Reactions of mu3-alkenyl triruthenium carbonyl clusters with alkynes: synthesis of trinuclear mu-//-alkyne, mu-vinylidene, and mu-dienoyl derivatives

The reactions of doubly face-capped triruthenium cluster complexes of the type [Ru(3)(mu(3)-kappa(2)-HNNMe(2))(mu(3)-kappa(2)-R(2)CCHR(1))(mu-CO)(2)(CO)(6)] (HNNMe(2) = 1,1-dimethylhydrazide; R(2)CCHR(1) = alkenyl ligand) with terminal and internal alkynes have been studied in refluxing toluene. The following derivatives have been isolated from these reactions: [Ru(3)(mu(3)-kappa(2)-HNNMe(2))(mu(3)-kappa(2)-R(2)CCHR(1))(mu-kappa(2)-//-HCCH)(CO)(7)] (R(1) = R(2) = H, 5; R(1) = Ph, R(2) = H, 6; R(1) = CH(2)OMe, R(2) = H, 7 a; R(1) = H, R(2) = CH(2)OMe, 7 b) from acetylene, [Ru(3)(mu(3)-kappa(2)-HNNMe(2))(mu(3)-kappa(2)-HCCH(2))(mu-kappa(2)-//-PhCCPh)(CO)(7)] (11) from diphenylacetylene, and three isomers of [Ru(3)(mu(3)-kappa(2)-HNNMe(2))(mu(3)-kappa(2)-HCCH(2))(mu-kappa(2)-//-PhCCH)(CO)(7)] (14, 15 a, and 15 b) from phenylacetylene. These products result from substitution of a CO ligand by the alkyne and contain an Ru--Ru edge bridged by the alkyne ligand in a parallel manner. DFT calculations on selected isomeric products have helped to establish that the type of Ru--Ru edge bridged by the alkyne depends more on kinetic factors related to the size of the alkyne substituents than on the thermodynamic stability of the final products. The preparation of triruthenium cluster complexes with mu-//-alkyne ligands is unprecedented and seems to relate to the fact that the starting trinuclear complexes have their two triangular faces protected by capping ligands. The clusters bearing mu-//-acetylene (5-7) are thermodynamically unstable with respect to their transformation into edge-bridging vinylidene derivatives, [Ru(3)(mu(3)-kappa(2)-HNNMe(2))(mu(3)-kappa(2)-HCCHR)(mu-kappa(1)-CCH(2))(CO)(7)] (R = H, 8; Ph, 9; CH(2)OMe, 10). DFT calculations have shown that complex 8 is 11.2 kcal mol(-1) more stable than its precursor 5. The thermolysis of compound 11 leads to [Ru(3)(mu(3)-kappa(2)-HNNMe(2))(mu-kappa(4)-H(2)CCHCPhCPhCO)(mu-CO)(2)(CO)(5)] (12), which contains a novel edge-bridging dienoyl ligand that arises from an unusual coupling of diphenylacetylene, carbon monoxide, and the ethenyl ligand of complex 11. A chloro-bridged dimer of trinuclear clusters, [Ru(6)(mu-Cl)(2)(mu(3)-kappa(2)-HNNMe(2))(2)(mu(3)-kappa(2)-HCCH(2))(2)(mu-kappa(2)-PhCCHPh)(2)(mu-CO)(2)(CO)(10)] (13), has been prepared by treating compound 11 with hydrogen chloride. Therefore, edge-bridging parallel alkynes are susceptible to protonation to give edge-bridging alkenyl ligands. Compound 13 is the first complex to contain two alkenyl ligands on a trinuclear cluster, one face-capping and the other edge-bridging.     

Titanium(IV) and zirconium(IV) sulfato complexes containing the Kläui tripodal ligand: molecular models of sulfated metal oxide surfaces

Treatment of titanyl sulfate in about 60 mM sulfuric acid with NaL(OEt) (L(OEt) (-)=[(eta(5)-C(5)H(5))Co{P(O)(OEt)(2)}(3)](-)) afforded the mu-sulfato complex [(L(OEt)Ti)(2)(mu-O)(2)(mu-SO(4))] (2). In more concentrated sulfuric acid (>1 M), the same reaction yielded the di-mu-sulfato complex [(L(OEt)Ti)(2)(mu-O)(mu-SO(4))(2)] (3). Reaction of 2 with HOTf (OTf=triflate, CF(3)SO(3)) gave the tris(triflato) complex [L(OEt)Ti(OTf)(3)] (4), whereas treatment of 2 with Ag(OTf) in CH(2)Cl(2) afforded the sulfato-capped trinuclear complex [{(L(OEt))(3)Ti(3)(mu-O)(3)}(mu(3)-SO(4)){Ag(OTf)}][OTf] (5), in which the Ag(OTf) moiety binds to a mu-oxo group in the Ti(3)(mu-O)(3) core. Reaction of 2 in H(2)O with Ba(NO(3))(2) afforded the tetranuclear complex (L(OEt))(4)Ti(4)(mu-O)(6) (6). Treatment of 2 with [{Rh(cod)Cl}(2)] (cod=1,5-cyclooctadiene), [Re(CO)(5)Cl], and [Ru(tBu(2)bpy)(PPh(3))(2)Cl(2)] (tBu(2)bpy=4,4'-di-tert-butyl-2,2'-dipyridyl) in the presence of Ag(OTf) afforded the heterometallic complexes [(L(OEt))(2)Ti(2)(O)(2)(SO(4)){Rh(cod)}(2)][OTf](2) (7), [(L(OEt))(2)Ti(O)(2)(SO(4)){Re(CO)(3)}][OTf] (8), and [{(L(OEt))(2)Ti(2)(mu-O)}(mu(3)-SO(4))(mu-O)(2){Ru(PPh(3))(tBu(2)bpy)}][OTf](2) (9), respectively. Complex 9 is paramagnetic with a measured magnetic moment of about 2.4 mu(B). Treatment of zirconyl nitrate with NaL(OEt) in 3.5 M sulfuric acid afforded [(L(OEt))(2)Zr(NO(3))][L(OEt)Zr(SO(4))(NO(3))] (10). Reaction of ZrCl(4) in 1.8 M sulfuric acid with NaL(OEt) in the presence Na(2)SO(4) gave the mu-sulfato-bridged complex [L(OEt)Zr(SO(4))(H(2)O)](2)(mu-SO(4)) (11). Treatment of 11 with triflic acid afforded [(L(OEt))(2)Zr][OTf](2) (12), whereas reaction of 11 with Ag(OTf) afforded a mixture of 12 and trinuclear [{L(OEt)Zr(SO(4))(H(2)O)}(3)(mu(3)-SO(4))][OTf] (13). The Zr(IV) triflato complex [L(OEt)Zr(OTf)(3)] (14) was prepared by reaction of L(OEt)ZrF(3) with Me(3)SiOTf. Complexes 4 and 14 can catalyze the Diels-Alder reaction of 1,3-cyclohexadiene with acrolein in good selectivity. Complexes 2-5, 9-11, and 13 have been characterized by X-ray crystallography.     

Dinuclear PCP pincer complexes from Lewis acidic [Pd(OTf)(PCP)] and basic [Pd(4-Spy)(PCP)] (OTf = triflate; 4-Spy = 4-pyridinethiolate; PCP = (-)CH(CH(2)CH(2)PPh(2))(2))

The Lewis acidic pincer with a labile triflate ligand, viz. [Pd(OTf)(PCP)] (PCP = (-)CH(CH(2)CH(2)PPh(2))(2)) was prepared from [PdCl(PCP)] with AgOTf. It reacts readily with neutral bidentate ligands [L = 4,4'-bipyridine (4,4'-bpy) and 1,1'-bis(diphenylphosphino)ferrocene (dppf)] to give dinuclear PCP pincers [{Pd(PCP)}(2)(micro-L)][OTf](2) (L = 4,4'-bpy, 2; dppf,3). [PdCl(PCP)] also reacts with 4-mercaptopyridine in the presence of KOH to give a Lewis basic pincer with a free pyridine functional group [Pd(4-Spy)(PCP)]4. Its metalloligand character is exemplified by the isolation of an asymmetric dinuclear double-pincer complex [{Pd(PCP)}(2)(micro-4-Spy)][PF(6)] 6 bridged by an ambidentate pyridinethiolato ligand. Complexes 1, 2, 3, 4 and 6 have been characterized by single-crystal X-ray diffraction analyses.     

Dinuclear palladium(ii) complexes with bridging amidate ligands

New homonuclear dimeric Pd(ii) complexes have been synthesized by the reaction of Pd(en)(2+) or Pd(bipy)(2+) (where en = ethylenediamine and bipy = 2,2'-bipyridine) units with acetamide or by the Pd(ii) mediated hydrolysis of CH(3)CN. In these dimers the two metal centers are bridged by either two amidates or by the combination of one hydroxo group and one amidate ligand. The crystal structures of complexes {[Pd(bipy)](2)(micro-1,3-CH(3)CONH)(2)}(NO(3))(2).H(2)O.1/2(CH(3))(2)CO.1/2CH(3)CN () and {[Pd(bipy)](2)(micro-1,3-CH(3)CONH)(2)}(OTf)(2) () showed intrametallic Pd-Pd distances of 2.8480(8) A () and 2.8384(7) A (), respectively, in accordance with the accepted values for a strong Pd-Pd interaction. The presence of pi[dot dot dot]pi interactions between the bipyridine ligands on the di-micro-amidate complexes of Pd(bipy)(2+) shortens the distance between the two Pd centers and allows the formation of the metal-metal interaction. By contrast, the crystal structure of complex {[Pd(en)](2)(micro-1,3-CH(3)CONH)(2)}(OTf)(2).H(2)O (), (where OTf = triflate) where there is no pi[dot dot dot]pi interaction between the ligands on the metal centers, is also reported, and no Pd-Pd interaction is observed. Additionally, one of the complexes, {[Pd(en)](2)(micro-OH)(micro-CH(3)CONH)}(NO(3))(2) (), presents an interesting hydrogen bonded 3-D network formed by nitrate ions and water molecules. All complexes have been characterized by infrared and (1)H NMR spectroscopy.     

Synthesis, characterization, crystal structure and preliminary reactivity behaviour of new heteropolytopic ligands based on the 1,3,5-triazine spacer and pyrazolyl, tris-pyrazolylmethyl and tris-pyrazolylethoxy bonding fragments

Four new potentially polytopic nitrogen donor ligands based on the 1,3,5-triazine fragment, L(1)-L(4) (L(1) = 2-chloro-4,6-di(1H-pyrazol-1-yl)-1,3,5-triazine, L(2) = N,N'-bis(4,6-di(1H-pyrazol-1-yl)-1,3,5-triazin-2-yl)ethane-1,2-diamine, L(3) = 2,4,6-tris(tri(1H-pyrazol-1-yl)methyl)-1,3,5-triazine, and L(4) = 2,4,6-tris(2,2,2-tri(1H-pyrazol-1-yl)ethoxy)-1,3,5-triazine) have been synthesized and characterized. The X-ray crystal structure of L(3) confirms that its molecular nature consists of a 1,3,5-triazine ring bearing three tripodal tris(pyrazolyl) arms. L(1), L(2), and L(4) react with Cu(I), Cu(II), Pd(II) and Ag(I) salts yielding mono-, di-, and oligonuclear derivatives: [Cu(L(1))(Cy(3)P)]ClO(4), [{Ag(2)(L(2))}(CF(3)SO(3))(2)]·H(2)O, [Cu(2)(L(2))(NO(3))(2)](NO(3))(2)·H(2)O, [Cu(2)(L(2))(CH(3)COO)(2)](CH(3)COO)(2)·3H(2)O, [Pd(2)(L(2))(Cl)(4)]·2H(2)O, [Ru(L(2))(Cl)(OH)]·CH(3)OH, [Ag(3)(L(4))(2)](CF(3)SO(3))(3) and [Ag(3)(L(4))(2)](BF(4))(3). The interaction of L(3) with Ag(I), Cu(II), Zn(II) and Ru(II) complexes unexpectedly produced the hydrolysis of the ligand with formation, in all cases, of tris(pyrazolyl)methane (TPM) derivatives. In detail, the already known [Ag(TPM)(2)](CF(3)SO(3)) and [Cu(TPM)(2)](NO(3))(2), as well as the new [Zn(TPM)(2)](CF(3)SO(3))(2) and [Ru(TMP)(p-cymene)]Cl(OH)·2H(2)O complexes have been isolated. Single-crystal XRD determinations on the latter derivatives confirm their formulation, evidencing, for the Ru(II) complex, an interesting supramolecular arrangement of the anions and crystallization water molecules.     

Protonation reactions of dinuclear pyrazolato iridium(I) complexes

The complex [[Ir(mu-Pz)(CNBu(t))(2)](2)] (1) undergoes double protonation reactions with HCl and with HO(2)CCF(3) to give the neutral dihydride complexes [[Ir(mu-Pz)(H)(X)(CNBu(t))(2)](2)] (X = Cl, eta(1)-O(2)CCF(3)), in which the hydride ligands were located trans to the X groups and in the boat of the complexes, both in the solid state and in solution. The complex [[Ir(mu-Pz)(H)(Cl)(CNBu(t))(2)](2)] evolves in solution to the cationic complex [[Ir(mu-Pz)(H)(CNBu(t))(2)](2)(mu-Cl)]Cl. Removal of the anionic chloride by reaction with methyltriflate allows the isolation of the triflate salt [[Ir(mu-Pz)(H)(CNBu(t))(2)](2)(mu-Cl)]OTf. This complex undergoes a metathesis reaction of hydride by chloride in CDCl(3) under exposure to the direct sunlight to give the complex [[Ir(mu-Pz)(Cl)(CNBu(t))(2)](2)(mu-Cl)]OTf. Protonation of both metal centers in [[Ir(mu-Pz)(CO)(2)](2)] with HCl occurs at low temperature, but eventually the mononuclear compound [IrCl(HPz)(CO)(2)] is isolated. The related complex [[Ir(mu-Pz)(CO)(P[OPh](3))](2)] reacts with HCl and with HO(2)CCF(3) to give the neutral Ir(III)/Ir(III) complexes [[Ir(mu-Pz)(H)(X)(CO)(P[OPh](3))](2)], respectively. Both reactions were found to take place stepwise, allowing the isolation of the intermediate monohydrides. They are of different natures, i.e., the metal-metal-bonded Ir(II)/Ir(II) compound [(P[OPh](3))(CO)(Cl)Ir(mu-Pz)(2)Ir(H)(CO)(P[OPh](3))] and the mixed-valence Ir(I)/Ir(III) complex [(P[OPh](3))(CO)Ir(mu-Pz)(2)Ir(H)(eta(1)-O(2)CCF(3))(CO)(P[OPh](3))].     

Supramolecular networks of silver(I) and iron(II) complexes of the third generation tris(pyrazolyl)methane ligand Ph(2)(O)POCH(2)C(pz)(3) (pz = pyrazolyl ring)

The new ligand Ph(2)(O)POCH(2)C(pz)(3) (pz = pyrazolyl ring), prepared from the reaction of HOCH(2)C(pz)(3) and Ph(2)P(O)Cl in the presence of base, reacts with either AgBF(4) or Fe(BF(4))(2).6H(2)O in a 2/1 molar ratio to yield {[Ph(2)(O)POCH(2)C(pz)(3)](2)Ag}(BF(4)) () and {[Ph(2)(O)POCH(2)C(pz)(3)](2)Fe}(BF(4))(2) (), respectively. In the structure of , the silver is in an unusual planar geometry with each of the ligands in a kappa(2)-kappa(0) coordination mode. Slow evaporation of a thf solution of yields crystalline [Ph(2)(O)POCH(2)C(pz)(3)Ag](2)(thf)(2)}(BF(4))(2) (). In each cationic unit of , the two Ph(2)(O)POCH(2)C(pz)(3) ligands coordinate to the same two silver(i) centers in a kappa(2)-kappa(1) bonding mode, with a silver atom separation of 3.36 A. The supramolecular structure of both and is dominated by a pair of cooperative hydrogen bonding interactions between the Ph(2)P(O) secondary tecton and a hydrogen atom from a methylene group situated on a neighboring building block, which arranges the cations in chains. The reaction of HC(pz)(3) and AgO(3)SCF(3) (AgOTf) yields {[HC(pz)(3)](2)Ag(2)}(OTf)(2) (). The cationic unit in has a structure very similar to that of , but with a much shorter distance between the silver atoms at 2.86 A. The supramolecular structure of is dominated by an unusual pyrazolyl embrace interaction where the acceptor ring in the C-Hpi interaction is the pyrazolyl ring kappa(1)-bonded to silver in the adjacent dimeric unit rather than the other ring in a kappa(2)-bonded Cpz(2) unit. This interaction arranges the cations in chains which are further organized into sheets by the triflate anions that link the chains via combined AgO/CHO interactions. The iron in is octahedral with each tris(pyrazolyl)methane unit in the kappa(3)-tripodal coordination mode. The supramolecular structure is sheets formed by hydrogen bonding between the Ph(2)P(O) oxygen and a meta-position hydrogen on one of the diphenylphosphine rings from an adjacent cation.     

Synthesis, structures and reactivity of ruthenium nitrosyl complexes containing Kläui's oxygen tripodal ligand

Ruthenium nitrosyl complexes containing the Kl?ui's oxgyen tripodal ligand L(OEt)(-) ([CpCo{P(O)(OEt)(2)}(3)](-) where Cp = η(5)-C(5)H(5)) were synthesized and their photolysis studied. The treatment of [Ru(N^N)(NO)Cl(3)] with [AgL(OEt)] and Ag(OTf) afforded [L(OEt)Ru(N^N)(NO)][OTf](2) where N^N = 4,4'-di-tert-butyl-2,2'-bipyridyl (dtbpy) (2·[OTf](2)), 2,2'-bipyridyl (bpy) (3·[OTf](2)), N,N,N'N'-tetramethylethylenediamine (4·[OTf](2)). Anion metathesis of 3·[OTf](2) with HPF(6) and HBF(4) gave 3·[PF(6)](2) and 3·[BF(4)](2), respectively. Similarly, the PF(6)(-) salt 4·[PF(6)](2) was prepared by the reaction of 4·[OTf](2) with HPF(6). The irradiation of [L(OEt)Ru(NO)Cl(2)] (1) with UV light in CH(2)Cl(2)-MeCN and tetrahydrofuran (thf)-H(2)O afforded [L(OEt)RuCl(2)(MeCN)] (5) and the chloro-bridged dimer [L(OEt)RuCl](2)(μ-Cl)(2) (6), respectively. The photolysis of complex [2][OTf](2) in MeCN gave [L(OEt)Ru(dtbpy)(MeCN)][OTf](2) (7). Refluxing complex 5 with RNH(2) in thf gave [L(OEt)RuCl(2)(NH(2)R)] (R = tBu (8), p-tol (9), Ph (10)). The oxidation of complex 6 with PhICl(2) gave [L(OEt)RuCl(3)] (11), whereas the reduction of complex 6 with Zn and NH(4)PF(6) in MeCN yielded [L(OEt)Ru(MeCN)(3)][PF(6)] (12). The reaction of 3·[BF(4)](2) with benzylamine afforded the μ-dinitrogen complex [{L(OEt)Ru(bpy)}(2)(μ-N(2))][BF(4)](2) (13) that was oxidized by [Cp(2)Fe]PF(6) to a mixed valence Ru(II,III) species. The formal potentials of the RuL(OEt) complexes have been determined by cyclic voltammetry. The structures of complexes 5,6,10,11 and 13 have been established by X-ray crystallography.     

Phosphato, chromato, and perrhenato complexes of titanium(IV) and zirconium(IV) containing Kläui's tripodal ligand

Treatment of titanyl sulfate in dilute sulfuric acid with 1 equiv of NaL(OEt) (L(OEt)(-) = [(eta(5)-C(5)H(5))Co{P(O)(OEt)(2)](3)](-)) in the presence of Na(3)PO(4) and Na(4)P(2)O(7) led to isolation of [(L(OEt)Ti)(3)(mu-O)(3)(mu(3-)PO(4))] (1) and [(L(OEt)Ti)(2)(mu-O)(mu-P(2)O(7))] (2), respectively. The structure of 1 consists of a Ti(3)O(3) core capped by a mu(3)-phosphato group. In 2, the [P(2)O(7)](4-) ligands binds to the two Ti's in a mu:eta(2),eta(2) fashion. Treatment of titanyl sulfate in dilute sulfuric acid with NaL(OEt) and 1.5 equiv of Na(2)Cr(2)O(7) gave [(L(OEt)Ti)(2)(mu-CrO(4))(3)] (3) that contains two L(OEt)Ti(3+) fragments bridged by three mu-CrO(4)(2-)-O,O' ligands. Complex 3 can act as a 6-electron oxidant and oxidize benzyl alcohol to give ca. 3 equiv of benzaldehyde. Treatment of [L(OEt)Ti(OTf)(3)] (OTf(-) = triflate) with [n-Bu(4)N][ReO(4)] afforded [[L(OEt)Ti(ReO(4))(2)](2)(mu-O)] (4). Treatment of [L(OEt)MF(3)] (M = Ti and Zr) with 3 equiv of [ReO(3)(OSiMe(3))] afforded [L(OEt)Ti(ReO(4))(3)] (5) and [L(OEt)Zr(ReO(4))(3)(H(2)O)] (6), respectively. Treatment of [L(OEt)MF(3)] with 2 equiv of [ReO(3)(OSiMe(3))] afforded [L(OEt)Ti(ReO(4))(2)F] (7) and [[L(OEt)Zr(ReO(4))(2)](2)(mu-F)(2)] (8), respectively, which reacted with Me(3)SiOTf to give [L(OEt)M(ReO(4))(2)(OTf)] (M = Ti (9), Zr (10)). Hydrolysis of [L(OEt)Zr(OTf)(3)] (11) with Na(2)WO(4).xH(2)O and wet CH(2)Cl(2) afforded the hydroxo-bridged complexes [[L(OEt)Zr(H(2)O)](3)(mu-OH)(3)(mu(3)-O)][OTf](4) (12) and [[L(OEt)Zr(H(2)O)(2)](2)(mu-OH)(2)][OTf](4) (13), respectively. The solid-state structures of 1-3, 6, and 11-13 have been established by X-ray crystallography. The L(OEt)Ti(IV) complexes can catalyze oxidation of methyl p-tolyl sulfide with tert-butyl hydroperoxide. The bimetallic Ti/ Re complexes 5 and 9 were found to be more active catalysts for the sulfide oxidation than other Ti(IV) complexes presumably because Re alkylperoxo species are involved as the reactive intermediates.     

Formation of [PtPd(2)(mu(3)-X)(2)(P-P)(dppmX)(2)](2+) (X = S, Se; P-P = dppe, 2 x PPh(3)) aggregates through activation of the chalcogen-rich [PtX(4)] ring by a Pd(I)-Pd(I) bond

Redox addition of the Pd-Pd bond in [Pd(2)Cl(2)(dppm)(2)] across S-S or Se-Se bond in [Pt(X(4)-kappa(2)X(1),X(4))(P-P)] (X = S, Se; P-P = dppe or 2 x PPh(3); dppm = bis(diphenylphosphino)methane, dppe = bis(diphenylphosphino)ethane) leads to the isolation of [PtPd(2)(mu(3)-X)(2)(P-P)(dppmX-kappa(2)X,P(4))(2)](2+) and represents an atom-economy process that converts chalcogen-rich complexes to heterometallic chalcogenide aggregates. Activation of the [PtX(4)] ring is achieved by tetrachalcogenide reduction and dual oxidation of palladium and phosphine.     

Synthesis and structure of a bismuth(III)/chromium(VI) oxo cluster containing a Bi4Cr4O12 core

Bismuth(III) compounds containing the Kl?ui's oxygen tripodal ligand [CpCo{P(O)(OEt)(2)}(3)](-) (L(OEt)(-)) have been synthesized, and their interactions with dichromate in aqueous media were studied. The treatment of Bi(5)O(OH)(9)(NO(3))(4) with NaL(OEt) in water afforded [L(OEt)Bi(NO(3))(2)](2) (1), whereas that of BiCl(3) with NaL(OEt) in CH(2)Cl(2) yielded L(OEt)BiCl(2) (2). Chloride abstraction of 2 with AgX afforded [L(OEt)BiX(2)](2) [X(-) = triflate (OTf(-)) (3), tosylate (OTs(-)) (4)]. In aqueous solutions at pH > 4, 4 underwent ligand redistribution to give the bis(tripod) complex [(L(OEt))(2)Bi(H(2)O)][OTs] (5). The treatment of 4 with Na(2)Cr(2)O(7) in acetone/water afforded the Bi(III)/Cr(VI) oxo cluster [(L(OEt))(4)Bi(4)(μ(3)-CrO(4))(2)(μ(3)-Cr(2)O(7))(2)] (6) containing a unique Bi(4)Cr(4)O(12) oxometallic core. Compound 6 oxidized benzyl alcohol to give ca. 6 equiv of benzaldehyde. The reaction between 2 and CrO(3) yielded [L(OEt)Bi(OCrO(2)Cl)](2)(μ-Cl)(2) (7). The crystal structures of complexes 4-7 have been determined.     

Reactivity of ammonia ligands of the antitumor agent cisplatin: a unique dodecanuclear Pt4,Pd4,Ag4 platform for four cytosine model nucleobases

The reaction of a potential mono(nucleobase) model adduct of cisplatin, cis-[Pt(NH(3))(2)(1-MeC-N3)(H(2)O)](2+) (6; 1-MeC: 1-methylcytosine), with the electrophile [Pd(en)(H(2)O)(2)](2+) (en: ethylenediamine) at pH approximately 6 yields a kinetic product X which is likely to be a dinuclear Pt,Pd complex containing 1-MeC(-)-N3,N4 and OH bridges, namely cis-[Pt(NH(3))(2)(1-MeC(-)-N3,N4)(OH)Pd(en)](2+). Upon addition of excess Ag(+) ions, conversion takes place to form a thermodynamic product, which, according to (1)H NMR spectroscopy and X-ray crystallography, is dominated by a mu-NH(2) bridge between the Pt(II) and Pd(II) centers. X-ray crystallography reveals that the compound crystallizes out of solution as a dodecanuclear complex containing four Pt(II), four Pd(II), and four Ag(+) entities: [{Pt(2)(1-MeC(-)-N3,N4)(2)(NH(3))(2)(NH(2))(2)(OH)Pd(2)(en)(2)Ag}(2){Ag(H(2)O)}(2)](NO(3))(10) 6 H(2)O (10) is composed of a roughly planar array of the 12 metal ions, in which the metal ions are interconnected by mu-NH(2) groups (between Pt and Pd centers), mu-OH groups (between pairs of Pt atoms), and metal-metal donor bonds (Pt-->Ag, Pd-->Ag). The four 1-methylcytosinato ligands, which are stacked pairwise, as well as the four NH(3) ligands and parts of the en rings, are approximately perpendicular to the metal plane. Two of the four Ag ions (Ag2, Ag2') of 10 are labile in solution and show the expected behavior of Ag(+) ions in water, that is, they are readily precipitated as AgCl by Cl(-) ions. The resulting pentanuclear complex [Pt(2)Pd(2)Ag(1-MeC(-))(2)(NH(2))(2)(OH)(NH(3))(2)(en)(2)](NO(3))(4)7 H(2)O (11) largely maintains the structural features of one half of 10. The other two Ag(+) ions (Ag1, Ag1') of 10 are remarkably unreactive toward excess NaCl. In fact, the pentanuclear complex [Pt(2)Pd(2)AgCl(1-MeC(-))(2)(NH(2))(2)(OH)(NH(3))(2)(en)(2)](NO(3))(3)4.5 H(2)O (12), obtained from 10 with excess NaCl, displays a Cl(-) anion bound to the Ag center (2.459(3) A) and is thus a rare case of a crystallized "AgCl molecule".     

Synthesis and structure of Pt(II) phosphonato-phosphine complexes and of a P,O-stabilized metal-metal-bonded Pt2Ag2 complex

As part of our interest in the design and reactivity of P,O ligands, and because the insertion chemistry of small molecules into a metal alkyl bond is very dependent on the ancillary ligands, the behavior of Pt-methyl complexes containing the beta-phosphonato-phosphine ligand rac-Ph2PCH(Ph)P(O)(OEt)2 (abbreviated PPO in the following) toward CO insertion has been explored. New, mononuclear Pt(II) complexes containing one or two PPO ligands, [PtClMe(kappa2-PPO)] (1), [Pt{C(O)Me}Cl(kappa2-PPO)] (2), [PtMe(CO)(kappa2-PPO)]OTf (3 x OTf), [PtMe(OTf)(kappa2-PPO)] (4), trans-[PtClMe(kappa1-PPO)2] (5), [PtMe(kappa2-PPO)(kappa1-PPO)]BF4 (6 x BF4), [PtMe(kappa2-PPO)(kappa1-PPO)]OTf (6 x OTf), and [Pt{C(O)Me}(kappa2-PPO)(kappa1-PPO)]BF4 (7 x BF4) have been prepared and characterized. Hemilability of the ligands is observed in the cations 6 and 7 in which the terminally bound and chelating PPO ligands exchange their role on the NMR time-scale. The acetyl complexes 2 and 7 are stable in solution, but the former deinserts CO upon chloride abstraction. We also demonstrate the ability of PPO to behave as an assembling ligand and to stabilize a heterometallic Pt-Ag metal complex, [PtMe(kappa2-PPO){mu-(eta1-P;eta1-O)PPO)}Ag(OTf)(Pt-Ag)]OTf (8 x OTf), which was obtained by reaction of 5 with AgOTf to generate more reactive, cationic complexes. Whereas the first equivalent of AgOTf abstracted the chloride ligand, the second equivalent added to the cationic complex with formation of a Pt-Ag bond (2.819(1) A). The complexes 1, 2, 4, 5 x CH2Cl2, and (8 x OTf)2 have been structurally characterized by single-crystal X-ray diffraction. The latter has a dimeric nature in the solid state, with two silver-bound triflates acting as bridging ligands between two Pt-Ag moieties. In addition to the Ag-Pt bond, the Ag+ cation is stabilized by a dative O -->Ag interaction involving one of the PPO ligands.     

1,2,4-Triazole functionalized adamantanes: a new library of polydentate tectons for designing structures of coordination polymers

A series of functionalized adamantanes: 1,3-bis(1,2,4-triazol-4-yl)(tr(2)ad); 1,3,5-tris(1,2,4-triazol-4-yl)-(tr(3)ad); 1,3,5,7-tetrakis(1,2,4-triazol-4-yl)adamantanes (tr(4)ad) and 3,5,7-tris(1,2,4-triazol-4-yl)-1-azaadamantane (tr(3)ada) were developed as a new family of geometrically rigid polydentate tectons for supramolecular synthesis of framework solids. The coordination compounds were prepared under hydrothermal conditions; their structures reveal a special potential of the triazolyl adamantanes for the generation of highly-connected and open frameworks as well as structures based upon polynuclear metal clusters assembled with short-distance N(1),N(2)-triazole bridges. Complexes [Cd{L}(2)]A·nH(2)O [L = tr(3)ad, A = 2NO(3)(-) (4), CdCl(4)(2-) (5); L = tr(3)ada, A = CdI(4)(2-) (7)] are isomorphous and adopt a layered 3,6-connected structure of CdI(2) type. [{Cu(3)(OH)}(2)(SO(4))(5)(H(2)O)(2){tr(3)ad}(3)]·26H(2)O (6) is a layered polymer based upon Cu(3)(μ(3)-OH) nodes and trigonal tr(3)ad links. In [Cu(3)(OH)(2){tr(3)ada}(2)(H(2)O)(4)](ClO(4))(4) (8), [Cu(2){tr(3)ada}(2)(H(2)O)(3)](SO(4))(2)·7H(2)O (9) and [Cd(2){tr(3)ada}(3)]Cl(4)·28H(2)O (10) (UCl(3)-type net) the organic tripodal ligands bridge polynuclear metal clusters. Complexes [Ag{tr(4)ad}]NO(3)·3.5H(2)O (11) and [Cu{tr(4)ad}(H(2)O)](ClO(4))(2)·3H(2)O (12) have 3D SrAl(2)-type frameworks with the metal ions and adamantane tectons as topologically equivalent tetrahedral nodes, while in [Cd(3)Cl(6){tr(4)ad}(2)]·9H(2)O (13) the ligands bridge trinuclear six-connected Cd(3)Cl(6)(μ-tr)(4)(tr)(2) clusters. In the compounds [Cd(2){tr(2)ad}(4)(H(2)O)(4)](CdBr(4))(2)·2H(2)O (2) and [Cd{tr(2)ad}(4){CdI(3)}(2)]·4H(2)O (3) the bitopic ligands provide simple links between the metal ions, while in [Ag(2){tr(2)ad}(2)](NO(3))(2)·2H(2)O (1) the ligand is tetradentate and generates a 3D framework.     

Tetravalent titanium, zirconium, and cerium oxo and peroxo complexes containing an imidodiphosphinate ligand

Dinuclear Ti(IV), Zr(IV), and Ce(IV) oxo and peroxo complexes containing the imidodiphosphinate ligand [N(i-Pr(2)PO)(2)](-) have been synthesized and structurally characterized. Treatment of Ti(O-i-Pr)(2)Cl(2) with KN(i-Pr(2)PO)(2) afforded the Ti(IV) di-μ-oxo complex [Ti{N(i-Pr(2)PO)(2)}(2)](2)(μ-O)(2) (1) that reacted with 35% H(2)O(2) to give the peroxo complex Ti[N(i-Pr(2)PO)(2)](2)(η(2)-O(2)) (2). Treatment of HN(i-Pr(2)PO)(2) with Zr(O-t-Bu)(4) and Ce(2)(O-i-Pr)(8)(i-PrOH)(2) afforded the di-μ-peroxo-bridged dimers [M{N(i-Pr(2)PO)(2)}(2)](2)(μ-O(2))(2) [M = Zr (3), Ce (4)]. 4 was also obtained from the reaction of Ce[N(i-Pr(2)PO)(2)](3) with 35% H(2)O(2). Treatment of (Et(4)N)(2)[CeCl(6)] with 3 equiv of KN(i-Pr(2)PO)(2) afforded Ce[N(i-Pr(2)PO)(2)](3)Cl (5). Reaction of (Et(4)N)(2)[CeCl(6)] with 2 equiv of KN(i-Pr(2)PO)(2) in acetonitrile, followed by treatment with Ag(2)O, afforded the μ-oxo-bridged complex [Ce{N(i-Pr(2)PO)(2)}Cl](2)[μ-N(i-Pr(2)PO)(2)](2)(μ-O) (6). 6 undergoes ligand redistribution in CH(2)Cl(2) in air to give 5. The solid-state structures of [K(2){N(i-Pr(2)PO)(2)}(2)(H(2)O)(8)](n) and complexes 1-6 have been determined.     

One-dimensional silver(I) coordination polymers containing cyclodiphosphazane, cis-{(o-MeOC(6)H(4)O)P(mu-N(t)Bu)}(2)

The 1:1 reaction between the cyclodiphosphazane cis-{(o-MeOC(6)H(4)O)P(mu-N(t)Bu)}(2) (1) and AgOTf afforded one-dimensional Ag(I) coordination polymer [Ag{mu-OTf-kappaO,kappaO}{mu-(o-MeOC(6)H(4)O)P(mu-N(t)Bu)-kappaP,kappaP}(2)](infinity) (2) containing bridging cyclodiphosphazane and trifluoromethanesulfonate (OTf) ligands. The 2:1 reaction of and AgOTf leads to the formation of simple mononuclear complex [Ag{OTf-kappaO,kappaO}({(o-MeOC(6)H(4)O)P(mu-N(t)Bu)-kappaP}(2))(2)] (3) in quantitative yield. Reaction of 1 with AgCN produces a strain-free zig-zag coordination polymer [({(o-MeOC(6)H(4)O)P(mu-N(t)Bu)-kappaP,kappaP}(2))(2)Ag(NCAgCN)](infinity) (4) irrespective of reaction stoichiometry and conditions. In complexes 3 and 4 cyclodiphosphazanes coordinate to Ag(I) centers in a monodentate fashion. Single crystal structures were established for the Ag(I) polymers 2 and 4.     

Different rotamer states of cytosine nucleobases in heteronuclear PtPd-, PtPd2, and Pt2Pd2Ag complexes derived from [Pt(2,2'-bpy)(1-MeC-N3)2]2+ (1-MeC = 1-methylcytosine): first examples of species with head-head oriented 1-MeC(-) ligands

[Pt(2,2'-bpy)(1-MeC-N3)(2)](NO(3))(2) (1) (2,2'-bpy = 2,2'-bipyridine; 1-MeC = 1-methylcytosine) exists in water in an equilibrium of head-tail and head-head rotamers, with the former exceeding the latter by a factor of ca. 20 at room temperature. Nevertheless, 1 reacts with (en)Pd(II) (en = ethylenediamine) to give preferentially the dinuclear complex [Pt(2,2'-bpy)(1-MeC(-)-N3,N4)(2)Pd(en)](NO(3))(2)·5H(2)O (2) with head-head arranged 1-methylctosinato (1-MeC(-)) ligands and Pd being coordinated to two exocyclic N4H(-) positions. Addition of AgNO(3) to a solution of 2 leads to formation of a pentanuclear chain compound [{Pt(2,2'-bpy)(1-MeC(-))(2)Pd(en)}(2)Ag](NO(3))(5)·14H(2)O (5) in which Ag(+) cross-links two cations of 2 via the four available O2 sites of the 1-MeC(-) ligands. 2 and 5 appear to be the first X-ray structurally characterized examples of di- and multinuclear complexes derived from a Pt(II) species with two cis-positioned cytosinato ligands adopting a head-head arrangement. (tmeda)Pd(II) (tmeda = N,N,N',N'-tetramethylethylenediamine) and (2,2'-bpy)Pd(II) behave differently toward 1 in that in their derivatives the head-tail orientation of the 1-MeC(-) nucleobases is retained. In [Pt(2,2'-bpy)(1-MeC(-))(2){Pd(2,2'-bpy)}(2)](NO(3))(4)·10H(2)O (4), both (2,2'-bpy)Pd(II) entities are pairwise bonded to N4H(-) and O2 sites of the two 1-MeC(-) rings, whereas in [Pt(2,2'-bpy)(1-MeC(-))(2){Pd(tmeda)}(2)(NO(3))](NO(3))(3)·5H(2)O (3) only one of the two (tmeda)Pd(II) units is chelated to N4H(-) and O2. The second (tmeda)Pd(II) is monofunctionally attached to a single N4H(-) site. On the basis of these established binding patterns, ways to the formation of mixed Pt/Pd complexes and possible intermediates are proposed. The methylene protons of the en ligand in 2 are special in that they display two multiplets separated by 0.64 ppm in the (1)H NMR spectrum.     

The supramolecular isomerism based on argentophilic interactions: the construction of helical chains with defined right-handed and left-handed helicity

The reactions of racemic and enantiopure macrocyclic compounds [Ni(alpha-rac-L)](ClO(4))(2) (containing equal amounts of SS and RR enantiomers), [Ni(alpha-SS-L)](ClO(4))(2), and [Ni(alpha-RR-L)](ClO(4))(2) with K[Ag(CN)(2)] in acetonitrile/water afford three 1D helical chains of {[Ni(f-rac-L)][Ag(CN)(2)](2)}(n) (1), {[Ni(f-SS-L)](2)[Ag(CN)(2)](4)}(n) (Delta-2), and {[Ni(f-RR-L)](2)[Ag(CN)(2)](4)}(n) (Lambda-2); one dimer of [Ni(f-rac-L)][Ag(CN)(2)](2) (3); and one trimer of [Ni(f-rac-L)Ag(CN)(2)](3).(ClO(4))(3) (4) (L = 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane). Compounds 1, Delta-2, Lambda-2, and 3, which are supramolecular isomers, are constructed via argentophilic interactions. In 1, [Ni(f-RR-L)][Ag(CN)(2)](2) enantiomers alternately connect with [Ni(f-SS-L)][Ag(CN)(2)](2) enantiomers through intermolecular argentophilic interactions to form a 1D meso-helical chain, and the 1D chains are further connected through the interchain hydrogen bonds to generate a 2D network. When chiral [Ni(alpha-SS-L)](ClO(4))(2) and [Ni(alpha-RR-L)](ClO(4))(2) were used as building blocks, two supramolecular stereoisomers of Delta-2 and Lambda-2 were obtained, which show the motif of homochiral right-handed and left-handed helical chains, respectively, and the 1D homochiral helical chains are linked by the interchain hydrogen bonds to form a 3D structure. In 3, a pair of enantiomers of [Ni(f-RR-L)][Ag(CN)(2)](2) and [Ni(f-SS-L)][Ag(CN)(2)](2) connect with each other through intermolecular argentophilic interactions to form a dimer. The reaction of [Ni(alpha-rac-L)](ClO(4))(2) with K[Ag(CN)(2)] in acetonitrile gives a trimer of 4; each trimer is chiral with unsymmetrical RR, RR, and SS, or RR, SS, and SS configurations. The homochiral nature of Delta-2 and Lambda-2 was confirmed by the results of solid circular dichroism spectra measurements. The solid samples of 1-4 show strong fluorescent emissions at room temperature.     

Three-component self-assembly of a series of triply interlocked Pd12 coordination prisms and their non-interlocked Pd6 analogues

Template-assisted formation of multicomponent Pd(6) coordination prisms and formation of their self-templated triply interlocked Pd(12) analogues in the absence of an external template have been established in a single step through Pd-N/Pd-O coordination. Treatment of cis-[Pd(en)(NO(3))(2)] with K(3) tma and linear pillar 4,4'-bpy (en=ethylenediamine, H(3) tma=benzene-1,3,5-tricarboxylic acid, 4,4'-bpy=4,4'-bipyridine) gave intercalated coordination cage [{Pd(en)}(6)(bpy)(3)(tma)(2)](2)[NO(3)](12) (1) exclusively, whereas the same reaction in the presence of H(3) tma as an aromatic guest gave a H(3) tma-encapsulating non-interlocked discrete Pd(6) molecular prism [{Pd(en)}(6)(bpy)(3)(tma)(2)(H(3)tma)(2)][NO(3)](6) (2). Though the same reaction using cis-[Pd(NO(3))(2)(pn)] (pn=propane-1,2-diamine) instead of cis-[Pd(en)(NO(3))(2)] gave triply interlocked coordination cage [{Pd(pn)}(6)(bpy)(3)(tma)(2)](2)[NO(3)](12) (3) along with non-interlocked Pd(6) analogue [{Pd(pn)}(6)(bpy)(3) (tma)(2)](NO(3))(6) (3'), and the presence of H(3) tma as a guest gave H(3) tma-encapsulating molecular prism [{Pd(pn)}(6)(bpy)(3)(tma)(2)(H(3) tma)(2)][NO(3)](6) (4) exclusively. In solution, the amount of 3' decreases as the temperature is decreased, and in the solid state 3 is the sole product. Notably, an analogous reaction using the relatively short pillar pz (pz=pyrazine) instead of 4,4'-bpy gave triply interlocked coordination cage [{Pd(pn)}(6) (pz)(3)(tma)(2)](2)[NO(3)](12) (5) as the single product. Interestingly, the same reaction using slightly more bulky cis-[Pd(NO(3))(2)(tmen)] (tmen=N,N,N',N'-tetramethylethylene diamine) instead of cis-[Pd(NO(3))(2)(pn)] gave non-interlocked [{Pd(tmen)}(6)(pz)(3)(tma)(2)][NO(3)](6) (6) exclusively. Complexes 1, 3, and 5 represent the first examples of template-free triply interlocked molecular prisms obtained through multicomponent self-assembly. Formation of the complexes was supported by IR and multinuclear NMR ((1)H and (13)C) spectroscopy. Formation of guest-encapsulating complexes (2 and 4) was confirmed by 2D DOSY and ROESY NMR spectroscopic analyses, whereas for complexes 1, 3, 5, and 6 single-crystal X-ray diffraction techniques unambiguously confirmed their formation. The gross geometries of H(3) tma-encapsulating complexes 2 and 4 were obtained by universal force field (UFF) simulations.     

Synthesis and mononuclear complexes of the bis-bidentate ligand 2,5-di(2-pyridyl)-1,3,4-thiadiazole (dptd): spin crossover in [Fe(II)(dptd)2(NCSe)2] and [Fe(II)(dptd)2(NCBH3)2]·H2O

A simple and convenient protocol for the synthesis of the ligand 2,5-di(2-pyridyl)-1,3,4-thiadiazole (dptd) has been developed. Five new 2?:?1-type iron(II), cobalt(II), nickel(II) and copper(II) complexes have been prepared and structurally characterised, all of which feature the mononuclear trans-(N',N(1))(2) coordination mode. Spin crossover behaviour has been found for [Fe(II)(dptd)(2)(NCSe)(2)] (2) and [Fe(II)(dptd)(2)(NCBH(3))(2)]·H(2)O (3·H(2)O) with T(1/2) = 192 and 285 K, respectively, reflecting the increasing ligand field strength of the respective co-ligands and showing that the [Fe(II)(dptd)(2)L(2)] unit is suitable for the investigation of the co-ligand field effects on T(1/2). In addition, the 3?:?1-type low-spin complexes [Fe(II)(dptd)(3)]{B(CN)(4)}(2)·3MeOH (4·3MeOH) and [Fe(II)(dptd)(3)](OTf)(2)·1.25DCM·0.5H(2)O (5·1.25DCM·0.5H(2)O) have been studied by X-ray diffraction and have been found to exist exclusively as the mer or fac stereoisomer, respectively, in the solid state. In MeCN-d(3) solution the latter two complexes, as well as [Fe(II)(dptd)(3)](ClO(4))(2)·H(2)O (6·H(2)O), show counterion-independent stereoisomerisation, each yielding a ca. 3?:?1 mixture of mer and fac stereoisomers as identified by (1)H NMR spectroscopy.