Bis(glycinato-kappa2N,O)dinitrosylmolybdenum(0) and bis(2-aminoethanethiolato-kappa2N,S)dinitrosylmolybdenum(0) acetonitrile monosolvate.

The title compounds, [Mo(C(2)H(4)NO(2))(2)(NO)(2)], (I), and [Mo(C(2)H(6)NS)(2)(NO)(2)].CH(3)CN, (II), contain distorted octahedral complexes in which the monoanionic N,S- and N,O-bidentate ligands coordinate the molybdenum centres in different modes. The anionic O atoms of the glycinate ligands in (I) are coordinated trans to the nitrosyl ligands and the amine N atoms are located trans to each other, whereas in (II) the anionic S atoms are coordinated trans to each other and the amine N atoms are located trans to the nitrosyl ligands. Each compound has a single complete complex in the asymmetric unit on a general position. Six N-H...O contacts with N...O distances of less than 3.2 A are observed in (I) between the amine groups and the nitrosyl and carboxylate O atoms. In the 1:1 solvate (II), the acetonitrile molecule forms short N-H...N contacts (N...N < 3.2 A) between the solvent N atoms and one of the amine H atoms. In addition, three weak intermolecular N-H...S interactions (N...S > 3.3 A) contribute to the stabilization of the structure of (II).

µ-1,2-Bis(diethyl-phosphino)ethane-κP:P'-bis-{[1,2-bis-(diethyl-phosphino)ethane-κP,P']trichloridonitrosyl-tungsten(II)}.

The title binuclear compound, [W(2)Cl(6)(NO)(2)(C(10)H(22)P(2))(3)], contains two W atoms which are bridged by a bis-(diethyl-phosphino)-ethane (depe) ligand. The seven-coord-inated tungsten(II) centres display distorted penta-gonal-bipyramidal geometries with trans nitrosyl and chloride ligands. The title mol-ecule lies on a crystallographic inversion centre. The ethane group of the non-bridging depe ligand is positionally disordered, with site-occupancy factors of 0.63 and 0.37. In the crystal structure, the binuclear mol-ecules are linked by weak inter-molecular C-H⋯O and C-H⋯Cl inter-actions. In addition, weak intra-molecular C-H⋯Cl inter-actions are also present.

Tetra-ethyl-ammonium tricarbonyl-chlorido(isoquinoline-1-carboxyl-ato-κN,O)technetate(I).

The asymmetric unit of the title compound, (C(8)H(20)N)[Tc(C(10)H(6)NO(2))Cl(CO)(3)], consists of two crystallographically independent technetium complexes related via a pseudo-inversion centre and two tetra-ethyl-ammonium cations. The Tc atoms have slightly distorted octa-hedral coordination geometries, and they are linked with the cations by inter-molecular C-H⋯O and C-H⋯Cl hydrogen-bonding contacts, forming two-dimensional columns, which lie approximately parallel to (001) in the crystal structure. The isochinolate (isoquinoline-1-carboxyl-ate) ligands link the columns by partial π-π stacking [centroid-centroid distance 4.3733 (11) Å], forming a three-dimensional network structure.

Developing iron nitrosyl complexes as NO donor prodrugs.

A novel class of water-soluble iron nitrosyl complexes has been developed for use as NO donor prodrugs. To elaborate these NO prodrugs various water-soluble ligands were used such as P(CH2OH)3, 1,3,5-triaza-7-phosphatricyclo[3.3.1.1]decane (PTA), 1,2-bis[bis(hydroxymethyl)phosphino]ethane (HMPE), 1,2-bis[bis(hydroxymethyl)phosphino]benzene (TMBz), cysteamine, cysteamine hydrochloride, L-cysteine ethyl ester hydrochloride (LCEE) and pyrimidine-2-thiol (pyrim). The mononuclear complexes Fe(NO)2P(CH2OH)3Cl , Fe(NO)2(P(CH2OH)3)2, Fe(NO)2(PTA)2, Fe(NO)2HMPE , Fe(NO)2TMBz , [Fe(NO)2pyrimI] , [Fe(NO)3P(CH2OH)3][X] (X=PF6, SbF6, BF4) and the dinuclear species [Fe(NO)2S(CH2)2NH3Cl]2, [Fe(NO)2S(CH2)2NH3I2] , [Fe(NO)2LCEE]2 and [Fe(NO)2pyrim]2 were obtained. Complexes , , , , , , and are water-soluble. , and were identified as nitroxyl and , , , and as nitric oxide donors by applying an EPR NO-trap assay. To determine the amount of nitric oxide which was released from the nitric oxide donors, an additional electrochemical methodology was used. The equilibrium release or the trapping concentration of NO was also studied by a UV-vis method, which allowed the rate constant of NO release to be determined.

trans-W(Cmesityl)(dmpe)2H: revealing a highly polar W-H bond and H-mobility in liquid and solid state.

The isotopomeric complexes trans-W(Cmesityl)[(C(H,D)3)2PCH2CH2P(C(H,D)3)2]2(H,D) 1-4 were prepared. 2 (W(Cmesityl)(dmpe)2D) was used to study the Deuterium Quadrupole Coupling Constant (DQCC) and the ionicity of the W-D bond (DQCC=34.1 kHz; ionicity 85%). 1 (W(Cmesityl)(dmpe)2H) shows several dynamic exchange processes in solution, such as HW/HW, HW/ortho-Memesityl, and HW/H2 exchanges observed by NMR in combination with deuterium labeling studies and double label crossover experiments. Except for the HW/H2, these reactions comprise elementary steps, which also appear along the isomerization pathway of 1 into (2,3,5-trimethylphenylcarbyne)(dmpe)2WH (5) at 60 degrees C. 5 was characterized by an X-ray diffraction study. In the solid state only an HW/Mep exchange process prevails appearing at higher temperatures, which was identified by NMR and by Quasielastic Neutron Scattering. The latter also provided an activation barrier of 5 kcal/mol and a "jump width" for the moving H nucleus in agreement with the HW...Mep distance of the X-ray diffraction study of 1.

Bis[1,2-bis-(dimethyl-phosphino)-ethane]-dichloridonitro-syltungsten(0) chloride.

In the crystal structure of the title compound, [WCl(2)(NO)(C(6)H(16)P(2))(2)]Cl, the seven-coordinated tungsten(II) center displays a distorted penta-gonal-bipyramidal geometry with trans nitrosyl and chloride ligands. The NO and Cl ligands are disordered over two positions; the site occupancy factors are 0.6 and 0.4.

Unprecedented ROMP activity of low-valent rhenium-nitrosyl complexes: Mechanistic evaluation of an electrophilic olefin metathesis system.

The reaction of [Re(H)(NO)2(PR3)2] complexes (1 a: R = PCy3; 1 b: R = PiPr3) with [H(OEt2)2][BAr(F)4] ([BAr(F)4] = tetrakis{3,5-bis(trifluoromethyl)phenyl}borate) in benzene at room temperature gave the corresponding cations [Re(NO)2(PR3)2][BAr(F)4] (2 a and 2 b). The addition of phenyldiazomethane to benzene solutions of 2 a and 2 b afforded the moderately stable cationic rhenium(I)-benzylidene-dinitrosyl-bis(trialkyl)phosphine complexes 3 a and 3 b as [BAr(F)4]- salts in good yields. The complexes 2 a and 2 b catalyze the ring-opening metathesis polymerization (ROMP) of highly strained nonfunctionalized cyclic olefins to give polymers with relatively high polydispersity indices, high molecular weights and over 80 % Z configuration of the double bonds in the chain backbone. However, these complexes do not show metathesis activity with acyclic olefins. The benzylidene derivatives 3 a and 3 b are almost inactive in ROMP catalysis with norbornene and in olefin metathesis. NMR experiments gave the first hints of the initial formation of carbene complexes from [Re(NO)2(PR3)2][BAr(F)4] (2 a and 2 b) and norbornene. In a detailed mechanistic study ESI-MS/MS measurements provided further evidence that the carbene formation is initiated by a unique reaction sequence where the cleavage of the strained olefinic bond starts with phosphine migration forming a cyclic ylide-carbene complex, capable of undergoing metathesis with alternating rhenacyclobutane formation and cycloreversion reactions ("ylide" route). However, even at an early stage the ROMP propagation route is expected to merge into an "iminate" route by attack by the ylide function on one of the N(NO) atoms followed by phosphine oxide elimination. The formation of phosphine oxide was confirmed by NMR spectroscopy. The proposed mechanism is supported further by detailed DFT calculations.

Hydride transfer reactivity of tetrakis(trimethylphosphine)(hydrido)(nitrosyl)molybdenum(0).

The tetrakis(trimethylphosphine) molybdenum nitrosyl hydrido complex trans-Mo(PMe(3))(4)(H)(NO) (2) and the related deuteride complex trans-Mo(PMe(3))(4)(D)(NO) (2a) were prepared from trans-Mo(PMe(3))(4)(Cl)(NO) (1). From (2)H T(1 min) measurements and solid-state (2)H NMR the bond ionicities of 2a could be determined and were found to be 80.0% and 75.3%, respectively, indicating a very polar Mo--D bond. The enhanced hydridicity of 2 is reflected in its very high propensity to undergo hydride transfer reactions. 2 was thus reacted with acetone, acetophenone, and benzophenone to afford the corresponding alkoxide complexes trans-Mo(NO)(PMe(3))(4)(OCHR'R'') (R' = R'' = Me (3); R' = Me, R'' = Ph (4); R' = R'' = Ph (5)). The reaction of 2 with CO(2) led to the formation of the formato-O-complex Mo(NO)(OCHO)(PMe(3))(4) (6). The reaction of with HOSO(2)CF(3) produced the anion coordinated complex Mo(NO)(PMe(3))(4)(OSO(2)CF(3)) (7), and the reaction with [H(Et(2)O)(2)][BAr(F)(4)] with an excess of PMe(3) produced the pentakis(trimethylphosphine) coordinated compound [Mo(NO)(PMe(3))(5)][BAr(F)(4)] (8). Imine insertions into the Mo-H bond of 2 were also accomplished. PhCH[double bond, length as m-dash]NPh (N-benzylideneaniline) and C(10)H(7)CH=NPh (N-1-naphthylideneaniline) afforded the amido compounds Mo(NO)(PMe(3))(4)[NR'(CH(2)R'')] (R' = R'' = Ph (9), R' = Ph, R'' = naphthyl (11)). 9 could not be obtained in pure form, however, its structure was assigned by spectroscopic means. At room temperature 11 reacted further to lose one PMe(3) forming 12 (Mo(NO)PMe(3))(3)[N(Ph)CH(2)C(10)H(6))]) with agostic stabilization. In a subsequent step oxidative addition of the agostic naphthyl C-H bond to the molybdenum centre occurred. Then hydrogen migration took place giving the chelate amine complex Mo(NO)(PMe(3))(3)[NH(Ph)(CH(2)C(10)H(6))] (15). The insertion reaction of 2 with C(10)H(7)N=CHPh led to formation of the agostic compound Mo(NO)(PMe(3))(3)[N(CH(2)Ph)(C(10)H(7))] (10). Based on the knowledge of facile formation of agostic compounds the catalytic hydrogenation of C(10)H(7)N=CHPh and PhN=CHC(10)H(7) with 2 (5 mol%) was tested. The best conversion rates were obtained in the presence of an excess of PMe(3), which were 18.4% and 100% for C(10)H(7)N=CHPh and PhN=CHC(10)H(7), respectively.

The chemistry of the fac-[Re(CO)2(NO)]2+ fragment in aqueous solution.

The anions [ReX3(CO)2(NO)]- (with X = Cl, 1; X = Br, 2) have been prepared with different counterions. Complex 1 was found to lose its chloride ligands in water within 24 h. The [Re(H2O)3(CO)2(NO)]2+ cation obtained after hydrolysis is a strong acid, which consequently undergoes a slow condensation reaction in water to form the very stable [Re(mu3-O)(CO)2(NO)]4 cluster 4 at pH > 2, that precipitates from the aqueous solution and is insoluble also in organic solvents. Fast deprotonation of [Re(H2O)3(CO)2(NO)]2+ did not lead to 4 but rather to the mononuclear species [Re(OH)(H2O)2(CO)2(NO)]+. Subsequent attack of OH- at a CO group resulted in the formation of a rhenacarboxylic acid and its carboxylate anion. For solutions of even higher pH, IR spectroscopy provided evidence for the formation of a Re(C(O)ON(O)) species. These processes were found to be reversible on lowering the pH. Starting from cluster 4 it was possible to obtain complexes of the types [ReX(CO)2(NO)L2] or [Re(CO)2(NO)L3](L2 = 2-picolinate, 2,2'-bipyridine, L-phenylalanate; L3 = tris(pyrazolyl)methane, 1,4,7-trithiacyclononane) in the presence of an acid in protic solvents, but only in low yields. In further synthetic studies, complexes 1 and 2 were found to be superior starting materials for substitution reactions to form [ReX(CO)2(NO)L2] or [Re(CO)2(NO)L3] complexes.

Insertion reactions of hydridonitrosyltetrakis(trimethylphosphine) tungsten(0).

[W(H)(NO)(PMe3)4] (1) was prepared by the reaction of [W(Cl)(NO)(PMe3)4] with NaBH4 in the presence of PMe3. The insertion of acetophenone, benzophenone and acetone into the W-H bond of 1 afforded the corresponding alkoxide complexes [W(NO)(PMe3)4(OCHR1R2)](R1 = R2 = Me (2); R1 = Me, R2 = Ph (3); R1 = R2 = Ph (4)), which were however thermally unstable. Insertion of CO2 into the W-H bond of yields the formato-O complex trans-W(NO)(OCHO)(PMe3)4 (5). Reaction of trans-W(NO)(H)(PMe3)4 with CO led to the formation of mer-W(CO)(NO)(H)(PMe3)3 (6) and not the formyl complex W(NO)(CHO)(PMe3)4. Insertion of Fe(CO)(5), Re2(CO)10 and Mn2(CO)10 into trans-W(NO)(H)(PMe3)4 resulted in the formation of trans-W(NO)(PMe3)4(mu-OCH)Fe(CO)4 (7), trans-W(NO)(PMe3)4(mu-OCH)Re2(CO)9 (8) and trans-W(NO)(PMe3)4(mu-OCH)Mn2(CO)9 (9). For Re2(CO)10, an equilibrium was established and the thermodynamic data of the equilibrium reaction have been determined by a variable-temperature NMR experiments (K(298K)= 104 L mol(-1), DeltaH=-37 kJ mol(-1), DeltaS =-86 J K(-1) mol(-1)). Both compounds 7 and 8 were separated in analytically pure form. Complex 9 decomposed slowly into some yet unidentified compounds at room temperature. Insertion of imines into the W-H bond of 1 was also additionally studied. For the reactions of the imines PhCH=NPh, Ph(Me)C=NPh, C6H5CH=NCH2C6H5, and (C6H5)2C=NH with only decomposition products were observed. However, the insertion of C10H7N=CHC6H5 into the W-H bond of led to loss of one PMe3 ligand and at the same time a strong agostic interaction (C17-H...W), which was followed by an oxidative addition of the C-H bond to the tungsten center giving the complex [W(NO)(H)(PMe3)3(C10H6NCH2Ph)] (10). The structures of compounds 1, 4, 7, 8 and 10 were studied by single-crystal X-ray diffraction.

Facile access to redox-active C2-bridged complexes with half-sandwich manganese end groups.

The dinuclear mixed-valent complex [(MeC5H4)(dmpe)MnC(2)Mn(dmpe)(C5H4Me)](+)[(eta2-MeC5H4)3Mn](-)[1](+)[2]- (dmpe=1,2-bis(dimethylphosphanyl)ethane) was prepared by the reaction of [Mn(MeC5H4)2] with dmpe and Me(3)SnC[triple chemical bond]CSnMe3. The reactions of [1](+)[2]- with K[PF6] and Na[BPh4] yielded the corresponding anion metathesis products [(MeC5H4)(dmpe)MnC2Mn(dmpe)(C5H4Me)][PF6] ([1][PF6]) and [(MeC5H4)(dmpe)MnC2Mn(dmpe)(C5H4Me)][BPh4] ([1][BPh4]). These mixed-valent species can be reduced to the neutral form by reaction with Na/Hg. The obtained complex [(MeC5H4)(dmpe)MnC2Mn(dmpe)(C5H4Me)] (1) displays a triplet/singlet spin equilibrium in solution and in the solid state, which was additionally studied by DFT calculations. The diamagnetic dicationic species [(MeC5H4)(dmpe)MnC2Mn(dmpe)(C5H4Me)][PF6]2 ([1][PF6]2) was obtained by oxidizing the mixed-valent complex [1][PF6] with one equivalent of [Fe(C5H5)2][PF6]. Both redox processes are fully reversible. The dinuclear compounds were characterized by NMR, IR, UV-visible, and Raman spectroscopy, cyclic voltammetry, and magnetic susceptibility measurements. X-ray diffraction studies were performed on [1][2], [1][PF6], [1][BPh4], and [1][PF6]2.

Light-induced metastable states in oxalatenitrosylruthenium(II) and terpyridinenitrosylruthenium(II) complexes.

Two extremely long lived metastable states (SI and SII) can be accessed by irradiation with light in the blue-green spectral range at temperatures below 200 K in Cs(2)[Ru(ox)(NO)Cl(3)], [Ni(cyclam)][Ru(ox)(NO)Cl(3)].3H(2)O, and [Ru(terpy)(NO)(OH)Cl][PF(6)]. The crystal structures of the ground states of the oxalate-containing compounds are presented, and the influence of the atomic distances of the cations/anions is discussed with respect to the decay temperatures. The radiationless thermal decay of the metastable states is detected by differential scanning calorimetry (DSC) for the three compounds. Both metastable states decay exponentially in time under isothermal conditions. The excited states are energetically separated from the ground state by potential barriers given by the activation energy of the Arrhenius law. In [Ni(cyclam)][Ru(ox)(NO)Cl(3)].3H(2)O the enthalpy maximum of the thermal decay of SII appears at 182 K, which is a relatively high decay temperature for SII. The reason for this strong temperature shift compared to those of the other compounds could be due to the polarization effect of Ni(2+) on the electron density at the Ru site via the Cl atom.

Head-to-head (HH) and head-to-tail (HT) conformers of cis-bis guanine ligands bound to the [Re(CO)3]+ core.

We have prepared four complexes of the type [Re(guanine)(2)(X)(CO)(3)] (guanine = 9-methylguanine or 7-methylguanine, X = H(2)O or Br) in order to understand the factors determining the orientation of coordinated purine ligands around the [Re(CO)(3)](+) core. The 9-methylguanine ligand (9-MeG) was chosen as the simplest N(9) derivatized guanine, and 7-methylguanine (7-MeG) was chosen because metal binding to N(9) does not impose steric hindrance. Two types of structures have been elucidated by X-ray crystallography, an HH (head-to-head) and HT (head-to-tail) conformer for each of the guanines. All complexes crystallize in monoclinic space groups: [Re(9-MeG)(2)(H(2)O)(CO)(3)]ClO(4) (2) in P2(1)/n with a = 12.3307(10) A, b = 16.2620(14) A, c = 13.7171(11) A, and beta = 105.525(9) degrees, V = 2650.2(4) A(3), with the two bases in HT orientation and its conformer [Re(9-MeG)(2)(H(2)O)(CO)(3)]Br (3) in P2(1)/n with a = 15.626(13) A, b = 9.5269(5) A, c = 15.4078(13) A, and beta = 76.951(1) degrees, V = 2234.5(3) A(3), and the two bases in an HH orientation. Similarly, [Re(7-MeG)(2)(H(2)O)(CO)(3)]ClO(4) (4) crystallizes in P2(1)/c with a = 13.0708(9) A, b = 15.4082(7) A, c = 14.316(9) A, and beta = 117.236(7) degrees, V = 2563.5(3) A(3), and exhibits an HT orientation and [ReBr(7-MeG)(2)(CO)(3)] (5) in P2/c with a = 17.5117(9) A, b = 9.8842(7) A, c = 15.3539(1) A, and beta = 100.824(7) degrees, V = 2610.3(3) A(3), and shows an HH orientation. When crystals of any of these complex pairs are dissolved in D(2)O, the (1)H NMR spectrum shows a single peak for the H(8) resonance of the respective coordinated purine indicating a rapid equilibrium between HH and HT conformations in solution. DFT calculations simulating the rotation of one ligand around its Re-N bond showed energetic barriers of less than 8.7 kcal/mol. We find no hypochromic effect in the Raman spectrum of 3, which showed base stacking in the solid state. Neither steric interactions nor hydrogen bonding are important in determining the orientation of the ligands in the coordination sphere.

Insertion reactions of trans-Mo(dmpe)2(H)(NO) with imines.

The insertion chemistry of the hydride complex trans-Mo(dmpe)(2)(H)(NO) (1) (dmpe = bis(dimethylphosphino)ethane) with imines has been investigated. It was found that disubstituted aromatic imines RCH[double bond]NR' (R, R' = Ar) insert into the Mo-H bond of 1, while a series of various mono- and other disubstituted imines do not react. The insertion products trans-Mo(dmpe)(2)(NO)[NR'(CH(2)R)] (R = R' = Ph (2); R = Cp(2)Fe, R' = Ph (3); R = Ph, R' = Cp(2)Fe (4); R = 1-naphthyl, R' = Ph (5)) have been isolated and fully characterized by elemental analysis, IR and NMR spectroscopy, and mass spectrometry. The imine PhCH[double bond]NC(10)H(7) (C(10)H(7) = 1-naphthyl) reacted with 1 establishing an equilibrium to produce the nonisolable complex trans-Mo(dmpe)(2)(NO)[NC(10)H(7)(CH(2)Ph)] (6). The equilibrium constant for this reaction has been derived from VT-NMR measurements, and the Delta H and Delta S values of this reaction were calculated to be -48.8 +/- 0.4 kJ.mol(-1) and -33 +/- 1 J.K(-1).mol(-1) reflecting a mild exothermic process and its associative nature. Single-crystal X-ray diffraction analyses were carried out on 2-5.

Generation and coupling of [Mn(dmpe)2(C triple bond CR)(C triple bond C)]* radicals producing redox-active C4-bridged rigid-rod complexes.

The symmetric d(5) trans-bis-alkynyl complexes [Mn(dmpe)(2)(C triple bond CSiR(3))(2)] (R = Me, 1 a; Et, 1 b; Ph, 1 c) (dmpe = 1,2-bis(dimethylphosphino)ethane) have been prepared by the reaction of [Mn(dmpe)(2)Br(2)] with two equivalents of the corresponding acetylide LiC triple bond CSiR(3). The reactions of species 1 with [Cp(2)Fe][PF(6)] yield the corresponding d(4) complexes [Mn(dmpe)(2)(C triple bond CSiR(3))(2)][PF(6)] (R = Me, 2 a; Et, 2 b; Ph, 2 c). These complexes react with NBu(4)F (TBAF) at -10 degrees C to give the desilylated parent acetylide compound [Mn(dmpe)(2)(C triple bond CH)(2)][PF(6)] (6), which is stable only in solution at below 0 degrees C. The asymmetrically substituted trans-bis-alkynyl complexes [Mn(dmpe)(2)(C triple bond CSiR(3))(C triple bond CH)][PF(6)] (R = Me, 7 a; Et, 7 b) related to 6 have been prepared by the reaction of the vinylidene compounds [Mn(dmpe)(2)(C triple bond CSiR(3))(C=CH(2))] (R = Me, 5 a; Et, 5 b) with two equivalents of [Cp(2)Fe][PF(6)] and one equivalent of quinuclidine. The conversion of [Mn(C(5)H(4)Me)(dmpe)I] with Me(3)SiC triple bond CSnMe(3) and dmpe afforded the trans-iodide-alkynyl d(5) complex [Mn(dmpe)(2)(C triple bond CSiMe(3))I] (9). Complex 9 proved to be unstable with regard to ligand disproportionation reactions and could therefore not be oxidized to a unique Mn(III) product, which prevented its further use in acetylide coupling reactions. Compounds 2 react at room temperature with one equivalent of TBAF to form the mixed-valent species [[Mn(dmpe)(2)(C triple bond CH)](2)(micro-C(4))][PF(6)] (11) by C-C coupling of [Mn(dmpe)(2)(C triple bond CH)(C triple bond C*)] radicals generated by deprotonation of 6. In a similar way, the mixed-valent complex [[Mn(dmpe)(2)(C triple bond CSiMe(3))](2)(micro-C(4))][PF(6)] [12](+) is obtained by the reaction of 7 a with one equivalent of DBU (1,8-diazabicyclo[5.4.0]undec-7-ene). The relatively long-lived radical intermediate [Mn(dmpe)(2)(C triple bond CH)(C triple bond C*)] could be trapped as the Mn(I) complex [Mn(dmpe)(2)(C triple bond CH)(triple bond C-CO(2))] (14) by addition of an excess of TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxy) to the reaction mixtures of species 2 and TBAF. The neutral dinuclear Mn(II)/Mn(II) compounds [[Mn(dmpe)(2)(C triple bond CR(3))](2)(micro-C(4))] (R = H, 11; R = SiMe(3), 12) are produced by the reduction of [11](+) and [12](+), respectively, with [FeCp(C(6)Me(6))]. [11](+) and [12](+) can also be oxidized with [Cp(2)Fe][PF(6)] to produce the dicationic Mn(III)/Mn(III) species [[Mn(dmpe)(2)(C triple bond CR(3))](2)(micro-C(4))][PF(6)](2) (R = H, [11](2+); R = SiMe(3), [12](2+)). Both redox processes are fully reversible. The dinuclear compounds have been characterized by NMR, IR, UV/Vis, and Raman spectroscopies, CV, and magnetic susceptibilities, as well as elemental analyses. X-ray diffraction studies have been performed on complexes 4 b, 7 b, 9, [12](+), [12](2+), and 14.

Volatile beta-ketoiminato- and beta-diketiminato-based zirconium complexes as potential MOCVD precursors.

An amine elimination pathway has been used to produce a number of homo- and heteroleptic zirconium complexes, starting from tetrakis(dialkylamido)zirconium complexes and beta-diketimine or, alternatively, Schiff Base compounds. Reaction of 2 equiv of the bidentate beta-diketimine (2Z,4E)-N-methyl-4-(methylimino)pent-2-en-2-amine with Zr(NR(2))(4) (R = Me, Et) affords the six-coordinate heteroleptic compounds bis(N-methyl-4-(methylimino)pent-2-en-2-amido)bis(dialkylamido)zirconium 1 (alkyl = Me) and 2 (alkyl = Et). The dynamic behavior of these two compounds in solution has been investigated. Reaction with the isopropyl-substituted beta-diketimine (2Z)-N-isopropyl-4-(isopropylimino)pent-2-en-2-amine gives the five-coordinate mono(diketiminato)-substituted compound (N-isopropyl-4-(isoropylimino)pent-2-en-2-amido)tris(dimethylamido )zirconium, 3. With employment of the Schiff base (3Z)-4-(methylamino)pent-3-en-2-one, it was also possible to prepare the six-coordinate bis(4-(methylamino)pent-3-en-2-onato)bis(diethylamido)zirconium compound 4. When the bidentate ligand bearing hydrogen as substituent on the imino-nitrogen atom was employed, homoleptic tetrakis(beta-ketoiminato)- and tetrakis(beta-diketiminato)zirconium compounds 5 and 6 can be obtained. Complexes 1 and 5 have been tested for their air stability with reference to Zr(NMe(2))(4). The stability order turned out to be 1 > 5 >> Zr(NMe(2))(4). The thermal properties and volatility of all the compounds are discussed in view of their potential application in metal-organic chemical vapor deposition processes (MOCVD) of zirconium nitride.

A facile and novel route to unprecedented manganese C4 cumulenic complexes.

The theoretically characterized (DFT) C4 cumulenic species Mn(C5H4R)(dmpe) [=C=C=C=C(SnPh3)2] was obtained by photolysis of the C(sp2)-Sn bond in the vinylidene complex Mn(C5H4R)(dmpe)[=C=C(SnPh3)-C[triple bond]CSnPh3], which in turn was prepared by a thermal reaction from MnC5H4R(dmpe)(C7H8) and Ph3Sn-C4-SnPh3.

Isomer abundance of bis(beta-diketonato) complexes of titanium(IV). Crystal structures of the antitumor compound budotitane [Ti(IV)(bzac)(2)(OEt)(2)] and of its dichloro-derivative [Ti(IV)(bzac)(2)Cl(2)] (bzac=1-phenylbutane-1,3-dionate).

The molecular tumor inhibiting titanium compound budotitane [Ti(IV)(bzac)(2)(OEt)(2)] (1) and its dichloro-derivative [Ti(IV)(bzac)(2)Cl(2)] (2) (bzac=1-phenylbutane-1,3-dionate) have been crystallized and characterized by X-ray crystallography and further physical methods. Budotitane (1) crystallizes in the tetragonal, non-centrosymmetric space group P4(1) with two molecules in the asymmetric unit. Both molecules adopt the cis-cis-trans configuration with the acetyl ends of the benzoylacetonate ligands in the trans position. The dichloro-derivative of budotitane, [Ti(IV)(bzac)(2)Cl(2)] (2) crystallizes in the monoclinic, centrosymmetric space group P2(1)/n with one molecule only in the asymmetric unit. In contrast to budotitane (1), (2) shows a cis-trans-cis arrangement with the benzoyl groups in the trans position. In both complexes there are equal numbers of Delta and Lambda enantiomers within the unit cell. The phenyl groups in (1) as well as in (2) are in approximately coplanar conjugation to the metal enolate rings. The thermal degradation of budotitane (1) was investigated in the temperature range from 25 degrees C up to 800 degrees C and reveals the formation of Ti(IV)O(bzac(2-)) as an intermediate and of the rutile phase of TiO(2) as a final product. It may be worthwhile to introduce budotitane in the form of isomerically pure crystals in the preparation of the drug used for future tests.

An unusual (10,3)-a racemic twofold interpenetrating network assembled from isolable tris(cyclopentadienyl)manganate and cesocene building blocks.

The syntheses and X-ray crystal structures of [([18]crown-6)2Cs](+)-[Cp3Mn]- (1), [([18]crown-6)2Cs](+)-[Cp'3Mn]- (2), [CsCp'] (3), [(CsCp')2-([18]crown-6)] (4), and Cs[MnCp3] (5), and the synthesis of Cs[MnCp'3] (6) are reported (Cp' = C5H4Me). The anions [Cp3Mn]- (1-) and [Cp'3Mn]- (2-) are characterized by eta 2 coordination of all three Cp or Cp' rings. Measurements of the magnetic susceptibilities chi M resulted in values of mu eff = 6.20 microB (300 K), mu eff = 6.33 microB (301 K), and mu eff = 5.83 microB (300 K) for 1, 2, and 5, respectively, which are indicative of high-spin d5-Mn2+ centers. Density functional calculations illustrate that the coordination mode of 1- is characteristic for its sextet electronic ground state. Compound 3 forms infinite chains of cesocene-type sandwiches in the solid state, which are broken up into small subunits by the addition of crown ether to form 4. Compound 5 is a rare example of a (10,3)-a racemic interpenetrating network that crystallizes in the orthorhombic space group Pbca.

Steps toward high specific activity labeling of biomolecules for therapeutic application: preparation of precursor [(188)Re(H(2)O)(3)(CO)(3)](+) and synthesis of tailor-made bifunctional ligand systems.

Two kit preparations of the organometallic precursor [(188)Re(H(2)O)(3)(CO)(3)](+) in aqueous media are presented. Method A uses gaseous carbon monoxide and amine borane (BH(3).NH(3)) as the reducing agent. In method B CO(g) is replaced by K(2)[H(3)BCO(2)] that releases carbon monoxide during hydrolysis. Both procedures afford the desired precursor in yields >85% after 10 min at 60 degrees C. HPLC and TLC analyses revealed 7 +/- 3% of unreacted (188)ReO(4)(-) and <5% of colloidal (188)ReO(2). Solutions of up to 14 GBq/mL Re-188 have been successfully carbonylated with these two methods. The syntheses of two tailor-made bifunctional ligand systems for the precursor [(188)Re(H(2)O)(3)(CO)(3)](+) are presented. The tridentate chelates consist of a bis[imidazol-2-yl]methylamine or an iminodiacetic acid moiety, respectively. Both types of ligand systems have been prepared with alkyl spacers of different length and a pendent primary amino or carboxylic acid functionality, enabling the amidic linkage to biomolecules. The tridentate coordination of the ligands to the rhenium-tricarbonyl core could be elucidated on the macroscopic level by X-ray structure analyses and 1D and 2D NMR experiments of two representative model complexes. On the nca level, the ligands allow labeling yields >95% with [(188)Re(H(2)O)(3)(CO)(3)](+) under mild reaction conditions (PBS buffer, 60 degrees C, 60 min) at ligand concentrations between 5 x 10(-4) M and 5 x 10(-5) M. Thus, specific activities of 22-220 GBq pe micromol of ligand could be achieved. Incubation of the corresponding Re-188 complexes in human serum at 37 degrees C revealed stabilities between 80 +/- 4% and 45 +/- 10% at 24 h, respectively, and 63 +/- 3% and 34 +/- 3% at 48 h postincubation in human serum depending on the chelating system. Decomposition product was mainly (188)ReO(4)(-). The routine kit-preparation of the precursor [(188)Re(H(2)O)(3)(CO)(3)](+) in combination with tailor-made ligand systems enables the organometallic labeling of biomolecules with unprecedented high specific activities.