Electron paramagnetic resonance and spectroscopic characteristics of electrogenerated mixed-valent systems [(eta 5-C5Me5)M(mu-L)M(eta 5-C5Me5)]+ (M = Rh, Ir; L = 2,5-diiminopyrazines) in relation to the radicals [(eta 5-C5Me5)ClM(mu-L)MCl(eta 5-C5Me5)]+ and [(eta 5-C5Me5)M(mu-L)MCl(eta 5-C5Me5)]2+

Electrochemical reduction of the dinuclear [(eta 5-C5Me5)ClM(mu-L)MCl(eta 5-C5Me5)]2+ ions (M = Rh, Ir; L = 2,5-bis(1-phenyliminoethyl)pyrazine (bpip) and 2,5-bis[1-(2,6-dimethylphenyl)iminoethyl]pyrazine (bxip)) proceeds via the paramagnetic intermediates [(eta 5-C5Me5)ClM(mu-L)MCl(eta 5-C5Me5)]+ (L = bpip) or [(eta 5-C5Me5)M(mu-L)MCl(eta 5-C5Me5)]2+ (L = bxip) and [(eta 5-C5Me5)M(mu-L)M(eta 5-C5Me5)]+. Whereas the first is clearly a radical species with a small g anisotropy, the chloride-free cations are distinguished by structured intervalence charge transfer (IVCT) bands in the near-infrared region and by rhombic electron paramagnetic resonance features between g = 1.9 and g = 2.3, which suggests considerable metal participation at the singly occupied MO. Alternatives for the d configuration assignment and for the role of the bisbidentate-conjugated bridging ligands will be discussed. The main difference between bpip and bxip systems is the destabilization of the chloride-containing forms through the bxip ligand for reasons of steric interference.     

Activation of SO2 with [(η5‐C5Me5)2Ln(THF)2] (Ln=Eu,Yb) Leading to Dithionite and Sulfinate Complexes

The reaction of decamethylytterbocene [(η⁵‐C₅Me₅)₂Yb(THF)₂] with SO₂ at low temperature gave two new compounds, namely, the Yb^III dithionite/sulfinate complex [{(η⁵‐C₅Me₅)₂Yb(μ₃,1κ²O^1,3,2κ³O^2,2′,4‐S₂O₄)}₂{(η⁵‐C₅Me₅)Yb(μ,1κO,2κO′‐C₅Me₅SO₂)}₂] ( 1 ) and the Yb^III dithionite complex [{(η⁵‐C₅Me₅)₂Yb}₂(μ,1κ²O^1,3,2κ²O^2,4‐S₂O₄)] ( 2 ). After extraction of 1 , the mixture was heated to give the dinuclear tetrasulfinate complex [{(η⁵‐C₅Me₅)Yb}₂(μ,κO,κO’‐C₅Me₅SO₂)₄] ( 3 a ). In contrast, from the reaction of [(η⁵‐C₅Me₅)₂Eu(THF)₂] with SO₂ only the tetrasulfinate complex [{(η⁵‐C₅Me₅)Eu}₂(μ,κO,κO’‐C₅Me₅SO₂)₄] ( 3 b ) was isolated. Two major reaction pathways were observed: 1) reductive coupling of two SO₂ molecules to form the dithionite anion S₂O₄^2?; and 2) nucleophilic attack of one metallocene C₅Me₅ ligand on the sulfur atom of SO₂. The compounds presented are the first dithionite and sulfinate complexes of the f‐elements.     

Syntheses of (C_5H_9C_5H_4)_2LnCl(THF)_n (Ln=Nd, Sm, Er, Yb) and crystal structure of [(C_5H_9C_5H_4)_2-LnCl(THF)_n]_2(Ln=Sm, n=1; Ln=Er, n=0)

Reactions of lanthanoid trichlorides with sodium cyclopentylcyclopentadienyl in THFafford bis(cyclopentylcyclopentadienyl) lanthanoid chloride complexes (C_5H_9C_5H_4)_2LnCl(THF)_n (Ln=Nd, Sm, n=1; Ln= Er, Yb, n= 0). The compound [CP'_2SmCl(THF)]_2 (2) (Cp' =cyclopentylcy-clopentadienyl) crystallizes from mixed solvent of hexane and THF in monoclinic space group P_2_1/cwith a = 11.583 (3), b = 23.019(6), c = 8.227 (2), β= 90.26 (2)°, V= 2194 (1)~3, D_c= 1.59 g/cm~3.μ= 28.6 cm~(-1), F(000) = 1060, Z= 2 (dimers). Its crystal molecule is a dimer with a crystallographicsymmetry center. The central metal atom Sm is coordinated to two Cp' rings, two bridging chlorineatoms and one THF forming a distorted trigonal bipyramid. The crystal of [Cp'_2ErCl]_2 (3) belongs tothe triclinic space group P with a = 11.264 (2), b= 13.296(5), c = 14.296(6), a = 96.99 (3), β=112.47(2), γ= 102.78(2)°, V= 1865(1)~3, D_c= 1.67 g /cm~3, μ= 48.0 cm~(-1), F(000) = 924, Z = 2 (dimers).The molecule is a dimer consisting of two Cp'_2 ErCl species bridged by two Cl atoms. The centralmetal atom Er is coordinated to two Cp' rings and two bridging chlorine atoms forming a pseudo-tetrahedron. All these complexes are soluble in THF, DME, Et_2O, toluene and hexane.     

On the origin of dinitrogen hydrogenation promoted by [(eta5-C5Me4H)2Zr]2(mu2,eta2,eta2-N2)

The origin of the hydrogenation of the dinitrogen ligand in [(eta5-C5Me4H)2Zr]2(mu2,eta2,eta2-N2) has been investigated by a combined computational and experimental study. Density functional theory calculations on the zirconocene dinitrogen complex demonstrate significant imido character in the zirconium nitrogen bonds, arising from effective pi-back-bonding from the low-valent zirconium and the side-on bound N2 ligand. The twisted ground-state structure of the N2 complex is a key requirement for nitrogen hydrogenation, as calculations on the model complex [(eta5-C5H5)2Zr]2(mu2,eta2,eta2-N2) reveal reduced overlap as the dihedral angle between the zirconocene wedges approaches 0 degrees . Experimentally, isotopic labeling studies on the microscopic reverse are consistent with a 1,2-addition mechanism for nitrogen hydrogenation.     

A monometallic f element complex of dinitrogen: (C5Me5)3U(eta1-N2)

The reactivities of (C5Me5)3U and (C5Me4H)3U were compared using both common (THF) and nontraditional (N2) ligands for f elements. THF coordinates the less-crowded (C5Me4H)3U to form (C5Me4H)3U(THF) while ring opening occurs with sterically crowded (C5Me5)3U. N2 at 80 psi reacts with (C5Me5)3U to form (C5Me5)3U(eta1-N2) [U-N(N2) = 2.492(10) A, nu(N2) = 2207 cm-1, and cnt-U-N2 = 90 degrees ], whereas only (C5Me4H)3U was isolated under 80 psi of N2.     

Synthetic utility of [(C5Me5)2Ln][(mu-Ph)2BPh] in accessing [(C5Me5)2LnR]x unsolvated alkyl lanthanide metallocenes, complexes with high C-H activation reactivity

The loosely ligated [BPh4]1- ion in [(C5Me5)2Ln][(mu-Ph)2BPh2] can be readily displaced by alkyllithium or potassium reagents to provide access to unsolvated alkyl lanthanide metallocenes, [(C5Me5)2LnR]x, which display high C-H activation reactivity. [(C5Me5)2SmMe]3, [(C5Me5)2LuMe]2, [(C5Me5)2LaMe]x, (C5Me5)2Sm(CH2Ph), [(C5Me5)2Sm(CH2SiMe3)]x, and [(C5Me5)2SmPh]2 were prepared in this way. [(C5Me5)2SmMe]3 metalates toluene, benzene, SiMe4, and (C5Me5)1- ligands to make (C5Me5)2Sm(CH2Ph), [(C5Me5)2SmPh]2, [(C5Me5)2Sm(CH2SiMe3)]x, and (C5Me5)6Sm4[C5Me3(CH2)2]2, respectively. These C-H activation reactions can be done using an in situ synthesis of [(C5Me5)2LnMe]x such that the [(C5Me5)2Ln][(mu-Ph)2BPh2]/LiMe/RH combination provides a facile route to a variety of unsolvated [(C5Me5)2LnR]x products.     

Syntheses and molecular structures of eta3-[(eta5-Cp*)(CO)2Fe-AsPC(SiMe3)2]M(CO)2(eta5-Cp)(M = Mo, W): the first complexes featuring eta3-arsaphosphaallyl ligands

Reaction of (eta5-Cp)(CO)2M=P=C(SiMe3)2 4a (M = Mo) and 4b (M = W) with (eta5-Cp*)(CO)2Fe-As=C(NMe2)2 5 affords the eta3-1-arsa-2-phosphaallyl complexes [(eta5-Cp*)(CO)2Fe-AsPC(SiMe3)2]M(CO)2(eta5-Cp) 6a and 6b, the molecular structures of which were determined by X-ray analyses.     

Synthesis, structure, and ligand-based reduction reactivity of trivalent organosamarium benzene chalcogenolate complexes (C(5)Me(5))(2)Sm(EPh)(THF) and [(C(5)Me(5))(2)Sm(mu-EPh)](2)

To compare the ligand-based reduction chemistry of (EPh)(-) ligands in a metallocene environment to the sterically induced reduction chemistry of the (C(5)Me(5))(-) ligands in (C(5)Me(5))(3)Sm, (C(5)Me(5))(2)Sm(EPh) (E = S, Se, Te) complexes were synthesized and treated with substrates reduced by (C(5)Me(5))(3)Sm: cyclooctatetraene; azobenzene; phenazine. Reactions of PhEEPh with (C(5)Me(5))(2)Sm(THF)(2) and (C(5)Me(5))(2)Sm produced THF-solvated monometallic complexes, (C(5)Me(5))(2)Sm(EPh)(THF), and their unsolvated dimeric analogues, [(C(5)Me(5))(2)Sm(mu-EPh)](2), respectively. Both sets of the paramagnetic benzene chalcogenolate complexes were definitively identified by X-crystallography and form homologous series. Only the (TePh)(-) complexes show reduction reactivity and only upon heating to 65 degrees C.     

Studies of the synthesis and thermochemistry of coordinatively unsaturated chelate complexes (eta 5-C5Me5)IrL2 (L2 = TsNCH2CH2NTs, TsNCH2CO2, CO2CO2)

A comparative synthetic, structural, and thermochemical study on a series of chelate complexes containing the fragment (eta 5-C5Me5)Ir [(eta 5-C5Me5)Ir(TsNCH2CH2NTs) (1), (eta 5-C5Me5)Ir(TsNCH2CO2) (2), (eta 5-C5Me5)Ir(CO2CO2) (3)] was performed to clarify the roles of carboxylato and sulfonamido ligands. Whereas 1 and 2 are monomeric in solution and in the solid state, 3 appears to exist as an oligomer or polymer, (3)n, which can be broken up by addition of a ligand L such as a phosphine, CO, or 2-methoxypyridine to form (eta 5-C5Me5)Ir(L)(CO2CO2) (6). The synthesis of (3)n from [(eta 5-C5Me5)IrCl(mu-Cl)]2 required the use of silver oxalate in CH3CN, but if other solvents were used, the bridging oxalato complex (eta 5-C5Me5)IrCl(mu-eta 2-eta 2-C2O4)ClIr(eta 5-C5Me5) (7) was obtained and identified by X-ray diffraction. Enthalpies for reaction of THF-soluble monomers 1 and 2 with PMe3 were determined to be -28.7(0.5) and -28.5(0.4) kcal mol-1, respectively. The oligomerization behavior of 3 may be a result of reduced sigma- or pi-donation of carboxylato ligands compared to N-tosylamido ligands, because the values for nu CO in oxalato and bissulfonamido complexes 6-CO and (eta 5-C5Me5)Ir(CO)(TsNCH2CH2NTs) (4-CO) were 2064 and 2042 cm-1, respectively.     

Synthesis and dynamic NMR studies of Pt(eta(5)-C(5)Me(5))(CO){C(O)NR(2)} complexes

The formation of Pt(eta(5)-C(5)Me(5))(CO){C(O)NR(2)} (R=Me, Et) complexes was established by spectroscopic analysis. The infrared spectra of these complexes showed a sharp absorption due to the presence of coordinated carbonyl group in the region 2017-2013cm(-1). The N,N-dialkylcarbamoyl ligands showed a characteristic CO stretching absorption in the range 1609-1616cm(-1). The proton NMR spectra of these complexes revealed the expected singlet arising from five equivalent methyl groups on the cyclopentadienyl ring with satellites due to coupling to (195)Pt. The N-methyl and N-ethyl protons exhibited very broad resonances due to restricted rotation about the N-C bond at room temperature. On cooling to -30 degrees C, the N,N-dimethyl protons for complex Pt(eta(5)-C(5)Me(5))(CO){C(O)NMe(2)} showed two sharp singlets at delta 2.86 and 3.09ppm as expected for the static structure. For the N,N-diethyl derivative, Pt(eta(5)-C(5)Me(5))(CO){C(O)NEt(2)}, the methyl protons exhibited only a single triplet at delta 1.06ppm at -10 degrees C due to coupling with the methylene protons. This single resonance arises through accidental overlap as the methylene protons of the ethyl groups are inequivalent at this temperature and each exhibited a quartet at delta 3.33 and 3.70ppm due to coupling with the methyl protons. The singlet resonances for the methyl and ring carbons of the eta(5)-C(5)Me(5) group found in (13)C{(1)H} NMR spectra are illustrative of the chemical equivalence of all the carbon atoms caused by free rotation of the ring in these complexes. The signals attributable to the carbonyl and carbamoyl carbon atom resonances are found downfield as two singlets each with a large coupling constant to platinum. The platinum coupling constants of the downfield resonances could not be identified for Pt(eta(5)-C(5)Me(5))(CO){C(O)NMe(2)} due to presence of impurities.     

Reaktion des hydridodicobalt-kations [(C5H5Co)2(μ-PMe2)2(μ-H)]+ mit C2(CO2Me)2: Bildung und kristallstruktur eines zweikernkomplexes mit O=C(OMe)CH=C(CO2Me)PMe2 als 6-elektronen-donorligand

[(C₅H₅Co)₂(μ-PMe₂)₂(μ-H)]BF₄ ([II]BF₄) reacts with C₂(CO₂Me)₂ to give the products III and IV. The ionic compound III which formally is a $\text{1}\text{1}$ adduct of [II]BF₄ and C₂(CO₂Me)₂ has been characterized by X-ray structure analysis. III contains the group O=C(OMe)CH=C(CO₂Me)PMe₂ as a 6-electron donor ligand chelated to a cobalt atom and π-bonded to the other cobalt atom. Complex IV is a neutral compound which also can be obtained from [C₅H₅Co(μ-PMe₂)]₂ (I) and C₂(CO₂Me)₂.     

Ln4(CH2)4 cubane-type rare-earth methylidene complexes consisting of "(C5Me4SiMe3)LnCH2" units (Ln = Tm, Lu)

Tetranuclear cubane-type rare-earth methylidene complexes consisting of four "Cp'LnCH(2)" units, [Cp'Ln(μ(3)-CH(2))](4) (4-Ln; Ln = Tm, Lu; Cp' = C(5)Me(4)SiMe(3)), have been obtained for the first time through CH(4) elimination from the well-defined polymethyl complexes [Cp'Ln(μ(2)-CH(3))(2)](3) (2-Ln) or mixed methyl/methylidene precursors such as [Cp'(3)Ln(3)(μ(2)-Me)(3)(μ(3)-Me)(μ(3)-CH(2))] (3-Ln). The reaction of the methylidene complex 4-Lu with benzophenone leads to C═O bond cleavage and C═C bond formation to give the cubane-type oxo complex [Cp'Lu(μ(3)-O)](4) and CH(2)═CPh(2), while the methyl/methylidene complex 3-Tm undergoes sequential methylidene addition to the C═O group and ortho C-H activation of the two phenyl groups of benzophenone to afford the bis(benzo-1,2-diyl)ethoxy-chelated trinuclear complex [Cp'(3)Tm(3)(μ(2)-Me)(3){(C(6)H(4))(2)C(O)Me}] (6-Tm).     

Planar trimethylenemethane dianion chemistry of lanthanide metallocenes: synthesis, structure, density functional theory analysis, and reactivity of [(C5Me5)2Ln]2[mu-eta3:eta3-C(CH2)(3] Complexes

The unusual formation of planar trimethylenemethane (TMM) dianion complexes of lanthanide metallocenes, [(C5Me5)2Ln]2[mu-eta3:eta3-C(CH2)3] (Ln = Sm, 1; La, 2; Pr, 3; Nd, 4; Y, 5) has been examined by synthesizing examples with metals from La to Y to examine the effects of radial size on structure and to provide closed shell examples for direct comparison with density functional theory (DFT) calculations. Synthetic routes to 1-4 have been expanded from the [(C5Me5)2Ln][(mu-Ph)2BPh2]/neopentyl lithium reaction involving beta-methyl elimination to a [(C5Me5)2Ln][(mu-Ph)2BPh2]/isobutyl lithium route. The synthetic pathways are sensitive to metal radius. To obtain 5, the methylallyl complex, (C5Me5)2Y[CH2C(Me)CH2], 6, was synthesized and treated with [(C5Me5)2YH]x. In the Lu case, the neopentyl complex [(C5Me5)2LuCH2C(CH3)3]x, 7, was isolated instead of the TMM product. X-ray crystallography showed that the metrical parameters of the planar TMM dianions in each complex are similar. The structural data have been compared with DFT calculations on the closed-shell lanthanum and lutetium complexes that suggest only limited covalent interactions with the lanthanide ion. Benzophenone (2 equiv) reacts with 1 to expand the original four-carbon TMM skeleton to a dianionic bis(alkoxide) ligand containing a symmetrically substituted C=CH2 moiety in [(C5Me5)2Sm]2[mu-(OCPh2CH2)2C=CH2], 8. In this reaction, the TMM complex reacts as a bifunctional bisallylic reagent that generates an organic framework containing a central vinyl group.     

Nitrogenase model complexes [Cp*Fe(mu-SR(1))2(mu-eta(2)-R(2)N=NH)FeCp*] (R(1) = Me, Et; R(2) = Me, Ph; Cp* = eta(5)-C5Me5): synthesis, structure, and catalytic N-N bond cleavage of hydrazines on diiron centers

The reactions of [Cp*Fe(mu-SR1)3FeCp*] (Cp* = eta5-C5Me5; R1 = Et, Me) with 1.5 equiv R2NHNH2 (R2 = Ph, Me) give the mu-eta2-diazene diiron thiolate-bridged complexes [Cp*Fe(mu-SR1)2(mu-eta2-R2N NH)FeCp*], along with the formation of PhNH2 and NH3. These mu-eta2-diazene diiron thiolate-bridged complexes exhibit excellent catalytic N-N bond cleavage of hydrazines under ambient conditions.     

Four-electron reduction of dinitrogen during solution disproportionation of the organodimetallic (eta-C5Me4R)2Ta2(mu-Cl)4(R = Me, Et) to a new mu-eta1,eta1-N2 complex and odd-electron organotrimetallic cluster

(C5Me5R)2Ta2Cl4 (d2-d2) disproportionates under dinitrogen to [(C5Me4R)TaCl2]2(mu-N2) and the D3h cluster cation (C5Me4R)3Ta3(mu-Cl)6+ with anionic (C5Me4R)TaCl4-.