 2-) (1red); X = P(OR)3 (n = 1-) (3red, 4red) with St = 1/2, SFe = 0 (or 1). Complex 1ox displays spin crossover behavior: St = 1/2 <--> St = 3/2 with intrinsic spin-state change SFe = 3/2 <--> SFe = 5/2. The electronic structures of 1 and 1(ox) have been established by density functional theoretical calculations: [Fe(II)(1L*)2(CN)]1- (SFe = 0, St = 0) and [Fe(III)(1L*)2(CN)]0 (SFe = 3/2, St = 1/2).     

Synthesis of layered (2-D) V-based bimetallic oxalates from non-aqueous media that cannot be synthesized from aqueous media

The reaction of (NBu4)3[V(III)(ox)3] (1, ox = oxalate) and M(II) (M = Fe, Co, Ni, Cu) ions in MeCN, leads to the isolation of V-based coordination polymers of [N(n-Bu)4][Fe(II)V(II)I(ox)3].0.30[[N(n-Bu)4](BF4)] (2), [N(n-Bu)4][Co(II)V(III)(ox)3].0.75[[N(n-Bu)4](BF4)] (3), [N(n-Bu)4][Ni(II)V(III)(ox)3].0.20[[N(n-Bu)4](BF4)].0.20MeCN (4), and [N(n-Bu)4][Cu(II)V(III)(ox)2](BF4)2 (5) composition. Due to the lability of [V(III)(ox)3]3- to dissociate ox2-, these compounds cannot be prepared from aqueous media. 5 is best described as [N(n-Bu)4][V(III)Cu(II)(ox)2](BF4)2, and 2, 3, 4, and 5 are proposed to have a layered (2-D) motif for the MM(ox)x (x = 2, 3) extended framework. The [V(III)Cu(II)(ox)2] composition of 5 is reported for the first time for a bimetallic oxalate. 2 shows a weak antiferromagnetic interaction between Fe(II), S = 2 and V(III), S = 1 ions (theta = -9.4 K) within the 2-D layers. 3 and 5 do not magnetically order above 2 K. 4 magnetically order as ferromagnets below 2.55 K [taken as the onset of magnetization in chi'(T)], and has a glass transition temperature (chi'(max) at 1000 Hz) at 2.26 K.     

Incorporation of substitutionally labile [V(III)(CN)6]3- into prussian blue type magnetic materials

A Prussian blue (PB) type material containing hexacyanovanadate(III), Mn(II)1.5[V(III)(CN)6].(0.30)MeCN (1), was formed from the reaction of [V(III)(CN)6](3-) with [Mn(NCMe)6](2+) in MeCN. This new material exhibits ferrimagnetic spin- or cluster-glass behavior below a Tc of 12K with observed magnetic hysteresis at 2 K (Hcr = 65 Oe and Mrem = 730 emu.Oe/mol). Reactions of [V(III)(CN)6](3-) with [M(II)(NCMe)6](2+) (M = Fe, Co, Ni) in MeCN lead to either partial (M = Co) or complete (M = Fe, Ni) linkage isomerization, resulting in compounds of Fe(II)(0.5)V(III)[Fe(II)(CN)6].(0.85)MeCN (2), (NEt4)(0.10)Co(II)(1.5- a)V(II)a[Co(III)(CN)6]a [V(III)(CN)6](1-a)(BF4)(0.10).(0.35)MeCN (3), and (NEt4)(0.20)V(III)[Ni(II)(CN)4](1.6).(0.10)MeCN (4) compositions. Compounds 2-4 do not magnetically order as a consequence of diamagnetic cyanometalate anions being present, i.e., [Fe(II)(CN)6](4-), [Co(III)(CN)6](3-), and [Ni(II)(CN)4](2-). Incorporation of [V(III)(CN)6](3-) into PB-type materials is synthetically challenging because of the lability of the cyanovanadate(III) anion.     

Synthesis, characterization, and electrochemical studies of beta,beta'-fused metallocenoporphyrins

Beta,beta'-Fused monoruthenocenylporphyrins, Cp*Ru(III)[1,2-[M(II)-5,10,15,20-tetrakis(3,5-di-tert-butylphenyl)-porphyrinato]-3-methyl-cyclopentadienide] (M = Ni (20), Cu (21), Zn (22)), and bisferrocenoporphyrins, Fe(II) bis[1,2-[M(II)-5,10,15,20-tetraphenylporphyrinato]-3-methyl-cyclopentadienide] (M = Ni (24), Cu (25), Zn (26)), were synthesized and characterized. A novel synthetic approach to beta,beta'-fused porphyrins through Pd(0)-catalyzed [3 + 2] cycloaddition was implemented in this work. UV-vis spectra of these compounds show largely broadened and red-shifted bands (relative to their precursors) indicating potential electronic communication between the attached organometallic moiety and the porphyrin core. The electrochemistry of these molecules suggests significant electronic interactions between the metallocene and metalloporphyrin in molecules 20 and 24. The crystal structure of the bisferrocenoporphyrin 26, Fe(II) bis[1,2-[Zn(II)-5,10,15,20-tetraphenylporphyrinato]-3-methyl-cyclopentadienide], was determined: [Cp2Fe[ZnTPP(THF)]2][Cp2Fe[ZnTPP(THF)ZnTPP(MeOH)]].3MeOH.6THF, M = 3804.35, monoclinic, space group P21/c, a = 33.327(5) A, b = 19.145(3) A, c = 29.603(5) A, beta = 106.309(2) degrees , V = 18128(5) A3, Z = 4. In this molecule, one porphyrin ring is rotated by about 72 degrees with respect to the other in the 5-fold axis of the Cp ring.     

Metal telluride clusters composed of niobocene carbonyl, telluride, and cobalt carbonyl units: syntheses, structures, and reactivity

Abstract: The reaction of [Cp#2NbTe2H] (1#; Cp# = Cp* (C5Me5) or Cp(x) (C5Me4Et)) with two equivalents of [Co2(CO)8] gives a series of cobalt carbonyl telluride clusters that contain different types of niobocene carbonyl fragments. At 0 degrees C, [Cp#2NbTe2CO3(CO)7] (2#) and [Co4Te2(CO)10] (3) are formed which disappear at higher temperatures: in boiling toluene a mixture of [cat2][Co9Te6(CO)8] (5#) (cat= [Cp#2Nb(CO)2]+) and [cat2][Co11Te7(CO)10] (6#) is formed along with [cat][Co(CO)4] (4#). Complexes 6# transform into [cat][Co11Te7(CO)10] (7#) upon interaction with HPF6 or wet SiO2. The molecular structures of 2(Cp(x)), 4(Cp(x)), 5(Cp*), 6(Cp*) and 7(Cp*) have been determined by X-ray crystallography. The structure of the neutral 2(Cp(x)) consists of a [Co3(CO)6Te2] bipyramid which is connected to a [(C5Me4Et)2Nb(CO)] fragment through a mu4-Te bridge. The ionic structures of 4(Cp(x)), 5(Cp*), 6(Cp*) and 7(Cp*) each contain one (4, 7) or two (5, 6) [Cp#2Nb(CO)2]+ cations. Apart from 4, the anionic counterparts each contain an interstitial Co atom and are hexacapped cubic cluster anions [Co9Te6(CO)8]2- (5) or heptacapped pentagonal prismatic cluster anions [Co11Te7(CO)10]n- (n=2: [6]2- , n=1: [7]-), respectively. Electrochemical studies established a reversible electron transfer between the anionic clusters [Co11,Te7(CO)10]- and [Co11Te7(CO)10]2in 6# and 7# and provided evidence for the existence of species containing [Co11Te7(CO),0] and [Co11Te7(CO)0]3-. The electronic structures of the new clusters and their relative stabilities are examined by means of DFT calculations.     

Re(eta(5)-C5H5)(CO)3]+ family of 17-electron compounds: monomer/dimer equilibria and other reactions

The anodic electrochemical oxidations of ReCp(CO)3 (1, Cp = eta(5)-C5H5), Re(eta(5)-C5H4NH2)(CO)3 (2), and ReCp*(CO)3 (3, Cp* = eta(5)-C5Me5), have been studied in CH2Cl2 containing [NBu4][TFAB] (TFAB = [B(C6F5)4]-) as supporting electrolyte. One-electron oxidations were observed with E(1/2) = 1.16, 0.79, and 0.91 V vs ferrocene for 1-3, respectively. In each case, rapid dimerization of the radical cation gave the dimer dication, [Re2Cp(gamma)2(CO)6]2+ (where Cp(gamma) represents a generic cyclopentadienyl ligand), which may be itself reduced cathodically back to the original 18-electron neutral complex ReCp(gamma)(CO)3. DFT calculations show that the SOMO of 1+ is highly Re-based and hybridized to point away from the metal, thereby facilitating the dimerization process and other reactions of the Re(II) center. The dimers, isolated in all three cases, have long metal-metal bonds that are unsupported by bridging ligands, the bond lengths being calculated as 3.229 A for [Re2Cp2(CO)6]2+ (1(2)2+) and measured as 3.1097 A for [Re2(C5H4NH2)2(CO)6]2+ (2(2)2+) by X-ray crystallography on [Re2(C5H4NH2)2(CO)6][TFAB]2. The monomer/dimer equilibrium constants are between K(dim) = 10(5) M(-1) and 10(7) M(-1) for these systems, so that partial dissociation of the dimers gives a modest amount of the corresponding monomer that is free to undergo radical cation reactions. The radical 1+ slowly abstracts a chlorine atom from dichloromethane to give the 18-electron complex [ReCp(CO)3Cl]+ as a side product. The radical cation 1+ acts as a powerful one-electron oxidant capable of effectively driving outer-sphere electron-transfer reactions with reagents having potentials of up to 0.9 V vs ferrocene.     

Syntheses of the 47 electron clusters [(Cp*Fe)3(mu3-X)2] (X = S, Se) and the First Fe/Sn/Se Heterocubane Cluster [(CpFe)3(SnCl3)(mu3-Se)4] x DME by the use of chalcogenostannate salts

By reacting 1-aminoethylammonium (H2NCH2CH2NH3+ = enH+) salts of [Sn2E6]4- anions (E = S, Se), [enH]4[Sn2S6] (1) and [enH]4[Sn2Se6] x en (2), with FeCl2/LiCp, three novel (partly) oxidized, Cp* ligated iron chalcogenide clusters were synthesized. Two of them, [(CpFe)3(mu3-S)2] (3) and [(Cp*Fe)3(mu3-Se)2] (4), contain formally 47 valence electrons. [(Cp*Fe)3(SnCl3)(mu3-Se)4] x DME (5) represents the first known mixed metal Fe/Sn/Se heterocubane type cluster. Compounds 3-5 were structurally characterized by single-crystal X-ray diffraction, and the odd valence electron number of the [Fe3E2] clusters (E = S, Se) was confirmed by density functional (DFT) investigations, mass spectrometry, cyclic voltammetry and a susceptibility measurement of 3.     

Electronic structure of nitric oxide adducts of bis(diaryl-1,2-dithiolene)iron compounds: four-membered electron-transfer series [Fe(NO)(L)2]z (z = 1+, 0, 1-, 2-)

Four members of the electron-transfer series [Fe(NO)(S(2)C(2)R(2))2]z (z = 1+, 0, 1-, 2-) have been isolated as solid materials (R = p-tolyl): [1a](BF4), [1a]0, [Co(Cp)2][1a], and [Co(Cp)2]2[1a]. In addition, complexes [2a]0 (R = 4,4-diphenyl), [3a]0 (R = p-methoxyphenyl), [Et(4)N][4a] (R = phenyl), and [PPh(4)][5a] (R = -CN) have been synthesized and the members of each of their electron-transfer series electrochemically generated in CH(2)Cl(2) solution. All species have been characterized electro- and magnetochemically. Their electronic, M?ssbauer, and electron paramagnetic resonance spectra as well as their infrared spectra have been recorded in order to elucidate the electronic structure of each member of the electron-transfer series. It is shown that the monocationic, neutral, and monoanionic species possess an {FeNO}6 (S = 0) moiety where the redox chemistry is sulfur ligand-based, (L)2-(L*)1-: [Fe(NO)(L*)2]+ (S = 0), [Fe(NO)(L*)(L)]0 <--> [Fe(NO)(L)(L*)]0 (S = 1/2), [Fe(NO)(L)2]- (S = 0). Further one-electron reduction generates a dianion with an {FeNO}7 (S = 1/2) unit and two fully reduced, diamagnetic dianions L2-: [Fe(NO)(L)2]2- (S = 1/2).     

Assembly of azido- or cyano-bridged binuclear complexes containing the bulky [Mn(phen)2]2+ building block: syntheses, crystal structures, and magnetic properties

Two new cyano-bridged heterobinuclear complexes, [Mn(II)(phen)2Cl][Fe(III)(bpb)(CN)2] x 0.5CH3CH2OH x 1.5H2O (1) and [Mn(II)(phen)2Cl][Cr(III)(bpb)(CN)2] x 2H2O (2) [phen = 1,10-phenanthroline; bpb(2-) = 1,2-bis(pyridine-2-carboxamido)benzenate], and four novel azido-bridged Mn(II) dimeric complexes, [Mn2(phen)4(mu(1,1)-N3)2][M(III)(bpb)(CN)2]2 x H2O [M = Fe (3), Cr (4), Co (5)] and [Mn2(phen)4(mu(1,3)-N3)(N3)2]BPh4 x 0.5H2O (6), have been synthesized and characterized by single-crystal X-ray diffraction analysis and magnetic studies. Complexes 1 and 2 comprise [Mn(phen)2Cl]+ and [M(bpb)(CN)2]- units connected by one cyano ligand of [M(bpb)(CN)2]-. Complexes 3-5 are doubly end-on (EO) azido-bridged Mn(II) binuclear complexes with two [M(bpb)(CN)2]- molecules acting as charge-compensating anions. However, the Mn(II) ions in complex 6 are linked by a single end-to-end (EE) azido bridging ligand with one large free BPh4(-) group as the charge-balancing anion. The magnetic coupling between Mn(II) and Fe(III) or Cr(III) in complexes 1 and 2 was found to be antiferromagnetic with J(MnFe) = -2.68(3) cm(-1) and J(MnCr) = -4.55(1) cm(-1) on the basis of the Hamiltonian H = -JS(Mn)S(M) (M = Fe or Cr). The magnetic interactions between two Mn(II) ions in 3-5 are ferromagnetic in nature with the magnetic coupling constants of 1.15(3), 1.05(2), and 1.27(2) cm(-1) (H = -JS(Mn1)S(Mn2)), respectively. The single EE azido-bridged dimeric complex 6 manifests antiferromagnetic interaction with J = -2.29(4) cm(-1) (H = -JS(Mn1)S(Mn2)). Magneto-structural correlationship on the EO azido-bridged Mn(II) dimers has been investigated.     

Preparation, UV-vis, IR, EPR and resonance Raman study of Fe, Ni, Co and Zn dioxolene complexes

An UV-vis, Raman, IR and EPR spectroscopic study was performed for the water soluble complexes of Fe(III), Ni(II), Co(II) and Zn(II) coordinated to dioxolene ligands derived from oxidized dopamine. The complexes were obtained and stabilized at neutral pH by the strong reducing agent sodium thiosulfate. Iron(III) stabilizes the ligand in catecholate form as [Fe(III)(Cat)2]1-, Cat=dopacatecholate, and the divalent metals as dopasemiquinone (SQ): [Ni(SQ)3]1-, [Co(SQ)3]1- and [Zn(SQ)3]1-. The resonance Raman spectra of the solid complexes as [CAT][Ni(SQ)3], [CTA][Co(SQ)3] and [CTA][Zn(SQ)3], CTA is the cetyltrimethylammonium, are very similar to the spectra of the complexes in solution, while the Fe(III) complex is a mixture of two iron complexes, with catecholate or dopasemiquinone ligands.     

Dinuclear Cp* cobalt complexes of the 1,2,4,5-benzenetetrathiolate bischelating ligand

The dinuclear Cp*Co dithiolene complex [Cp*Co(btt)CoCp*] ( 1) is prepared in high yield from the reaction of the bis(dibutyltin) complex of 1,2,4,5-benzenetetrathiolate (btt) with 2 equiv of [Cp*Co(CO)I 2]. Mononuclear complexes are also obtained from 1,2,4,5-tetrakis(isopropylthio)benzene ( 2) and sodium in pyridine, from benzo[1,2- d;4,5- d ']bis(1,3-dithiolane-2,6-dione) ( 3) and ( t )BuOK in tetrahydrofuran, or from benzo[ d]-1,3-dithiolane-2-one ( 7) and ( t )BuOK to afford respectively 4a, 4b, and [Cp*Co(bdt)] ( 6), while [Cp*Co(dmit)] ( 8) is obtained by literature methods. The X-ray structures of the dinuclear complex 1 and the mononuclear complexes 4a and 6 were determined. They are all characterized by Cp* . . . btt face-to-face intermolecular interactions, leading to a recurrent 4-fold symmetry motif. The cyclic voltammograms of the [Cp*Co(dithiolene)] complexes performed in CH 2Cl 2 show reversible Co (III) to Co (II) reduction but irreversible oxidation waves. The large potential difference between the two reduction waves of the bimetallic complex 1 (269 mV) indicates a stable mixed-valence Co (III)-Co (II) state for the reduced [Cp*Co(btt)CoCp*] (-) anion. Upon trimethyl phosphite addition, the mono-P(OMe) 3 adduct [ 1.P(OMe) 3] exhibits a red shift of the low-energy absorption band to the IR region (856 nm, = 13 000 M (-1).cm (-1)), while [ 8.P(OMe) 3] exhibits a 150 nm blue shift. The stability constants of these P(OMe) 3 adducts were determined from UV-vis spectroscopic titration experiments, with, for example, log( K/mol (-1).dm (3)) values of 3.1 and 0.52 for the mono- and bis-adduct of 1, respectively. The electrochemical investigation of 1 and 8 in excess phosphite shows a strong current enhancement upon oxidation, attributable to the catalytic generation of the radical cation P(OMe) 3 (*+).     

Synthesis, structures, and properties of group 9- and group 10-group 6 heterodinuclear nitrosyl complexes

The reaction of the group 9 bis(hydrosulfido) complexes [Cp*M(SH)2(PMe3)] (M=Rh, Ir; Cp*=eta(5)-C 5Me5) with the group 6 nitrosyl complexes [Cp*M'Cl2(NO)] (M'=Mo, W) in the presence of NEt3 affords a series of bis(sulfido)-bridged early-late heterobimetallic (ELHB) complexes [Cp*M(PMe3)(mu-S)2M'(NO)Cp*] (2a, M=Rh, M'=Mo; 2b, M=Rh, M'=W; 3a, M=Ir, M'=Mo; 3b, M=Ir, M'=W). Similar reactions of the group 10 bis(hydrosulfido) complexes [M(SH)2(dppe)] (M=Pd, Pt; dppe=Ph 2P(CH2) 2PPh2), [Pt(SH)2(dppp)] (dppp=Ph2P(CH2) 3PPh2), and [M(SH)2(dpmb)] (dpmb=o-C6H4(CH2PPh2)2) give the group 10-group 6 ELHB complexes [(dppe)M(mu-S)2M'(NO)Cp*] (M=Pd, Pt; M'=Mo, W), [(dppp)Pt(mu-S)2M'(NO)Cp*] (6a, M'=Mo; 6b, M'=W), and [(dpmb)M(mu-S)2M'(NO)Cp*] (M=Pd, Pt; M'=Mo, W), respectively. Cyclic voltammetric measurements reveal that these ELHB complexes undergo reversible one-electron oxidation at the group 6 metal center, which is consistent with isolation of the single-electron oxidation products [Cp*M(PMe3)(mu-S)2M'(NO)Cp*][PF6] (M=Rh, Ir; M'=Mo, W). Upon treatment of 2b and 3b with ROTf (R=Me, Et; OTf=OSO 2CF 3), the O atom of the terminal nitrosyl ligand is readily alkylated to form the alkoxyimido complexes such as [Cp*Rh(PMe3)(mu-S)2W(NOMe)Cp*][OTf]. In contrast, methylation of the Rh-, Ir-, and Pt-Mo complexes 2a, 3a, and 6a results in S-methylation, giving the methanethiolato complexes [Cp*M(PMe3)(mu-SMe)(mu-S)Mo(NO)Cp*][BPh 4] (M=Rh, Ir) and [(dppp)Pt(mu-SMe)(mu-S)Mo(NO)Cp*][OTf], respectively. The Pt-W complex 6b undergoes either S- or O-methylation to form a mixture of [(dppp)Pt(mu-SMe)(mu-S)W(NO)Cp*][OTf] and [(dppp)Pt(mu-S) 2W(NOMe)Cp*][OTf]. These observations indicate that O-alkylation and one-electron oxidation of the dinuclear nitrosyl complexes are facilitated by a common effect, i.e., donation of electrons from the group 9 or 10 metal center, where the group 9 metals behave as the more effective electron donor.     

A new route into single-crystalline partially oxidized cobalt compounds: reactions with zintl-type hexaselenodistannate(III) K6Sn2Se6 as mild oxidant

Reactions of K6Sn2Se6 (1) with [Cp*CoCl]2 were investigated in order to probe the stability of the formal +3 oxidation state at Sn and possible ligand properties of heteroatomic zintl-type anion "Sn2Se6(6)- ". From these experiments, we obtained the following compounds that are oxidized to different extent as a result of the reaction with SnIII: [Cp2*Co][Cl2Co(mu2-Cl)2Li(thf)2] (2), [(Cp*Co)3(mu-Se)2] (3), [(Cp*Co)3(mu3-Se)2][Cl2Co(mu2-Cl)2Li(thf)2] (4), and [(Cp*Co)4(mu3-Se)4] (5). These compounds were structurally characterized by single-crystal X-ray diffractometry. It shows that the reaction conditions strongly affect the type and oxidation state of the isolated product. Two of the observed compounds, 3 and 4, are closely related both structurally and electronically; this is discussed and further illustrated by cyclovoltammetric measurements. The choice of the terminal Cp* ligand attached to the transition metal in the reactand complex is assumed to be basically dependent for the alignment of unexpected structural details when compared with known compounds of similar compositions. In conclusion, 1 is observed to act as mild oxidant as well as selenide donor, but is not in the position to keep its Sn-Se framework under the given reaction conditions.     

Magnetic properties of cyano-bridged Ln3+-M3+ complexes. Part I: trinuclear complexes (Ln3+ = La, Ce, Pr, Nd, Sm; M3+ = FeLS, Co) with bpy as blocking ligand

The reaction of Ln(NO3)3(aq) with K3[Fe(CN)6] or K3[Co(CN)6] and 2,2'-bipyridine in water/ethanol led to eight trinuclear complexes: trans-[M(CN)4(mu-CN)2{Ln(H2O)4(bpy)2}2][M(CN)6].8H2O (M = Fe3+ or Co3+, Ln = La3+, Ce3+, Pr3+, Nd3+, and Sm3+). The structures for the eight complexes [La2Fe] (1), [Ce2Fe] (2), [Pr2Fe] (3), [Nd2Fe] (4), [Ce2Co] (5), [Pr2Co] (6), [Nd2Co] (7), and [Sm2Co] (8) have been solved; they crystallize in the triclinic space group P and are isomorphous. They exhibit a supramolecular 3D architecture through hydrogen bonding and pi-pi stacking interactions. A stereochemical study of the nine-vertex polyhedra of the lanthanide ions, based on continuous shape measures, is presented. No significant magnetic interaction was found between the lanthanide(III) and the iron(III) ions.     

Entrapment of [Ru(bpy)3]2+ in the anionic metal-organic framework: novel photoluminescence behavior exhibiting dual emission at room temperature

[Ru(bpy)(3)](2+) (bpy = 2,2'-bipyridine) ions were entrapped into the cavities of two-dimensional anionic sheet-like coordination polymeric networks of [M(dca)(3)](-) (dca = dicyanamide; M = Mn(II) and Fe(II)). The prepared compounds, {[Ru(bpy)(3)][Mn(dca)(3)](2)}(n) (1) and {[Ru(bpy)(3)][Fe(dca)(3)](2)}(n) (2), were structurally characterized by X-ray single crystal analysis. The spectroscopic properties of the [Ru(bpy)(3)](2+) ion dramatically changed on its entrapment in [M(dca)(3)](-). The [Ru(bpy)(3)](2+) moiety present in 1 and 2 exhibits novel dual photo-emission at room temperature.