Self-assembly, structures, and photophysical properties of 4,4'-bipyrazolate-linked metallo-macrocycles with dimetal clips

By employing functional diimine ligands coordinated dipalladium(II,II) or diplatinum(II,II) clips as corners and the coplanar 4,4'-bipyrazolate dianion (L(2-)) ligand as linker, a series of bipyrazolate-bridged metallo-macrocycles, namely, [M8L4](NO3)8 (M = Pd(dmbpy), 1; Pd(bpy), 2; Pt(bpy), 3a; Pd(phen), 4; Pt(phen), 5; Pd(15-crown-5-phen), 6; Pd(18-crown-6-phen), 8; Pd(benzo-24-crown-8-phen), 10a; Pt(15-crown-5-phen), 7a, Pt(18-crown-6-phen), 9a; Pt(benzo-24-crown-8-phen), 11a) and [M6L3](NO3)6 (M = Pt(bpy), 3b; Pt(15-crown-5-phen), 7b; Pt(18-crown-6-phen), 9b; Pd(benzo-24-crown-8-phen), 10b; Pt(benzo-24-crown-8-phen), 11b), have been synthesized through a directed self-assembly approach that involves spontaneous deprotonation of the 1H-bipyrazolyl ligands in aqueous solution. All these compounds have a crown-shaped cavity that can serve as host to solvent molecules and anions. The structures are characterized by elemental analysis, (1)H and (13)C NMR, ESI-MS, and in the cases of 1a (the BF4(-) salt of 1), 2a (the BF4(-) salt of 2), and 3b by single-crystal X-ray diffraction analysis. Photophysical properties for complexes 1 and 2 are discussed.     

Properties of the polyhydride anions [WH5(PMe2Ph)3]- and [ReH4(PMePh2)3]- and periodic trends in the acidity of polyhydride complexes

The new anionic complexes [K(18-crown-6)][WH5(PMe2Ph)3], [K(1,10-diaza-18-crown-6)][WH5(PMe2Ph)3], [K(2,2,2-crypt)][ReH4(PMePh2)3], and [K(1,10-diaza-18-crown-6)][ReH4(PMePh2)3] were prepared by reaction of KH/crown or KH/crypt with the appropriate neutral polyhydride WH6(PMe2Ph)3 or ReH5(PMePh2)3. The rate of deprotonation of the rhenium hydride in THF is much greater for the reaction involving crypt compared with that of crown. The structure of [ReH4(PMePh2)3]- is distorted pentagonal bipyramidal as determined by an X-ray diffraction study of the crypt salt. No hydridic-protonic M-H...HN bonding is detected between the hydrides of the anionic hydrides and the amino hydrogens of the cations [K(1,10-diaza-18-crown-6)]+ suggesting that stronger M-H...K interactions are present. Acid dissociation constants Ka of polyhydride complexes in THF, approximately corrected for ion pairing, are determined by NMR in order to better understand the periodic trends of metal hydrides. The pKalphaTHF of (WH6(PMe2Ph)3/[WH5(PMe2Ph)3]-) is 42+/-4 according to the equilibrium set up by reacting WH6(PMe2Ph)3 with [K(2,2,2-crypt)][ReH6(PCy3)2]. The pKalphaTHF for ReH5(PMePh2)3 can be estimated as greater than the pKalphaTHF of 38 for HNPh2 and less than the pKalphaTHF of 41 for ReH7(PCy3)2. Reaction of the phosphazene base P4-tBu with ReH7(PCy3)2 gave an equilibrium with [HP4-tBu]+[ReH6(PCy3)2]- whereas reaction with WH6(PMe2Ph)3 gave an equilibrium with [HP4-tBu]+[WH5(PMe2Ph)3]-. From these and a related equilibrium, the pKalphaTHF of [HP4-tBu]+ is found to be 40+/-4. In general, neutral complexes MHx(PR3)n (M=W, Re, Ru, Os, Ir; n=3, 2) studied to date have pKalphaTHF values from 30 to 44 on going from phenyl-substituted to alkyl-substituted phosphine ligands whereas MHx(PR3)n+ (M=Re, Fe, Ru, Os, Co, Rh, Ni, Pd, Pt; n=4, 3), including diphosphine ligands ((PR3)2=PR2-PR2), have values from 12 to 23. From the equilibrium established from the reaction of [HP2-tBu][BPh4] and [K(2,2,2-crypt)][OP(OEt)2NPh], [HP2-tBu]+ was calculated to have a pKalphaTHF of 30+/-4. The equilibrium constant for the similar deprotonation reaction with [K(18-crown-6)][{ReH2(PMePh2)2}2(mu-H)3] confirmed this value.     

Synthesis, structure, and magnetic properties of the oxalate-based bimetallic ferromagnetic chain {[K(18-crown-6)][Mn(H2O)2Cr(ox)3]}infinity (18-crown-6 = C12H24O6, ox = C2O4(2-))

The salt [K(18-crown-6)][Mn(H2O)2Cr(ox)3.0.5(18-crown-6) (1) has been prepared and structurally and magnetically characterized. It crystallizes in the P2(1)/c space group [a = 21.011(2) A, b = 11.265(2) A, c = 15.748(3) A, beta = 105.952(6) degrees , V = 3584(1) A3, and Z = 4] and contains [Mn(H2O)2Cr(ox)3]infinity chains connected through hydrogen bonding to form 2D anionic networks. The magnetic exchange is ferromagnetic [J = +2.23(2) cm(-1)] in the chain and also in between chains, reaching bulk ferromagnetic ordering below 3.5 K.     

Synergic effect of two metal centers in catalytic hydrolysis of methionine-containing peptides promoted by dinuclear palladium(II) hexaazacyclooctadecane complex

The species obtained by the reaction of [Pd2([18]aneN6)Cl2](ClO4)2(where [18]aneN6 is 1,4,7,10,13,16-hexaazacyclooctadecane) with AgBF4 have been determined by electrospray ionization mass spectrometry (ESI-MS) to be an equilibrium mixture of three major types of dinuclear Pd(II) complex cations, [Pd2(mu-O)([18]aneN6)]2+, [Pd2(mu-OH)([18]aneN6)]3+ and [Pd2(H2O)(OH)([18]aneN6)](3+), in aqueous solution. The hydroxo-group-bridged one, [Pd2(mu-OH)([18]aneN6)]3+, is a dominant species, whose crystal structure has been obtained. The crystal structure of [Pd2(mu-OH)([18]aneN6)](ClO4)3 shows that each Pd(II) ion in the dinuclear complex is tetra-coordinated by three nitrogen atoms and one hydroxo group bridge in a distorted square configuration. The two Pd(II) ions are 3.09 A apart from each other. The dinuclear Pd(II) complex cations [Pd2(mu-OH)([18]aneN6)]3+ and [Pd2(H2O)(OH)([18]aneN6)]3+ can efficiently catalyze hydrolysis of the amide bond involving the carbonyl group of methionine in methionine-containing peptides with turnover number of larger than 20. In these hydrolytic reactions, the two Pd(II) ions are synergic; one Pd(II) ion anchors to the side chain of methionine and the other one delivers hydroxo group or aqua ligand to carbonyl carbon of methionine, or acts as a Lewis acid to activate the carbonyl group of methionine, resulting in cleavage of Met-X bond. The binding constant of dinuclear Pd(II) complex cations with AcMet-Gly and AcMet were determined by 1H NMR titration to be 282 +/- 2 M(-1) and 366 +/- 4 M(-1), respectively. The relatively low binding constants enable the catalytic cycle and the possible catalytic mechanism is proposed. This is the first artificial mimic of metallopeptidases with two metal active centers.     

Synthesis of neutral (Pd(II), Pt(II)), cationic (Pd(II)), and water-induced anionic (Pd(II)) complexes containing new mesocyclic thioether-aminophosphonite ligands and their application in the Suzuki cross-coupling reaction

Mesocyclic thioether-aminophosphonite ligands, {-OC10H6(mu-S)C10H6O-}PNC4H8O (2a, 4-(dinaphtho[2,1-d:1',2'-g][1,3,6,2]dioxathiaphosphocin-4-yl)morpholine) and {-OC10H6(mu-S)C10H6O-}PNC4H8NCH3 (2b, 1-(dinaphtho[2,1-d:1',2'-g][1,3,6,2]dioxathiaphosphocin-4-yl)-4-methylpiperazine) are obtained by reacting {-OC10H6(mu-S)C10H6O-}PCl (1) with corresponding nucleophiles. The ligands 2a and 2b react with (PhCN)2PdCl2 or M(COD)Cl2 (M = Pd(II) or Pt(II)) to afford P-coordinated cis-complexes, [{(-OC10H6(mu-S)C10H6O-)PNC4H8X-kappaP}2MCl2] (3a, M = Pd(II), X = O; 3b, M = Pd(II), X = NMe; 4a, M = Pt(II), X = O; 4b, M = Pt(II), X = NMe). Compounds 2a and 2b, upon treatment with [Pd(eta3-C3H5)Cl]2 in the presence of AgOTf, produce the P,S-chelated cationic complexes, [{(-OC10H6(mu-S)C10H6O-)PNC4H8X-kappaP,kappaS}Pd(eta3-C3H5)](CF3SO3) (5a, X = O and 5b, X = NMe). Treatment of 2a and 2b with (PhCN)2PdCl2 in the presence of trace amount of H2O affords P,S-chelated anionic complexes, [{(-OC10H6(mu-S)C10H6O-)P(O)-kappaP,kappaS}PdCl2](H2NC4H8X) (6a, X = O and 6b, X = NMe), via P-N bond cleavage. The crystal structures of compounds 1, 2a, 2b, 4a, and 6a are reported. Compound 6a is a rare example of crystallographically characterized anionic transition metal complex containing a thioether-phosphonate ligand. Most of these palladium complexes proved to be very active catalysts for the Suzuki-Miyaura reaction with excellent turnover number ((TON), up to 9.2 x 10(4) using complex 6a as a catalyst).     

Vibrational study of new Pt(II) and Pd(II) complexes with functionalized nitrogen-containing tertiary phosphine oxides. Ab initio study of ortho-, meta- and para-dimethylphosphinylmethyleneoxyaniline

Vibrational study of new Pt(II) and Pd(II) complexes of functionalized nitrogen-containing tertiary phosphine oxides, namely ortho-, meta- and para-dimethylphosphinylmethyleneoxyaniline (o-, m- and p-dpmoa), (CH3)2P(O)CH2OC6H4NH2, have been presented. Geometry optimization of the ligands was performed at HF/6-31G* and B3LYP/6-31G* levels of the theory. Harmonic frequencies were calculated at HF/6-31G* optimized geometries. Relative gas-phase and solution-phase (H2O and CH3CN) basicities of o-, m- and p-dpmoa ligands have been determined by ab initio calculations at STO-3G level with the Onsager reaction field model. On the basis of the vibrational study, physical and analytical data it was suggested that the ligands in the complexes studied coordinate through the amino group and form square-planar platinum and palladium complexes of the general formula ML2Cl2 (M = Pt, Pd, L = o-, m- and p-dpmoa).     

A new tridentate pincer phosphine/n-heterocyclic carbene ligand: palladium complexes, their structures, and catalytic activities

A new imidazolium salt, 1,3-bis(2-diphenylphosphanylethyl)-3H-imidazol-1-ium chloride (2), for the phosphine/N-heterocyclic carbene-based pincer ligand, PC(NHC)P, and its palladium complexes were reported. The complex, [Pd(PC(NHC)P)Cl]Cl (4), was prepared by the common route of silver carbene transfer reaction and a novel direct reaction between the ligand precursor, PC(NHC)P.HCl and PdCl(2) without the need of a base. Metathesis reactions of 4 with AgBF(4) in acetonitrile produced [Pd(PC(NHC)P)(CH(3)CN)](BF(4))(2) (5). The same reaction in the presence of excess pyridine gave [Pd(PC(NHC)P)(py)](BF(4))(2) (6). The X-ray structure determination on 4-6 revealed the chiral twisting of the central imidazole rings from the metal coordination plane. In solution, fast interconversion between left- and right-twisted forms occurs. The twisting reflects the weak pi-accepting property of the central NHC in PC(NHC)P. The uneven extent of twisting among the three complexes further implies the low rotational barrier about the Pd-NHC bond. Related theoretical computations confirm the small rotational energy barrier about the Pd-NHC bond (ca. 4 kcal/mol). Catalytic applications of 4 and 5 have shown that the complexes are modest catalysts in Suzuki coupling. The complexes were active catalysts in Heck coupling reactions with the dicationic complex 5 being more effective than the monocationic complex 4.     

Homolytic alkylation of quinaldine and quinoxaline with 18-crown-6

Homolytic alkylation of protonated quinoxaline with 18-crown-6, initiated by the system pivalic acid-iron(II) sulfate at 20–25C, gives (quinoxalin-2-yl)-18-crown-6 in 85% yield. Under analogous conditions, the reaction with quinoline affords two isomers: (quinolin-4-yl)-18-crown-6 and (quinolin-2-yl)-18-crown-6, in yields of 20 and 30% respectively.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 75–76, January, 1988.     

Stepwise phosphine sulfide formation and metal-bridging reaction of tetradentate and tridentate phosphine ligands on palladium(II)

Kinetic studies on the stepwise phosphine sulfide formation reaction of the five-coordinate trigonal-bipyramidal Pd(II) complexes with the tripodal tetradentate phosphine ligand, [PdCl(pp₃)]Cl and [Pd(4-Cltp)(pp₃)](BF₄) (pp₃ = tris[2-(diphenylphosphino)ethyl]phosphine; 4-Cltp = 4-chlorothiophenolate), were carried out, and it was revealed that the reactions proceeded via the intermediate with a pendant dissociated phosphino group. Formation of the intermediate was utilized for the bridging reaction onto Pt(II) to form the phosphine-bridged linear trinuclear and cyclic tetranuclear mixed-metal complexes. Difference in the steric conversion mechanism in the phosphine-bridging reaction between the linear tridentate phosphine (bis[2-(diphenylphosphino)ethyl]phenylphosphine) and pp₃ is also reported.     

Preparation of anionic phosphine ligands in situ for the palladium-catalyzed Buchwald/Hartwig amination reactions of aryl halides

2-Phenylindenyl phosphine ligand can be changed into anionic phosphine ligand in situ and utilized in the palladium-catalyzed Buchwald/Hartwig amination reactions in DME, providing good to excellent yields of amination products from aryl chlorides, bromides and iodides. ³¹P NMR studies show that the resonance for the anionic phosphine appeared between those of the (2-phenylindenyl)-dicyclohexyl phosphonium salt and (2-phenylindenyl)dicyclohexylphosphine. The calculated results were consistent with the experimental results.     

A family of diruthenium compounds with dianionic tridentate ligands of N-(2-pyridyl)-2-oxy-5-R-benzylaminate (R = H, Me, Cl, Br, NO(2)): isolation, structure determination, and electrochemistry

The ligand substitution reaction of Ru(2)(O(2)CCH(3))(4)Cl with 5-substituted N-(2-pyridyl)-2-oxy-5-R-benzylaminate (R = H, Me, Cl, Br, NO(2)) resulted in a family of anionic diruthenium species of [Ru(2)(O(2)CCH(3))(2)(R-salpy)(2)](-) that were isolated by using Na(+)- or K(+)-18-crown-6-ether as the countercation: [A(18-crown-6)(S)(x)()][Ru(2)(O(2)CCH(3))(2)(R-salpy)(2)] (A = Na(+), K(+); S = solvent; R = H, 1; Me, 2; Cl, 3; Br, 4; NO(2), 5). All compounds were structurally characterized by X-ray crystallography. The structural features of the anionic parts are very similar among the compounds: two acetate and two R-salpy(2)(-) ligands are, respectively, located around the Ru(2) unit in a trans fashion, where the R-salpy(2)(-) ligand acts as a tridentate ligand having both bridging and chelating characters to form the M-M bridging/axial-chelating mode. Compounds 1 and 5 with K(+)-18-crown-6-ether have one-dimensional chain structures, the K(+)-18-crown-6-ether interacting with phenolate oxygens of the [Ru(2)(O(2)CCH(3))(2)(R-salpy)(2)](-) unit to form a repeating unit, [.K.O-Ru-Ru-O.], whereas 2-4 are discrete. Cyclic voltammetry and differential pulse voltammetry revealed systematic redox activities based on the dimetal center and the substituted ligand, obeying the Hammett law with the reaction constants per substituent, rho, for the redox processes being 127 mV for Ru(2)(5+)/Ru(2)(4+), 185 mV for Ru(2)(6+)/Ru(2)(5+), 92 mV for Ru(2)(7+)/Ru(2)(6+), and 179 mV for R-salpy(-)/R-salpy(2)(-). For 3, the singly oxidized and reduced species, Ru(2)(6+) and Ru(2)(4+), respectively, generated by bulk controlled-potential electrolyses were finally monitored by spectroscopy. The singly oxidized species can also be slowly generated by air oxidation.     

Cation-π Interactions. Synthesis and Crystal Structure of Palladium Complex: [K(DB18C6)]2[Pd(SCN)4]

A novel Pd(II)-dibenzo-18-crown-6 (DB18C6) complex [K(DB18C6)]2[Pd(SCN)4] has been isolated and characterized by X-ray diffraction analysis. In the solid state, it displays a quasi-one-dimensional infinite chain of two [K(DB18C6)] + complex cations and a [Pd(SCN)4]2- anion bridged by K+-p interactions between adjacent [K(DB18C6)] + units.     

The palladium-catalyzed cross-coupling reaction of carboxylic anhydrides with arylboronic acids: a DFT study

The mechanism of the cross-coupling of phenylboronic acid with acetic anhydride, a viable model of the widely used Suzuki reaction, has been studied by DFT calculations at the BP86/6-31G level of theory. Two alternative catalytic cycles have been investigated, one starting from a neutral Pd(0)L(2) complex, the other from an anionic "Jutand-type" [Pd(0)L(2)X](-) species. The reaction profiles are in good agreement with the experimental findings, as both pathways require only moderate activation energies. Both pathways are dominated by cis-configured square-planar palladium(II)diphosphine intermediates. Despite careful investigations, we did not find in this model reaction any evidence for five-coordinate palladium(II) intermediates, which are commonly believed to cause the profound effects of counterions in palladium-catalyzed transformations. Instead, our calculations suggest that the higher catalytic activity of anionic complexes, such as [Pd(PMe(3))(2)OAc](-), may arise from their stronger ability to coordinate to carbon electrophiles. The transmetalation sequence is the same for both catalytic cycles, involving the dissociation of one phosphine ligand from the palladium. In the decisive transition state, in which the phenyl group is transferred from boron to palladium, the acetate base is found to be in a bridging coordination between these two atoms.     

New palladium(II)-(eta(3/5)- or eta1-indenyl) and dipalladium(I)-(mu,eta3-indenyl) complexes

Reaction of the dimeric species [(eta3-Ind)Pd(mu-Cl)]2 (1) (Ind = indenyl) with NEt3 gives the complex (eta(3-5)-Ind)Pd(NEt3)Cl (3), whereas the analogous reactions with BnNH2 (Bn = PhCH2) or pyridine (py) afford the complexes trans-L2Pd(eta1-Ind)Cl (L = BnNH2 (4), py (5)). Similarly, the one-pot reaction of 1 with a mixture of BnNH2 and the phosphine ligands PR3 gives the mixed-ligand, amino and phosphine species (PR3)(BnNH2)Pd(eta1-Ind)Cl (R = Cy (6a), Ph (6b)); the latter complexes can also be prepared by addition of BnNH2 to (eta(3-5)-Ind)Pd(PR3)Cl (R = Cy (2a), Ph (2b)). Complexes 6 undergo a gradual decomposition in solution to generate the dinuclear Pd(I) compounds (mu,eta3-Ind)(mu-Cl)Pd2(PR3)2 (R = Cy (7a), Ph (7b)) and the Pd(II) compounds (BnNH2)(PR3)PdCl2 (R = Cy (8a), Ph (8b)), along with 1,1'-biindene. The formation of 7 is proposed to proceed by a comproportionation reaction between in situ-generated Pd(II) and Pd0 intermediates. Interestingly, the reverse of this reaction, disproportionation, also occurs spontaneously to give 2. All new compounds have been characterized by NMR spectroscopy and, in the case of 3, 4, 5, 6a, 7a, 7b, and 8a, by X-ray crystallography.     

一维链状冠醚配合物[k(18-C-6)]~2[M(NO~2)~4](H~2O)(M=Pd,Pt) 的合成与结构

研究了18-C-6分别与k~2[Pd(NO~2~4],k~2[Pt(NO~2)~4])的反应,并通过元素分析、红外光谱、单晶X射线衍射对生成的配合物[k(18-C-6)]~2[Pd(NO~2)~4](H~2O)~0.5(1)和[k(18-C-6)]~2,k~2[Pt(NO~2)~4])(H~2O)(2)进行了表征,两个配合匀匀为单斜晶系,空间P2~1/c.1的晶体学数据：α=1,7104(3),c=1,5763(3)nm,β=93.49(3)°,V=3.9987(14)nm^3,Z=4,D~c=1.507g/cm^3,F(000)=1880,R~1=0.0681,~wR~2=0.1004。2的晶体学数据：a=1.1312(3)nm,b=1.4227(2)nm,c=1.2266(3)nm,β93.141(10)°,V=1.9711(8)nm^3,Z=4,D~c=1.614g/cm^3,F(000)=936,R~1=0.0265,~wR~2=0.0721。在固态,配合物1具有[(18-c-6)]~2[Pd(NO~2)~4](H~2O)(1a)和[(18---c-6)]~2[Pd·(NO~2)~4](1b)两个分子,两者比例这1：1前者相邻的两个分子通过水分是的氧原子相连接形成一维链状结构,后者形面假一维链状结构,在配合物2中相邻的两个分子通过品分子中的氧原子相连接形成一维链状结构。     

Bis(isothiocyanato)bis(phosphine) complexes of group 10 metals: reactivity toward organic isocyanides

Treatment of Ni(NCS)2(PMe2Ph)2 with organic isocyanides CN-R gave five-coordinate isocyanide Ni(II) complexes, Ni(CN-R)(NCS)2(PMe2Ph)2 (R = C6H3-2,6-Me2 (1), t-Bu (2)). Interestingly, the corresponding reaction of Ni(NCS)2(P(n-Pr)3)2 with 2 equiv. of CN-t-Bu gave an unusual compound, which exists as an ion pair of the trigonal bipyramidal cation [Ni(P(n-Pr)3)2(CN-t-Bu)3]2+ (3) and the dinuclear NCS-bridged anion [Ni(1,3-micro-NCS)(NCS)3]2(2-) (4). In contrast, Pd(NCS)2(P(n-Pr)3)2 underwent substitution with 2 equiv. of CN-t-Bu to give the four-coordinate mono(isocyanide) Pd(II) complex Pd(NCS)(SCN)(CN-t-Bu)(P(n-Pr)3) (5) via phosphine dissociation. Reactions of M(NCS)2L2 (M = Pd, Pt; L = PMe3, PEt3, PMePh2, P(n-Pr)3) with two equiv. of CN-R (R = t-Bu, i-Pr, C6H3-2,6-Me2) gave the corresponding bis(isocyanide) complexes [M(CN-R)2(PR3)2](SCN)2 (7-13), except for Pd(NCS)2(PEt3)2 that reacted with CN-R' (R' = i-Pr, C6H3-2,6-Me2) and produced the mono(isocyanide) Pd(II) complexes [Pd(CN-R')(SCN)(PEt3)2](SCN) (14 and 15). Finally, treatment of M(NCS)2(PMe3)2 (M = Ni, Pd, Pt) with sterically bulky isocyanide CN-C6H3-2,6-i-Pr2 gave various products, (16-18) depending on the identity of the metal.     

Pd-catalysed regioselective C-H functionalisation of 2-pyrones

A new synthetic methodology for the catalytic C-H functionalisation of 2-pyrones is described which proceeds regioselectively at the C3 position, mirroring the observed regioselectivity in 6π-electrocyclisation/oxidative aromatisation reactions of related compounds. Insight into the reaction mechanism is provided, with support for a neutral palladium(II) pathway. Cationic palladium(II) complexes possessing 2-pyrones are unstable and readily undergo Pd(II)→P transfer at ambient temperature resulting in phosphonium salt formation (and Pd(0)L(n) species).     

Stereoselective preparation, structures, and reactivities of phosphine-bridged mixed-metal trinuclear and pentanuclear complexes with tris[2-(diphenylphosphino)ethyl]phosphine

The phosphine-bridged linear trinuclear and pentanuclear complexes with Pd(II)-Pt(II)-Pd(II), Ni(II)-Pt(II)-Ni(II), and Rh(III)-Pd(II)-Pt(II)-Pd(II)-Rh(III) metal-ion sequences were almost quantitatively formed by the stepwise phosphine-bridging reaction of the terminal phosphino groups of tris[2-(diphenylphosphino)ethyl]phosphine (pp3), which is the tetradentate bound ligand of the starting Pd(II) and Ni(II) complexes. The solid-state structures of the trinuclear complexes were determined by X-ray structural analyses, and the structures of the polynuclear complexes in solution were characterized by NMR spectroscopy. The trans and cis isomers of the trinuclear and pentanuclear complexes, which arise from the geometry around the Pt(II) center, were selectively obtained simply by changing the counteranion of the starting complexes: the tetrafluoroborate salts, [MX(pp3)](BF4) [M = Pd(II) or Ni(II), X = Cl- or 4-chlorothiophenolate (4-Cltp-)], gave only the trans isomers, and the chloride salt, [PdCl(pp3)]Cl, gave only the cis isomers. The formation of the trinuclear complex with the 4-Cltp- and chloro ligands, trans-[Pt(4-Cltp)2{PdCl(pp3)}2](BF4)2, proceeded with exchange between the thiolato ligand in the starting Pd(II) complex, [Pd(4-Cltp)(pp(3))](BF4), and the chloro ligands in the starting Pt(II) complex, trans-[PtCl2(NCC6H5)2], retaining the trans geometry around the Pt(II) center. In contrast, the formation reaction between [PdCl(pp3)]Cl and trans-[PtCl2(NCC6H5)2] was accompanied by the trans-to-cis geometrical change on the Pt(II) center to give the trinuclear complex, cis-[PtCl2{PdCl(pp3)}2]Cl2. The mechanisms of these structural conversions during the formation reactions were elucidated by the 31P NMR and absorption spectral changes. The differences in the catalytic activity for the Heck reaction were discussed in connection with the bridging structures of the polynuclear complexes in the catalytic cycle.     

Highly air-stable anionic mononuclear and neutral binuclear palladium(II) complexes for C-C and C-N bond-forming reactions

The short-bite aminobis(phosphonite), PhN{P(-OC10H6(mu-S)C10H6O-)}2 (2), containing a mesocyclic thioether backbone is synthesized by either treating PhN(PCl2)2 with 2 equiv of thiobis(2,2'-naphthol) or reacting chlorophosphite (-OC10H6(mu-S)C10H6O-)PCl (1) with aniline in the presence of a base. Treatment of 2 with an equimolar amount of Pd(COD)Cl2 in the presence of H2O affords a P-N-P-bridged and P,S-metalated binuclear complex, [PhN(P(-OC10H6(mu-S)C10H6O-)-kappaP)2Pd2Cl2{P(-OC10H6(mu-S)C10H6O-)(O)-kappaP,kappaS}2] (3), whereas the same reaction with 2 equiv of Pd(COD)Cl2 in the presence of H2O and Et3N produces the mononuclear anionic complex [{(-OC10H6(mu-S)C10H6O-)P(O)-kappaP,kappaS}PdCl2](Et3NH) (5). By contrast, reaction of 2 with 2 equiv of Pd(COD)Cl2 and H2O in the absence of Et3N gives the hydrogen phosphonate coordinated complex [{(-OC10H6(mu-S)C10H6O-)P(OH)}PdCl2] (4) which converts to the anionic complex in solution or in the presence of a base. Compound 2 on treatment with Pt(COD)X2 (X = Cl or I) afforded P-coordinated four-membered chelate complexes [PhN(P(-OC10H6(mu-S)C10H6O-)-kappaP)2PtX2] (6 X = Cl, 7 X = I). The crystal structures of compounds 2, 3, 5, and 7 are reported. Compound 3 is the first example of a crystallographically characterized binuclear palladium complex containing a bidentate bridging ligand and its hydrolyzed fragments forming metallacycles containing a palladium-phosphorus sigma bond. All palladium complexes proved to be very good catalysts for the Suzuki-Miyaura and Mizoroki-Heck cross-coupling and amination reactions with excellent turnover numbers (TON up to 1.46 x 105 in the case of the Suzuki-Miyaura reaction).     

Dimers of heptapnictide anions: As14 4- and P14 4- in the crystal structures of [Rb(18-crown-6)]4As14.6NH3 and [Li(NH3)4]4P14.NH3

Compounds [Rb(18-crown-6)]4As14.6NH3 (1) and [Li(NH3)4]4P14.NH3 (2) were prepared by the reaction of Rb4As6 with SbPh3 and 18-crown-6 and by the reduction of white phosphorus with elemental lithium in liquid ammonia, respectively. Both were characterized by low-temperature single-crystal X-ray structure analysis. They were found to contain the Ci symmetrical Pn14(4-) anion (Pn = P, As), which consists of two nortricyclane-like Pn7-cages connected by a single bond. Molecular complexes of [Rb(18-crown-6)(NH3)]2[Rb(18-crown-6)]2As14 are formed in 1, which are connected to fanfold sheets via N-H...O bonds. The anion is isolated in 2, and N-H...N bonds result in the formation of {[Li(NH3)4](mu-NH3)2[Li(NH3)4]}2+ cationic complexes.