Divalent dirhodium imido complexes: formation, structure, and alkyne cycloaddition reactivity

Dirhodium amido complexes [(Cp*Rh)2(mu2-NHPh)(mu2-X)] (X = NHPh (2), Cl (3), OMe (4); Cp* = eta5-C5Me5) were prepared by chloride displacement of [Cp*Rh(mu2-Cl)]2 (1) and have been used as precursors to a dirhodium imido species [Cp*Rh(mu2-NPh)RhCp*]. The imido species can be trapped by PMe3 to give the adduct [Cp*Rh(mu2-NPh)Rh(PMe3)Cp*] (5) and undergoes a formal [2 + 2] cycloaddition reaction with unactivated alkynes to give the azametallacycles [Cp*Rh(mu2-eta2:eta3-R1CCR2NPh)RhCp*] (R1 = R2 = Ph (6a), R1 = H, R2 = t-Bu (6b), R1 = H, R2 = p-tol (6c)). Isolation of a relevant unsaturated imido complex [Cp*Rh(mu2-NAr)RhCp*] (7) was achieved by the use of a sterically hindered LiNHAr (Ar = 2,6-diisopropylphenyl) reagent in a metathesis reaction with 1. X-ray structures of 2, 6a, 7 and the terminal isocyanide adduct [Cp*Rh(mu2-NAr)Rh(t-BuNC)Cp*] (8) are reported.     

Reactions of [Cp*Ru(H2O)(NBD)]+ with alkynes

Formal [2 + 2 + 2] addition reactions of [Cp*Ru(H₂O)(NBD)]BF₄ (NBD = norbornadiene) with PhC?CR (R = H, COOEt) give [Cp*Ru(η⁶‐C₆H₅? C₉H₈R)] BF₄ (1a, R = H; 2a, R = COOEt). Treatment of [Cp*Ru(H₂O)(NBD)]BF₄ with PhC?C? C?CPh does not give [2 + 2 + 2] addition product, but [Cp*Ru(η⁶‐C₆H₅? C?C? C?CPh)] BF₄(3a). Treatment of 1a, 2a, 3a with NaBPh₄ affords [Cp*Ru(η⁶‐C₆H₅? C₉H₈R)] BPh₄ (1b, R = H; 2b, R = COOEt) and [Cp*Ru(η⁶‐C₆H₅? C?C? C?CPh)] BPh₄(3b). The structures of 1b, 2b and 3b were determined by X‐ray crystallography. Copyright © 2007 John Wiley & Sons, Ltd.     

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.     

Heterolytic cleavage of dihydrogen promoted by sulfido-bridged tungsten-ruthenium dinuclear complexes

A series of sulfido-bridged tungsten-ruthenium dinuclear complexes Cp*W(mu-S)(3)RuX(PPh(3))(2) (4a; X = Cl, 4b; X = H), Cp*W(O)(mu-S)(2)RuX(PPh(3))(2) (5a; X = Cl, 5b; X = H), and Cp*W(NPh)(mu-S)(2)RuX(PPh(3))(2) (6a; X = Cl, 6b; X = H) have been synthesized by the reactions of (PPh(4))[Cp*W(S)(3)] (1), (PPh(4))[Cp*W(O)(S)(2)] (2), and (PPh(4))[Cp*W(NPh)(S)(2)] (3), with RuClX(PPh(3))(3) (X = Cl, H). The heterolytic cleavage of H(2) was found to proceed at room temperature upon treating 5a and 6a with NaBAr(F)(4) (Ar(F) = 3, 5-C(6)H(3)(CF(3))(2)) under atmospheric pressure of H(2), which gave rise to [Cp*W(OH)(mu-S)(2)RuH(PPh(3))(2)](BAr(F)(4)) (7a) and [Cp*W(NHPh)(mu-S)(2)RuH(PPh(3))(2)](BAr(F)(4)) (8), respectively. When Cp*W(O)(mu-S)(2)Ru(PPh(3))(2)H (5b) was treated with a Br?nstead acid, [H(OEt(2))(2)](BAr(F)(4)) or HOTf, protonation occurred exclusively at the terminal oxide to give [Cp*W(OH)(mu-S)(2)RuH(PPh(3))(2)](X) (7a; X = BAr(F)(4), 7b; X = OTf), while the hydride remained intact. The analogous reaction of Cp+W(mu-S)(3)Ru(PPh(3))(2)H (4b) led to immediate evolution of H(2). Selective deprotonation of the hydroxyl group of 7a or 7b was induced by NEt(3) and 4b, generating Cp*W(O)(mu-S)(2)Ru(PPh(3))(2)H (5b). Evolution of H(2) was also observed for the reactions of 7a or 7b with CH(3)CN to give [Cp*W(O)(mu-S)(2)Ru(CH(3)CN)(PPh(3))(2)](X) (11a; X = BAr(F)(4), 11b; X = OTf). We examined the H/D exchange reactions of 4b, 5b, and 7a with D(2) and CH(3)OD, and found that facile H/D scrambling over the W-OH and Ru-H sites occurred for 7a. Based on these experimental results, the mechanism of the heterolytic H(2) activation and the reverse H(2) evolution reactions are discussed.     

Mechanistic aspects of samarium-mediated sigma-bond activations of arene C-H and arylsilane Si-C bonds.

To investigate the potential role of Sm-Ph species as intermediates in the samarium-catalyzed redistribution of PhSiH3 to Ph2SiH2 and SiH4, the samarium phenyl complex [Cp*2SmPh]2 (1) was prepared by oxidation of Cp2*Sm (2) with HgPh2. Compound 1 thermally decomposes to yield benzene and the phenylene-bridged disamarium complex Cp*2Sm(mu-1,4-C6H4)SmCp*2 (3). This decomposition reaction appears to proceed through dissociation of 1 into monomeric Cp*2SmPh species which then react via unimolecular and bimolecular pathways, involving rate-limiting Cp* metalation and direct C-H activation, respectively. The observed rate law for this process is of the form: rate = k1[1] + k2[1]2. Complex 1 efficiently transfers its phenyl group to PhSiH3, with formation of Ph2SiH2 and [Cp*2Sm(mu-H)]2 (4). Quantitative Si-C bond cleavage of C6F5SiH3 is effected by the samarium hydride complex 4, yielding silane and [Cp*2Sm(mu-C6F5)]2 (5). In contrast, Si-H activation takes place upon reaction of 4 with o-MeOC6H4SiH3, affording the samarium silyl species [structure: see text] Cp*2SmSiH2(o-MeOC6H4) (7). Complex 7 rapidly decomposes to [Cp*2Sm(mu-o-MeOC6H4)]2 (6) and other samarium-containing products. Compounds 5 and 6 were prepared independently by oxidation of 2 with Hg(C6F5)2 and Hg(o-MeOC6H4)2, respectively. The mechanism of samarium-mediated redistribution at silicon, and chemoselectivity in sigma-bond metathesis reactions, are discussed.     

Trapping unstable terminal M-O multiple bonds of monocyclopentadienyl niobium and tantalum complexes with Lewis acids

Hydrolysis of [NbCp'Cl(4)] (Cp' = η(5)-C(5)H(4)SiMe(3)) with the water adduct H(2)O·B(C(6)F(5))(3) afforded the oxo-borane compound [NbCp'Cl(2){O·B(C(6)F(5))(3)}] (2a). This compound reacted with [MgBz(2)(THF)(2)] giving [NbCp'Bz(2){O·B(C(6)F(5))(3)}] (2b), whereas [NbCp'Me(2){O·B(C(6)F(5))(3)}] (2c) was obtained from the reaction of [NbCp'Me(4)] with H(2)O·B(C(6)F(5))(3). Addition of Al(C(6)F(5))(3) to solutions containing the oxo-borane compounds [MCp(R)X(2){O·B(C(6)F(5))(3)}] (M = Ta, Cp(R) = η(5)-C(5)Me(5) (Cp*), X = Cl 1a, Bz 1b, Me 1c; M = Nb, Cp(R) = Cp', X = Cl 2a) afforded the oxo-alane complexes [MCp(R)X(2){O·Al(C(6)F(5))(3)}] (M = Ta, Cp(R) = Cp*, X = Cl 3a, Bz 3b, Me 3c; M = Nb, Cp(R) = Cp', X = Cl 4a), releasing B(C(6)F(5))(3). Compound 3a was also obtained by addition of Al(C(6)F(5))(3) to the dinuclear μ-oxo compound [TaCp*Cl(2)(μ-O)](2), meanwhile addition of the water adduct H(2)O·Al(C(6)F(5))(3) to [TaCp*Me(4)] gave complex 3c. The structure of 2a and 3a was obtained by X-ray diffraction studies. Density functional theory (DFT) calculations were carried out to further understand these types of oxo compounds.     

Syntheses and skeletal transformations of NCNH- and NCN-bridged tetrairidium(III) cages

The diiridium complex [Cp*IrCl2]2 (Cp* = eta5-C5Me5) reacts with 2 equiv of Na(NCNH) at room temperature to afford the 16-membered macrocyclic tetrairidium complex [Cp*IrCl(mu2-NCNH-N,N')]4 (1a). Treatment of 1a with 4 equiv of triethylamine at room temperature leads to the formation of the "C3-elongated cubane-like" tetrairidium complex [Cp*Ir(mu3-NCN-N,N,N')3(IrCp*)3(mu3-NCN-N,N,N)] (2) as the major product, which is further converted into the cubane-type complex [Cp*Ir(mu3-NCN-N,N,N)]4 (3) on refluxing in p-xylene. The molecular structures of [Cp*IrI(mu3-NCNH-N,N')]4.C7H8 (1b.C7H8), 2.0.5C7H8, and 3 have been determined by X-ray analyses.     

Sulfur-bridged early-late heterobimetallics synthesized by incorporation of titanium,vanadium, and molybdenum into bis(hydrosulfido) templates of group 9 metals

Reactions of the bis(hydrosulfido) complexes [Cp*Rh(SH)(2)(PMe(3))] (1a; Cp* = eta(5)-C(5)Me(5)) with [CpTiCl(3)] (Cp = eta(5)-C(5)H(5)) and [TiCl(4)(thf)(2)] in the presence of triethylamine led to the formation of the sulfido-bridged titanium-rhodium complexes [Cp*Rh(PMe(3))(micro(2)-S)(2)TiClCp] (2a) and [Cp*Rh(PMe(3))(micro2-S)(2)TiCl(2)] (3a), respectively. Complex 3a and its iridium analogue 3b were further converted into the bis(acetylacetonato) complexes [Cp*M(PMe(3))(micro(2)-S)(2)Ti(acac)(2)] (4a, M = Rh; 4b, M = Ir) upon treatment with acetylacetone. The hydrosulfido complexes 1a and [Cp*Ir(SH)(2)(PMe(3))] (1b) also reacted with [VCl(3)(thf)(3)] and [Mo(CO)(4)(nbd)] (nbd = 2,5-norbornadiene) to afford the cationic sulfido-bridged VM2 complexes [(Cp*M(PMe(3))(micro2-S)(2))2V](+) (5a(+), M = Rh; 5b(+), M = Ir) and the hydrosulfido-bridged MoM complexes [Cp*M(PMe(3))(micro2-SH)(2)Mo(CO)(4)] (6a, M = Rh; 6b, M = Ir), respectively.     

The chemoselective reactions of tyrosine-containing G-protein-coupled receptor peptides with [Cp*Rh(H2O)3](OTf)2, including 2D NMR structures and the biological consequences

The bioconjugation of organometallic complexes with peptides has proven to be a novel approach for drug discovery. We report the facile and chemoselective reaction of tyrosine-containing G-protein-coupled receptor (GPCR) peptides with [Cp*Rh(H(2)O)(3)](OTf)(2), in water, at room temperature, and at pH 5-6. We have focused on three important GPCR peptides; namely, [Tyr(1)]-leu-enkephalin, [Tyr(4)]-neurotensin(8-13), and [Tyr(3)]-octreotide, each of which has a different position for the tyrosine residue, together with competing functionalities. Importantly, all other functional groups present, i.e., amino, carboxyl, disulfide, phenyl, and indole, were not prominent sites of reactivity by the Cp*Rh tris aqua complex. Furthermore, the influence of the Cp*Rh moiety on the structure of [Tyr(3)]-octreotide was characterized by 2D NMR, resulting in the first representative structure of an organometallic-peptide complex. The biological consequences of these Cp*Rh-peptide complexes, with respect to GPCR binding and growth inhibition of MCF7 and HT29 cancer cells, will be presented for [(η(6)-Cp*Rh-Tyr(1))-leu-enkephalin](OTf)(2) and [(η(6)-Cp*Rh-Tyr(3))-octreotide](OTf)(2).     

Construction of trinuclear iridium clusters through ancillary ortho-carborane-1,2-diselenolato ligands, with simultaneous iridium-induced B-H activation

The reaction of the 16-electron "pseudo-aromatic" complex Cp*Ir[Se2C2(B10H10)] (1, Cp* = eta5-C5Me5) with [Ir(cod)(micro-OC2H5)]2 leads to the trinuclear iridium complexes {(cod)Ir[Se2C2(B10H8)(OC2H5)]}Ir{[Se2C2(B10H10)]IrCp*} (2), {(cod)Ir[Se2C2(B10H8)(OC2H5)]}Ir{[Se2C2(B10H9)]IrCp*} (3), {Cp*Ir[Se2C2(B10H9)]}{IrSe(2)[C2(B10H9)(OC2H5)]}{[Se2C2(B10H10)] IrCp*} (4) and one mononuclear complex Cp*Ir[Se2C2(B10H8)(OC2H5)(2)] (5). The reactivity of 2 was investigated and revealed that transformation from 2 to 3 occurred thermally in solution. The transoid complex 2 (with the carborane diselenolato units in trans position) can be converted in nearly 90% yield to the cisoid complex 3. In complexes 2, 3, two diselenolato carborane ligands bridge the Ir(3) core, which consists of Ir-Ir metal bonds. Compared with transoid 2, the cisoid 3 contains two iridium-boron bonds. Complex 4 consists of three different coordination environment carborane ligands (Ir-B(cluster): {Cp*Ir[Se2C2(B10H9)]}, O-B(cluster): {[Se2C2(B10H9)](OC2H5)}, and intact carborane: {Cp*Ir[Se2C2 (B10H10)]}) without the presence of a metal-metal bond. Analogous reaction of 1 with [Ir(cod)(micro-OCH(3))](2) results in formation of the trinuclear complex {Cp*Ir[Se2C2(B10H9)]}{IrSe(2)[C2(B10H9)(OCH3)]}{[Se2C2(B10H10)]IrCp*} (6) and mononuclear complex Cp*Ir[Se2C2(B10H8)(OCH3)(2)] (7). The structures of 2, 3, 4, 5, 6 and 7 have been determined by crystallographic studies.     

Organometallic early lanthanide clusters: syntheses and X-ray structures of new monocyclopentadienyl complexes

The reaction of Ln(BH(4))(3)(THF)(3) or LnCl(3)(THF)(3) with 1 equiv of KCp*' ligand (Cp' = C(5)Me(4)n-Pr) afforded the new monocyclopentadienyl complexes Cp*'LnX(2)(THF)(n) (X = BH(4), Ln = Sm, n = 1, 1a, Ln = Nd, n = 2, 1b; X = Cl, Ln = Sm, n = 1, 3a) and [Cp*'LnX(2)](n') (X = BH(4), n' = 6, Ln = Sm, 2a, Ln = Nd, 2b; X = Cl, Ln = Nd, 4b). All these compounds were characterized by elemental analysis and (1)H NMR. Crystals of mixed borohydrido/chloro-bridged [Cp*'(6)Ln(6)(BH(4))(12-x))Cl(x)(THF)(n')] (x = 10, n' = 4, Ln = Sm, 2a', Ln = Nd, 2b'; x = 5, n = 2, Ln = Sm, 2a' ') were also isolated. Compounds 2a, 2b, 2a', 2b', and 2a' were structurally characterized; they all exhibit a hexameric structure in the solid state containing the [Cp*(3)Ln(3)X(5)(THF)] building block. The easy clustering of THF adducts first isolated is illustrative of the well-known bridging ability of the BH(4) group. Hexameric 2a was found to be unstable in the presence of THF vapors; this may be correlated to the opening of unsymmetrical borohydride bridges observed in the molecular structure.     

Transition metal complexes of the chelating phosphine borane ligand Ph2PCH2Ph2P.BH3

Chromium and ruthenium complexes of the chelating phosphine borane H(3)B.dppm are reported. Addition of H(3)B.dppm to [Cr(CO)(4)(nbd)](nbd = norbornadiene) affords [Cr(CO)(4)(eta1-H(3)B.dppm)] in which the borane is linked to the metal through a single B-H-Cr interaction. Addition of H(3)B.dppm to [CpRu(PR(3))(NCMe)(2)](+)(Cp =eta5)-C(5)H(5)) results in [CpRu(PR(3))(eta1-H(3)B.dppm)][PF(6)](R = Me, OMe) which also show a single B-H-Ru interaction. Reaction with [CpRu(NCMe)(3)](+) only resulted in a mixture of products. In contrast, with [Cp*Ru(NCMe)(3)](+)(Cp*=eta5)-C(5)Me(5)) a single product is isolated in high yield: [Cp*Ru(eta2-H(3)B.dppm)][PF(6)]. This complex shows two B-H-Ru interactions. Reaction with L = PMe(3) or CO breaks one of these and the complexes [Cp*Ru(L)(eta1-H(3)B.dppm)][PF(6)] are formed in good yield. With L = MeCN an equilibrium is established between [Cp*Ru(eta2-H(3)B.dppm)][PF(6)] and the acetonitrile adduct. [Cp*Ru (eta2-H(3)B.dppm)][PF(6)] can be considered as being "operationally unsaturated", effectively acting as a source of 16-electron [Cp*Ru (eta1-H(3)B.dppm)][PF(6)]. All the new compounds (apart from the CO and MeCN adducts) have been characterised by X-ray crystallography. The solid-state structure of H(3)B.dppm is also reported.     

Construction of halide-bridged tungsten-copper-sulfide double cubanelike clusters from a new precursor [(Tp*WS2)2(μ-S2)

Treatment of [Et(4)N][Tp*WS(3)] (1) (Tp* = hydridotris(3,5-dimethylpyrazol-1-yl)borate) with 2 equiv of AgSCN in MeCN afforded a novel neutral compound [(Tp*WS(2))(2)(μ-S(2))] (2). Reactions of 2 with excess CuX (X = Cl, Br, I) in MeCN and CH(2)Cl(2) or CHCl(3) formed three neutral W/Cu/S clusters [{Tp*W(μ(3)-S)(3)Cu(3)(μ-Cl)}(2)Cu(μ-Cl)(2)(μ(7)-Cl)(MeCN)](2) (3), [{Tp*W(μ(3)-S)(3)Cu(3)}(2)Br(μ-Br)(2)(μ(4)-Br)(MeCN)] (4), and [{Tp*W(μ(3)-S)(3)Cu(3)}(2){Cu(2)(μ-I)(4)(μ(3)-I)(2)}] (5), respectively. On the other hand, treatment of 2 with CuX (X = Cl, Br) in the presence of Et(4)NX (X = Cl, Br) produced two anionic W/Cu/S clusters [Et(4)N][{Tp*W(μ(3)-S)(3)Cu(3)X}(2)(μ-X)(2)(μ(4)-X)] (6: X = Cl; 7 X = Br). Compounds 2-7 were characterized by elemental analysis, IR, UV-vis, (1)H NMR, electrospray ionization (ESI) mass spectra, and single-crystal X-ray crystallography. The dimeric structure of 2 can be viewed as two [Tp*WS(2)] fragments in which two W atoms are connected by one S(2)(2-) dianion. Compounds 3-7 all possess unique halide-bridged double cubanelike frameworks. For 3, two [Tp*W(μ(3)-S)(3)Cu(3)](2+) dications are linked via a μ(7)-Cl(-) bridge, two μ-Cl(-) bridges, and a [Cu(MeCN)(μ-Cl)(2)](+) bridge. For 4, one [Tp*W(μ(3)-S)(3)Cu(3)(MeCN)](2+) dication and one [Tp*W(μ(3)-S)(3)Cu(3)Br](+) cation are linked via a μ(4)-Br(-) and two μ-Br(-) bridges. For 5, the two [Tp*W(μ(3)-S)(3)Cu(3)](2+) dications are bridged by a linear [(μ-I)(2)Cu(μ(3)-I)(2)Cu(μ-I)(2)](4+) species. For 6 and 7, two [Tp*W(μ(3)-S)(3)Cu(3)X](+) cations are linked by a μ(4)-X(-) and two μ-X(-) bridges (X = Cl, Br). In addition, the third-order nonlinear optical (NLO) properties of 2-7 in MeCN/CH(2)Cl(2) were investigated by using femtosecond degenerate four-wave mixing (DFWM) technique.     

Ligand effects on structures and spectroscopic properties of pyridine-2-aldoxime complexes of Re(CO)3(+): DFT/TDDFT theoretical studies

The series of novel rhenium(I) tricarbonyl mixed-ligand complexes Re(X)(CO)(3)(N^N) (N^N = pyridine-2-aldoxime; X = -Cl, 1; X = -CN, 2; and X = -C≡C, 3) has been investigated theoretically to explore the ligand X effect on their electronic structures and spectroscopic properties. The contribution of the X ligand to the highest occupied molecular orbital (HOMO) and HOMO-1 decreases in the order of 3 > 1 > 2, in line with the π-donating abilities of the X: -C≡C > -Cl > -CN. The reorganization energy (λ) calculations show that 1 and 3 will result in the higher efficiency of organic light-emitting diodes than 2. The lowest-lying absorptions of 1 and 3 can be assigned to the {[d(xz), d(yz)(Re) + π(CO) + π(X)] → [π* (N^N)]} transition with mixing metal-to-ligand, ligand-to-ligand, and X ligand-to-ligand charge transfer (MLCT/LLCT/XLCT) character, whereas this absorption at 354 nm (H-1 → L) of 2 is assigned to {[d(xz), d(yz)(Re) + π(CO) + π(N^N)] → [π* (N^N)]} transition with MLCT/LLCT/ILCT (intraligand charge transfer). Furthermore, the absorptions are red-shifted in the order 2, 1, and 3, with the increase of π-donating abilities of X ligands. The solvent effects cause red shifts of the absorption and emission spectra with decreasing solvent polarity.     

Synthesis and characterization of heterometallic clusters (Ir2Rh, Ir2W, Rh3) Containing 1,2-dicarba-closo-dodecaborane(12)-1,2-dithiolate chelate ligands, [(B10H10)C2S2]2-

The 16-electron half-sandwich complex [Cp*Ir[S2C2(B10H10)]] (Cp* = eta5-C5Me5) (1a) reacts with [[Rh(cod)(mu-Cl)]2] (cod = cycloocta-1,5-diene, C8H12) in different molar ratios to give three products, [[Cp*Ir[S2C2(B10H9)]]Rh(cod)] (2), trans-[[Cp*Ir[S2C2(B10H9)]]Rh[[S2C2(B10H10)]IrCp*]] (3), and [Rh2(cod)2[(mu-SH)(mu-SC)(CH)(B10H10)]] (4). Complex 3 contains an Ir2Rh backbone with two different Ir-Rh bonds (3.003(3) and 2.685(3) angstroms). The dinuclear complex 2 reacts with the mononuclear 16-electron complex 1a to give 3 in refluxing toluene. Reaction of 1a with [W(CO)3(py)3] (py = C5H5N) in the presence of BF3.EtO2 leads to the trinuclear cluster [[Cp*Ir[S2C2(B10H10)]]2W(CO)2] (5) together with [[Cp*Ir(CO)[S2C2(B10H10)]]W(CO)5] (6), and [Cp*Ir(CO)[S2C2(B10H10)]] (7). Analogous reactions of [Cp*Rh[S2C2(B10H10)]] (1 b) with [[Rh(cod)(mu-Cl)]2] were investigated and two complexes cis-[[Cp*Rh[S2C2(B10H10)]]2Rh] (8) and trans-[[Cp*Rh[S2C2(B10H10)]]2Rh] (9) were obtained. In refluxing THF solution, the cisoid 8 is converted in more than 95 % yield to the transoid 9. All new complexes 2-9 were characterized by NMR spectroscopy (1H, 11B NMR) and X-ray diffraction structural analyses are reported for complexes 2-5, 8, and 9.     

Tetraphosphinite resorcinarene complexes: silver(I) capsule complexes

Resorcinarene tetraphosphinite ligands, P4, react with silver(I) trifluoroacetate or silver(I) triflate, AgX, to give the corresponding [Ag4X4(P4)] complexes. The resorcinarene skeleton in these complexes adopts a boat conformation with the silver(I) phosphinite units on the horizontal, rather than the upright, arene units of the resorcinarene. The [Ag4X4(P4)] complexes react with free P4 ligand to yield the [Ag2X2(P4)] or [AgX(P4)] complexes, which are characterized in solution by NMR spectroscopy to have a conformation opposite to that of the [Ag4X4(P4)] complexes; the silver(I) phosphinite groups are on the upright arene rings of the resorcinarene "boat" instead of the horizontal arene units. There is an easy equilibrium between these complexes. When X = triflate, the [Ag4X4(P4)] complexes disproportionate and add aqua ligands during slow crystallization to give "capsule complexes", which are characterized crystallographically as [Ag10(O3SCF3)10(OH2)6(P4)2], [Ag10(O3SCF3)6(OH2)8(P4)2][O3SCF3]4, or [Ag13(O3SCF3)13(OH2)7(P4)2] depending on the resorcinarene tetraphosphinite ligand P4 used. These unusual capsule complexes are formed by the tail-to-tail self-assembly of pairs of [Ag4(P4)]4+ units linked by additional silver ions that bind to the phenyl substituents of one resorcinarene through {Ag(eta2-C6H5)}+ binding and to the bridging triflate ligands, aqua ligands, or both of the other resorcinarene unit.     

Multiphoton dissociation dynamics of BrCl and the BrCl+ cation

Ion imaging methods have enabled identification of three mechanisms by which (79)Br(+) and (35)Cl(+) fragment ions are formed following one-color multiphoton excitation of BrCl molecules in the wavelength range 324.6 > lambda > 311.7 nm. Two-photon excitation within this range populates selected vibrational levels (v'= 0-5) of the [X (2)Pi(1/2)]5ssigma Rydberg state. Absorption of a third photon results in branching between (i) photoionization (i.e. removal of the Rydberg electron-a traditional 2 + 1 REMPI process) and (ii)pi*<--pi excitation within the core, resulting in formation of one or more super-excited states with Omega= 1 and configuration [A (2)Pi(1/2)]5ssigma. The fate of the latter states involves a further branching. They can autoionize (yielding BrCl(+)(X (2)Pi) ions in a wider range of v(+) states than formed by direct 2 + 1 REMPI). Further, one-photon absorption by the parent ions resulting from direct ionization or autoionization leads to formation of Br(+) and (energy permitting) Cl(+) fragment ions. Alternatively, the super-excited molecules can fragment to neutral atoms, one of which is in a Rydberg state. Complementary ab initio calculations lead to the conclusion that the observed [Cl**[(3)P(J)]4s + Br/Br*] products result from direct dissociation of the photo-prepared super-excited states, whereas [Br**[(3)P(J)]5p + Cl/Cl*] product formation involves interaction between the [A (2)Pi(1/2)]5ssigma and [X (2)Pi(1/2)]5psigma Rydberg potentials at extended Br-Cl bond lengths. Absorption of one further photon by the resulting Br** and Cl** Rydberg atoms leads to their ionization, and thus their appearance in the Br(+) and Cl(+) fragment ion images.     

Interlayer interaction of two-dimensional layered spin crossover complexes [FeIIH3L(Me)][FeIIL(Me)]X (X-=ClO4-, BF4-, PF6-, AsF6-, and SbF6-; H3L(Me)=tris[2-(((2-methylimidazol-4-yl)methylidene)amino)ethyl]amine)

A series of two-dimensional (2D) spin crossover complexes, [FeIIH3L(Me)][FeIIL(Me)]X (X-=ClO4-, BF4-, PF6-, AsF6-, SbF6-) 1-5, have been synthesized, where H3L(Me) denotes an hexadentate N6 tripodlike ligand containing three imidazole groups, tris[2-(((2-methylimidazol-4-yl)methylidene)amino)ethyl]amine. Compounds 1-5 exhibit a two-step (HS-[FeIIH3L(Me)](2+) + HS-[FeIIL(Me)]-) <--> (HS-[FeIIH3L(Me)](2+) + LS-[FeIIL(Me)]-) <--> (LS-[FeIIH3L(Me)](2+) + LS-[FeIIL(Me)]-) spin-transition. The crystal structure of [FeIIH3L(Me)][FeIIL(Me)]PF6 (3) was determined at 295, 200, and 100 K. The structure consists of homochiral extended 2D puckered sheets, in which the complementary [FeIIH3L(Me)](2+) and [FeIIL(Me)]- capped tripodlike components, linked together by imidazole-imidazolate hydrogen bonds, are alternately arrayed in an up-and-down mode. The Fe-N bond distances and angles revealed that the FeII sites of both constituting units are in the high-spin (HS) state at 295 K; at 200 K, the FeII sites of [FeIIH3L(Me)](2+) and [FeIIL(Me)]- are in the HS and low-spin (LS) states, respectively. The FeII sites of both constituting units are in the LS state at 100 K. The size of the counteranion affects significantly the intra- and interlayer interactions leading to modifications of the spin crossover behavior. The onset of the second spin-transition of the ClO4- (1) and BF4- (2) salts adjoins the first spin-transition, while a mixed (HS-[FeIIH3L(Me)](2+) + LS-[FeIIL(Me)]-) spin-state spans a temperature range as wide as 70 K for salts 3-5 with larger counteranions, PF6-, AsF6-, and SbF6-, respectively. Compounds 1 and 2 showed remarkable LIESST (light induced excited spin state trapping) and reverse-LIESST effects, whereas 3-5 showed no remarkable LIESST effect. The interlayer interaction due to the size of the counteranion is an important factor governing the spin crossover behavior and LIESST effect.     

Inter- and intramolecular activation of aromatic C-H bonds by diphosphine and hydrido-bridged dinuclear iridium complexes

Reactions of [(Cp*Ir)2(mu-dmpm)(mu-H)2]2+ (1) with NaOtBu in aromatic solvent at room temperature give [(Cp*Ir)(H)(mu-dmpm)(mu-H)(Cp*Ir)(Ar)]+ [Ar = Ph (3), p-Tol (4a), m-Tol (4b), 2-furanyl (5a), 3-furanyl (5b)] via intermolecular aromatic C-H activation. Treatment of [(Cp*Ir)2(mu-dppm)(mu-H)2]2+ (2) with base (Et2NH) results in intramolecular C-H activation of the phenyl group in the dppm ligand to give [(Cp*Ir)(H){mu-PPh(C6H4)CH2PPh2}(mu-H)(Cp*Ir)]+ (6). The structures of 3, 5a, and 6 have been determined by X-ray diffraction methods.     

Synthesis, reactivity, spectroscopic characterization, X-ray structures, PGSE, and NOE NMR studies of (eta5-C5Me5)-rhodium and -iridium derivatives containing bis(pyrazolyl)alkane ligands

Rhodium(III) and iridium(III) complexes containing bis(pyrazolyl)methane ligands (pz = pyrazole, L' in general; specifically, L1 = H2C(pz)2, L2 = H2C(pzMe2)2, L3 = H2C(pz4Me)2, L4 = Me2C(pz)2), have been prepared in a study exploring the reactivity of these ligands toward [Cp*MCl(mu-Cl)]2 dimers (M = Rh, Ir; Cp* = pentamethylcyclopentadienyl). When the reaction was carried out in acetone solution, complexes of the type [Cp*M(L')Cl]Cl were obtained. However, when L1 and L2 ligands have been employed with excess [Cp*MCl(mu-Cl)]2, the formation of [Cp*M(L')Cl][Cp*MCl3] species has been observed. PGSE NMR measurements have been carried out for these complexes, in which the counterion is a cyclopentadienyl metal complex, in CD2Cl2 as a function of the concentration. The hydrodynamic radius (rH) and, consequently, the hydrodynamic volume (VH) of all the species have been determined from the measured translational self-diffusion coefficients (Dt), indicating the predominance of ion pairs in solution. NOE measurements and X-ray single-crystal studies suggest that the [Cp*MCl3]- approaches the cation, orienting the three Cl-legs of the "piano-stool" toward the CH2 moieties of the bis(pyrazolyl)methane ligands. The reaction of 1 equiv of [Cp*M(L')Cl]Cl or [Cp*M(L')Cl][Cp*MCl3] with 1 equiv of AgX (X = ClO4 or CF3SO3) in CH2Cl2 allows the generation of [Cp*M(L')Cl]X, whereas the reaction of 1 equiv of [Cp*M(L')Cl] with 2 equiv of AgX yields the dicationic complexes [Cp*M(L')(H2O)][X]2, where single water molecules are directly bonded to the metal atoms. The solid-state structures of a number of complexes were confirmed by X-ray crystallographic studies. The reaction of [Cp*Ir(L')(H2O)][X]2 with ammonium formate in water or acetone solution allows the generation of the hydride species [Cp*Ir(L')H][X].