Linear metal-metal-bonded tetranuclear M-Mo-Mo-M complexes (M = Ir and Rh): oxidative metal-metal bond formation in a tetrametallic system and 1,4-addition reaction of alkyl halides

Reaction of Mo2(pyphos)4 (1) with [MCl(CO)2]2 (M = Ir and Rh) afforded linear tetranuclear complexes of a formula Mo2M2(CO)2(Cl)2(pyphos)4 (2, M = Ir; 3, M = Rh). X-ray diffraction studies confirmed that two "MCl(CO)" fragments are introduced into both axial sites of the Mo2 core in 1 and coordinated by two PPh2 groups in a trans fashion, thereby forming a square-planar geometry around each M(I) metal. Treatment of 2 and 3 with an excess amount of tBuNC and XylNC induced dissociation of the carbonyl and chloride ligands to yield the corresponding dicationic complexes [Mo2M2(pyphos)4(tBuNC)4](Cl)2 (5a, M = Ir; 6a, M = Rh) and [Mo2M2(pyphos)4(XylNC)4](Cl)2 (7, M = Ir; 8, M = Rh). Their molecular structures were characterized by spectroscopic data as well as X-ray diffraction studies of BPh4 derivatives [Mo2M2(pyphos)4(tBuNC)4](BPh4)2 (5b, M = Ir; 6c, M = Rh), which confirmed that there is no direct sigma-bonding interaction between the M(I) atom and the Mo2 core. The M(I) atom in 5 and 6 can be oxidized by either 2 equiv of [Cp2Fe][PF6] or an equimolar amount of I2 to afford Mo(II)2M(II)2 complexes, [Mo2M2(X)2(tBuNC)4(pyphos)4]2+ in which two Mo-M(II) single bonds are formed and the bond order of the Mo-Mo moiety has been decreased to three. The Ir(I) complex 5a reacted not only with methyl iodide but also with dichloromethane to afford the 1,4-oxidative addition products [Mo2Ir2(CH3)(I)(tBuNC)4(pyphos)4](Cl)2 (13) and [Mo2Ir2(CH2Cl)(Cl)(tBuNC)4(pyphos)4](Cl)2 (15), respectively, although the corresponding reactions using the Rh(I) analogue 6 did not proceed. Kinetic analysis of the reaction with CH3I suggested that the 1,4-oxidative addition to the Ir(I) complex occurs in an SN2 reaction mechanism.     

A new atropisomeric P,N ligand for rhodium-catalyzed asymmetric hydroboration

A new optically active and large dihedral angle atropisomeric P,N ligand, pyphos, which contains a tertiary phosphine and pyridine moiety, was prepared and resolved through diastereomeric complexation with chiral palladium amine complexes. The hexafluorophosphate salt of the diastereomers were found to be separable by fractional recyrstallization, while the corresponding chloride salt did not. [Rh(COD)pyphos]PF(6) complex was synthesized by metalation of pyphos with [Rh(COD)Cl](2) followed by anion exchange with NH(4)PF(6) in excellent yield, and the target rhodium complex was characterized by single-crystal X-ray crystallography. The chiral cationic rhodium complex was utilized in the enantioselective hydroboration of vinylarenes. Excellent regioselectivity and good enantioselectivity were observed, and the ee values were found to be dependent on the electronic properties of para-substituted styrenes.     

Synthesis, structure, and reactivity of rhodium and iridium complexes of the chelating bis-sulfoxide tBuSOC2H4SOtBu. Selective O-H activation of 2-hydroxy-isopropyl-pyridine

The chloro-bridged rhodium and iridium complexes [M2(BTSE)2Cl2] (M = Rh 1, Ir 2) bearing the chelating bis-sulfoxide tBuSOC2H4SOtBu (BTSE) were prepared by the reaction of [M2(COE)4Cl2] (M = Rh, Ir; COE = cyclooctene) with an excess of a racemic mixture of the ligand. The cationic compounds [M(BTSE)2][PF6] (M = Rh 3, Ir 4), bearing one S- and one O-bonded sulfoxide, were also obtained in good yields. The chloro-bridges in 2 can be cleaved with 2-methyl-6-pyridinemethanol and 2-aminomethyl pyridine, resulting in the iridium(I) complexes [Ir(BTSE)(Py)(Cl)] (Py = 2-methyl-6-pyridinemethanol 5, 2-aminomethyl-pyridine 6). In case of the bulky 2-hydroxy- isopropyl-pyridine, selective OH oxidative addition took place, forming the Ir(III)-hydride [Ir(BTSE)(2-isopropoxy-pyridine)(H)(Cl)] 7, with no competition from the six properly oriented C-H bonds. The cationic rhodium(I) and iridium(I) compounds [M(BTSE)(2-aminomethyl-pyridine)][X] (M = Rh 8, Ir 10), [Rh(BTSE)(2-hydroxy- isopropyl-pyridine)][X] 9(stabilized by intramolecular hydrogen bonding), [Ir(BTSE)(pyridine)2][PF6] 12, [Ir(BTSE)(alpha-picoline)2][PF6] 13, and [Rh(BTSE)(1,10-phenanthroline)][PF6] 14 were prepared either by chloride abstraction from the dimeric precursors or by replacement of the labile oxygen bonded sulfoxide in 3 or 4. Complex 14 exhibits a dimeric structure in the solid state by pi-pi stacking of the phenanthroline ligands.     

Rhodium dimers with 2,2-dimethyl-1,3-diisocyano and bis(diphenylphosphino)methane bridging ligands

Four rhodium dimers have been synthesized with a bridging diisocyanide ligand, dmb (2,2-dimethyl-1,3-diisocyanopropane): [Rh2(dmb)4](BPh4)2, [Rh2(dmb)4Cl2]Cl2, [Rh2(dmb)4I2](PF6)2, and [Rh2(dmb)2(dppm)2](BPh4)2 (dppm = bis(diphenylphosphino)methane). The complexes have been characterized by elemental analysis and mass spectrometry, as well as UV-visible, IR, and 1H NMR spectroscopies. X-ray crystal structures of the rhodium(I) complexes, [Rh2(dmb)4](BPh4)2 . 1.5CH3CN (3.2330(4), 3.2265(4) A) and [Rh2(dmb)2(dppm)2](BPh4)2.0.5CH3OH . 0.2H2O (3.0371(5) A), confirm the existence of short Rh...Rh interactions. The metal-metal separation for the rhodium(II) adduct, [Rh(2)(dmb)4Cl2]Cl2.6CHCl3 (2.8465(6) A), is consistent with a formal Rh-Rh bond. For the two luminescent rhodium(I) dimers and six previously investigated diisocyano-bridged dimers with and without dppm ligands, the intense spin-allowed dsigma-->psigma absorption band maximum shifts to longer wavelengths with decreasing Rh...Rh separation, and there is an approximate correlation between band energy and the inverse of the metal-metal separation cubed. Both [Rh2(dmb)4]2+ and [Rh2(dmb)4(dppm)2]2+ undergo oxidative addition in the presence of iodine. In the conversion of [Rh2(dmb)4]2+ to [Rh2(dmb)4I2]2+, the observed intermediate is tentatively assigned to a tetramer composed of two rhodium dimers. In the case of [Rh2(dmb)2(dppm)2]2+, no intermediate was detected.     

Linear Trinuclear Pt.Mo-Mo Complexes [Mo(2)PtX(2)(pyphos)(2)(O(2)CR)(2)](2) (X = Cl, Br, I; R = CH(3), C(CH(3))(3); pyphos = 6-(Diphenylphosphino)-2-pyridonate) with an Axial Interaction between the Quadruply Bonded Mo(2) Moiety and the Platinum Atom

An example of a direct axial interaction of a platinum(II) atom with a Mo(2) core through a uniquely designed tridentate ligand 6-(diphenylphosphino)-2-pyridonate (abbreviated as pyphos) is described. Treatment of PtX(2)(pyphosH)(2) (2a, X = Cl; 2b, X = Br; 2c, X = I) with a 1:1 mixture of Mo(2)(O(2)CCH(3))(4) and [Mo(2)(O(2)CCH(3))(2)(NCCH(3))(6)](2+) (3a) in dichloromethane afforded the linear trinuclear complexes [Mo(2)PtX(2)(pyphos)(2)(O(2)CCH(3))(2)](2) (4a, X = Cl; 4b, X = Br; 4c, X = I). The reaction of [Mo(2)(O(2)CCMe(3))(2)(NCCH(3))(4)](2+) (3b) with 2a-c in dichloromethane afforded the corresponding pivalato complexes [Mo(2)PtX(2)(pyphos)(2)(O(2)CCMe(3))(2)](2) (5a, X = Cl; 5b, X = Br; 5c, X = I), whose bonding nature is discussed on the basis of the data from Raman and electronic spectra as well as cyclic voltammograms. The linear trinuclear structures in 4b and 5a-c were confirmed by NMR studies and X-ray analyses: 4b, monoclinic, space group C2/c, a = 34.733(4) ?, b = 17.81(1) ?, c = 22.530(5) ?, beta = 124.444(8) degrees, V = 11498(5) ?(3), Z = 8, R = 0.060 for 8659 reflections with I > 3sigma(I) and 588 parameters; 5a, triclinic, space group P&onemacr;, a = 13.541(3) ?, b = 17.029(3) ?, c = 12.896(3) ?, alpha = 101.20(2) degrees, beta = 117.00(1) degrees, gamma = 85.47(2) degrees, V = 2599(1) ?(3), Z = 2, R = 0.050 for 8148 reflections with I > 3sigma(I) and 604 parameters; 5b, triclinic, space group P&onemacr;, a = 12.211(2) ?, b = 20.859(3) ?, c = 10.478(2) ?, alpha = 98.88(1) degrees, beta = 112.55(2) degrees, gamma = 84.56(1) degrees, V = 2433.3(8) ?(3), Z = 2, R = 0.042 for 8935 reflections with I > 3sigma(I) and 560 parameters; 5c, monoclinic, space group P2(1)/n, a = 13.359(4) ?, b = 19.686(3) ?, c = 20.392(4) ?, beta = 107.92(2) degrees, V = 5101(2) ?(3), Z = 4, R = 0.039 for 8432 reflections with I > 3sigma(I) and 560 parameters.     

Synthesis and characterization of ethylbis(2-pyridylethyl)amineruthenium complexes and two different types of C-H bond cleavage at an ethylene arm

Ruthenium complexes bearing ethylbis(2-pyridylethyl)amine (ebpea), which has flexible -C(2)H(4)- arms between the amine and the pyridyl groups and coordinates to a metal center in facial and meridional modes, have been synthesized and characterized. Three trichloro complexes, fac-[Ru(III)Cl(3)(ebpea)] (fac-[1]), mer-[Ru(III)Cl(3)(ebpea)] (mer-[1]), and mer-[Ru(II)Cl(3){η(2)-N(C(2)H(5))(C(2)H(4)py)═CH-CH(2)py}] (mer-[2]), were synthesized using the Ru blue solution. Formation of mer-[2] proceeded via a C-H activation of the CH(2) group next to the amine nitrogen atom of the ethylene arm. Reduction reactions of fac- and mer-[1] afforded a triacetonitrile complex mer-[Ru(II)(CH(3)CN)(3)(ebpea)](PF(6))(2) (mer-[3](PF(6))(2)). Five nitrosyl complexes fac-[RuX(2)(NO)(ebpea)]PF(6) (X = Cl for fac-[4]PF(6); X = ONO(2) for fac-[5]PF(6)) and mer-[RuXY(NO)(ebpea)]PF(6) (X = Cl, Y = Cl for mer-[4]PF(6); X = Cl, Y = CH(3)O for mer-[6]PF(6); X = Cl, Y = OH for mer-[7]PF(6)) were synthesized and characterized by X-ray crystallography. A reaction of mer-[2] in H(2)O-C(2)H(5)OH at room temperature afforded mer-[1]. Oxidation of C(2)H(5)OH in H(2)O-C(2)H(5)OH and i-C(3)H(7)OH in H(2)O-i-C(3)H(7)OH to acetaldehyde and acetone by mer-[2] under stirring at room temperature occurred with formation of mer-[1]. Alternative C-H activation of the CH(2) group occurred next to the pyridyl group, and formation of a C-N bond between the CH moiety and the nitrosyl ligand afforded a nitroso complex [Ru(II)(N(3))(2){N(O)CH(py)CH(2)N(C(2)H(5))C(2)H(4)py}] ([8]) in reactions of nitrosyl complexes with sodium azide in methanol, and reaction of [8] with hydrochloric acid afforded a corresponding chloronitroso complex [Ru(II)Cl(2){N(O)CH(py)CH(2)N(C(2)H(5))C(2)H(4)py}] ([9]).     

Dimolybdenum bis-2,4,6-triisopropyl-benzoate bis-4-isonicotinate: a redox active analogue of 4,4'-bipyridine with ambivalent properties

The reaction between Mo2(TiPB)4 and 4-iso-nicotinic acid (2 equiv) in ethanol leads to the formation of trans-Mo2(TiPB)2(nic)2, I, where TiPB = 2,4,6-triisopropylbenzoate and nic = 4-isonicotinate. The molecular structures of I and I x 2DMSO were determined in the solid state by a single-crystal X-ray study, and its electronic structure was determined by DFT calculations on a model compound, where formate ligands were substituted for the bulky TiPB. The physicochemical properties of I are reported, and its potential as a redox active building block, a quasi-metalloorganic analogue of 4,4'-bipyridine, is described in the synthesis of molecular and solid-state assemblies. The molecular structure of I in the solid state consists of a 3-dimensional network in which each unit of Mo2(TiPB)2(nic)2 acts as a donor and acceptor via N to Mo coordination. In the structure of I x 2DMSO, the DMSO ligands coordinate axially with the Mo-Mo bond via oxygen. The reaction between I and Rh2(O2CMe)4 is shown to give a 1-D polymeric chain in the solid state: [{Rh2(O2CMe)4}{Mo2(TiPB)2(nic)2}] infinity, II. A similar structure was found for the product involving Rh2(O2CCMe3)4. Evidence is also reported for the formation of [(1,5-COD)MePt]2[mu-Mo2(TiPB)2(nic)2](PF6)2, III, and [(1,5-COD)Pt(mu-I)(PF6)2]n.     

Heterobimetallic, cubane-like Mo(3)S(4)M' cluster cores containing the noble metals M' = Ru, Os, Rh, Ir. Unprecedented tri(mu-carbonyl) bridge between ruthenium atoms in [(eta(5)-Cp')(3)Mo(3)S(4)Ru)2(mu-CO)3]2+

Reaction of the methylcyclopentadienyl (Cp') cluster compound [(eta(5)-Cp')(3)Mo(3)S(4)][pts] (pts = p-toluenesulfonate) with noble metal alkene complexes resulted in the formation of four new heterobimetallic cubane-like Mo(3)S(4)M' cluster cores (M' = Ru, Os, Rh, Ir). Thus, reaction with [(1,5-cod)Ru(CO)(3)] or [(1,3-cod)Os(CO)(3)] (cod = cyclooctadiene) afforded [(eta(5)-Cp')(3)Mo(3)S(4)M'(CO)(2)][pts] (M' = Ru: [1][pts]; M' = Os: [2][pts]). When [1][pts] was kept in CH(2)Cl(2)/pentane solution, partial loss of carbonyl ligands occurred and the carbonyl-bridged dicubane cluster [((eta(5)-Cp')(3)Mo(3)S(4)Ru)(2)(mu-CO)(3)][pts](2) was isolated. An X-ray crystal structure revealed the presence of the hitherto unobserved Ru(mu-CO)(3)Ru structural element. The formation of cluster compounds containing Mo(3)S(4)Rh and Mo(3)S(4)Ir cores was achieved in boiling methanol by reacting [(eta(5)-Cp')(3)Mo(3)S(4)][pts] with [M'Cl(cyclooctene)(2)](2) (M' = Rh, Ir) in the presence of PPh(3). In this way [(eta(5)-Cp')(3)Mo(3)S(4)M'Cl(PPh(3))][pts] (M' = Rh, Ir) could be isolated. An alternative route to the Mo(3)S(4)Rh cluster core was found in the reaction of [(eta(5)-Cp')(3)Mo(3)S(4)][pts] with [RhCl(1,5-cod)](2), which yielded [(eta(5)-Cp')(3)Mo(3)S(4)Rh(cod)][pts](2) ([7][pts](2)). Substitution of the cod ligand in [7][pts](2) by 1,3-bis(diphenylphosphanyl)propane (dppp) gave [(eta(5)-Cp')(3)Mo(3)S(4)Rh(dppp)][pts](2).     

Syntheses and characterization of oxygen/sulfur-bridged incomplete cubane-type clusters, [Mo3S4Tp3]+ and [Mo3OS3Tp3]+, and a mixed-metal cubane-type cluster, [Mo3FeS4ClTp3]. X-ray structures of [Mo3S4Tp3]Cl, [Mo3OS3Tp3]PF6, and [Mo3FeS4ClTp3

The reaction of [Mo3S4(H2O)9]4+ (1) with hydrotris(pyrazolyl)borate (Tp) ligands produced [Mo3S4Tp3]Cl x 4 H2O ([3]Cl x 4 H2O) in an excellent yield. An X-ray structure analysis of [3]Cl x 4 H2O revealed that each molybdenum atom bonded to the Tp ligand. We report four salts of 3, [3]Cl x 4 H2O, [3]tof x 2 H2O, [3]PF6 x H2O, and [3]BF4 x 2 H2O in this paper. The solubility and stability of the chloride salt in organic solvents differ completely from those of the other salts. We have also prepared a new compound, [Mo3OS3Tp3]PF6 x H2O ([4]PF6 x H2O), via the reaction of [Mo3OS3(H2O)9]4+ (2) with KTp in the presence of NH4PF6. All the molybdenum atoms bonded to Tp ligand. 1H NMR signals corresponding to nine protons bonded to three pyrazole rings in one Tp were observed in a spectrum (at 253 K) of [3]BF4 x 2 H2O. It shows that cluster 3 has a 3-fold rotation axis in CD2Cl2 solution. Twenty-one 1H NMR signals corresponding to twenty-seven protons bonded to nine pyrazole rings in three Tp ligands were observed in a spectrum (at 233 K) of [4]PF6 x H2O; obviously, 4 has no 3-fold rotation axis, in contrast to 3. The short CH...mu3S distance caused large upfield chemical shifts in the 1H NMR spectra of 3 and 4. The reaction of 3 with metallic iron in CH2Cl2 produced [Mo3FeS4XTp3] (X = Cl (5), Br (6)). X-ray structure analysis of 5 has revealed the existence of a cubane-type core Mo3FeS4. Complex 3 functions as a metal-complex ligand for preparing a novel mixed-metal complex even in nonaqueous solvents. The cyclic voltammogram of 5 shows two reversible one-electron couples (E(1/2) = -1.40 and 0.52 V vs SCE) and two irreversible one-electron oxidation processes (E(pc) = 1.54 and 1.66 V vs SCE).     

3[(dx2-y2,dxy)(pz)] excited state of binuclear copper(I) phosphine complexes: effect of copper-ligand and copper-copper interactions on excited state properties and photocatalytic reductions of the 4,4'-dimethyl-2,2'-bipyridinium ion in alcohols

A comprehensive study of the structural and spectroscopic properties of two-, three-, and four-coordinate copper(I) complexes with aliphatic phosphine ligands is presented. All complexes described in this work are characterized by X-ray crystallography. The intramolecular Cu...Cu separations in [Cu2(dcpm)2]X2, [Cu2(dcpm)2-(CH3CN)2]X2, and [Cu2(dmpm)3]-(ClO4)2 (dcpm=bis(dicyclohexylphosphino)methane; dmpm=bis(dimethylphosphino)methane; X=ClO4- and PF6-) are in the range 2.639(2)-3.021(2) A. The anion...CuI interaction is weak, as evidenced by the nearest O...Cu separation of 2.558(6) A in [Cu2(dcpm)2](ClO4)2 and the closest Cu...F separation of 2.79(1) A in [Cu2(dcpm)2](PF6)2. The absorption bands of [Cu2(dcpm)2]X2 and [Cu2(dcpm)2(CH3CN)2]X2 (X=ClO4- and PF6-) at lambda max 307-311 nm in CH2Cl2 are assigned as 1[3d sigma* --> 4p sigma] transitions; this has been confirmed by resonance Raman spectroscopy. The triplet emissions in the visible region from these complexes exhibit long lifetimes and are sensitive to the environment. The lowest emissive excited state is tentatively ascribed as 3[(dx2-y2, dxy)(pz)] in nature. For [Cu2(dcpm)2]2+ salts in CH3CN, the emissive species is postulated to be [Cu2(dcpm)2(CH3CN)n]2+ (n > or = 3). Efficient photocatalytic reduction of MV2+ (4,4'-dimethyl-2,2'-bipyridinium) to MV+ in alcoholic solutions by using [Cu2(dcpm)2](PF6)2 or [Cu2(dppm)2(CH3CN)4](ClO4)2 (dppm=bis(diphenylphosphino)methane) as a catalyst has been observed. The addition of CH3CN or use of [Cu2(dmpm)3]-(ClO4)2 as a catalyst did not allow photocatalytic reduction processes to occur.     

Cationic and neutral diphenyldiazomethanerhodium(I) complexes as catalytically active species in the C-C coupling reaction of olefins and diphenyldiazomethane

Cationic rhodium(I) complexes cis-[Rh(acetone)2(L)(L')]+ (2: L = L'=C8H14; 3: L=C8H14; L'=PiPr3; 4: L=L'=PiPr3), prepared from [RhCl(C8H14)2]2] and isolated as PF6 salts, catalyze the C-C coupling reaction of diphenyldiazomethane with ethene, propene, and styrene. In most cases, a mixture of isomeric olefins and cyclopropanes were obtained which are formally built up by one equivalent of RCH=CH2 (R = H, Me, Ph) and one equivalent of CPh2. The efficiency and selectivity of the catalyst depends significantly on the coordination sphere around the rhodium(I) center. Treatment of 4 with Ph2CN2 in the molar ratio of 1:1 and 1:2 gave the complexes trans-[Rh(PiPr3)2(acetone)(eta1-N2CPh2)]PF6 (8) and trans-[Rh(PiPr3)2(eta1-N2CPh2)2]PF6 (9), of which 8 was characterized by X-ray crystallography. Since 8 and 9 not only react with ethene but also catalyze the reaction of C2H4 and free Ph2CN2, they can be regarded as intermediates (possibly resting states) in the C-C coupling process. The lability of 8 and 9 is illustrated by the reactions with pyridine and NaX (X=Cl, Br, I, N3) which afford the mono(diphenyldiazomethane)rhodium(I) compounds trans-[Rh(PiPr3)2(py)(eta1-N2CPh2)]PF6 (10) and trans-[RhX(eta1-N2CPh2)(PiPr3)2] (11-14), respectively. The catalytic activity of the neutral complexes 11 - 14 is somewhat less than that of the cationic species 8, 9 and decreases in the order Cl > Br> I > N3.     

Butterfly and Nest-Shaped Tp*-W-Cu-S Cluster Monomers and Dimers with Hexamethylenetetramine as Ligand: Anion-Dependent Structures and Nonlinear Optical Properties

The assembly of[Et4N][Tp*WS3](1) with CuX (Tp* =hydridotris(3,5-dimethylpyrazol-1-yl)borate;X =Cl,Br,and I) or[Cu(MeCN)4][PF6]in the presence of tetratopic liga...     

Assembly of a new family of mercury(II) zwitterionic thiolate complexes from a preformed compound [Hg(Tab)2](PF6)2 [Tab = 4-(trimethylammonio)benzenethiolate

Reactions of Hg(OAc)2 with 2 equiv of TabHPF6 [TabH = 4-(trimethylammonio)benzenethiol] in MeCN/MeOH afforded a mononuclear linear complex [Hg(Tab)2](PF6)2 (1). By using 1 as a precursor, a new family of mercury(II) zwitterionic thiolate complexes, [Hg2(Tab)6](PF6)4.2MeCN (2.2MeCN), [Hg(Tab)2(SCN)](PF6) (3), [Hg(Tab)2(SCN)2] (4), [Hg(Tab)I2] (5), {[Hg(Tab)2]4[HgI2][Hg2I6]}(PF6)2(NO3)4 (6), [Hg(Tab)2][HgI4] (7), [Hg(Tab)2][HgCl2(SCN)2] (8), [Tab-Tab]2[Hg3Cl10] (9), and [Hg2(Tab)6]3(PF6)Cl11 (10), were prepared and characterized by elemental analysis, IR spectra, UV-vis spectra, 1H NMR, and single-crystal X-ray crystallography. The [Hg2(Tab)6]4+ tetracation of 2 or 10 contains an asymmetrical Hg2S2 rhomb with an inversion center lying on the midpoint of the Hg...Hg line. The Hg atom of the [Hg(Tab)2]2+ dication of 3 is coordinated to one SCN-, forming a rare T-shaped coordination geometry, while in 4, the Hg atom of [Hg(Tab)2]2+ is coordinated to two SCN-, forming a seesaw-shaped coordination geometry. Through weak secondary Hg...S coordinations, each cation in 3 is further linked to afford a one-dimensional zigzag chain. The trigonal [Hg(Tab)I2] molecules in 5 are held together by weak secondary Hg...I and Hg...S interactions, forming a one-dimensional chain structure. In 6, the four [Hg(Tab)2]2+ dications, one HgI2 molecule, one [Hg2I6]2- dianion, one PF6-, and four NO3- anions are interconnected by complicated secondary Hg...I and Hg...O interactions, forming a scolopendra-like chain structure. The secondary Hg...I interactions, [Hg(Tab)2]2+ and [HgI4]2- in 7, are combined to generate a one-dimensional chain structure, while [Hg(Tab)2]2+ and [HgCl2(SCN)2]2- in 8 are interconnected by secondary Hg...N interactions to form a one-dimensional zigzag chain structure. Compound 9 consists of two [Tab-Tab]2+ dications and one [Hg3Cl10]4- tetraanion. The facile approach to the construction of 2-8 and 10 from 1 may be applicable to the mimicking of a coordination sphere of the Hg sites of metallothioneins.     

Autoionization of homogeneous nickel(II) diphosphane hydrogenation catalysts. An NMR study and crystal structures of [Ni(o-MeO-dppe)I2] and [Ni(o-MeO-dppe)I2](PF6)2

The synthesis of a number of nickel(II) complexes containing the didentate phosphane ligand 1,2-bis(di(o-methoxyphenyl)phosphino)ethane (o-MeO-dppe) is reported. Two types of complexes have been synthesized, i.e., the mono(chelate) complex (1) of the general formula [Ni(o-MeO-dppe)X2] (where X = Cl, Br or I) and the bis(chelate) complex (2) of the general formula [Ni(o-MeO-dppe)2]Y2 (where Y = PF6 or trifluoroacetate (TFA)). These complexes have been characterized using electronic absorption and NMR spectroscopy. The structures of the mono(chelate) complex [Ni(o-MeO-dppe)I2] (1c) and of the bis(chelate) complex [Ni(o-MeO-dppe)2](PF6)2 (2e) have been determined by X-ray crystallography. [Ni(o-MeO-dppe)I2] crystallizes in the monoclinic space group P2(1)/c with Z = 4, a = 12.1309(1) A, b = 16.5759(3) A, c = 17.6474(2) A, beta = 119.3250(10) degrees. [Ni(o-MeO-dppe)2](PF6)2 crystallizes in the monoclinic space group C2/c with Z = 4, a = 22.5326(3) A, b = 13.6794(2) A, c = 21.7134(3) A, beta = 107.1745(7) degrees. In both structures the nickel ion is in a square-planar geometry with a NiP2I2 and NiP4 chromophore, respectively. Using 1H and 31P[1H] NMR spectroscopy the behavior of the complexes in various solvents has been studied. It appears that in solution these nickel complexes are involved in an autoionization equilibrium: 2[Ni(o-MeO-dppe)X2] <==>[Ni(o-MeO-dppe)2](2+) + ["NiX(4)"](2-). The ionized complex (3) consists of a cationic unit in which a nickel atom is surrounded by two didentate phosphane ligands, and an anionic unit that stoichiometrically consists of a nickel atom and four anions. The position of the autoionization equilibrium is highly dependent on the anion and the solvent used. In a polar solvent in combination with weakly coordinating anions only the ionized complex is observed, whereas in an apolar solvent in combination with coordinating anions only the mono(chelate) complex occurs. A comparison of the behavior of o-MeO-dppe with its unsubstituted analogue dppe in combination with nickel(II) acetate using 31P[1H] NMR spectroscopy shows that the latter is more readily oxidized.     

Various forms of linear dipyridyls in discrete rectangles, dinuclear rods, and one-dimensional networks containing (eta5-pentamethylcyclopentadienyl)rhodium(III)

[Cp*Rh(eta1-NO3)(eta2-NO3)] (1) reacted with pyrazine (pyz) to give a dinuclear complex [Cp*Rh(eta1-NO3)(mu-pyz)(0.5)]2.CH2Cl2(3.CH2Cl2). Tetranuclear rectangles of the type [Cp*Rh(eta1,mu-X)(mu-L)(0.5)]4(OTf)4(4a: X = N3, L = bpy; 4b: X = N3, L = bpe; 4c: X = NCO, L = bpy) were prepared from [Cp*Rh(H2O)3](OTf)2 (2), a pseudo-halide (Me3SiN3 or Me3SiNCO), and a linear dipyridyl [4,4'-bipyridine (bpy) or trans-1,2-bis(4-pyridyl)ethylene (bpe)] by self-assembly through one-pot synthesis at room temperature. Treating complex with NH4SCN and dipyridyl led to the formation of dinuclear rods, [Cp*Rh(eta1-SCN)3]2(LH2) (5a: L = bpy; 5b: L = bpe), in which two Cp*Rh(eta1-SCN)3 units are connected by the diprotonated dipyridyl (LH2(2+)) through N(+)-H...N hydrogen bonds. Reactions of complex 2 with 1-(trimethylsilyl)imidazole (TMSIm) and dipyridyl (bpy or bpe) also produced another family of dinuclear rods [Cp*Rh(ImH)3]2.L (6a: L = bpy; 6b: L = bpe). Treating 1 and 2 with TMSIm and NH4SCN (in the absence of dipyridyl) generated a 1-D chain [Cp*Rh(ImH)3](NO3)2 (7) and a 1-D helix [Cp*Rh(eta1-SCN)2(eta1-SHCN)].H2O (8.H2O), respectively. The structures of complexes 3.CH2Cl2, 4a.H2O, 4c.2H2O, 5b, 6a, 7 and 8.H2O were determined by X-ray diffraction.     

New diphosphine ligands containing ethyleneglycol and amino alcohol spacers for the rhodium-catalyzed carbonylation of methanol

The new diphosphine ligands Ph(2)PC(6)H(4)C(O)X(CH(2))(2)OC(O)C(6)H(4)PPh(2) (1: X=NH; 2: X=NPh; 3: X=O) and Ph(2)PC(6)H(4)C(O)O(CH(2))(2)O(CH(2))(2)OC(O)C(6)H(4)PPh(2) (5) as well as the monophosphine ligand Ph(2)PC(6)H(4)C(O)X(CH(2))(2)OH (4) have been prepared from 2-diphenylphosphinobenzoic acid and the corresponding amino alcohols or diols. Coordination of the diphosphine ligands to rhodium, iridium, and platinum resulted in the formation of the square-planar complexes [(Pbond;P)Rh(CO)Cl] (6: Pbond;P=1; 7: Pbond;P=2; 8: Pbond;P=3), [(Pbond;P)Rh(CO)Cl](2) (9: Pbond;P=5), [(P-P)Ir(cod)Cl] (10: Pbond;P=1; 11: Pbond;P=2; 12: Pbond;P=3), [(Pbond;P)Ir(CO)Cl] (13: Pbond;P=1; 14: Pbond;P=2; 15: Pbond;P=3), and [(Pbond;P)PtI(2)] (18: Pbond;P=2). In all complexes, the diphosphine ligands are trans coordinated to the metal center, thanks to the large spacer groups, which allow the two phosphorus atoms to occupy opposite positions in the square-planar coordination geometry. The trans coordination is demonstrated unambiguously by the single-crystal X-ray structure analysis of complex 18. In the case of the diphosphine ligand 5, the spacer group is so large that dinuclear complexes with ligand 5 in bridging positions are formed, maintaining the trans coordination of the P atoms on each metal center, as shown by the crystal structure analysis of 9. The monophosphine ligand 4 reacts with [[Ir(cod)Cl](2)] (cod=cyclooctadiene) to give the simple derivative [(4)Ir(cod)Cl] (16) which is converted into the carbonyl complex [(4)Ir(CO)(2)Cl] (17) with carbon monoxide. The crystal structure analysis of 16 also reveals a square-planar coordination geometry in which the phosphine ligand occupies a position cis with respect to the chloro ligand. The diphosphine ligands 1, 2, 3, and 5 have been tested as cocatalysts in combination with the catalyst precursors [[Rh(CO)(2)Cl](2)] and [[Ir(cod)Cl](2)] or [H(2)IrCl(6)] for the carbonylation of methanol at 170 degrees C and 22 bar CO. The best results (TON 800 after 15 min) are obtained for the combination 2/[[Rh(CO)(2)Cl](2)]. After the catalytic reaction, complex 7 is identified in the reaction mixture and can be isolated; it is active for further runs without loss of catalytic activity.     

Mono-, bi-, and trinuclear CuII-Cl containing products based on the tris(2-pyridylmethyl)amine chelate derived from copper(I) complex dechlorination reactions of chloroform

The ligand TMPA (tris(2-pyridylmethyl)amine) and its copper complexes have played a prominent role in recent (bio)inorganic chemistry studies; the copper(I) complex [CuI(TMPA)(CH3CN)]+ possesses an extensive dioxygen reactivity, and it is also known to effect the reductive dechlorination of substrates such as dichloromethane and benzyl and allyl chlorides. In this report, we describe a set of new analogues of TMPA, ligand 6TMPAOH, binucleating Iso-DO, and trinucleating SYMM. Copper(I) complexes with these ligands and a previously described binucleating ligand DO react with chloroform, resulting in reductive dechlorination and production of [CuIIx(L)Clx]x+ (x = 1, 2, or 3). X-ray crystal structures of [CuII(6TMPAOH)Cl]PF6, [CuII2(Iso-DO)Cl2](PF6)2, [CuII2(DO)Cl2](PF6)2, and [Cu3(SYMM)Cl3](PF6)3 are presented, and the compounds are also characterized by UV-vis and EPR spectroscopies as well as cyclic voltammetry. The steric influence of a pyridyl 6-substituent (in the complexes with 6TMPAOH, Iso-DO, and SYMM) on the solid state and solution structures and redox potentials are compared and contrasted to those chlorocopper(II) complexes with a pyridyl 5'-substituent (in [CuII2(DO)Cl2](PF6)2 and in [CuII(TMPA)Cl]+). Some insights into the reductive dechlorination process have been obtained by using 2H NMR spectroscopy in following the reaction of [Cu2(Iso-DO)(CH3CN)2](PF6)2 with CDCl3, in the presence or absence of a radical trap, 2,4-di-tert-butylphenol.     

Anionic Halomolybdate(III) Chemistry. Tetrahydrofuran Loss from [MoX(3)Y(THF)(2)](-) (X, Y = Cl, Br, I), Preparation and Properties of [Mo(3)X(12)](3)(-) (X = Br, I), and Crystal Structure of the Edge-Sharing Trioctahedral [PPh(4)](3)[Mo(3)I(12)

By interaction of MoX(3)(THF)(3) with [Cat]X in THF, the salts [Cat][MoX(4)(THF)(2)] have been synthesized [X = I, Cat = PPh(4), NBu(4), NPr(4), (Ph(3)P)(2)N; X = Br, Cat = NBu(4), PPh(4) (Ph(3)P)(2)N]. Mixed-halide species [MoX(3)Y(THF)(2)](-) (X, Y = Cl, Br, I) have also been generated in solution and investigated by (1)H-NMR. When the tetraiodo, tetrabromo, and mixed bromoiodo salts are dissolved in CH(2)Cl(2), clean loss of all coordinated THF is observed by (1)H-NMR. On the other hand, [MoCl(4)(THF)(2)](-) loses only 1.5 THF/Mo. The salts [Cat](3)[Mo(3)X(12)] (X = Br, I) have been isolated from [Cat][MoX(4)(THF)(2)] or by running the reaction between MoX(3)(THF)(3) and [Cat]X directly in CH(2)Cl(2). The crystal structure of [PPh(4)](3)[Mo(3)I(12)] exhibits a linear face-sharing trioctahedron for the trianion: triclinic, space group P&onemacr;; a = 11.385(2), b = 12.697(3), c = 16.849(2) ?; alpha = 76.65(2), beta = 71.967(12), gamma = 84.56(2) degrees; Z = 1; 431 parameters and 3957 data with I > 2sigma(I). The metal-metal distance is 3.258(2) ?. Structural and magnetic data are consistent with the presence of a metal-metal sigma bond order of (1)/(2) and with the remaining 7 electrons being located in 7 substantially nonbonding orbitals. The ground state of the molecule is predicted to be subject to a Jahn-Teller distortion, which is experimentally apparent from the nature of the thermal ellipsoid of the central Mo atom. The [Mo(3)X(12)](3)(-) ions reacts with phosphines (PMe(3), dppe) to form products of lower nuclearity by rupture of the bridging Mo-X bonds.     

Unprecedented cage-carbon to cage-boron NMe(3) transfer in a monocarbon Molybdenacarborane

The reagent Li(2)[7-NMe(3)-nido-7-CB(10)H(10)] reacts with [Mo(CO)(3)(NCMe)(3)] in THF-NCMe (THF = tetrahydrofuran) to give a molybdenacarborane intermediate which, upon oxidation by CH(2)[double bond]CHCH(2)Br or I(2) and then addition of [N(PPh(3))(2)]Cl, gives the salts [N(PPh(3))(2)][2,2,2-(CO)(3)-2-X-3-NMe(3)-closo-2,1-MoCB(10)H(10)] (X = Br (1) or I (2)). During the reaction, the cage-bound NMe(3) substituent is transferred from the cage-carbon atom to an adjacent cage-boron atom, a feature established spectroscopically in 1 and 2, and by X-ray diffraction studies on several of their derivatives. When [Rh(NCMe)(3)(eta(5)-C(5)Me(5))][BF(4)](2) is used as the oxidizing agent, the trimetallic compound [2,2,2-(CO)(3)-7-mu-H-2,7,11-[Rh(2)(mu-CO)(eta(5)-C(5)Me(5))(2)]-closo-2,1-MoCB(10)H(9)] (10) is formed, the NMe(3) group being lost. Reaction of 1 in CH(2)Cl(2) with Tl[PF(6)] in the presence of donor ligands L affords neutral zwitterionic compounds [2,2,2-(CO)(3)-2-L-3-NMe(3)-closo-2,1-MoCB(10)H(10)] for L = PPh(3) (4) or CNBu(t) (5), and [2-Bu(t)C[triple bond]CH-2,2-(CO)(2)-3-NMe(3)-closo-2,1-MoCB(10)H(10)] (6) when L = Bu(t)C[triple bond]CH. When 1 is treated with CNBu(t) and X(2), the metal center is oxidized, and in the products obtained, [2,2,2,2-(CNBu(t))(4)-2-Br-3-X-closo-2,1-MoCB(10)H(10)] (X = Br (7), I (8)), the B-NMe(3) bond is replaced by B-X. In contrast, treatment of 2 with I(2) and cyclo-1,4-S(2)(CH(2))(4) in CH(2)Cl(2) results in oxidative substitution of the cluster and retention of the NMe(3) group, giving [2,2,2-(CO)(3)-2-I-3-NMe(3)-6-[cyclo-1,4-S(2)(CH(2))(4)]-closo-2,1-MoCB(10)H(9)] (9). The unique structural features of the new compounds were confirmed by single-crystal X-ray diffraction studies upon 6, 7, 9 and 10.     

Adventures in crystallization. Crystalline salts containing one, two, or even three chemically distinct cations obtained from solutions of [(cyclohexyl isocyanide)(4)Rh(I)]+

By judicious selection of crystallization conditions, it has been possible to obtain the salts of a common building block, [(RNC)4Rh(I)]+, in single-crystal form suitable for X-ray diffraction. Salts that contain a single type of cation include deep green [(C6H11NC)12Rh(I)3](SbF6)3, deep green [(C6H11NC)12Rh(I)3](AsF6)3, and straw yellow [(C6H11NC)8Rh(II)2Cl2](BF4)2 (in addition to the previously isolated trimeric deep green [(i-PrNC)12RhI3]Cl3 x 4.5 H2O, monomeric, [(C6H11NC)4 Rh(I)](BPh4), and [(i-PrNC)4Rh(I)](BPh4) (both yellow), and red, dimeric [(C6H11NC)8Rh(I)2]Cl2 x 0.5C6H6 x 2H2O). Ordered crystals of [(C6H11NC)12Rh(I)3](SbF6)3 contain linear Rh3 units, while those of [(C6H11NC)12Rh(I)3](AsF6)3 show disorder which is consistent with the presence of linear or bent Rh3 units. The formation of green [(C6H11NC)12Rh(V/III)3Cl2][(C6H11NC)12Rh(I)3]Cl6, and brown [(C6H11NC)12Rh(V/III)3Cl2][(C6H11NC)8Rh(I)2][(C6H11NC)4RhI]Cl6 x 16H2O x 3C6H6 along with unidentified red-brown cubes from an air-exposed solution of [(C6H11NC)4Rh(I)]Cl is reported. As their formulas indicate, green [(C6H11NC)12Rh(V/III)3Cl2][(C6H11NC)12Rh(I)3]Cl6, and brown [(C6H11NC)12Rh(V/III)3Cl2][(C6H11NC)8Rh(I)2][(C6H11NC)8Rh(I)]Cl6 x 16H2O x 3C6H6 contain two or three chemically distinct cations, respectively, but again are built from a common precursor, [(C6H11NC)4Rh(I)]+.