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The reaction of TPypA (tris(2-pyridylmethyl)amine) and Fe(BF4)2 and sodium nitraniIate (Na21NO2) or Mn(O2CMe)2 with chloranilic acid (H21Cl) respectively forms [FeIII(TPyA)1NO2]2O and MnII(TPyA)1Cl, respectively. The structures of these 7-coordinate compounds have been determined. The former is a dinuclear FeIII compound possessing equivalent Fe(III) sites, and the latter forms a 1-D zigzag chain based upon the two bridging 1NO22− ions. The isomer shift and quadrupole splitting of the 57Fe Mossbauer spectra of [Fe(TPyA)1NO2]2O are consistent binuclear seven-coordinate high-spin FeIII state. Below 35 K a single quadrupole doublet split onto two doublets of equal intensities and equal isomer shifts as a result of structural non-equivalency of two iron sites within a dimer. The magnetic properties of [FeIII(TPyA)1NO2]2O can be fit the a homonuclear S = 5/2 ± 5/2 dinuclear spin model with strong intradimer antiferromagnetic coupling of J/kB = −146 K (−101 cm−1) and g = 2.00, and interdimer coupling of θ = −5 K (H = −2JSa·Sb). MnII(TPyA)1Cl can be fit the a homonuclear S = 5/2 1-D Fisher chain expression with weak intrachain antiferromagnetic coupling with J/kB = −0.33 K (−0.23 cm−1) and g = 2.06.

Multimetallic complexes containing disparate metals have been established to have practical utilities. We previously reported a strategy for preparing such species by using combinations of neutral pyrazole (Hpyz, C3N2H4) and anionic pyrazolyl ligands (pyz, C3N2H3–), and herein are reported several new complexes that should be capable of incorporating a second metal center. Two of the complexes, [Ru(1,5-cod)(Hpyz)3Cl][BPh4] and Ru(1,5-cod)(Hpyz)2(pyz)2 (cod = cyclooctadiene), were prepared from [Ru(cod)Cl2]2, while [Ru(tmeda)(Hpyz)2Cl2][BF4] (tmeda = tetramethylethylenediamine) was prepared from the neutral Ru(II) complex Ru(tmeda)(Hpyz)2Cl2 via one electron oxidation by the ferricinium ion. The first two complexes, one cationic and the other uncharged, involve Ru(II), while the tmeda complex involves Ru(III). All three species have been structurally characterized.

Metal–flavonolate compounds are of significant current interest as synthetic models for quercetinase enzymes and as bioactive compounds of importance to human health. Zinc–3-hydroxyflavonolate compounds, including those of quercetin, kampferol, and morin, generally exhibit bidentate coordination to a single ZnII center. The bipyridine-ligated zinc–flavonolate compound reported herein, namely bis(μ-4-oxo-2-phenyl-4H-chromen-3-olato)-κ3 O 3:O 3,O 4;κ3 O 3,O 4:O 3-bis[(2,2′-bipyridine-κ2 N,N′)zinc(II)] bis(perchlorate), {[Zn2(C15H9O3)2(C10H8N2)2](ClO4)2} n , (1), provides an unusual example of bridging 3-hydroxyflavonolate ligation in a dinuclear metal complex. The symmetry-related ZnII centers of (1) exhibit a distorted octahedral geometry, with weak coordination of a perchlorate anion trans to the bridging deprotonated O atom of the flavonolate ligand. Variable-concentration conductivity measurements provide evidence that, when (1) is dissolved in CH3CN, the complex dissociates into monomers. 1H NMR resonances for (1) dissolved in d 6-DMSO were assigned via HMQC to the H atoms of the flavonolate and bipyridine ligands. In CH3CN, (1) undergoes quantitative visible-light-induced CO release with a quantum yield [0.004 (1)] similar to that exhibited by other mononuclear zinc–3-hydroxyflavonolate complexes. Mass spectroscopic identification of the [(bpy)2Zn(O-benzoylsalicylate)]+ ion provides evidence of CO release from the flavonol and of ligand exchange at the ZnII center.

The properties of the extended flavonol 3-hydroxy-2-phenyl-benzo[g]chromen-4-one (2a) in DMSO : aqueous buffer solutions at pH = 7.4, including in the presence of metal ions, surfactants and serum albumin proteins, have been examined. Absorption and emission spectral studies of 2a in 1 : 1 DMSO : PBS buffer (pH = 7.4) indicate that a mixture of neutral and anionic forms of the flavonol are present. Notably, in 1 : 1 DMSO : TRIS buffer (pH = 7.4) only the neutral form of the flavonol is present. These results indicate that the nature of the buffer influences the acid/base equilibrium properties of 2a. Introduction of a Zn(II) complex of 2a− to a 1 : 1 DMSO : aqueous buffer (TRIS or PBS, pH = 7.4) solution produces absorption and emission spectral features consistent with the presence of a mixture of neutral 2a along with Zn(II)-coordinated or free 2a−. The nature of the anionic species present depends on the buffer composition. PBS buffered solutions (pH = 7.4) containing the surfactants CTAB or SDS enable 2a to be solubilized at a much lower percentage of DMSO (3.3–4.0%). Solutions containing the cationic surfactant CTAB include a mixture of 2a and 2a− whereas only the neutral flavonol is present in SDS-containing buffered solution. Compound 2a is also solubilized in TRIS buffer solutions at low cocentrations of DMSO (3.3%, pH = 7.4) in the presence of serum albumin proteins. Stern–Volmer analysis of the quenching of the inherent protein fluorescence indicates static binding of 2a to the proteins. The binding constant for this interaction is lower than that found for naturally-occurring flavonols (quercetin or morin) or 3-hydroxyflavone. Compound 2a binds to Site I of bovine and human serum albumin proteins as indicated by competition studies with warfarin and ibuprofen, as well as by docking investigations. The quantum yield for CO release from 2a (λirr = 419 nm) under aqueous conditions ranges from 0.0006(3) when the compound is bound to bovine serum albumin to 0.017(1) when present as a zinc complex in a 1 : 1 DMSO : H2O solution. Overall, the results of these studies demonstrate that 2a is a predictable visible light-induced CO release compound under a variety of aqueous conditions, including in the presence of proteins.

Although low-dimensional S = 1 antiferromagnets remain of great interest, difficulty in obtaining high-quality single crystals of the newest materials hinders experimental research in this area. Polycrystalline samples are more readily produced, but there are inherent problems in extracting the magnetic properties of anisotropic systems from powder data. Following a discussion of the effect of powder-averaging on various measurement techniques, we present a methodology to overcome this issue using thermodynamic measurements. In particular we focus on whether it is possible to characterise the magnetic properties of polycrystalline, anisotropic samples using readily available laboratory equipment. We test the efficacy of our method using the magnets [Ni(H2O)2(3,5-lutidine)4](BF4)2 and Ni(H2O)2(acetate)2(4-picoline)2, which have negligible exchange interactions, as well as the antiferromagnet [Ni(H2O)2(pyrazine)2](BF4)2, and show that we are able to extract the anisotropy parameters in each case. The results obtained from the thermodynamic measurements are checked against electron-spin resonance and neutron diffraction. We also present a density functional method, which incorporates spin–orbit coupling to estimate the size of the anisotropy in [Ni(H2O)2(pyrazine)2](BF4)2.

A series of (dppf)Ni(ketene) complexes were synthesized and fully characterized. In the solid state, the complexes possess η2-(C,O) coordination of the ketene in an overall planar configuration. They display similar structure in solution, except in some cases, the η2-(C,C) coordination mode is also detected. A combination of kinetic analysis and DFT calculations reveals the complexes undergo thermal decomposition by isomerization from η2-(C,O) to η2-(C,C) followed by scission of the C═C bond, which is usually rate limiting and results in an intermediate carbonyl carbene complex. Subsequent rearrangement of the carbene ligand is rate limiting for electron poor and sterically large ketenes, and results in a carbonyl alkene complex. The alkene readily dissociates, affording alkenes and (dppf)Ni(CO)2. Computational modeling of the decarbonylation pathway with partial phosphine dissociation reveals the barrier is reduced significantly, explaining the instability of ketene complexes with monodentate phosphines.

The crystal structure, redox electrochemical stability, and reaction chemistry of 1,4-dicyanotetrazine (DCNT) has been experimentally characterized. These experimental results were rationalized by the results of theoretical calculations of the electronic structure, spin and charge distributions, electronic absorption spectra, and electron affinity and compared with the results for related the tetracyano electron acceptors tetracyanoethylene (TCNE), 7,7,8,8-tetracyano-p-quinodimethane (TCNQ), and 2,3,5,6-tetracyanopyrazine (TCNP). DCNT is made from the dehydration of 1,2,4,5-tetrazine-3,6-dicarboxamide, and because of the unusual deep-magenta color of the dicarboxamide in the solid state, its hydrogen-bonded layered structure, electronic structure, and electronic absorption spectra were determined. The magenta color is attributed to its absorptions at 532 nm (18 800 cm(-1)), and this corresponds to normalized chromaticity coordinates of x = 0.42 and y = 0.31 in the pink/red/orange part of the 1931 CIE chromaticity diagram. In contrast with previous reports, DCNT exhibits an irreversible one-electron reduction at -0.09 V vs SCE (MeCN), and reduced forms of DCNT have yet to be isolated and characterized. In addition, the reactions of DCNT with V(CO)6, Fe(II)(C5Me5)2, and I(-) are discussed.

The new [(teeda)CdFe(CO)4]2 complex has been isolated from the reaction of [(NH3)2CdFe(CO)4]n with tetraethylethylenediamine. Unlike previous structural reports of ligand adducts of [L2CdFe(CO)4]x complexes, which have all been trimeric species composed of six-membered Cd3Fe3 rings, the teeda complex crystallized as a dimer, analogous to [(2,2-bpy)ZnFe(CO)4]2. As in the zinc dimer, significant distortion arises from steric interactions between the axial carbonyl ligands on opposing iron centers. The complex sits on an inversion center, leading to two independent Cd–Fe distances, 2.7244(6) and 2.7433(6) Å, and crystallizes in the monoclinic space group P21/a with a = 14.8546(2) Å, b = 15.1647(3) Å, c = 15.5252(3) Å, β = 90.9517(12)°, and Dcalc = 1.719 g/cm3 at 150(1) K.

The synthesis, characterization, and photoinduced CO-release reactivity of [(6-Ph2TPA)Pb(3-Hfl)]ClO4 (1; 6-Ph2TPA = N,N-bis((6-phenyl-2-pyridyl)methyl)-N-((2-pyridyl)methyl)amine; 3-Hfl = anion of 3-hydroxyflavone) is reported and compared with Group 12 analogues ([(6-Ph2TPA)M(3-Hfl)]ClO4 (M = Hg(II) (2), Cd(II) (3), Zn(II) (4)). The Pb(II) complex exhibits unique features within this group of complexes in terms of its structural and spectroscopic features involving the coordinated flavonolate ligand. Similar to the Group 12 compounds, irradiation of 1 at 300 nm in an O2-containing environment results in the quantitative release of CO and the formation of a Pb(II) O-benzoylsalicylate (O-bs, depside) complex via a photoinduced dioxygenase-type reaction. Comparison of the quantum yield for the reaction of the Pb(II) flavonolate complex (Φ = 0.21(6)) versus the reactions of the structurally-related Group 12 metal complexes (6-Ph2TPA)M(3-Hfl)]ClO4 (M = Hg(II) (2, Φ = 0.31(2)), Cd(II) (3, Φ = 0.28(2)), Zn(II) (4), Φ = 0. 09(1)) revealed that flavonolate complexes of a heavy metal ion (Cd(II), Hg(II), Pb(II)) exhibit a higher reaction quantum yield than the Zn(II) derivative. Both Pb(II) and Zn(II) flavonolate complexes were found to be catalysts for the oxidative photoinduced degradation of 3-hydroxyflavone. The combined results of these investigations suggest that metal contaminants typically present in soil, including toxic heavy metal ions, might facilitate the oxidative decomposition of plant-derived flavonols via photoinduced reactions.

The new (Hpyz)3Co(μ2-pyz)3Co complex has been isolated as the nitrate salt through a reaction of Co(II) nitrate, Hpyz (pyrazole), triethylamine, and oxygen. The salt crystallizes in the monoclinic space group P21/m with a = 12.5977(3) Å, b = 15.3387(4) Å, c = 14.0800(3) Å, β = 93.0868(15)°, and = 1.464 g/cm3 at 150(1) K. The complex, with pseudo-octahedral coordination about the equivalent cobalt centers, has shorter Co–N distances for the bridging anionic pyz ligands as compared to the neutral Hpyz ligands, with the averages being 1.918(2) and 1.966(4), respectively. The Co–Co separation is 3.568 Å, reflecting the absence of any significant metal-metal interaction.

Two new Pb(II) complexes of the amide-appended nitrogen/sulfur epppa (N-((2-ethylthio)ethyl)-N-((6-pivaloylamido-2-pyridyl)methyl)-N-((2-pyridyl)methyl)amine) chelate ligand, [(epppa)Pb(NO3)2] (4-NO3) and [(epppa)Pb(ClO4)2] (4-ClO4), were prepared and characterized. In the solid state, 4-NO3 exhibits κ(5)-epppa chelate ligand coordination as well as the coordination of two bidentate nitrate ions. In acetonitrile, 4-NO3 is a 1:1 electrolyte with a coordinated NO3(-), whereas 4-ClO4 is a 1:2 electrolyte. Treatment of 4-ClO4 with 1 equiv Me4NOH·5H2O in CH3CN:CH3OH (3:5) results in amide methanolysis in a reaction that is akin to that previously reported for the Zn(II) analogue [(epppa)Zn](ClO4)2 (3-ClO4). (1)H NMR kinetic studies of the amide methanolysis reactions of 4-ClO4 and 3-ClO4 as a function of temperature revealed free energies of activation of 21.3 and 24.5 kcal/mol, respectively. The amide methanolysis reactions of 4-ClO4 and 3-ClO4 differ in terms of the effect of the concentration of methanol (saturation kinetics for 4-ClO4; second-order behavior for 3-ClO4), the observation of a small solvent kinetic isotope effect (SKIE) only for the reaction of the Zn(II)-containing 3-ClO4, and the properties of an initial intermediate isolated from each reaction upon treatment with Me4NOH·5H2O. These experimental results, combined with computational studies of the amide methanolysis reaction pathways of 4-ClO4 and 3-ClO4, indicate that the Zn(II)-containing 3-ClO4 initially undergoes amide deprotonation upon treatment with Me4NOH·5H2O. Subsequent amide protonation from coordinated methanol yields a structure containing a coordinated neutral amide and methoxide anion from which amide cleavage can then proceed. The rate-determining step in this pathway is either amide protonation or protonation of the leaving group. The Pb(II)-containing 4-ClO4 instead directly forms a neutral amide-containing, epppa-ligated Pb(II)-OH/Pb(II)-OCH3 equilibrium mixture upon treatment with Me4NOH·5H2O in methanol. The rate-determining step in the amide methanolysis pathway of 4-ClO4 is nucleophilic attack of the Pb(II)-OCH3 moiety on the coordinated amide. Overall, it is the larger size of the Pb(II) center and the availability of coordination positions that enable direct formation of a Pb(II)-OH/Pb(II)-OCH3 mixture versus the initial amide deprotonation identified in the reaction of the Zn(II)-containing 3-ClO4.

The reaction of first row transition M(II) ions with KSCN in various solvents form tetrahedral (NMe4)2[M(II)(NCS)4] (M = Fe, Co), octahedral trans-M(II)(NCS)2(Sol)4 (M = Fe, V, Ni; Sol = MeCN, THF), and K4[M(II)(NCS)6] (M = V, Ni). The reaction of M(NCS)2(OCMe2)2 (M = Cr, Mn) in MeCN and [Co(NCMe)6](BF4)2 and KSCN in acetone and after diffusion of diethyl ether form M(NCS)2(Sol)2 that structurally differ as they form one-dimensional (1-D) (M = Co; Sol = THF), two-dimensional (2-D) (M = Mn; Sol = MeCN), and three-dimensional (3-D) (M = Cr; Sol = MeCN) extended structures. 1-D Co(NCS)2(THF)2 has trans-THFs, while the acetonitriles have a cis geometry for 2- and 3-D M(NCS)2(NCMe)2 (M = Cr, Mn). 2-D Mn(NCS)2(NCMe)2 is best described as Mn(II)(μ(N,N)-NCS)(μ(N,S)-NCS)(NCMe)2 [= Mn2(μ(N,N)-NCS)2(μ(N,S)-NCS)2(NCMe)4] with the latter μ(N,S)-NCS providing the 2-D connectivity. In addition, the reaction of Fe(NCS)2(OCMe2)2 and 7,7,8,8-tetracyanoquino-p-dimethane (TCNQ) forms 2-D structured Fe(II)(NCS)2TCNQ. The magnetic behavior of 1-D Co(NCS)2(THF)2 can be modeled by a 1-D Fisher expression (H = -2JS(i)·S(j)) with g = 2.4 and J/kB = 0.68 K (0.47 cm(-1)) and exhibit weak ferromagnetic coupling. Cr(NCS)2(NCMe)2 and Fe(II)(NCS)2TCNQ magnetically order as antiferromagnets with Tc's of 37 and 29 K, respectively, while Mn(NCS)2(NCMe)2 exhibits strong antiferromagnetic coupling. M(NCS)2(THF)4 and K4[M(NCS)6] (M = V, Ni) are paramagnets with weak coupling between the octahedral metal centers.

The new [Co(pydz)6]2+ ion (pydz = pyridazine) has been prepared by a straightforward route in aqueous solution, and isolated as its hexafluorophosphate salt. The salt crystallizes in the monoclinic space group C2/c with a = 18.4796(3) A, b = 10.6846(2) A, c = 16.3404(2) A, β = 92.0518(11)o, V = 3224.30(9) A3, Dcalc = 1.709 at 150(1) K. The dication has crystallographically imposed 2 symmetry. The analogous, previously reported ruthenium complex ion could be isolated as its tetraphenylborate salt following the reaction of [RuCl2(1,5-COD)] x ·(COD = cyclooctadiene) with pyridazine in the presence of hydrogen gas. This salt also crystallizes in the monoclinic space group C2/c, with a = 17.8441(3) A, b = 19.8693(4) A, c = 38.4545(7) A, β = 95.4231(6)o, V = 13573.0(4) A3, Dcalc = 1.321 at 150(1) K. The hexakis(pyridazine)metal dications of cobalt and ruthenium have been synthesized and structurally characterized.

Aliphatic oxidative carbon-carbon bond cleavage reactions involving Cu(II) catalysts and O2 as the terminal oxidant are of significant current interest. However, little is currently known regarding how the nature of the Cu(II) catalyst, including the anions present, influence the reaction with O2. In previous work, we found that exposure of the Cu(II) chlorodiketonate complex [(6-Ph2TPA)Cu(PhC(O)CClC(O)Ph)]ClO4 (1) to O2 results in oxidative aliphatic carbon-carbon bond cleavage within the diketonate unit, leading to the formation of benzoic acid, benzoic anhydride, benzil, and 1,3-diphenylpropanedione as organic products. Kinetic studies of this reaction revealed a slow induction phase followed by a rapid decay of the absorption features of 1. Notably, the induction phase is not present when the reaction is performed in the presence of a catalytic amount of chloride anion. In the studies presented herein, a combination of spectroscopic (UV-vis, EPR) and density functional theory (DFT) methods have been used to examine the chloride and benzoate ion binding properties of 1 under anaerobic conditions. These studies provide evidence that each anion coordinates in an axial position of the Cu(II) center. DFT studies reveal that the presence of the anion in the Cu(II) coordination sphere decreases the barrier for O2 activation and the formation of a Cu(II)-peroxo species. Notably, the chloride anion more effectively lowers the barrier associated with O-O bond cleavage. Thus, the nature of the anion plays an important role in determining the rate of reaction of the diketonate complex with O2. The same type of anion effects were observed in the O2 reactivity of the simple Cu(II)-bipyridine complex [(bpy)Cu(PhC(O)C(Cl)C(O)Ph)ClO4] (3).

The reactions of the α,ω-diimines (CH2) n [N=CH(C6H5)]2 with Zr(6,6-dmch)2(PMe3)2 (dmch = dimethylcyclohexadienyl) lead to couplings of both imine carbon atoms, each to one of a single dmch ligand’s termini, which thereby also leads to the formation of two Zr–N bonds, and release of the phosphine ligands. The resulting complexes possess 18 electron configurations by virtue of a remaining η5-6,6-dmch ligand, η3-allyl coordination by the coupled 6,6-dmch ligand, and π-amide coordination by each nitrogen donor center. The η5-6,6-dmch ligand displays the distortions expected for a high valent metal pentadienyl complex. The n = 3 complex crystallized in the monoclinic space group P21/c with a = 8.5687(2) A, b = 27.8768(6) A, c = 11.7747(3) A, β = 103.6081(8)°, V = 2,733.64(11) A3, Dcalc = 1.351 g/cm3 at 150(1) K. For the n = 4 complex, the triclinic space group P $$ \overline{1} $$ is adopted, with a = 11.1279(3) A, b = 11.3846(3) A, c = 14.9154(3) A, α = 81.6030(13)°, β = 69.8503(13)°, γ = 84.6588(12)°, V = 1,753.05(7) A3, Dcalc = 1.283 g cm−3 at 150(1) K. The reactions of the Zr(6,6-dimethylcyclohexadienyl)2 fragment with α,ω-diimines (CH2) n [N=CH(C6H5)]2 led to couplings between the imine carbon atoms and the dienyl termini, thereby resulting in 12- and 13-membered ring constructions.

Treatment of RuCl2(PPh3)3 and RuHCl(PPh3)3 with the tin compound CH2C(Me)CHC(Me)CH2SnMe3 gives the corresponding acyclic pentadienyl half-sandwich (η5-CH2C(Me)CHC(Me)CH2)RuX(PPh3)2 [X = Cl, (2); H, (3)]. The steric congestion in 2 is most effectively relieved by formation of the cyclometalated complex (η5-CH2C(Me)CHC(Me)CH2)Ru(C6H4PPh2)(PPh3) (4). Addition of 1 equiv of PHPh2 to (η5-CH2CHCHCHCH2)RuCl(PPh3)2 (1) affords the chiral complex (η5-CH2CHCHCHCH2)RuCl(PPh3)(PHPh2) (5), while compound (η5-CH2C(Me)CHC(Me)CH2)RuCl(PPh3)(PHPh2)] (6) is directly obtained from the reaction of RuCl2(PPh3)3 with CH2C(Me)CHC(Me)CH2Sn(Me)3 and PHPh2. Treatment of RuCl2(PPh3)3 with the corresponding Me3SnCH2CH═CHCH═NR (R = Cy, t-Bu) affords (1-3,5-η-CH2CHCHCHNCy)RuCl(PPh3)2 (7) and [1-3,5-η-CH2CHCHCHN(t-Bu)]RuCl(PPh3)2 (8). The hydrolysis of 7, on a silica gel chromatography column, allows the isolation of RuCl(η5-CH2CHCHCHO)(PPh3)2 (9). The azapentadienyl complex 7 reacts with 1 equiv of PHPh2 to afford [1-3,5-η-CH2CHCHCHN(...

Irradiation of 3-hydroxyflavonolato (3-Hfl) complexes of MnII, CoII, NiII and CuII (1–4) at 300 nm under aerobic conditions results in dioxygenase-type reactivity and the formation of the corresponding divalent metal O-benzoylsalicylato (O-bs) complexes 8–11 and CO. The latter were characterized by using multiple methods, including elemental analysis, X-ray crystallography, NMR and/or EPR spectroscopy, mass spectrometry and IR spectroscopy. Compounds 1–4 serve as catalysts for the photoinduced reactivity of 3-hydroxyflavonol (3-HflH) to produce O-benzoylsalicylic acid as the major product. Spectroscopic studies (UV/Vis and 1H NMR) show that each O-benzoylsalicylato complex 8–11 reacts with one equiv. of 3-hydroxyflavonol to regenerate 1–4 and enable turnover reactivity. Unlike what is observed for free 3-HflH, photoinduced reactions involving 1–4 and excess flavonol show only minor amounts of flavonol isomerization reactivity. These results indicate that the presence of a metal ion, whether under stoichiometric or catalytic conditions, facilitates the photoinduced degradation of 3-HflH to produce a carboxylic acid and CO as products.

Treatment of Zn(II) and Cd(II) hydroxide complexes of the tris(2-pyridylmethyl)amine (TPA) ligand with COS or CS2 in protic solvents (MeOH or EtOH) resulted in [(TPA)Zn–SC(S)OCH3]ClO4 (1), [(TPA)Zn– SC(O)OCH3]BF4 (2), [(TPA)Zn–SC(O)OCH3]ClO4 (3), [(TPA)Zn–SC(O)OCH2CH3]BF4 (4), [(TPA)Cd– SC(S)OCH3]ClO4 (5) and [(TPA)Cd–SC(O)OCH3]ClO4 (6). The molecular structures of 1, 2, 5 and 6 were determined by X-ray crystallography. Complexes 2, 3 and 4, unlike 1, 5 and 6, are easily hydrolyzed upon treatment with water in CH3CN to give zinc hydrosulfide complexes of the form [(TPA)Zn–SH]X (X = BF4

Admixture of the chelate ligand bmnpa (N,N-bis(2-methylthio)ethyl-N-((6-neopentylamino-2-pyridyl)methyl)amine) with an equimolar amount of Hg(ClO4)2·3H2 Oi n CH 3OH/CH2Cl2, followed by recrystallization from CH3CN/Et2O, yielded the Hg(II) perchlorate complex ((bmnpa)Hg(ClO4)2 )( 1). Addition of an equimolar amount of Me4NOH·5H2 Ot o aC H 3CN solution of 1, followed by recrystallization from CH3OH/Et2O, yielded the dinuclear Hg2 2+ complex ((bmnpaHg)2)(ClO4)2 (4). X-ray crystallographic characterization of 1·0.5CH3CN revealed a mononuclear structure having a primary coordination number of two with a distorted linear geometry, and four secondary bonds for an effective coordination number of six. The 1 H NMR spectrum of 1 in CD3CN shows distinctive 3 J199Hg−1H coupling in the benzylic -CH2 - and thioether −SCH3 resonances. Complex 4·CH3OH exhibits a structure in the solid state wherein each mercury center of the Hg2 2+ ion displays thioether coordination and a distorted tetrahedral geometry. Complex 4 is the first dimercurous complex for which J199Hg−1H coupling involving a -SCH3 appendage is reported.

Three mononuclear Ni(II) complexes containing a 2-chloro-1,3-diketonate ligand and supported by the 6-Ph(2)TPA chelate, as well as analogues that lack the 2-chloro substituent on the β-diketonate ligand, have been prepared and characterized. Upon irradiation at 350 nm under aerobic conditions, complexes containing the 2-chloro-substituted ligands undergo reactions to generate products resulting from oxidative cleavage, α-cleavage, and radical-derived reactions involving the 2-chloro-1,3-diketonate ligand. Mechanistic studies suggest that the oxidative cleavage reactivity, which leads to the production of carboxylic acids, is a result of the formation of superoxide, which occurs through reaction of reduced nickel complexes with O(2). The presence of the 2-chloro substituent was found to be a prerequisite for oxidative carbon-carbon bond-cleavage reactivity, as complexes lacking this functional group did not undergo these reactions following prolonged irradiation. The approach toward investigating the oxidative reactivity of metal β-diketonate species outlined herein has yielded results of relevance to the proposed mechanistic pathways of metalloenzyme-catalyzed β-diketonate oxidative cleavage reactions.

A straightforward route to Ru(pyz)2(Hpyz)4 (Hpyz = pyrazole) has been developed. This has been found to react readily with a modified Co(pyrazolylborate)Cl complex in the presence of triethylamine as an HCl acceptor to yield a bimetallic cobalt–ruthenium complex, in which the two metals are each six-coordinate, and bridged by three pyrazolyl anions. Both species have been characterized structurally, as has a modified Co(pyrazolylborate)2 complex.

The reactions of Ti(C5H5)(6,6-dmch)(PMe3) and Zr(C5H5)(6,6-dmch)(PMe3)2 with two equivalents of C6H5C(H)=N(C6H5) have led to couplings of the imines to the 1,5 (terminal) positions of the 6,6-dmch ligands. In both cases the PMe3 ligands are lost, and the metal complexes each attain 18 electron configurations via η5-(C5H5), η3-allyl, and bis(π-amide) coordination. The complexes each crystallize in the monoclinic space group P21/c. For the titanium complex, a = 10.4336(1) A, b = 9.0407(1) A, c = 32.5547(6) A, β = 94.2939(5)°, V = 3062.17(7) A3, Dcalc = 1.264 at 200(1) K. For the zirconium complex, a = 13.8900(3) A, b = 10.0873(2) A, c = 22.4543(6) A, β = 90.7638(7)°, V = 3145.85(12) A3, Dcalc = 1.322 at 150(1) K. The reactions of M(C5H5)(6,6-dmch) fragments (M = Ti, Zr; dmch = dimethylcyclohexadienyl) with two equivalents of (C6H5)(H)C=N(C6H5) have led to couplings at the dienyl termini, resulting in 18 electron π-allyl, bis(π-amide) complexes.

The structure of WCl2(PMe3)4 has been determined in order to allow for a comparison with its molybdenum analogue. The complexes are isomorphous, and exhibit trans-pseudooctahedral coordination, with crystallographically imposed $$\overline{4}2m$$ (D2d) symmetry. A significant distortion occurs involving the PMe3 ligands, through which one opposing pair tilts upward toward one axial chloride ligand, while the other pair tilts in an opposite manner, by 9.33°. The complex crystallizes in the tetragonal space group $$I\overline{4}2m$$ , with a = b = 9.4987(4) A, c = 12.1058(5) A, V = 1092.25(8) A3, D calc = 1.700 at 150(1) K. For a better comparison, the structure of the molybdenum complex was redetermined, at a low temperature. Its space group is also $$I\overline{4}2m$$ with a = b = 9.5193(3) A, c = 12.1083(5) A, V = 1097.22 A3, D calc = 1.426 at 150(1) K. In accord with the larger cell volume, the molybdenum complex possesses slightly longer M–Cl and M–P bonds.

Two 16 electron titanacyclobutanes of the formula Ti(C5H4R)2(μ2-CH2)2C(CH3)(i-C3H7) (R=H, CH3) have been prepared from the reaction of Ti(C5H5)2(μ2-CH2)(μ2-Cl)Al(CH3)2 or Ti(C5H4CH3)2(μ2-CH2)(μ2-Cl)Al(CH3)2 with H2C=C(CH3)(i-C3H7). Structural parameters, most notably lengthened C–C bonds in the titanacyclobutane ring, for both complexes reveal the expected presence of (C–C)→Ti agostic interactions. The complexes are isomorphous, crystallizing in the monoclinic space group Cc. For Ti(C5H5)2(μ2-CH2)2C(CH3)(i-C3H7), a = 11.3459(3) A, b = 16.2108(4) A, c = 8.1646(2) A, β = 105.5276(16)°, V = 1446.87(6)°, Dcalc = 1.268 at 150(1) K. For Ti(C5H4CH3)2(μ2-CH2)2C(CH3)(i-C3H7), a = 12.6591(2) A, b = 16.2795(4) A, c = 8.2462(2) A, β = 107.2421(14)°, V = 1623.04(6) A3, Dcalc = 1.245 at 150(1) K. Structural studies of two 16 electron titanacyclobutanes reveal lengthened C–C bonds in the four-membered ring, indicative of agostic (C–C)→Ti interactions, as found in related species.

The reactions of the half-open trozircene [(η7-C7H7)Zr(η5-2,4-C7H11)] (1) with the two-electron donor ligands tert-butyl isocyanide (CN-tBu), 1,2-bis(dimethylphosphino)ethane (dmpe), trimethylphosphine (PMe3) and 1,3,4,5-tetramethylimidazolin-2-ylidene (IMe, :C[N(Me)C(Me)]2) have led to the 1:1 adducts 3, 4, 5 and 6, respectively. The latter three were structurally characterized by X-ray diffraction analysis. Additionally, the stability of the adducts was probed by DFT calculations employing the B3LYP and M05-2X functionals showing that the strongly σ-basic N-heterocyclic carbene forms a thermodynamically much more stable adduct than the other three.

The interaction of molecular hydrogen with a novel microporous dinuclear Cu(II) complex, [bis-μ-di(4-pyridyl)methanol-1,4,7-triazacyclononane copper(II)] triflate (1), and its derivatives formed from oxidation and solvent removal was studied with 2H NMR and density functional theory (DFT). The Cu-complex 1 was characterized with X-ray diffraction methods and consists of a dinuclear macrocycle that forms one-dimensional channels of 9.55 A in diameter. 2H NMR studies of deuterium gas adsorption by 1 suggest that physisorption condensation of D2 occurs within two distinct microenvironments: in the interior and in-between the microtubular structures. The assignment of NMR resonances to specific adsorption sites is supported by spectral decomposition and analysis of the line widths and integrated signal intensities of the components. The dynamics of the system are probed by spin−lattice relaxation time measurements and spectral hole-burn experiments as a function of temperature and pressure. NMR and DFT calcul...

Organic semiconductor materials composed of &pi, &ndash, &pi, stacking aromatic compounds have been under intense investigation for their potential uses in flexible electronics and other advanced technologies. Herein we report a new family of seven &pi, stacking compounds of silver(I) bis-N-(4-pyridyl) benzamide with varying counterions, namely [Ag(NPBA)2]X, where NPBA is N-(4-pyridyl) benzamine, X = NO3&minus, (1), ClO4&minus, (2), CF3SO3&minus, (3), PF6&minus, (4), BF4&minus, (5), CH3PhSO3&minus, (6), and PhSO3&minus, (7), which form extended &pi, &minus, stacking networks in one-dimensional (1D), 2D and 3D directions in the crystalline solid-state via the phenyl moiety, with average inter-ring distances of 3.823 &Aring, Interestingly, the counterions that contain &pi, stacking-capable groups, such as in 6 and 7, can induce the formation of mesomorphic phases at 130 &deg, C in dimethylformamide (DMF), and can generate highly branched networks at the mesoscale. Atomic force microscopy studies showed that 2D interconnected fibers form right after nucleation, and they extend from ~30 nm in diameter grow to reach the micron scale, which suggests that it may be possible to stop the process in order to obtain nanofibers. Differential scanning calorimetry studies showed no remarkable thermal behavior in the complexes in the solid state, which suggests that the mesomorphic phases originate from the mechanisms that occur in the DMF solution at high temperatures. An all-electron level simulation of the band gaps using NRLMOL (Naval Research Laboratory Molecular Research Library) on the crystals gave 3.25 eV for (1), 3.68 eV for (2), 1.48 eV for (3), 5.08 eV for (4), 1.53 eV for (5), and 3.55 eV for (6). Mesomorphic behavior in materials containing &pi, stacking aromatic interactions that also exhibit low-band gap properties may pave the way to a new generation of highly branched organic semiconductors.

The reactions of imines of the formula (C6H5)CH=NR (R = C6H5, i-C3H7) with Ti(C5H5)(2,4-C7H11)(PMe3) (C7H11 = dimethylpentadienyl) lead to expulsion of the PMe3 and coupling between the imine’s carbon atom and a single terminus of the 2,4-C7H11 ligand, resulting in C5H5, “diene,” and π-amide coordination in the 16 electron products. Examination of the Ti–C and C–C bonding parameters for the “diene” ligands reveals that they may be more appropriately regarded as enediyl ligands, leading to a formal +4 oxidation state for titanium. Both complexes crystallize in the triclinic space group $$ P\overline{1} $$ . For the R = C6H5 coupling product, a = 10.4590(2) A, b = 11.6407(2) A, c = 17.3729(3) A, α = 74.7610(7)°, β = 79.8600(6)°, γ = 82.2895(11)°, V = 2000.28(6) A3, D calc = 1.293 g/cm3 at 150(1) K. For the R = i-C3H7 coupling product, a = 8.1039(2) A, b = 9.4115(2) A, c = 13.0116(4) A, α = 88.9906(18)°, β = 73.2780(15)°, γ = 83.3088(16)°, V = 943.82(4) A3, D calc = 1.250 g/cm3 at 150(1) K. Structural studies of the coupling products between imines and the Ti(C5H5)(2,4-C7H11) (C7H11 = dimethylpentadienyl) fragment reveal significant shortening of the Ti–N bond when a more electron donating substituent is present on the nitrogen center.

The structure of the previously reported (py)3ZnFe(CO)4 (py = pyridine) has been determined, confirming the monomeric nature of this species. The complex has average Zn–N and Zn–Fe bond lengths of 2.0970(7) and 2.4017(3) A, and features a coordination geometry about Fe which is intermediate between trigonal bipyramidal and face monocapped tetrahedral. The space group is P21/c, with a = 8.22080(10) A, b = 16.1668(3) A, c = 15.4669(3) A, β = 102.5869(11)°, V = 2006.21(6) A3, Dcalc. = 1.558 g/cm3 at 150(1) K. A monomeric cadmium analogue, (pyridine)(neocuproin)CdFe(CO)4, has also been synthesized, and found to possess a similar geometry, with average Cd–N and Cd–Fe bond lengths of 2.352(2) and 2.5380(5) A. The space group is $$ P\overline{1} $$ with a = 10.8900(2) A, b = 11.3042(3) A, c = 15.5488(4) A, α = 85.1251(10)°, β = 84.3468(14)°, γ = 72.0377(15)°, V = 1808.93(7) A3, Dcalc. = 1.478 g/cm3 at 150(1) K. The structures of the monomeric (py)3ZnFe(CO)4 and (py)(neocuproin)CdFe(CO)4 complexes have been determined, and suggest the use of significantly greater s character in the main group elements’ bonds with iron as opposed to nitrogen.

Refluxing WCl4(PMe3)3 under a nitrogen atmosphere in the presence of two equivalents of sodium amalgam leads to a reduction to the W(II) complex [cis,mer-WCl2(PMe3)3]2N2 (1), which can be converted to [mer,trans-WCl3(PMe3)2]2N2 (2) via appropriate oxidation/chlorination. Structural data have been obtained for both complexes, and demonstrate significantly increased steric crowding in 1 due to PMe3/PMe3 interactions. The N–N bond distances in the two compounds are similar, at 1.279(4) and 1.243(18) A, respectively.

The previously reported [Ru(naph)4]2+ complex (naph = 1,8-naphthyridine) has been prepared by a simplified route using [RuCl2(1,5-COD)] x (COD = cyclooctadiene) as starting material and isolated as its tetraphenylborate salt. The salt crystallizes in the monoclinic space group P21/n with a = 13.6531(3) A, b = 12.5389(4) A, c = 20.0349(5) A, β = 96.5884(15)o, V = 3407.22(16) A, D calc = 1.300 at 150(1) K. The dication has crystallographically imposed inversion symmetry. Although the iron analogue has been found to have a coordination number of eight, the ruthenium complex is only six-coordinate, which is achieved by the presence of two monodentate and two bidentate 1,8-naphthyridine ligands. The observation of a higher coordination number for Fe(II) vs. Ru(II) can be explained by the high spin nature of the iron complex. A byproduct complex, [Ru(1,5-COD)(naph)2][B(C6H5)4]2, could also be synthesized, isolated pure, and structurally characterized. The organometallic complex possesses an 18 electron configuration by virtue of the dicationic metal center being coordinated by the diene ligand and all four nitrogen lone pairs. This salt crystallizes in the triclinic space group $$ {\text{P}}\bar{1} $$ with a = 12.9538(3) A, b = 14.9485(3) A, c = 17.4291(3) A, α = 69.0649(11)o, β = 78.3211(9)o, γ = 78.5629(10)o, V = 3057.50(11) A3, D calc = 1.293 at 150(1) K. The [Ru(1,8-naphthyridine)4]2+ ion has been shown to have a coordination number of six, as opposed to the eight-coordinate [Fe(1,8-naphthyridine)4]2+.

The reactions of Zr(C7H7)(Cl)(tmeda) (tmeda = tetramethylethylenediamine) with pentadienyl anions lead to formally tetravalent Zr(C7H7)(Pdl) complexes, for Pdl = C5H7, 2,4-C7H11, 6,6-dmch, and c-C7H9 (C7H11 = dimethylpentadienyl, dmch = dimethylcyclohexadienyl, c-C7H9 = cycloheptadienyl). Structural characterizations of the first three have been carried out, revealing much shorter Zr−C distances for the C7H7 ligand and a pattern of Zr−C bond distances for the pentadienyl ligands that is consistent with a formally high (+4) metal oxidation state, which is also supported by DFT calculations. As had been found for the analogous Cp complexes, these 16-electron species are susceptible to Lewis base coordination, and the 2,6-xylyl isocyanide adducts of the 2,4-C7H11 and 6,6-dmch complexes have been isolated and characterized by IR spectroscopy and single-crystal X-ray diffraction studies. The IR spectroscopic studies indicate that the pentadienyl ligands are serving as better net electron donors than Cp ligands...

The experimental electron density study of Ti(C(5)H(4)Me)(2)[(CH(2))(2)CMe(2)] provides direct evidence for the presence of (C-C)--Ti agostic interactions. In accord with the model of Scherer and McGrady, the C(alpha)-C(beta) bond densities no longer show cylindrical symmetry in the vicinity of the Ti atom and differ markedly from those of the other C-C bonds. At the points along the C(alpha)-C(beta) bond where the deviation is maximal the electron density is elongated toward the metal center. The distortion is supported by parallel theoretical calculations. A calculation on an Mo complex in which the agostic interaction is absent supports the Scherer and McGrady criterion for agostic interactions. Despite the formal d(0) electron configuration for this Ti(IV) species, a significant nonzero population is observed for the d orbitals, the d orbital population is largest for the d(xy) orbital, the lobes of which point toward the two C(alpha) atoms. Of the three different basis sets for the Ti atom used in theoretical calculations with the B3LYP functional, only the 6-311++G** set for Ti agrees well with the experimental charge density distribution in the Ti-(C(alpha)-C(beta))(2) plane.

The reaction of the edge-bridged open zirconocene, Zr(6,6-dmch) 2 (PMe 3 ) 2 (dmch = dimethylcyclohexadienyl) with two equivalents of PhC 2 SiMe 3 leads to a 5 + 2 + 2 ring construction, resulting in a 4.3.1 bicyclodecadienyl skeleton. The resulting complex, with η 3 -allyl, η 4 -diene, and η 5 -dienyl coordination, has a formal 16 electron configuration, and contains close contacts between the metal center and two lengthened C–C bonds, indicative of weak agostic interactions.

The reaction between [Cr-II(NCMe)(4)][BF4](2) and the different cations of [C-3(CN)(5)](-), i.e. [PPN](+) [PPN = bis(triphenylphosphoranylidene)ammonium] and [NMe4](+) in different solvents led to two different tri-solvated structures possessing Cr-II[C-3(CN)(5)](2): Cr-II [C-3(CN)(5)](2).2MeCN.H2O (1) and Cr-II[C-3(CN)(5)](2).(THF) 2THF (2). 2 possesses layers of mu-1, 1'-[C-3(CN)(5)](-) while 1 contain a three- and six-connected 3D pyrite network structure with mu(3)-1,1',3-[C-3(CN)(5)](-) trigonal nodes. Both compounds possess a tetragonally elongated distorted Cr(II) site. Magnetic susceptibility measurements between 5 and 300 K reveal significant antiferromagnetic interactions for both 1 and 2, with theta = -26 and -23 K, respectively, from a fit to the Curie-Weiss law. Upon a comparison to related and similarly structured materials the coupling increases as Cr-II > Fe-II > Mn-II. (C) 2008 Elsevier B.V. All rights reserved.

Using a new N(4)-donor chelate ligand having a mixture of hydrophobic phenyl and hydrogen-bond-donor appendages, a trinuclear nickel(II) complex of the doubly deprotonated form of 2-hydroxy-1,3-diphenylpropane-1,3-dione was isolated, characterized (X-ray crystallography, elemental analysis, UV-vis, (1)H NMR, FTIR, and magnetic moment measurement), and evaluated for O(2) reactivity. This complex, [(6-NA-6-Ph(2)TPANi)(2)(mu-PhC(O)C(O)C(O)Ph)(2)Ni](ClO(4))(2) (4), has two terminal pseudooctahedral Ni(II) centers supported by the tetradentate chelate ligand and a central square-planar Ni(II) ion ligated by oxygen atoms of two bridging enediolate ligands. In CH(3)CN, 4 exhibits a deep orange/brown color and lambda(max) = 463 nm (epsilon = 16 000 M(-1)cm(-1)). The room temperature magnetic moment of 4, determined by Evans method, is mu(eff) = 5.3(2) mu(B). This is consistent with the presence of two noninteracting high-spin Ni(II) centers, a diamagnetic central Ni(II) ion, and an overall quintet ground state. Exposure of a CH(3)CN solution of 4 to O(2) results in the rapid loss of the orange/brown color to give a green solution. The products identified from this reaction are [(kappa(3)-6-NA-6-Ph(2)TPA)Ni(O(2)Ph)(H(2)O)]ClO(4) (5), benzil [PhC(O)C(O)Ph], and CO. Identification of 5 was achieved via its independent synthesis and a comparison of its (1)H NMR and mass spectral features with those of the 6-NA-6-Ph(2)TPA-containing product generated upon reaction of 4 with O(2). The independently prepared sample of 5 was characterized by X-ray crystallography, elemental analysis, UV-vis, mass spectrometry, and FTIR. The O(2) reactivity of 4 has relevance to the active-site chemistry of Ni(II)-containing acireductone dioxygenase (Ni(II)ARD).

Reactions of NbCl4(PMe3)2 and HfCl4(PMe3)2 with four equivalents of the 6,6-dimethylcyclohexadienyl anion lead to Nb(6,6-dmch)[η2,4-(dmch)2](PMe3) and Hf(6,6-dmch)[η3,4-(dmch)3](PMe3). Each complex has been crystallographically characterized, and found to contain one η5-bound 6,6-dmch ligand, with the other dmch units coupled together to yield olefin, allyl, and diene coordinations, resulting in 18 electron configurations for these compounds.

The reaction of Zr(C5H5)2Br2 with bromine can be used as an effective route to Zr(C5H5)Br3. Through the slow addition of reactants, Zr(C5H5)Br3 can be isolated in crystalline form. An X-ray diffrac...

The syntheses of the new compounds Fe(3-Me3Si-6,6-dmch)2, 2, and Fe[3-(i-Pr)3Si-6,6-dmch]2, 3, are reported, along with X-ray structural studies of these species, and of the previously reported Fe(1,3,5,6-temch)2 (dmch = dimethylcyclohexadienyl; temch = tetramethylcyclohexadienyl). Each species crystallized in something close to the expected gauche-eclipsed conformation. In accord with previous work on Fe(6,6-dmch)2, but in contrast to results for open ferrocenes such as Fe(2,4-C7H11)2 (C7H11 = dimethylpentadienyl), the three species under study undergo reversible one-electron oxidations at room temperature to stable 17-electron cations, with potentials for oxidation being more favorable than that for ferrocene by 0.51–0.78 V. The edge-bridged open ferrocenes also react in a 1:1 ratio with TCNE (TCNE = tetracyanoethylene), yielding salts that were shown spectroscopically to contain the expected cationic 17-electron metal complexes and the TCNE radical anion.

Divalent zinc, cobalt, and nickel complexes of an amide-appended N3O-donor ligand (mpppa, N-methyl-N-((6-pivaloylamido-2-pyridyl)methyl)-N-(2-pyridylethyl)amine) have been prepared and characterized. X-ray crystallographic studies indicate that [(mpppa)Zn(CH3CN)](ClO4)2 (1) exhibits a distorted square pyramidal geometry, whereas [(mpppa)M(CH3OH)(H2O)](ClO4)2 (M=Co (2·H2O), Ni (3)) exhibit distorted octahedral structures. Each complex was also characterized by analytical and spectroscopic methods. Treatment of 1 with Me4NOH·5H2O in methanol-containing solutions results in amide methanolysis. This reaction proceeds via the initial formation of a deprotonated amide intermediate, [(mpppa−)Zn]ClO4 (4), which has been isolated and characterized. Kinetic studies performed as a function of the amount of methanol present revealed saturation behavior with respect to the alcohol concentration. Variable temperature kinetic studies yielded activation parameters (ΔH ‡=19.8kcal/mol; ΔS ‡=−3.8(1) eu) that are interesting...

Divalent nickel, cobalt and iron complexes {[(bmppa)Ni(CH3CN)](ClO4)2 (1), [(bmppa)Co(CH3CN)](ClO4)2 (2), [(bmppa)Fe(CH3CN)](ClO4)2 (3)} of an amide-appended N2S2-donor ligand {bmppa = N,N-bis(2-methylthio)ethyl-N-[(6-pivaloylamido-2-pyridyl)methyl]amine} have been prepared and characterized using 1H NMR, IR, UV/Vis, elemental analysis and magnetic moment measurements. The complexes 2 and 3 were also characterized by X-ray crystallography. When treated with 1 equiv. of Me4NOH·5H2O in methanol, 1 and 2 form deprotonated amide complexes {[(bmppa–)Ni]ClO4 (4), [(bmppa–)Co]ClO4·H2O (5)} which were isolated and characterized by 1H NMR, IR, UV/Vis, elemental analysis and magnetic moment measurements. Treatment of the FeII complex 3 with 1 equiv. of Me4NOH·5H2O in methanol produced the free bmppa chelate ligand and a precipitate of an unidentified iron species. Heating of 5 at 50 °C in methanol for 5 d resulted in a ca. 50 % yield of amide methanolysis products and a small amount of products resulting from oxidative N-dealkylation of the bmppa ligand. It has been previously shown that a zinc analog of 5 undergoes quantitative amide methanolysis under milder conditions. Complex 4 does not undergo amide cleavage upon heating at 50 °C in methanol for 5 d. A rationale for the metal-dependent amide methanolysis reactivity of these complexes is proposed on the basis of structural differences in the “parent” protonated complexes. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

The synthesis and characterization of the new, 16 electron half-open zirconocenes, Zr(C5H5)(c-C8H11)(PR3) (R = Me, Et) are reported, together with a structural study of the PEt3 complex. As with other low valent half-open zirconocenes, the Zr–C distances are significantly shorter on average for the electronically open dienyl ligand than those for the C5H5 ligand, 2.343 vs. 2.512 A. Reaction of either of these compounds with PhC2Ph led to the incorporation of two equivalents of the alkyne, resulting in a formally 14 electron complex with coordination from cyclopentadienyl, allyl, σ-alkyl, and σ-vinyl units.