[Re5(μ-H)4(CO)20]− and [Re5(μ-H)5(CO)20], Two Isolobal Analogues of Cyclopentane

The first five-membered rings of metal atoms connected by M–M or M-H-M bonds only have been obtained by a Re₂+Re₃ condensation in which a polyhydride acts as a bridging bidentate ligand toward a coordinatively unsaturated fragment (see scheme below). In spite of the octahedral coordination of the Re centers, the Re₅ rings display conformations (twisted and envelope) comparable with those observed for organic five-membered rings of tetrahedral carbon atoms.     

New Dinuclear Ru2(CO)4 Sawhorse‐Type Complexes Containing Bridging Carboxylato Ligands

The thermal reaction of Ru₃(CO)₁₂ with ethacrynic acid, 4‐[bis(2‐chlorethyl)amino]benzenebutanoic acid (chlorambucil), or 4‐phenylbutyric acid in refluxing solvents, followed by addition of two‐electron donor ligands (L), gives the diruthenium complexes Ru₂(CO)₄(O₂CR)₂L₂ ( 1 : R = CH₂O‐C₆H₂Cl₂‐COC(CH₂)C₂H₅, L = C₅H₅N; 2 : R = CH₂O‐C₆H₂Cl₂‐COC(CH₂)C₂H₅, L = PPh₃; 3 : R = C₃H₆‐C₆H₄‐N(C₂H₄‐Cl)₂, L = C₅H₅N; 4 : R = C₃H₆‐C₆H₄‐N(C₂H₄‐Cl)₂, L = PPh₃; 5 : R = C₃H₆‐C₆H₅, L = C₅H₅N; 6 : R = C₃H₆‐C₆H₅, L = PPh₃). The single‐crystal structure analyses of 2 , 3 , 5 and 6 reveal a dinuclear Ru₂(CO)₄ sawhorse structure, the diruthenium backbone being bridged by the carboxylato ligands, while the two L ligands occupy the axial positions of the diruthenium unit.     

Syntheses and structural characterizations of rhenium carbonyl complexes of a bitopic ferrocene-linked bis(pyrazolyl)methane ligand

The reaction between Fe[C₅H₄CH(pz)₂]₂ (pz = pyrazolyl ring) and two equivalents of Re(CO)₅Br in refluxing toluene produces Fe[C₅H₄CH(pz)₂Re(CO)₃Br]₂ (1) in high yield. A similar reaction with a ligand/rhenium ratio of slightly greater than one yields mainly 1 and a low yield of Fe[C₅H₄CH(pz)₂Re(CO)₃Br][C₅H₄CH(pz)₂] (2). The compound H₂C(pz)₂Re(CO)₃Br (3) was prepared by the reaction of H₂C(pz)₂ and Re(CO)₅Br. Compounds 1 and 2 show a reversible oxidation at ca. 0.9 V (Ag/AgCl) that can be assigned to the oxidation of the ferrocene moiety and one irreversible oxidation at ca. 1.4 V assigned to the oxidation of the rhenium metal center. The solid-state structures of 1 · CH₃NO₂, 1 · 2CH₃NO₂, 1 · 2CH₃CN and 2 · 1/2Et₂O · 1/2C₃H₆O have been determined, with 1 · 2CH₃NO₂ and 1 · 2CH₃CN being isomorphous. All four are organized into supramolecular structures by the interactions of the acidic hydrogens of the pyrazolyl and methine groups with either the bromine atoms or carbonyl ligand oxygen atoms, and in 2 the lone pairs on the uncomplexed bis(pyrazolyl)methane units.     

Synthesis and Structural Characterization of Novel Neutral Higher‐Coordinate Silicon(IV) Complexes with SiON3C and SiON4C Skeletons

The neutral pentacoordinate silicon(IV) complex 10 (SiON₃C skeleton) and the neutral hexacoordinate silicon(IV) complex 11 (SiON₄C skeleton) were synthesized, starting from methyldi(thiocyanato‐N)silane ( 7 ). In addition to their monodentate thiocyanato‐N and methyl ligands, these compounds contain a tridentate dianionic O,N,N ligand ( 10 ) or a tridentate monoanionic O,N,N ligand ( 11 ). Compounds 10 and 11 were characterized by single‐crystal X‐ray diffraction and solid‐state and solution NMR spectroscopy. According to these studies, compounds 10 and 11 exist in solution as well.     

Substituent Effects on the Spin-Transition Temperature in Complexes with Tris(pyrazolyl) Ligands

Summary.  Iron (II) complexes with substituted tris(pyrazolyl) ligands, which exhibit a thermally driven transition from a low-spin state at low temperatures to a high-spin state at elevated temperatures, have been studied by M?ssbauer spectroscopy and magnetic susceptibility measurements. From the observed spectra the molar high-spin fraction and the transition temperature have been extracted. All substituents, except for bromine, lead to a decrease of the transition temperature. Density functional calculations have been carried out to compare the experimentally observed shifts of the transition temperature with those derived from theory. Corresponding author. E-mail: paulsen@physik.uni-luebeck.de Received June 26, 2002; accepted July 22, 2002     

Rhenium(I) Tellurolate,Telluroether and Bidentate-Telluroether Complexes: Crystal Structures of Re(CO)3Br(PhTe(CH2)3TePh), PhTeRe(CO)5 Re2(μ-SePh)2(CO)8 and [(PhTeMe)Re(CO)5][BF4]

The monomeric rhenium(I) complex with bidentate telluroether ligand Re(CO)₃Br(PhTe(CH₂)₃TePh) (1) was accessible via reaction of the PhTe(CH₂)₃TePh with Re(CO)₅Br. This chelate complex crystallized in triclinic space group $ {\rm P}\bar 1 $ with a = 9.390(5) Å, b = 10.961(3) Å, c = 11.849(4) Å a = 63.30(3)°, β = 87.49(4)° γ = 69.31(4)°, V = 1009.5(7) ų Z = 2, R = 0.033, and R_w = 0.034. Reaction of Re(CO)₅Cl with NaTePh yielded the Re(I) specics PhTeRe(CO)₅ (2). This complex crystallized in triclinic space group $ {\rm P}\bar 1 $ with a = 7.085(1) Å, b = 9.203(1) Å, c = 11.341(1) Å, α = 107.24(1)°, β = 100.56(1)°, γ = 96.47(1)°, V = 683.2(2) ų, Z = 2, R = 0.027, R_w = 0.022. Reaction of PhTeRe(CO)₅ and (PhSe)₂ in THF at 65 °C yielded a product that was confirmed crystallographically to be the known species Re₂(μ-SePh)₂(CO)₈ (3), in which two phenylselenolate ligands bridge the two Re(I). Compound 3 crystallized in monoclinic space group P2₁/n with a = 7.210(2) Å, b = 18.862(6) Å, c = 9.083(3) Å, β = 107.48(3)° V = 1178.2(7) ų, Z = 2, R = 0.046, and R_w = 0.051. Methylation of PhTeRe(CO)₅ with [Me₃O][BF₄] afforded Re(I) product [(PhTeMe)Re(CO)₅][BF₄] (4). This monodentate telluroether species crystallized in monoclinic space group P2₁/n with a = 8.405(1) Å, b = 13.438(3) Å, c = 15.560(2) Å, β = 92.59(1)° V = 1755.5(5) ų, Z = 4, R = 0.035, and R_w = 0.035.     

Phosphaniminato‐Komplexe von Rhenium(VII). Synthesen und Kristallstrukturen von [ReO3(NPR3)] (R = Ph,Et) sowie von [ReO(OSiMe3)3(Me3SiNPEt3)]

Phosphoraneiminato Complexes of Rhenium(VII). Syntheses and Crystal Structures of [ReO₃(NPR₃)] (R = Ph, Et) and of [ReO(OSiMe₃)₃(Me₃SiNPEt₃)] The phosphoraneiminato complexes [ReO₃(NPR₃)] with R = Ph ( 1 ) and R = Et ( 2 ) are made from dirhenium heptaoxide and the silylated phosphoraneimines Me₃SiNPR₃. The complexes 1 and 2 as well as the red silanolate [ReO(OSiMe₃)₃(Me₃SiNPEt₃)] ( 3 ), which is formed as a by‐product in the synthesis of 2 , are characterized crystallographically. 1 and 2 are monomeric molecules, in which the phosphoraneiminato ligands NPR₃^– realize short ReN bonds of 179.3 pm ( 1 ) and 178.6 pm ( 2 ), respectively, with large ReNP bond angles of 162.0° ( 1 ) and 160.6° ( 2 ), respectively. In the rhenium(V) complex 3 the oxoligand occupies the apical position of the tetragonal pyramidal coordination of the rhenium atom, while the oxygen atoms of the Me₃SiO^– groups take the basic positions along with the nitrogen atom of the phosphaneimine molecule.     

Structures and Properties of Novel Mononuclear Iron(III) Complexes with Benzimidazole Containing Tripodal Tetradentate Ligands

The iron(III) complexes of the tripodal benzimidazole‐containing ligands tris(2‐benzimidazolylmethyl)amine (ntb), bis(2‐benzimidazolylmethyl)(2‐hydroxyethyl)‐amine (bbimae) and tris(5,6‐dimethyl‐2‐benzimidazolylmethyl)amine (me₂ntb) are structural and functional models for intradiol cleaving catechol dioxygenases. The complexes [Fe(ntb)Cl₂]Cl · 3 CH₃OH ( 1 ; P 1, a = 9.830(2) Å, b = 12.542(3) Å, c = 13.139(3) Å, α = 82.88(3)°, β = 73.45(3)°, γ = 85.53(3)°, V = 1539.2(6) ų; Z = 2) and [Fe(bbimae)Cl₂]Cl ( 2 ; P2₁/n, a = 7.461(2) Å, b = 18.994(5) Å, c = 14.515(4) Å, β = 98.22(2)°, V = 2035.8(9) ų, Z = 4) have been characterized by X‐ray crystallography and spectroscopic methods. In the octahedrally coordinated complexes two cis coordination sites – essential for catechol binding – are occupied by chloride ligands. The significant intradiol cleaving catechol dioxygenase activity of the model complexes was examined using 3,5‐di‐tert‐butylcatechol as a substrate.     

Preparation and characterization of rhenium (I) tricarbonyl dithiocarbamate compounds; Re(CO)3(S2CNMe2)(L)

The title compounds were prepared in good yield by treatment of Re(CO)₅Cl or [Re(CO)₃(H₂O)₃]Br with sodium dimethyldithiocarbamate hydrate (NaS₂CNMe₂·H₂O) and a neutral ligand yielding eight Re(CO)₃(S₂CNMe₂)(L) derivatives: L = NH₃1, pyridine (py) 2, imidazole (im) 3, pyrazole (pz) 4, triphenylphospine (PPh₃) 5, 1,3,5-triaza-7-phosphaadamantane (PTA) 6, t-butyl isocyanide (t-BuNC) 7, and cyclohexyl isocyanide (CyNC) 8. The resulting new complexes were characterized by ¹H and ¹³C NMR and infrared spectroscopy. Each was also structurally elucidated by X-ray crystallography. General structural features in all eight compounds were similar. The orientation of the three single-faced ligands, py, im and pz, demonstrates an interaction with the filled π orbital of the dithiocarbamate. Compounds were tested for stability under conditions that mimic physiological conditions; 1-4 quickly decomposed, 7 and 8 decomposed over 24 h while 5 and 6 were stable.     

Preparation and characterization of [Re(bpy)(CO) 3L][SbF6] (L = phosphine, phosphite)

A series of rhenium complexes [fac-Re(bpy)(CO)₃L][SbF₆] (bpy = 2,2′-bipyridine, L = P(ⁿBu)₃, PEt₃, PPh₃, P(OMe)Ph₂, P(OⁱPr)₃, P(OEt)₃, P(OMe)₃, P(OPh)₃) has been prepared and characterized by the IR, UV-vis, ¹H NMR, ³¹P NMR, X-ray photoelectron spectroscopy and electrochemical techniques. Variations in the electronic properties, i.e. CO stretching, metal-to-ligand charge transfer transition, and ³¹P NMR chemical shifts were interpreted on the basis of the electron-acceptor strength of L. However, the redox potential corresponding to [Re(bpy)(CO)₃L]⁺/[Re(bpy⁻)(CO)₃L]showed ‘V-character type’ changes after the increase in the electron-acceptor strength of L. Variation of the P(2p) binding energy of the phosphorus atom indicated that the electronic structure of the coordinated phosphorus atom was strongly influenced by the electronic properties of the directly attached substituents.     

Anion-Coordination-Assisted Assembly of Supramolecular Charge-Transfer Complexes Based on Tris(urea) Ligands

Charge-transfer (CT) complexes, formed by noncovalent bonding between electron-rich (donor, D) and electron-deficient (acceptor, A) molecules (or moieties) have attracted considerable attention due to their fascinating structures and potential applications. Herein, we demonstrate that anion coordination is a promising strategy to promote CT complex formation between anion-binding, electron-rich tris(urea) donor ligands (D) and electron-deficient viologen cation acceptors (A), which form co-crystals featuring infinite ⋅⋅⋅DADA⋅⋅⋅ or discrete (circular DADA or three-decker DAD) π-stacking interactions. These CT complexes were studied by X-ray diffraction, UV/Vis spectroscopy, electric conductivity measurements, charge displacement curve (CDC) calculations, and DFT computations.     

Oxidation and β‐Alkylation of Alcohols Catalysed by Iridium(I) Complexes with Functionalised N‐Heterocyclic Carbene Ligands

The borrowing hydrogen methodology allows for the use of alcohols as alkylating agents for C?C bond forming processes offering significant environmental benefits over traditional approaches. Iridium(I)‐cyclooctadiene complexes having a NHC ligand with a O‐ or N‐functionalised wingtip efficiently catalysed the oxidation and β‐alkylation of secondary alcohols with primary alcohols in the presence of a base. The cationic complex [Ir(NCCH₃)(cod)(MeIm(2‐ methoxybenzyl))][BF₄] (cod=1,5‐cyclooctadiene, MeIm=1‐methylimidazolyl) having a rigid O‐functionalised wingtip, shows the best catalyst performance in the dehydrogenation of benzyl alcohol in acetone, with an initial turnover frequency (TOF₀) of 1283 h^?1, and also in the β‐alkylation of 2‐propanol with butan‐1‐ol, which gives a conversion of 94 % in 10 h with a selectivity of 99 % for heptan‐2‐ol. We have investigated the full reaction mechanism including the dehydrogenation, the cross‐aldol condensation and the hydrogenation step by DFT calculations. Interestingly, these studies revealed the participation of the iridium catalyst in the key step leading to the formation of the new C?C bond that involves the reaction of an O‐bound enolate generated in the basic medium with the electrophilic aldehyde.     

Synthesis,Characterization, and Crystal Structure of Mononuclear and Dinuclear Dioxomolybdenum(VI) Complexes with Tridentate Schiff‐base Ligands. Part 2

Mononuclear [MoO₂LD], and dinuclear [MoO₂L]₂ or [MoO₂L]₂ · D dixomolybdenum(VI) complexes have been prepared by the reaction of tridentate Schiff‐base ligands L with [MoO₂(acac)₂]. The Schiff‐base ligands have been synthesized from salicylaldehyde ( 1 , 1a , 1c , 1d ), 2‐hydroxy‐1‐naphthaldehyde ( 2 , 2c ) and 2‐hydroxy‐3‐methoxybenzaldehyde ( 3a , 3b , 3c , 3d , 3e ) with 2‐amino‐p‐cresol. All prepared complexes consist of cis‐MoO₂²⁺core coordinated by Schiff‐base ligand through two deprotonated hydroxyl groups and one imino nitrogen atom. The usual octahedral coordination around the molybdenum atoms is completed by the neutral ligand D (methanol, ethanol, dimethyl sulfoxide, imidazole or 4, 4′‐bipyridine). All compounds were characterized by elemental analyses, IR spectroscopy and some of them by X‐ray crystallography ( 1a , 2c , 3a , 3b , 3c and 3e ).     

[M(CO)2(NO)], a new core in bioorganometallic chemistry: model complexes of [Re(CO)2(NO)] and [Tc(CO)2(NO)]

In this study selected bidentate (L²) and tridentate (L³) ligands were coordinated to the Re(I) or Tc(I) core [M(CO)₂(NO)]²⁺ resulting in complexes of the general formula fac-[MX(L²)(CO)₂(NO)] and fac-[M(L³)(CO)₂(NO)] (M = Re or Tc; X = Br or Cl). The complexes were obtained directly from the reaction of [M(CO)₂(NO)]²⁺ with the ligand or indirectly by first reacting the ligand with [M(CO)₃]⁺ and subsequent nitrosylation with [NO][BF₄] or [NO][HSO₄]. Most of the reactions were performed with cold rhenium on a macroscopic level before the conditions were adapted to the n.c.a. level with technetium (^99mTc). Chloride, bromide and nitrate were used as monodentate ligands, picolinic acid (PIC) as a bidentate ligand and histidine (HIS), iminodiacetic acid (IDA) and nitrilotriacetic acid (NTA) as tridentate ligands. We synthesised and describe the dinuclear complex [ReCl(μ-Cl)(CO)₂(NO)]₂ and the mononuclear complexes [NEt₄][ReCl₃(CO)₂(NO)], [NEt₄][ReBr₃(CO)₂(NO)], [ReBr(PIC)(CO)₂(NO)], [NMe₄][Re(NO₃)₃(CO)₂(NO)], [Re(HIS)(CO)₂(NO)][BF₄], [⁹⁹Tc(HIS)(CO)₂(NO)][BF₄], [^99mTc(IDA)(CO)₂ (NO)] and [^99mTc(NTA)(CO)₂(NO)]. The chemical and physical characteristics of the Re and Tc-dicarbonyl-nitrosyl complexes differ significantly from those of the corresponding tricarbonyl compounds.     

Exploring the nitrosyl-approach: “Re(CO)2(NO)”- and “Tc(CO)2(NO)”-complexes provide new pathways for bioorganometallic chemistry

Nitrosylation reactions are rare in the context of low valent Re(I)- and Tc(I)-tricarbonyl complexes so far. We herein describe a method for the conversion of a “M(CO)₃-moiety” (M = Re, Tc) into a dicarbonyl-nitrosyl moiety “M(CO)₂NO”, the synthesis of important precursor complexes and intermediates and possible applications for this new kind of Re- and Tc-chemistry.The behavior of the complex [ReCl₃(CO)₂(NO)]⁻ in water was studied in detail and compared to that of [ReCl₃(CO)₃]²⁻. Contrary to the conversion of [ReCl₃(CO)₃]²⁻ to the mixed aquo-carbonyl complex [Re(OH₂)₃(CO)₃]⁺ in water, one chloride remains initially bound to the metal center in the dicarbonyl-nitrosyl complex, making [ReCl(OH₂)₂(CO)₂(NO)]⁺ the main species for further reactions. In this context, we isolated and characterized the complex [Re(μ₃-O)(CO)₂(NO)]₄. Examples of complexes with different bi- and tridentate ligands based on ReCl₃(CO)₂(NO)]⁻ are discussed.For the development of potential new radiopharmaceuticals we also adapted the nitrosylation technique to the n.c.a. level with ^99mTc. [^99mTc(OH₂)₃(CO)₃]⁺ served as starting material to form a ^99mTc(CO)₂(NO)-core. Labelling reactions with ligands such as iminodiacetic acid (IDA), nitrilotriacetic acid (NTA) and diethylenetriamine pentaacetic acid (DTPA) were performed, resulting in the complexes [^99mTc(IDA)(CO)₂(NO)], [^99mTc(NTA)(CO)₂(NO)] and [^99mTc(DTPA)(CO)₂(NO)]. In this way, the “nitrosyl-approach” adds a new and challenging synthetic tool to the already established organometallic chemistry of Re- and Tc-tricarbonyl complexes.     

Preparation and Reactivity of Mixed‐Ligands Hydride Complexes [RuHCl(CO)(PPh3)2{P(OR)3}]

Mixed‐ligands hydride complexes [RuHCl(CO)(PPh₃)₂{P(OR)₃}] ( 2 ) (R = Me, Et) were prepared by allowing [RuHCl(CO)(PPh₃)₃] ( 1 ) to react with an excess of phosphites P(OR)₃ in refluxing benzene. Treatment of hydrides 2 first with triflic acid and next with an excess of hydrazine afforded hydrazine complexes [RuCl(CO)(κ¹‐NH₂NHR1)(PPh₃)₂{P(OR)₃}]BPh₄ ( 3 , 4 ) (R1 = H, CH₃). Diethylcyanamide derivatives [RuCl(CO)(N≡CNEt₂)(PPh₃)₂{P(OR)₃}]BPh₄ ( 5 ) were also prepared by reacting 2 first with HOTf and then with N≡CNEt₂. The complexes were characterized spectroscopically and by X‐ray crystal structure determination of [RuHCl(CO)(PPh₃)₂{P(OEt)₃}] ( 2b ).     

Coordination of bidentate aniline derivatives to the fac-[Re(CO)3] core

A series of rhenium(I) tricarbonyl complexes, containing bidentate derivatives of aniline, was synthesized and structurally characterized. With 1,2-diaminobenzene (Hpda) the ‘2+1’ complex salt fac-[Re(CO)₃(Hpda)₂]Br was isolated. The neutral complex [Re(CO)₃(Hapa)Br] was formed with 2-aminodiphenylamine (Hapa) as ligand. 2-Aminophenol (Hopa) also produced the neutral ‘2+1’ complex [Re(CO)₃(opa)₂(Hopa)], but with 2-mercaptophenol (Hspo) the bridged dimer [Re₂(CO)₇(spo)₂] was found. In the complex [Re(CO)₃(Htpn)Br] (Htpn = N′-{(2-methylthio)benzylidene}benzene-1,2-diamine) the potentially tridentate ligand Htpn is coordinated via the methylthio sulfur and imino nitrogen atoms only, with a free amino group.     

Anion and Additive Effects on the Structure of Mercury(II) Halides Complexes with Tripodal Ligand

The metal complexes [Hg₂(tbim)₂Br₄]·2DMF ( 1 ) and [Hg₂(tbim)I₄]·1.5DMF ( 2 ) were prepared by reactions of 1,3,5‐tris(benzimidazol‐1‐ylmethyl)‐2,4,6‐trimethylbenzene (tbim) with HgBr₂, HgI₂, respectively, and [Hg₂(tbim)I₄]·0.5(FeCp₂)·H₂O ( 3 ) was obtained by the same method with addition of ferrocene (FeCp₂) as additive. Their structures were determined by X‐ray crystallographic analyses. Complex 1 has a macrocyclic binuclear structure with one benzimidazole arm of the ligand free of coordination and the binuclear units are further connected by C‐H···N hydrogen bonds to give an infinite zigzag chain. Complexes 2 and 3 have a 2D network structure in which tbim serves as a tridentate ligand. The results showed that the halides of bromide and iodide have remarkable impact on the structure of the complexes. The FeCp₂ molecules are trapped in the voids of framework 3 .     

Syntheses of Cationic, Six-Coordinate Cadmium(II) Complexes Containing Tris(pyrazolyl)methane Ligands. Influence of Charge on Cadmium-113 NMR Chemical Shifts

Treating a thf (thf = tetrahydrofuran) suspension of Cd(acac)(2) (acac = acetylacetonate) with 2 equiv of HBF(4).Et(2)O results in the immediate formation of [Cd(2)(thf)(5)](BF(4))(4) (1). Crystallization of this complex from thf/CH(2)Cl(2) yields [Cd(thf)(4)](BF(4))(2) (2), a complex characterized in the solid state by X-ray crystallography. Crystal data: monoclinic, P2(1)/n, a = 7.784(2) ?, b = 10.408(2) ?, c = 14.632(7) ?, beta = 94.64(3) degrees, V = 1181.5(6) ?(3), Z = 2, R = 0.0484. The geometry about the cadmium is octahedral with a square planar arrangement of the thf ligands and a fluorine from each (BF(4))(-) occupying the remaining two octahedral sites. Reactions of [Cd(2)(thf)(5)](BF(4))(4) with either HC(3,5-Me(2)pz)(3) or HC(3-Phpz)(3) yield the dicationic, homoleptic compounds {[HC(3,5-Me(2)pz)(3)](2)Cd}(BF(4))(2) (3) and {[HC(3-Phpz)(3)](2)Cd}(BF(4))(2) (4) (pz = 1-pyrazolyl). The solid state structure of 3 has been determined by X-ray crystallography. Crystal data: rhombohedral, R&thremacr;, a = 12.236(8) ?, c = 22.69(3) ?, V = 2924(4) ?(3), Z = 3, R = 0.0548. The cadmium is bonded to the six nitrogen donor atoms in a trigonally distorted octahedral arrangement. Four monocationic, mixed ligand tris(pyrazolyl)methane-tris(pyrazolyl)borate complexes {[HC(3,5-Me(2)pz)(3)][HB(3,5-Me(2)pz)(3)]Cd}(BF(4)) (5), {[HC(3,5-Me(2)pz)(3)][HB(3-Phpz)(3)]Cd}(BF(4)) (6), {[HC(3-Phpz)(3)][HB(3,5-Me(2)pz)(3)]Cd}(BF(4)) (7), and {[HC(3-Phpz)(3)][HB(3-Phpz)(3)]Cd}(BF(4)) (8) are prepared by appropriate conproportionation reactions of 3or 4 with equimolar amounts of the appropriate homoleptic neutral tris(pyrazolyl)borate complexes [HB(3,5-Me(2)pz)(3)](2)Cd or [HB(3-Phpz)(3)](2)Cd. Solution (113)Cd NMR studies on complexes 3-8 demonstrate that the chemical shifts of the new cationic, tris(pyrazolyl)methane complexes are very similar to the neutral tris(pyrazolyl)borate complexes that contain similar substitution of the pyrazolyl rings.     

Koordinationseigenschaften der isolobalen Phosphaniminatound Cyclopentadienyl‐Liganden in TiCl3(NPH3), TiCl3Cp,ReO3(NPH3) und ReO3Cp

Coordination Behaviour of the Isolobal Phosphoraneiminato and Cyclopentadienyl Ligands in TiCl₃(NPH₃), TiCl₃Cp, ReO₃(NPH₃), and ReO₃Cp The phosphoraneiminato and cyclopentadienyl complexes TiCl₃(NPH₃) ( 1 ), ReO₃(NPH₃) ( 2 ), TiCl₃Cp ( 3 ), and ReO₃Cp ( 4 ) have been investigated quantum chemically at the BP86/TZ(2)P level of nonlocal density functional theory (DFT). The metal–ligand bonds turn out to dissociate homolytically with the computed values for the corresponding bond dissociation energies amounting to 79.6 ( 1 ), 103.4 ( 2 ), 58.1 ( 3 ) and 45.0 ( 4 ) kcal/mol. Whereas the M–N–P unit in the titanium complex 1 is linear, we find a bent structure for the corresponding rhenium complex 2 (∠ Re–N–P = 136.4°). It turns out that the potential energy surface of the phosphoraneiminato complexes is extremely shallow with respect to the M–N–P angle; a variation over 50° is associated with an energy change of less than 2 kcal/mol. Furthermore, we have carried out a detailed analysis of the bonding in our model complexes to elucidate the difference in metal–ligand bond strengths between the isolobal phosphoraneiminato and cyclopentadienyl ligands.