The metalla-Pinner reaction between Pt(IV)-bound nitriles and alkylated oxamic and oximic forms of hydroxamic acids

The nitrile ligands in the platinum(IV) complexes trans-[PtCl4(RCN)2] (R=Me, Et, CH2Ph) and cis/trans-[PtCl4(MeCN)(Me2SO)] are involved in a metalla-Pinner reaction with N-methylbenzohydroxamic acid (N-alkylated form of hydroxamic acid, hydroxamic form; F1), PhC(=O)N(Me)OH, to achieve the imino species [PtCl4[NH=C(R)ON(Me)C(=O)Ph]2 (1-3) and [PtCl4[NH=C(Me)ON(Me)C(=O)Ph](Me2SO)] (7), respectively. Treatment of trans-[PtCl4(RCN)2] (R=Me, Et) and cis/trans-[PtCl4(MeCN)(Me2SO)] with the O-alkylated form of a hydroxamic acid (hydroximic form), i.e. methyl 2,4,6-trimethylbenzohydroximate, 2,4,6-(Me3C6H2)C(OMe)=NOH (F2A), allows the isolation of [PtCl4[NH=C(R)ON=C(OMe)(2,4,6-Me3C6H2)]2] (5, 6) and [PtCl4[NH=C(Me)ON=C(OMe)(2,4,6-Me3C6H2)](Me2SO)] (8), correspondingly. In accord with the latter reaction, the coupling of nitriles in trans-[PtCl4(EtCN)2] with methyl benzohydroximate, PhC(OMe)=NOH (F2B), gives [PtCl4[NH=C(Et)ON=C(OMe)Ph]2] (4). The addition proceeds faster with the hydroximic F2, rather than with the hydroxamic form F1. The complexes 1-8 were characterized by C, H, N elemental analyses, FAB+ mass-spectrometry, IR, 1H and 13C[1H] NMR spectroscopies. The X-ray structure determinations have been performed for both hydroxamic and hydroximic complexes, i.e. 2 and 6, indicating that the imino ligands are mutually trans and they are in the E-configuration.     

Platinum(IV) analogues of AMD473 (cis-[PtCl2(NH3)(2-picoline)]): preparative, structural, and electrochemical studies

The preparation and oxidation of the anticancer drug AMD473, cis-[PtCl2(NH3)(2-pic)] (2-pic = 2-methylpyridine), has been investigated. cis-[PtCl2(NH3)(2-pic)] is readily oxidized with peroxide to give the trans-dihydroxoplatinum(IV) complex cis,trans,cis-[PtCl2(OH)2(NH3)(2-pic)]. The crystal structure of this complex reveals that it is highly strained as a result of a steric clash between the methyl group of the 2-picoline ligand and an axial hydroxo ligand, with the Pt-N-C angle adjacent to this clash opened up to an unprecedented 138.6(6) degrees . Attempts at converting the dihydroxoplatinum(IV) complex to dichloro and diacetato analogues were unsuccessful with reaction with HCl leading to loss and protonation of the 2-picoline ligand to form the salt (2-picH)[PtCl5(NH3)] and the platinum(II) complex cis-[PtCl2(NH3)(2-pic)], both confirmed by crystallography. Electrochemical studies revealed that cis,trans,cis-[PtCl2(OH)2(NH3)(2-pic)] is reduced more readily (-714 mV vs Ag/AgCl) than its pyridine analogue cis,trans,cis-[PtCl2(OH)2(NH3)(pyridine)] (-770 mV vs Ag/AgCl) consistent with the steric clash in the former complex destabilizing the platinum(IV) oxidation state.     

Push-pull nitrile ligands exhibit specific hydration patterns

The reaction between K[PtCl(3)(Me(2)SO)] or prepared in this work cis- and trans-[PtCl(2)(NCNR(2))(Me(2)SO)] (R(2) = Me(2), 1; C(4)H(8)O, 2; C(5)H(10) 3) with an excess of NCNR(2) in water gives the cationic bischelate [Pt{κ(2)-N,N'-NH=C(NMe(2))OC(NMe(2))=NH}(2)](2+) (4(2+)) and the monochelates [PtCl{κ(2)-N,O-NH=C(NR(2))NC(NR(2))=O}(Me(2)SO)] (R(2) = C(4)H(8)O, 5; C(5)H(10), 6). Complex 4(2+) was released from the reaction mixture as 4·[PtCl(3)(Me(2)SO)](2)·(H(2)O)(2) or it was precipitated as 4·[A](2) (A = pic, 4·[pic](2); PF(6), 4·[PF(6)](2); BPh(4), 4·[BPh(4)](2)·(NH(2)CONMe(2))) by addition of picric acid, NaPF(6), or NaBPh(4), respectively, to the filtrate obtained after separation of 4·[PtCl(3)(Me(2)SO)](2)·(H(2)O)(2). In 2, the dialkylcyanamide ligand undergoes bond cleavage giving the known trans-[PtCl(2){N(H)C(4)H(8)O}(Me(2)SO)] (trans-7). All complexes were characterized by elemental analyses (C, H, N), high resolution ESI-MS, IR, (1)H and (13)C{(1)H} NMR spectroscopic techniques, including 2D NMR correlation experiments ((1)H,(1)H-COSY, (1)H,(13)C-HMQC/(1)H,(13)C HSQC, (1)H,(13)C-HMBC, and (1)H,(1)H-NOESY). The structures of cis-1, cis-3, 4·[PtCl(3)(Me(2)SO)](2)·(H(2)O)(2), 4·[BPh(4)](2)·(NH(2)CONMe(2)) and 5 were determined by a single-crystal X-ray diffraction.     

Mechanistic Study on the Monofunctional Binding of Hydrolysis Products of Non-planar Heterocyclic Complexes Trans-[PtCl_2NH_3（piperidine）] and Trans-[PtCl_2（piperidine）_2] to DNA Purine Bases

The monofunctional substitution reactions between trans-[PtCl(H2O)(NH3)(pip)]+,trans-[Pt(H2O)2(NH3)(pip)]2+,trans-[PtCl(H2O)(pip)2]+,trans-[Pt(H2O)2(pip)2]2+ (pip = piperidine) and adenine/guanine nucleotides are explored by using B3LYP hybrid functional and IEF-PCM salvation models. For the trans-[Pt(H2O)2(NH3)(pip)]2+ and trans-[PtCl(H2O)(NH3)(pip)]+ complexes,the computed barrier heights in aqueous solution are 13.5/13.5 and 11.6/11.6 kcal/mol from trans-Pt-chloroaqua complex to trans/cis-monoadduct for adenine and guanine,and the corresponding values are 20.7/20.7 and 18.8/18.8 kcal/mol from trans-Pt-diaqua complex to trans/cis-monoadduct for adenine and guanine,respectively. For trans-[PtCl(H2O)(pip)2]+ and trans-[Pt(H2O)2(pip)2]2+,the corresponding values are 21.5/21.3 and 19.4/19.4 kcal/mol,and 26.0/26.0 and 20.7/20.8 kal/mol for adenine and guanine,respectively. Our calculations demonstrate that the barrier heights of chloroaqua are lower than the corresponding values of diaqua for adenine and guanine. In addition,the free energies of activation for guanine in aqueous solution are all smaller than that for adenine,which predicts a preference of 1.9 kcal/mol when trans-[PtCl(H2O)(NH3)(pip)]+ and trans-[Pt(H2O)2(NH3)(pip)]2+ are the active agents and ～1.9 and ～ 5.3 kcal/mol when trans-[PtCl(H2O)(pip)2]+ and trans-[Pt(H2O)2(pip)2]2+ are the active agents,respectively. For the reaction of trans-Pt-chloroaqua (or diaqua) to cis-monoadduct,we obtain the same transition-state structure as from the reaction of trans-Pt-chloroaqua (or diaqua) to trans-monoadduct,which seems that the trans-Pt-chloroaqua (or diaqua) complex can generate trans-or cis-monoadduct via the same transition-state.     

Mass spectrometric studies of the formation and reactivity of trans-[PtCl2(Am)(piperidinopiperidine)] x HCl complexes with ubiquitin

trans-[PtCl2(Am)(pip-pip)] x HCl complexes, where Am = ammine, methylamine and dimethylamine, react with ubiquitin to form 1:1 covalent adducts. The platinum complexes bind exclusively to Met1 of ubiquitin forming trans-[PtCl(S-Met1-Ub)(Am)(pip-pip)] adducts. These adducts are reactive towards nucleophiles and react with deoxyguanosine (dGMP) to form the ternary trans-[Pt(dGMP)(S-Met1-Ub) (Am)(pip-pip)] complex which is stable in water and even in the presence of excess glutathione (GSH). Reaction of trans-[PtCl(S-Met1-Ub)(Am)(pip-pip)] with GSH resulted in the rapid formation of the ternary complex trans-[Pt(GS)(S-Met1-Ub)(Am)(pip-pip)] which was not stable and slowly lost the platinum moiety; after 7 days the platinum moiety was completely removed and the native ubiquitin was regenerated.     

Novel pyrimidine-bridged platinum(II) complexes: multinuclear magnetic resonance spectroscopy and crystal structures of (NR4)2[(PtCl3)2(mu-pyrimidine)] and cis- and trans-[Pt(R2SO)Cl2]2(mu-pyrimidine)

Two new types of pyrimidine-bridged Pt(II) complexes, (NR4)2[(PtCl3)2(mu-pm)] and cis- and trans-[Pt(R2SO)Cl2]2(mu-pm) where pm = pyrimidine, were synthesized and characterized by IR and multinuclear magnetic resonance spectroscopies and by crystallographic methods. Compounds with dimethylsulfoxide, tetramethylenesulfoxide, di-n-propylsulfoxide (DPrSO), di-n-butylsulfoxide (DBuSO), dibenzylsulfoxide (DBzSO), and diphenylsulfoxide were studied. The aqueous reaction of K2PtCl4 with pyrimidine produced the [(PtCl3)2(mu-pm)](2-) ions, which can be precipitated with a NR4(+) salt. The aqueous reaction of K[Pt(R2SO)Cl3] with pyrimidine in a 2:1 ratio produced the dinuclear species trans-[Pt(R2SO)Cl2]2(mu-pm). With DBuSO and DBzSO, the analogous cis isomers were also obtained. The 195Pt NMR resonances of the trans dimeric complexes were observed at higher field (av -3088 ppm) than the cis compounds (av -2948 ppm). The 195Pt coupling constants with the atoms of pyrimidine 3J(195Pt-1H) and 3J(195Pt-13C) are larger in the cis configuration than in the trans analogues. The crystal structures of two ionic complexes, (NR4)2[(PtCl3)2(mu-pm)] (R = Me and n-Bu), and of three mixed-ligands dimers, trans-[Pt(R2SO)Cl2]2(mu-pm) (R2SO = DMSO, DPrSO) and cis-Pt(DBuSO)Cl2]2(mu-pm), were determined.     

Mixed unsymmetric oxadiazoline and/or imine platinum(II) complexes

Iminoacylation of acetone oxime Me(2)C[double bond, length as m-dash]NOH upon reaction with trans-[PtCl(2)(NCCH(2)CO(2)Me)(2)] and [2 + 3] cycloaddition of acyclic nitrone (-)O(+)N(Me) = C(H)(C(6)H(4)Me-4) to a nitrile ligand in lead to the formation of mono-imine trans-[PtCl(2)(imine-a)(NCCH(2)CO(2)Me)] [imine-a = NH[double bond, length as m-dash]C(CH(2)CO(2)Me)ON = CMe(2)] and mono-oxadiazoline trans-[PtCl(2)(oxadiazoline-a)(NCCH(2)CO(2)Me)] [oxadiazoline-a = [upper bond 1 start]N[double bond, length as m-dash]C(CH(2)CO(2)Me)ON(Me)C[upper bond 1 end](H)(C(6)H(4)Me-4)] unsymmetric mixed ligand complexes, respectively, as the main products. Reactions of or with acetone oxime , cyclic nitrone (-)O(+)N = CHCH(2)CH(2)C[upper bond 1 end]Me(2) or N,N-diethylhydroxylamine give access, in moderate to good yields, to the unsymmetric mixed ligand oxadiazoline and/or imine complexes trans-[PtCl(2)(oxadiazoline-a)(imine-a)] , trans-[PtCl(2)(oxadiazoline-a)(oxadiazoline-b)] [oxadiazoline-b = [upper bond 1 start]N[double bond, length as m-dash]C(CH(2)CO(2)Me)O[lower bond 1 start]NC[upper bond 1 end](H)CH(2)CH(2)C[lower bond 1 end]Me(2)], trans-[PtCl(2)(imine-a)(imine-b)] [imine-b = NH = C(CH(2)CO(2)Me)ONEt(2)] or trans-[PtCl(2)(imine-a)(oxadiazoline-b)] . The cis mono-imine mixed ligand complex cis-[PtCl(2)(imine-a)(NCCH(2)CO(2)Me)] is the major product from the reaction of cis-[PtCl(2)(NCCH(2)CO(2)Me)(2)] with the oxime , while the di-imine compound cis-[PtCl(2)(imine-a)(2)] is a minor product. Reaction of cis-[PtCl(2)(imine-a)(NCCH(2)CO(2)Me)] with N,N-diethylhydroxylamine or the cyclic nitrone affords, in good yields, the unsymmetric mixed ligand complexes cis-[PtCl(2)(imine-a)(imine-b)] or cis-[PtCl(2)(imine-a)(oxadiazoline-b)] , respectively. All these complexes were characterized by elemental analyses, IR and (1)H, (13)C and (195)Pt NMR spectroscopies, and FAB(+)-MS. The X-ray structural analysis of trans-[PtCl(2){NH=C(CH(2)CO(2)Me)ON=CMe(2)}(NCCH(2)CO(2)Me)] is also reported.     

New synthetic routes to biscarbonylbipyridinerhenium(I) complexes cis,trans-[Re(X2bpy)(CO)2(PR3)(Y)n+ (X2bpy = 4,4'-X2-2,2'-bipyridine) via photochemical ligand substitution reactions, and their photophysical and electrochemical properties

Photochemical ligand substitution of fac-[Re(X2bpy)(CO)3(PR3)]+ (X2bpy = 4,4'-X2-2,2'-bipyridine; X = Me, H, CF3; R = OEt, Ph) with acetonitrile quantitatively gave a new class of biscarbonyl complexes, cis,trans[Re(X2bpy)(CO)2(PR3)(MeCN)]+, coordinated with four different kinds of ligands. Similarly, other biscarbonylrhenium complexes, cis,trans-[Re(X2bpy)(CO)2(PR3)(Y)]n+ (n = 0, Y = Cl-; n = 1, Y = pyridine, PR'3), were synthesized in good yields via photochemical ligand substitution reactions. The structure of cis,trans-[Re(Me2bpy)(CO)2[P(OEt)3](PPh3)](PF6) was determined by X-ray analysis. Crystal data: C38H42N2O5F6P3Re, monoclinic, P2(1/a), a = 11.592(1) A, b = 30.953(4) A, c = 11.799(2) A, V = 4221.6(1) A3, Z = 4, 7813 reflections, R = 0.066. The biscarbonyl complexes with two phosphorus ligands were strongly emissive from their 3MLCT state with lifetimes of 20-640 ns in fluid solutions at room temperature. Only weak or no emission was observed in the cases Y = Cl-, MeCN, and pyridine. Electrochemical reduction of the biscarbonyl complexes with Y = Cl- and pyridine in MeCN resulted in efficient ligand substitution to give the solvento complexes cis,trans-[Re(X2bpy)(CO)2(PR3)(MeCN)]+.     

Reactivity of trans-[PtX(2)(ketoxime)(2)] Complexes toward m-Chloroperoxybenzoic Acid: An Efficient Route to Coordinated Nitrosoalkanes and Solvent Dependence of the Reaction

The platinum(II) compounds trans-[PtX(2)(RR'C=NOH)(2)] [X = Cl, R = R' = Me, RR' = (CH(2))(4), (CH(2))(5); X = Br, R = R' = Me] react with m-chloroperoxybenzoic acid (MCPBA) in dimethylformamide to give the platinum(II) complexes [PtX(2){N(=O)CRR'ONCRR'}] containing coordinated nitrosoalkane ligands. The complexes [PtX(2){N(=O)CRR'ONCRR'}] were characterized by elemental analysis, EI-MS, IR, electronic absorption, and (1)H NMR spectroscopy; X-ray structure analysis was performed for [PtCl(2){N(=O)CC(5)H(10)ONCC(5)H(10)}]. The latter compound crystallizes in the triclinic P&onemacr; space group with a = 9.214(2) ?, b = 9.577(2) ?, c = 10.367(2) ?, alpha = 109.14(2) degrees, beta = 91.87(2) degrees, gamma = 115.62(2) degrees, V = 762.8(3) ?(3), Z = 2, and rho(calcd) = 2.135 g cm(-)(3). The reaction between trans-[PtX(2)(RR'C=NOH)(2)] and MCPBA displays a solvent dependence: interaction of these reagents in ketones, R(1)R(2)C=O, yields the platinum(IV) chelates [PtX(2)(OCR(1)R(2)ON=CRR')(2)], while the oxidation state of the oxime N atom remains unchanged. Heating [PtCl(2)(OCR(1)R(2)ON=CRR')(2)] in DMF or in DMF-d(7) at 100 degrees C leads to the extrusion of R(1)R(2)C=O and the formation of [PtCl(2){N(=O)CRR'ONCRR'}].     

Facile cyanamide-ammonia coupling mediated by cis- and trans-[PtIIL2] centers and giving metal-bound guanidines

Diffusion of ammonia into CH(2)Cl(2) solutions of the dialkylcyanamide complexes cis- or trans-[PtCl(2)(RCN)(2)] (R = NMe(2), NEt(2), NC(5)H(10)) at 20-25 degrees C leads to metal-mediated cyanamide-ammonia coupling to furnish, depending on reaction time, one or another type of novel bisguanidine compound, i.e. the molecular cis- or trans-[PtCl(2){NH=C(NH(2))R}(2)] (cis- and trans-) and the cationic cis- or trans-[Pt(NH(3))(2){NH=C(NH(2))R}(2)](Cl)(2) (cis- and trans-) complexes. Compounds cis- or trans- were converted to cis- or trans-, accordingly, upon prolonged treatment with NH(3) in CH(2)Cl(2). The ammination of the relevant nitrile complexes cis- or trans-[PtCl(2)(RCN)(2)] (R = Et, CH(2)Ph, Ph) in CH(2)Cl(2) solutions affords only the cationic compounds cis- or trans-[Pt(NH(3))(2){NH=C(NH(2))R}(2)](Cl)(2) (cis- and trans-). The formulation of was supported by satisfactory C, H and N elemental analyses, agreeable ESI(+)-MS (or FAB(+)-MS), IR, (1)H and (13)C NMR spectroscopies. The structures of trans-, trans-, cis-, trans-, cis-, and cis- were determined by single-crystal X-ray diffraction disclosing structural features and showing that the ammination gives ligated guanidines and amidines in the E- and Z-forms, respectively, where both correspond to the trans-addition of NH(3) to the nitrile species.     

Synthesis, structure, and reactivity of ruthenium carboxylato and 2-oxocarboxylato complexes bearing the bis(3,5-dimethylpyrazol-1-yl)acetato ligand

A series of ruthenium(II) acetonitrile, pyridine (py), carbonyl, SO2, and nitrosyl complexes [Ru(bdmpza)(O2CR)(L)(PPh3)] (L = NCMe, py, CO, SO2) and [Ru(bdmpza)(O2CR)(L)(PPh3)]BF4 (L = NO) containing the bis(3,5-dimethylpyrazol-1-yl)acetato (bdmpza) ligand, a N,N,O heteroscorpionate ligand, have been prepared. Starting from ruthenium chlorido, carboxylato, or 2-oxocarboxylato complexes, a variety of acetonitrile complexes [Ru(bdmpza)Cl(NCMe)(PPh3)] (4) and [Ru(bdmpza)(O2CR)(NCMe)(PPh3)] (R = Me (5a), R = Ph (5b)), as well as the pyridine complexes [Ru(bdmpza)Cl(PPh3)(py)] (6) and [Ru(bdmpza)(O2CR)(PPh3)(py)] (R = Me (7a), R = Ph (7b), R = (CO)Me (8a), R = (CO)Et (8b), R = (CO)Ph) (8c)), have been synthesized. Treatment of various carboxylato complexes [Ru(bdmpza)(O2CR)(PPh3)2] (R = Me (2a), Ph (2b)) with CO afforded carbonyl complexes [Ru(bdmpza)(O2CR)(CO)(PPh3)] (9a, 9b). In the same way, the corresponding sulfur dioxide complexes [Ru(bdmpza)(O2CMe)(PPh3)(SO2)] (10a) and [Ru(bdmpza)(O2CPh)(PPh3)(SO2)] (10b) were formed in a reaction of the carboxylato complexes with gaseous SO2. None of the 2-oxocarboxylato complexes [Ru(bdmpza)(O2C(CO)R)(PPh3)2] (R = Me (3a), Et (3b), Ph (3c)) showed any reactivity toward CO or SO2, whereas the nitrosyl complex cations [Ru(bdmpza)(O2CMe)(NO)(PPh3)](+) (11) and [Ru(bdmpza)(O2C(CO)Ph)(NO)(PPh3)](+) (12) were formed in a reaction of the acetato 2a or the benzoylformato complex 3c with an excess of nitric oxide. Similar cationic carboxylato nitrosyl complexes [Ru(bdmpza)(O2CR)(NO)(PPh3)]BF4 (R = Me (13a), R = Ph (13b)) and 2-oxocarboxylato nitrosyl complexes [Ru(bdmpza)(O2C(CO)R)(NO)(PPh3)]BF4 (R = Me (14a), R = Et (14b), R = Ph (14c)) are also accessible via a reaction with NO[BF4]. X-ray crystal structures of the chlorido acetonitrile complex [Ru(bdmpza)Cl(NCMe)(PPh3)] (4), the pyridine complexes [Ru(bdmpza)(O2CMe)(PPh3)(py)] (7a) and [Ru(bdmpza)(O2CC(O)Et)(PPh3)(py)] (8b), the carbonyl complex [Ru(bdmpza)(O2CPh)(CO)(PPh3)] (9b), the sulfur dioxide complex [Ru(bdmpza)(O2CPh)(PPh3)(SO2)] (10b), as well as the nitrosyl complex [Ru(bdmpza)(O2C(CO)Me)(NO)(PPh3)]BF4 (14a), are reported. The molecular structure of the sulfur dioxide complex [Ru(bdmpza)(O2CPh)(PPh3)(SO2)] (10b) revealed a rather unusual intramolecular SO2-O2CPh Lewis acid-base adduct.     

Orientation and Restricted Rotation of Lopsided Aromatic Ligands. Octahedral Complexes Derived from cis-RuCl(2)(Me(2)SO)(4)

The solution and solid state structures of two octahedral Ru(II) complexes, cis,cis,cis-RuCl(2)(Me(2)SO)(2)(py)(Me(3)Bzm) (Me(3)Bzm = 1,5,6-trimethylbenzimidazole, py = pyridine) (1) and cis,cis,cis-RuCl(2)(Me(2)SO)(2)(Me(3)Bzm)(2) (2), were compared. 2, the subject of a preliminary report, is described in more detail here. 1 has two possible geometric isomers with py trans to Cl in one (position "a") and trans to Me(2)SO in the other (position "b"), Me(3)Bzm occupying the other position in each isomer. The X-ray structure of 1 revealed that py is at "a". Since Me(3)Bzm is lopsided, each Me(3)Bzm has two possible orientations related by a rotation of approximately 180 degrees about the Ru-N3 bond; there are two possible atropisomers for each geometric isomer of 1 and four for 2. For 1, the solid state structure shows that Me(3)Bzm adopts the orientation with H2 (H on C between the two N's) pointing between the two cis Cl ligands, the same disposition as Me(3)Bzm "b" in 2 in the solid. For 1, the py signals (two broad py alpha and beta signals, a sharp gamma signal) in CDCl(3) show that py "a" is rotating on the NMR time scale and that only one atropisomer is present. This interpretation was supported by ROESY and EXSY (1)H NMR spectra. The (1)H NMR shift pattern and the NOE data can be understood best if Me(3)Bzm "b" remains primarily in the orientation found in the solid. The solution data for 1, with the nonlopsided and sterically less demanding py ligand, provide insight into the more complicated properties of 2. For 2, there is a marked dispersion of (1)H NMR signals of Me(3)Bzm "a" between the two atropisomers, which have nearly equal stability. One atropisomer is a head-to-head (HH) and the other a head-to-tail (HT) species. Me(3)Bzm "a" flips between the two species. Thus, ligand "a" is fluxional in both complexes. The dispersion of Me(3)Bzm "a" signals is due to the effect of Me(3)Bzm "b" anisotropy. For 1 and both atropisomers of 2, Me(3)Bzm "b" prefers one orientation, which appears to be the most hindered orientation. We postulate that the H2 of Me(3)Bzm "b" is electrostatically attracted to the two cis halides, accounting for this surprising result. Crystallographic details for 1 are as follows: C(19)H(29)Cl(2)N(3)O(2)RuS(2), P2(1)/c, a = 10.947(1) ?, b = 9.046(1) ?, c = 24.221(2) ?, D(calcd) = 1.580 g cm(-)(3), Z = 4, R = 0.026 for 4627 independent reflections.     

Synthesis and reactivity of Ir(I) and Ir(III) complexes with MeNH2, Me2C=NR (R = H, Me), C,N-C6H4{C(Me)=N(Me)}-2, and N,N'-RN=C(Me)CH2C(Me2)NHR (R = H, Me) ligands

Complexes [Ir(Cp*)Cl(n)(NH2Me)(3-n)]X(m) (n = 2, m = 0 (1), n = 1, m = 1, X = Cl (2a), n = 0, m = 2, X = OTf (3)) are obtained by reacting [Ir(Cp*)Cl(mu-Cl)]2 with MeNH2 (1:2 or 1:8) or with [Ag(NH2Me)2]OTf (1:4), respectively. Complex 2b (n = 1, m = 1, X = ClO 4) is obtained from 2a and NaClO4 x H2O. The reaction of 3 with MeC(O)Ph at 80 degrees C gives [Ir(Cp*){C,N-C6H4{C(Me)=N(Me)}-2}(NH2Me)]OTf (4), which in turn reacts with RNC to give [Ir(Cp*){C,N-C6H4{C(Me)=N(Me)}-2}(CNR)]OTf (R = (t)Bu (5), Xy (6)). [Ir(mu-Cl)(COD)]2 reacts with [Ag{N(R)=CMe2}2]X (1:2) to give [Ir{N(R)=CMe2}2(COD)]X (R = H, X = ClO4 (7); R = Me, X = OTf (8)). Complexes [Ir(CO)2(NH=CMe2)2]ClO4 (9) and [IrCl{N(R)=CMe2}(COD)] (R = H (10), Me (11)) are obtained from the appropriate [Ir{N(R)=CMe2}2(COD)]X and CO or Me4NCl, respectively. [Ir(Cp*)Cl(mu-Cl)]2 reacts with [Au(NH=CMe2)(PPh3)]ClO4 (1:2) to give [Ir(Cp*)(mu-Cl)(NH=CMe2)]2(ClO4)2 (12) which in turn reacts with PPh 3 or Me4NCl (1:2) to give [Ir(Cp*)Cl(NH=CMe2)(PPh3)]ClO4 (13) or [Ir(Cp*)Cl2(NH=CMe2)] (14), respectively. Complex 14 hydrolyzes in a CH2Cl2/Et2O solution to give [Ir(Cp*)Cl2(NH3)] (15). The reaction of [Ir(Cp*)Cl(mu-Cl)]2 with [Ag(NH=CMe2)2]ClO4 (1:4) gives [Ir(Cp*)(NH=CMe2)3](ClO4)2 (16a), which reacts with PPNCl (PPN = Ph3=P=N=PPh3) under different reaction conditions to give [Ir(Cp*)(NH=CMe2)3]XY (X = Cl, Y = ClO4 (16b); X = Y = Cl (16c)). Equimolar amounts of 14 and 16a react to give [Ir(Cp*)Cl(NH=CMe2)2]ClO4 (17), which in turn reacts with PPNCl to give [Ir(Cp*)Cl(H-imam)]Cl (R-imam = N,N'-N(R)=C(Me)CH2C(Me)2NHR (18a)]. Complexes [Ir(Cp*)Cl(R-imam)]ClO4 (R = H (18b), Me (19)) are obtained from 18a and AgClO4 or by refluxing 2b in acetone for 7 h, respectively. They react with AgClO4 and the appropriate neutral ligand or with [Ag(NH=CMe2)2]ClO4 to give [Ir(Cp*)(R-imam)L](ClO4)2 (R = H, L = (t)BuNC (20), XyNC (21); R = Me, L = MeCN (22)) or [Ir(Cp*)(H-imam)(NH=CMe2)](ClO4)2 (23a), respectively. The later reacts with PPNCl to give [Ir(Cp*)(H-imam)(NH=CMe2)]Cl(ClO4) (23b). The reaction of 22 with XyNC gives [Ir(Cp*)(Me-imam)(CNXy)](ClO4)2 (24). The structures of complexes 15, 16c and 18b have been solved by X-ray diffraction methods.     

Kinetics and mechanism for reversible chloride transfer between mercury(II) and square-planar platinum(II) chloro ammine, aqua, and sulfoxide complexes. Stabilities, spectra, and reactivities of transient metal-metal bonded platinum-mercury adducts

The Hg2+aq- and HgCl+aq-assisted aquations of [PtCl4]2- (1), [PtCl3(H2O)]- (2), cis-[PtCl2(H2O)2] (3), trans-[PtCl2(H2O)2] (4), [PtCl(H2O)3]+ (5), [PtCl3Me2SO]- (6), trans-[PtCl2(H2O)Me2SO] (7), cis-[PtCl(H2O)2Me2SO]+ (8), trans-[PtCl(H2O)2M32SO]+ (9), trans-[PtCl2(NH3)2] (10), and cis-[PtCl2(NH3)2] (11) have been studied at 25.0 degrees C in a 1.00 M HClO4 medium buffered with chloride, using stopped-flow and conventional spectrophotometry. Saturation kinetics and instantaneous, large UV/vis spectral changes on mixing solutions of platinum complex and mercury are ascribed to formation of transient adducts between Hg2+ and several of the platinum complexes. Depending on the limiting rate constants, these adducts are observed for a few milliseconds to a few minutes. Thermodynamic and kinetics data together with the UV/vis spectral changes and DFT calculations indicate that their structures are characterized by axial coordination of Hg to Pt with remarkably short metal-metal bonds. Stability constants for the Hg2+ adducts with complexes 1-6, 10, and 11 are (2.1 +/- 0.4) x 10(4), (8 +/- 1) x 10(2), 94 +/- 6, 13 +/- 2, 5 +/- 2, 60 +/- 6, 387 +/- 2, and 190 +/- 3 M-1, respectively, whereas adduct formation with the sulfoxide complexes 7-9 is too weak to be observed. For analogous platinum(II) complexes, the stabilities of the Pt-Hg adducts increase in the order sulfoxide < aqua < ammine complex, reflecting a sensitivity to the pi-acid strength of the Pt ligands. Rate constants for chloride transfer from HgCl+ and HgCl2 to complexes 1-11 have been determined. Second-order rate constants for activation by Hg2+ are practically the same as those for activation by HgCl+ for each of the platinum complexes studied, yet resolved contributions for Hg2+ and HgCl+ reveal that the latter does not form dinuclear adducts of any significant stability. The overall experimental evidence is consistent with a mechanism in which the accumulated Pt(II)-Hg2+ adducts are not reactive intermediates along the reaction coordinate. The aquation process occurs via weaker Pt-Cl-Hg or Pt-Cl-HgCl bridged complexes.     

Regioselective HON-addition of bifunctional hydrazone oximes to Pt(IV)-bound nitriles

Treatment of trans-[PtCl(4)(RCN)(2)](R = Me, Et) with the hydrazone oximes MeC(=NOH)C(R')=NNH(2)(R' = Me, Ph) at 45 degrees C in CH(2)Cl(2) led to the formation of trans-[PtCl(4)(NH=C(R)ON=C(Me)C(R')=NNH(2))(2)](R/R' = Me/Ph 1, Et/Me 2, Et/Ph 3) due to the regioselective OH-addition of the bifunctional MeC(=NOH)C(R')=NNH(2) to the nitrile group. The reaction of 3 and Ph(3)P=CHCO(2)Me allows the formation of the Pt(II) complex trans-[PtCl(2)(NH=C(Et)ON=C(Me)C(Ph)=NNH(2))2](4). In 4, the imine ligand was liberated by substitution with 2 equivalents of bis(1,2-diphenylphosphino)ethane (dppe) in CDCl(3) to give, along with the free ligand, the solid [Pt(dppe)(2)]Cl(2). The free iminoacyl hydrazone, having a restricted life-time, decomposes at 20-25 degrees C in about 20 h to the parent organonitrile and the hydrazone oxime. The Schiff condensation of the free NH(2) groups of 4 with aromatic aldehydes, i.e. 2-OH-5-NO(2)-benzaldehyde and 4-NO(2)-benzaldehyde, brings about the formation of the platinum(II) complexes trans-[PtCl(2)(NH=C(Et)ON=C(Me)C(Ph)=NN=CH(C(6)H(3)-2-OH-5-NO(2))2](5) and trans-[PtCl(2)(NH=C(Et)ON=C(Me)C(Ph)=NN=CH(C(6)H(4)-4-NO(2))2](6), respectively, containing functionalized remote peripherical groups. Metallization of 5, which can be considered as a novel type of metallaligand, was achieved by its reaction with M(OAc)(2).nH(2)O (M = Cu, n= 2; M = Co, n= 4) in a 1:1 molar ratio furnishing solid heteronuclear compounds with composition [Pt]:[M]= 1:1. The complexes were characterized by C, H, N elemental analyses, FAB+ mass-spectrometry, IR, 1H, 13C[1H] and (195)Pt NMR spectroscopies; X-ray structures were determined for 3, 4 and 5.     

Amidoximes provide facile platinum(II)-mediated oxime-nitrile coupling

The nucleophilic addition of amidoximes R'C(NH(2))═NOH [R' = Me (2.Me), Ph (2.Ph)] to coordinated nitriles in the platinum(II) complexes trans-[PtCl(2)(RCN)(2)] [R = Et (1t.Et), Ph (1t.Ph), NMe(2) (1t.NMe(2))] and cis-[PtCl(2)(RCN)(2)] [R = Et (1c.Et), Ph (1c.Ph), NMe(2) (1c.NMe(2))] proceeds in a 1:1 molar ratio and leads to the monoaddition products trans-[PtCl(RCN){HN═C(R)ONC(R')NH(2)}]Cl [R = NMe(2); R' = Me ([3a]Cl), Ph ([3b]Cl)], cis-[PtCl(2){HN═C(R)ONC(R')NH(2)}] [R = NMe(2); R' = Me (4a), Ph (4b)], and trans/cis-[PtCl(2)(RCN){HN═C(R)ONC(R')NH(2)}] [R = Et; R' = Me (5a, 6a), Ph (5b, 6b); R = Ph; R' = Me (5c, 6c), Ph (5d, 6d), correspondingly]. If the nucleophilic addition proceeds in a 2:1 molar ratio, the reaction gives the bisaddition species trans/cis-[Pt{HN═C(R)ONC(R')NH(2)}(2)]Cl(2) [R = NMe(2); R' = Me ([7a]Cl(2), [8a]Cl(2)), Ph ([7b]Cl(2), [8b]Cl(2))] and trans/cis-[PtCl(2){HN═C(R)ONC(R')NH(2)}(2)] [R = Et; R' = Me (10a), Ph (9b, 10b); R = Ph; R' = Me (9c, 10c), Ph (9d, 10d), respectively]. The reaction of 1 equiv of the corresponding amidoxime and each of [3a]Cl, [3b]Cl, 5b-5d, and 6a-6d leads to [7a]Cl(2), [7b]Cl(2), 9b-9d, and 10a-10d. Open-chain bisaddition species 9b-9d and 10a-10d were transformed to corresponding chelated bisaddition complexes [7d](2+)-[7f](2+) and [8c](2+)-[8f](2+) by the addition of 2 equiv AgNO(3). All of the complexes synthesized bear nitrogen-bound O-iminoacylated amidoxime groups. The obtained complexes were characterized by elemental analyses, high-resolution ESI-MS, IR, and (1)H NMR techniques, while 4a, 4b, 5b, 6d, [7b](Cl)(2), [7d](SO(3)CF(3))(2), [8b](Cl)(2), [8f](NO(3))(2), 9b, and 10b were also characterized by single-crystal X-ray diffraction.     

Synthesis of acetimino complexes of Pt(II) and Pt(IV) and the first heteronuclear mu-acetimido complexes

The reactions of [Ag(NH=CMe2)2]ClO4 with cis-[PtCl2L2] in a 1:1 molar ratio give cis-[PtCl(NH=CMe2)(PPh3)2]ClO4 (1cis) or cis-[PtCl(NH=CMe2)2(dmso)]ClO4 (2), and in 2:1 molar ratio, they produce [Pt(NH=CMe2)2L2](ClO4)2 [L = PPh3 (3), L2= tbbpy = 4,4'-di-tert-butyl-2,2'-dipyridyl (4)]. Complex 2 reacts with PPh3 (1:2) to give trans-[PtCl(NH=CMe2)(PPh3)2]ClO(4) (1trans). The two-step reaction of cis-[PtCl2(dmso)2], [Au(NH=CMe2)(PPh3)]ClO4, and PPh3 (1:1:1) gives [SP-4-3]-[PtCl(NH=CMe2)(dmso)(PPh3)]ClO4 (5). The reactions of complexes 2 and 4 with PhICl2 give the Pt(IV) derivatives [OC-6-13]-[PtCl3(NH=CMe2)(2)(dmso)]ClO4 (6) and [OC-6-13]-[PtCl2(NH=CMe2)2(dtbbpy)](ClO4)2 (7), respectively. Complexes 1cis and 1trans react with NaH and [AuCl(PPh3)] (1:10:1.2) to give cis- and trans-[PtCl{mu-N(AuPPh3)=CMe2}(PPh3)2]ClO4 (8cis and 8trans), respectively. The crystal structures of 4.0.5Et2O.0.5Me2CO and 6 have been determined; both exhibit pseudosymmetry.     

Fluoride-bridged {Ln(2)Cr(2)} polynuclear complexes from semi-labile mer-[CrF(3)(py)(3)] and [Ln(hfac)(3)(H(2)O)(2)

The trifluorido complex mer-[CrF(3)(py)(3)] (py = pyridine) reacts with 1 equiv. of [Ln(hfac)(3)(H(2)O)(2)] and depending on the solvent forms the tetranuclear clusters [Cr(2)Ln(2)(μ-F)(4)(μ-OH)(2)(py)(4)(hfac)(6)], 1Ln, and [Cr(2)Ln(2)(μ-F)(4)F(2)(py)(6)(hfac)(6)], 2Ln, in acetonitrile and 1,2-dichloroethane, respectively (Ln = Y, Gd, Tb, Dy, Ho, and Er; hfacH = 1,1,1,5,5,5-hexafluoroacetylacetone). Reaction with [Dy(hfac)(3)(H(2)O)(2)] in dichloromethane produces the dinuclear cluster [CrDy(μ-F)F(OH(2))(py)(3)(hfac)(4)], 3Dy. All the clusters feature fluoride bridges between the chromium(iii) and lanthanide(iii) centres. Fits of susceptibility data for 1Gd and 2Gd reveal the fluoride-mediated chromium(iii)-lanthanide(iii) exchange interactions to be 0.43(5) cm(-1) and 0.57(7) cm(-1), respectively (in the convention). Heat capacity measurements on 2Gd reveal a moderate magneto-caloric effect (MCE) reaching -ΔS(m)(T) = 11.4 J kg(-1) K(-1) for ΔB(0) = 9 T → 0 T at T = 4.1 K. Out-of-phase alternating-current susceptibility (χ') signals are observed for 1Dy, 2Dy and 2Tb, demonstrating slow relaxation of the magnetization.     

Racemic monoperoxovanadium(V) complexes with achiral OO and ON donor set heteroligands: synthesis, crystal structure and stereochemistry of [NH3(CH2)2NH3][VO(O2)(ox)(pic)].2H2O and [NH3(CH2)2NH3][VO(O2)(ox)(pca)

Monoperoxovanadium(V) complexes, [NH3(CH2)2NH3][VO(O2)(ox)(pic)].2H2O (1) and [NH3(CH2)2NH3][VO(O2)(ox)(pca)] (2) [NH3(CH2)2NH3 = ethane-1,2-diammonium(2+), ox=oxalate(2-), pic=pyridine-2-carboxylate(1-), pca=pyrazine-2-carboxylate(1-)], were synthesized and characterized by X-ray analysis, IR and Raman spectroscopies. The five equatorial positions of the pentagonal bipyramid around the vanadium atoms are occupied by the eta2-peroxo ligand, two oxygen atoms of the ox, and the nitrogen atom of the pic or pca ligands, respectively. The oxo ligand and the oxygen atom of pic or pca are in the axial positions. Networks of X-HO (X=C, N or O) hydrogen bonds, and pi-pi interactions between aromatic rings in and anion-pi interactions in , determine the molecular packings and build up the supramolecular architecture. Three stereochemical rules for occupation of the donor sites in two-heteroligand [VO(O2)(L1)(L2)] complexes (L1, L2 are bidentate neutral or differently charged anionic heteroligands providing an OO, NN or ON donor set) are discussed. and crystallize as racemic compounds. The 51V NMR spectra proved that the parent complex anions of and partially decompose on dissolution in water to the monoperoxo-ox, -pic or -pca complexes.     

Reactivity of [Re[kappa(3)-H(mu-H)B(tim(Me))(2)](CO)(3)] (tim(Me) = 2-mercapto-1-methylimidazolyl) toward neutral substrates

The complex [Re[kappa(3)-H(mu-H)B(tim(Me))(2)](CO)(3)] (2a) (tim(Me) = 2-mercapto-1-methylimidazolyl) reacts with a variety of neutral substrates to afford new complexes featuring the dihydrobis(2-mercapto-1-methylimidazolyl)borate coordinated in a bidentate or unidentate fashion. By treating 2a with unidentate ligands, the mononuclear complexes [Re[kappa(2)-H(2)B(tim(Me))(2)](CO)(3)(L)] (L = imidazole (5), 4-(dimethylamino)pyridine (6), tert-butylisonitrile (7), triphenylphosphine (8)) were formed, upon replacement of the agostic B-H...Re bond by the correspondent unidentate ligand. With potentially bidentate substrates, 2a is transformed into mononuclear or dinuclear complexes, depending on the atom donor set of the reacting substrates. Reaction of compound 2a with ethylenediamine (en) gave the complex [Re[kappa(1)-H(2)B(tim(Me))(2)](CO)(3)(en)] (9), because of cleavage of the agostic interaction, dechelation of one mercaptoimidazolyl ring, and bidentate coordination of the amine. By contrast, 1,2-bis(diphenyl)phosphinoethane (dppe) is not able to replace the mercaptoimidazolyl ring, and the dimer [Re[kappa(2)-H(2)B(tim(Me))(2)](CO)(3)](2)(mu-dppe) (10) was formed. The novel Re(I) tricarbonyl complexes (5-10) have been fully characterized, including by X-ray diffraction analysis in the case of 6, 8, 9, and 10. The X-ray diffraction study confirmed the unprecedented unidentate coordination mode of the dihydrobis(2-mercapto-1-methylimidazolyl)borate in complex 9.