Coordination chemistry of the cyclo-(P(5)tBu(4))(-) ion: monomeric and oligomeric copper(I), silver(I) and gold(I) complexes

[Na{cyclo-(P(5)tBu(4))}] (1) reacts with [CuCl(PCyp(3))(2)] (Cyp=cyclo-C(5)H(9)) and [CuCl(PPh(3))(3)] (1:1) to give the corresponding copper(I) complexes with a tetra-tert-butylcyclopentaphosphanide ligand, [Cu{cyclo- (P(5)tBu(4))}(PCyp(3))(2)] (2) and [Cu{cyclo-(P(5)tBu(4))}(PPh(3))(2)] (3). The CuCl adduct of 2, [Cu(2)(mu-Cl){cyclo-(P(5)tBu(4))}(PCyp(3))(2)] (4), was obtained from the reaction of 1 with [CuCl(PCyp(3))(2)] (1:2). Compounds 2 and 3 rearrange, even at -27 degrees C, to give [Cu(4){cyclo- (P(4)tBu(3))PtBu}(4)] (5), in which ring contraction of the [cyclo-(P(5)tBu(4))](-) anion has occurred. The reaction of 1 with [AgCl(PCyp(3))](4) or [AgCl(PPh(3))(2)] (1:1) leads to the formation of [Ag(4){cyclo-(P(4)tBu(3))PtBu}(4)] (6). Intermediates, which are most probably mononuclear, "[Ag{cyclo-(P(5)tBu(4))}(PR(3))(2)]" (R=Cyp, Ph) could be detected in the reaction mixtures, but not isolated. Finally, the reaction of 1 with [AuCl(PCyp(3))] (1:1) yielded [Au{cyclo-(P(5)tBu(4))}(PCyp(3))] (7), whereas an inseparable mixture of [Au(3){cyclo-(P(5)tBu(4))}(3)] (8) and [Au(4){cyclo-(P(4)tBu(3))PtBu}(4)] (9) was obtained from the analogous reaction with [AuCl(PPh(3))]. Complexes 3-7 were characterised by (31)P NMR spectroscopy, and X-ray crystal structures were determined for 3-9.     

Remarkable reactions of cyclooctatetraene diiron-bridging carbyne complexes with amino and amido compounds: nucleophilic addition to and breaking of the cyclooctatetraene ring

The reactions of the cationic, diiron-bridging carbyne complexes [Fe(2)(mu-CAr)(CO)(4)(eta(8)-C(8)H(8))]BF(4) (1, Ar=C(6)H(5); 2, Ar=p-CH(3)C(6)H(4); 3, Ar=p-CF(3)C(6)H(4)) with LiN(C(6)H(5))(2) in THF at low temperature gave novel N-nucleophilic-addition products, namely, the neutral, diiron-bridging carbyne complexes [Fe(2)(mu-CAr)(CO)(4)(eta(7)-C(8)H(8)N(C(6)H(5))(2))] (4, Ar=C(6)H(5); 5, Ar=p-CH(3)C(6)H(4); 6, Ar=p-CF(3)C(6)H(4))). Cationic bridging carbyne complexes 1-3 react with (C(2)H(5))(2)NH, (iC(3)H(7))(2)NH, and (C(6)H(11))(2)NH under the same conditions with ring cleavage of the COT ligand to produce the novel diiron-bridging carbene inner salts [Fe(2)[mu-C(Ar)C(8)H(8)NR(2)](CO)(4)] (7, Ar=C(6)H(5), R=C(2)H(5); 8, Ar=p-CH(3)C(6)H(4), R=C(2)H(5); 9, Ar=p-CF(3)C(6)H(4), R=C(2)H(5); 10, Ar=C(6)H(5), R=iC(3)H(7); 11, Ar=p-CH(3)C(6)H(4), R=iC(3)H(7); 12, Ar=p-CF(3)C(6)H(4), R=iC(3)H(7); 13, Ar=C(6)H(5), R=C(6)H(11); 14, Ar=p-CH(3)C(6)H(4), R=C(6)H(11), 15, Ar=p-CF(3)C(6)H(4), R=C(6)H(11)). Piperidine reacts similarly with cationic carbyne complex 3 to afford the corresponding bridging carbene inner salt [Fe(2)[mu-C(Ar)C(8)H(8)N(CH(2))(5)](CO)(4)] (16). Compound 9 was transformed into a new diiron-bridging carbene inner salt 17, the trans isomer of 9, by heating in benzene. Unexpectedly, the reaction of C(6)H(5)NH(2) with 2 gave a novel COT iron-carbene complex [Fe(2)[=C(C(6)H(4)CH(3)-p)NHC(6)H(5)](mu-CO)(CO)(3)(eta(8)-C(8)H(8))] (18). However, the analogous reactions of 2-naphthylamine with 2 and of p-CF(3)C(6)H(4)NH(2) with 3 produce novel chelated iron-carbene complexes [Fe(2)[=C(C(6)H(4)CH(3)-p)NC(10)H(7)](CO)(4)(eta(2):eta(3):eta(2)-C(8)H(9))] (19) and [Fe(2)[=C(C(6)H(4)CF(3)-p)NC(6)H(4)CF(3)-p](CO)(4)(eta(2):eta(3):eta(2)-C(8)H(9))] (20), respectively. Compound 18 can also be transformed into the analogous chelated iron-carbene complex [Fe(2)[=C(C(6)H(4)CH(3)-p)NC(6)H(5)](CO)(4)(eta(2):eta(3):eta(2)-C(8)H(9))] (21). The structures of complexes 6, 9, 15, 17, 18, and 21 have been established by X-ray diffraction studies.     

Organic acid solutions in the chromatography of inorganic ions VIII. Cation-exchange of Mn(II), Cd(II), Co(II), Ni(II), Zn(II), Cu(II), Fe(III), Sc(III), Y(III), Eu(III), Dy(III), Ho(III), Yb(III), Ti(IV) and Nb(V) in malate media

Summary The cation-exchange behaviour of Mn(II), Cd(II), Co(II), Ni(II), Zn(II), Cu(II), Fe(III), Sc(III), Y(III), Eu(III), Dy(III), Ho(III), Yb(III), Ti(IV) and Nb(V) in malate media at various concentrations and pH, was studied with Dowex 50 WX8 resin (200–400 mesh) in the ammonium form. Separation of Fe(III)/Cu(II), Fe(III)/Cu(II)/Zn(II), Fe(III)/Co(II)/Mn(II), Cu(II)/Ni(II)/Mn(II), Fe(III)/Cu(II)/Co(II)/Mn(II), Fe(III)/Cu(II)/Ni(II)/Cd(II), Yb(III)/Eu(III), Sc(III)/Y(III),Sc(III)/Yb(III)/Dy(III) and Nb(V)/Yb(III)/Ho(III) has been achieved, among others.This work was supported by C.N.R. of Italy.     

Molecular nitrides containing group 4 and 5 metals: single and double azatitanocubanes

Treatment of [[Ti(eta(5)-C(5)Me(5))(micro-NH)](3)(micro(3)-N)] (1) with the imido complexes [Ti(NAr)Cl(2)(py)(3)] (Ar=2,4,6-C(6)H(2)Me(3)) and [Ti(NtBu)Cl(2)(py)(3)] in toluene affords the single azatitanocubanes [[Cl(2)(ArN)Ti]( micro(3)-NH)(3)[Ti(3)(eta(5)-C(5)Me(5))(3)(micro(3)-N)]].(C(7)H(8)) (2.C(7)H(8)) and [[Cl(2)Ti](micro(3)-N)(2)(micro(3)-NH)[Ti(3)(eta(5)-C(5)Me(5))(3)(micro(3)-N)]] (3), respectively. Similar reactions of complex 1 with the niobium and tantalum imido derivatives [[M(NtBu)(NHtBu)Cl(2)(NH(2)tBu)](2)] (M=Nb, Ta) in toluene give the single azaheterometallocubanes [[Cl(2)(tBuN)M](micro(3)-N)(micro(3)-NH)(2)[Ti(3)(eta(5)-C(5)Me(5))(3)(micro(3)-N)]] (M=Nb (4), Ta (5)), both complexes react with 2,4,6-trimethylaniline to yield the analogous species [[Cl(2)(ArN)M](micro(3)-N)(micro(3)-NH)(2)[Ti(3)(eta(5)-C(5)Me(5))(3)(micro(3)-N)]].(C(7)H(8)) (Ar=2,4,6-C(6)H(2)Me(3), M=Nb (6.C(7)H(8)), Ta (7.C(7)H(8))). Also the azaheterodicubanes [M[micro(3)-N)(2)(micro(3)-NH)](2)[Ti(3)(eta(5)-C(5)Me(5))(3)(micro(3)-N)](2)].2C(7)H(8) [M=Ti (8.2C(7)H(8)), Zr (9.2C(7)H(8))], and [M[(micro(3)-N)(5)(micro(3)-NH)][Ti(3)(eta(5)-C(5)Me(5))(3)(micro(3)-N)](2)].2 C(7)H(8) (Nb (10.2C(7)H(8)), Ta (11.2C(7)H(8))) were prepared from 1 and the homoleptic dimethylamido complex [M(NMe(2))(x)] (x=4, M=Ti, Zr; x=5, M=Nb, Ta) in toluene at 150 degrees C. X-ray crystal structure determinations were performed for 6 and 10, which revealed a cube- and double-cube-type core, respectively. For complexes 2 and 4-7 we observed and studied by DNMR a rotation or trigonal-twist of the organometallic ligands [[Ti(eta(5)-C(5)Me(5))(micro-NH)](3)(micro(3)-N)] (1) and [(micro(3)-N)(micro(3)-NH)(2)[Ti(3)(eta(5)-C(5)Me(5))(3)(micro(3)-N)]](1-). Density functional theory calculations were carried out on model complexes of 2, 3, and 8 to establish and understand their structures.     

C-H activation and C=C double bond formation reactions in iridium ortho-methyl arylphosphane complexes

The Vaska-type iridium(I) complex [IrCl(CO){PPh(2)(2-MeC(6)H(4))}(2)] (1), characterized by an X-ray diffraction study, was obtained from iridium(III) chloride hydrate and PPh(2)(2,6-MeRC(6)H(3)) with R=H in DMF, whereas for R=Me, activation of two ortho-methyl groups resulted in the biscyclometalated iridium(III) compound [IrCl(CO){PPh(2)(2,6-CH(2)MeC(6)H(3))}(2)] (2). Conversely, for R=Me the iridium(I) compound [IrCl(CO){PPh(2)(2,6-Me(2)C(6)H(3))}(2)] (3) can be obtained by treatment of [IrCl(COE)(2)](2) (COE=cyclooctene) with carbon monoxide and the phosphane in acetonitrile. Compound 3 in CH(2)Cl(2) undergoes intramolecular C-H oxidative addition, affording the cyclometalated hydride iridium(III) species [IrHCl(CO){PPh(2)(2,6-CH(2)MeC(6)H(3))}{PPh(2)(2,6-Me(2)C(6)H(3))}] (4). Treatment of 2 with Na[BAr(f) (4)] (Ar(f)=3,5-C(6)H(3)(CF(3))(2)) gives the fluxional cationic 16-electron complex [Ir(CO){PPh(2)(2,6-CH(2)MeC(6)H(3))}(2)][BAr(f) (4)] (5), which reversibly reacts with dihydrogen to afford the delta-agostic complex [IrH(CO){PPh(2)(2,6-CH(2)MeC(6)H(3))}{PPh(2)(2,6-Me(2)C(6)H(3))}][BAr(f)(4)] (6), through cleavage of an Ir-C bond. This species can also be formed by treatment of 4 with Na[BAr(f)(4)] or of 2 with Na[BAr(f)(4)] through C-H oxidative addition of one ortho-methyl group, via a transient 14-electron iridium(I) complex. Heating of the coordinatively unsaturated biscyclometalated species 5 in toluene gives the trans-dihydride iridium(III) complex [IrH(2)(CO){PPh(2)(2,6-MeC(6)H(3)CH=CHC(6)H(3)Me-2,6)PPh(2)}][BAr(f) (4)] (7), containing a trans-stilbene-type terdentate ligand, as result of a dehydrogenative carbon-carbon double bond coupling reaction, possibly through an iridium carbene species.     

Formation of dinuclear titanium and zirconium complexes by olefin metathesis--catalytic preparation of organometallic catalyst systems

The titanium complex [(C(5)H(4)bond;allyl)TiCl(3)] (2) undergoes olefin metathesis coupling when treated with 3 mol % of [Cl(2)(L(1))(L(2))Ru=CHPh] (L(1)=L(2)=PCy(3), 4 a; L(1)=PCy(3), L(2)=(H(2)IMes), 4 b) to yield the dimetallic complex [Cl(3)Ti(C(5)H(4))-CH(2)CH=CHCH(2)-(C(5)H(4))TiCl(3)] (5). The allyl-substituted titanocene complex [Cp(C(5)H(4)bond;allyl)TiCl(2)] (3) analogously yields the dimetallic system 6 when treated with 4. The ansa-zirconocene complex [Me(2)Si(C(5)H(4))(C(5)H(3)bond;allyl)ZrCl(2)] (7) cleanly yields the analogous dimetallic coupling product 8 (>95 % isomerically pure), when treated with catalytic amounts of 4 b in toluene. Complex 8 gives an active homogeneous ethene or propene polymerization catalyst, especially at elevated temperatures, when treated with excess methylalumoxane.     

The nature of unsupported uranium-ruthenium bonds: a combined experimental and theoretical study

Four new uranium-ruthenium complexes, [(Tren(TMS))URu(η(5)-C(5)H(5))(CO)(2)] (9), [(Tren(DMSB))URu(η(5)-C(5)H(5))(CO)(2)] (10), [(Ts(Tolyl))(THF)URu(η(5)-C(5)H(5))(CO)(2)] (11), and [(Ts(Xylyl))(THF)URu(η(5)-C(5)H(5))(CO)(2)] (12) [Tren(TMS)=N(CH(2)CH(2)NSiMe(3))(3); Tren(DMSB)=N(CH(2)CH(2)NSiMe(2)tBu)(3)]; Ts(Tolyl)=HC(SiMe(2)NC(6)H(4)-4-Me)(3); Ts(Xylyl)=HC(SiMe(2)NC(6)H(3)-3,5-Me(2))(3)], were prepared by a salt-elimination strategy. Structural, spectroscopic, and computational analyses of 9-12 shows: i) the formation of unsupported uranium-ruthenium bonds with no isocarbonyl linkages in the solid state; ii) ruthenium-carbonyl backbonding in the [Ru(η(5)-C(5)H(5))(CO)(2)](-) ions that is tempered by polarization of charge within the ruthenium fragments towards uranium; iii) closed-shell uranium-ruthenium interactions that can be classified as predominantly ionic with little covalent character. Comparison of the calculated U-Ru bond interaction energies (BIEs) of 9-12 with the BIE of [(η(5)-C(5)H(5))(3)URu(η(5)-C(5)H(5))(CO)(2)], for which an experimentally determined U-Ru bond disruption enthalpy (BDE) has been reported, suggests BDEs of approximately 150 kJ mol(-1) for 9-12.     

1,4-dicyanobenzene as a scaffold for the preparation of bimetallic actinide complexes exhibiting metal-metal communication

Reaction of two equivalents of [(C(5)Me(4)Et)(2)U(CH(3))(Cl)] (6) or [(C(5)Me(5))(2)Th(CH(3))(Br)] (7) with 1,4-dicyanobenzene leads to the formation of the novel 1,4-phenylenediketimide-bridged bimetallic organoactinide complexes [{(C(5)Me(4)Et)(2)(Cl)U}(2)(mu-{N==C(CH(3))-C(6)H(4)-(CH(3))C==N})] (8) and [{(C(5)Me(5))(2)(Br)Th}(2)(mu-{N==C(CH(3))-C(6)H(4)- (CH(3))C==N})] (9), respectively. These complexes were structurally characterized by single-crystal X-ray diffraction and NMR spectroscopy. Metal-metal interactions in these isovalent bimetallic systems were assessed by means of cyclic voltammetry, UV-visible/NIR absorption spectroscopy, and variable-temperature magnetic susceptibility. Although evidence for magnetic coupling between metal centers in the bimetallic U(IV)/U(IV) (5f(2)-5f(2)) complex is ambiguous, the complex displays appreciable electronic communication between the metal centers through the pi system of the dianionic diketimide bridging ligand, as judged by voltammetry. The transition intensities of the f-f bands for the bimetallic U(IV)/U(IV) system decrease substantially compared to the related monometallic ketimide chloride complex, [(C(5)Me(5))(2)U(Cl){-N==C(CH(3))-(3,4,5-F(3)-C(6)H(2))}] (11). Also reported herein are new synthetic routes to the actinide starting materials [(C(5)Me(4)Et)(2)U(CH(3))(Cl)] (6) and [(C(5)Me(5))(2)Th(CH(3))(Br)] (7) in addition to the syntheses and structures of the monometallic uranium complexes [(C(5)Me(4)Et)(2)UCl(2)] (3), [(C(5)Me(4)Et)(2)U(CH(3))(2)] (4), [(C(5)Me(4)Et)(2)U{-N==C(CH(3))-C(6)H(4)-C==N}(2)] (10), and 11.     

A combination of lacunary polyoxometalates and high-nuclear transition-metal clusters under hydrothermal conditions. Part II: From double cluster, dimer, and tetramer to three-dimensional frameworks

The hydrothermal reactions of trivacant Keggin A-alpha-XW(9)O(34) polyoxoanions (X=P(V)/Si(IV)) with transition-metal ions (Ni(II)/Cu(II)/Fe(II)) in the presence of amines result in eight novel high-nuclear transition-metal-substituted polyoxotungstates [{Ni(7)(mu(3)-OH)(3)O(2)(dap)(3)(H(2)O)(6)}(B-alpha-PW(9)O(34))][{Ni(6)(mu(3)-OH)(3)(dap)(3)(H(2)O)(6)}(B-alpha-PW(9)O(34))][Ni(dap)(2)(H(2)O)(2)]4.5 H(2)O (1), [Cu(dap)(H(2)O)(3)](2)[{Cu(8)(dap)(4)(H(2)O)(2)}(B-alpha-SiW(9)O(34))(2)]6 H(2)O (2), (enH(2))(3)H(15)[{Fe(II) (1.5)Fe(III) (12)(mu(3)-OH)(12)(mu(4)-PO(4))(4)}(B-alpha-PW(9)O(34))(4)]ca.130 H(2)O (3), [{Cu(6)(mu(3)-OH)(3)(en)(3) (H(2)O)(3)}(B-alpha-PW(9)O(34))]7 H(2)O (4), [{Ni(6)(mu(3)-OH)(3)(en)(3)(H(2)O)(6)}(B-alpha-PW(9)O(34))]7 H(2)O (5), [{Ni(6)(mu(3)-OH)(3)(en)(2)(H(2)O)(8)}(B-alpha-PW(9)O(34))]7 H(2)O (6), [{Ni(6)(mu(3)-OH)(3)(dap)(2)(H(2)O)(8)}(B-alpha-PW(9)O(34))] 7 H(2)O (7), and [{Ni(6)(mu(3)-OH)(3)(en)(3)(H(2)O)(6)}(B-alpha-SiW(9)O(34))][Ni(0.5)(en)] 3.5 H(2)O (8) (en=ethylenediamine, dap=1,2-diaminopropane). These compounds have been structurally characterized by elemental analyses, IR spectra, diffuse reflectance spectra, thermogravimatric analysis, and X-ray crystallography. The double-cluster complex of phosphotungstate 1 simultaneously contains hepta- and hexa-Ni(II)-substituted trivacant Keggin units [{Ni(7)(mu(3)-OH)(3)O(2)(dap)(3)(H(2)O)(6)}(B-alpha-PW(9)O(34))](2-) and [{Ni(6)(mu(3)-OH)(3)(dap)(3)(H(2)O)(6)}(B-alpha-PW(9)O(34))]. The dimeric silicotungstate 2 is built up from two trivacant Keggin [B-alpha-SiW(9)O(34)](10-) fragments linked by an octa-Cu(II) cluster. The main skeleton of 3 is a tetrameric cluster constructed from four tri-Fe(III)-substituted [Fe(III) (3)(mu(3)-OH)(3)(B-alpha-PW(9) O(34))](3-) Keggin units linked by a central Fe(II) (4)O(4) cubane core and four mu(4)-PO(4) bridges. Complex 4 is an unprecedented three-dimensional extended architecture with hexagonal channels built by hexa-Cu(II) clusters and trivacant Keggin [B-alpha-PW(9)O(34)](9-) fragments. The common feature of 5-8 is that they contain a B-alpha-isomeric trivacant Keggin fragment capped by a hexa-Ni(II) cluster, very similar to the hexa-Ni(II)-substituted trivacant Keggin unit in 1. Magnetic measurements illustrate that 1, 2, and 5 have ferromagnetic couplings within the magnetic metal centers, whereas 3 and 4 reveal the antiferromagnetic exchange interactions within the magnetic metal centers. Moreover, the magnetic behavior of 4 and 5 have been theoretically simulated by the MAGPACK magnetic program package.     

Binding N2, N2H2, N2H4, and NH3 to transition-metal sulfur sites: modeling potential intermediates of biological N2 fixation

In the quest for low-molecular-weight metal sulfur complexes that bind nitrogenase-relevant small molecules and can serve as model complexes for nitrogenase, compounds with the [Ru(PiPr(3))('N(2)Me(2)S(2)')] fragment were found ('N(2)Me(2)S(2)'(2-)=1,2-ethanediamine-N,N'-dimethyl-N,N'-bis(2-benzenethiolate)(2-)). This fragment enabled the synthesis of a first series of chiral metal sulfur complexes, [Ru(L)(PiPr(3))('N(2)Me(2)S(2)')] with L=N(2), N(2)H(2), N(2)H(4), and NH(3), that meet the biological constraint of forming under mild conditions. The reaction of [Ru(NCCH(3))(PiPr(3))('N(2)Me(2)S(2)')] (1) with NH(3) gave the ammonia complex [Ru(NH(3))(PiPr(3))('N(2)Me(2)S(2)')] (4), which readily exchanged NH(3) for N(2) to yield the mononuclear dinitrogen complex [Ru(N(2))(PiPr(3))('N(2)Me(2)S(2)')] (2) in almost quantitative yield. Complex 2, obtained by this new efficient synthesis, was the starting material for the synthesis of dinuclear (R,R)- and (S,S)-[micro-N(2)[Ru(PiPr(3))('N(2)Me(2)S(2)')](2)] ((R,R)-/(S,S)-3). (Both 2 and 3 have been reported previously.) The as-yet inexplicable behavior of complex 3 to form also the R,S isomer in solution has been revealed by DFT calculations and (2)D NMR spectroscopy studies. The reaction of 1 or 2 with anhydrous hydrazine yielded the hydrazine complex [Ru(N(2)H(4))(PiPr(3))('N(2)Me(2)S(2)')] (6), which is a highly reactive intermediate. Disproportionation of 6 resulted in the formation of mononuclear diazene complexes, the ammonia complex 4, and finally the dinuclear diazene complex [micro-N(2)H(2)[Ru(PiPr(3))('N(2)Me(2)S(2)')](2)] (5). Dinuclear complex 5 could also be obtained directly in an independent synthesis from 1 and N(2)H(2), which was generated in situ by acidolysis of K(2)N(2)(CO(2))(2). Treatment of 6 with CH(2)Cl(2), however, formed a chloromethylated diazene species [[Ru(PiPr(3))('N(2)Me(2)S(2)')]-micro-N(2)H(2)[Ru(Cl)('N(2)Me(2)S(2)CH(2)Cl')]] (9) ('N(2)Me(2)S(2)CH(2)Cl'(2-) =1,2-ethanediamine-N,N'-dimethyl-N-(2-benzenethiolate)(1-)-N'-(2-benzenechloromethylthioether)(1-)]. The molecular structures of 4, 5, and 9 were determined by X-ray crystal structure analysis, and the labile N(2)H(4) complex 6 was characterized by NMR spectroscopy.     

Convenient syntheses of fluorous aryl iodides and hypervalent iodine compounds: ArI(L)n reagents that are recoverable by simple liquid/liquid biphase workups,and applications in oxidations of hydroquinones

Iodinations of the ortho, meta, and para fluorous arenes (R(f8)CH(2)CH(2)CH(2))(2)C(6)H(4) (R(f8)=(CF(2))(7)CF(3)) with I(2)/H(5)IO(6) in AcOH/H(2)SO(4)/H(2)O give 3,4-(R(f8)CH(2)CH(2)CH(2))(2)C(6)H(3)I (5) and the analogous 2,4- (6) and 2,5- (7) isomers, respectively. Spectroscopic yields are >90 %, but 5 and 7 must be separated by chromatography from by-products (yields isolated: 70 %, 97 %, 61 %). Reaction of 1,3,5-(R(f8)CH(2)CH(2)CH(2))(3)C(6)H(3) with PhI(OAc)(2)/I(2) gives 2,4,6-(R(f8)CH(2)CH(2)CH(2))(3)C(6)H(2)I (8) on multigram scales in 97 % yield. The CF(3)C(6)F(11)/toluene partition coefficients of 5-8 (24 degrees C: 69.5:30.5 (5), 74.7:25.3 (6), 73.9:26.1 (7), 98.0:2.0 (8)) are lower than those of the precursors, but CF(3)C(6)F(11)/MeOH gives higher values (97.0:3.0 (5), 98.6:1.4 (6), 98.0:2.0 (7), >99.3:<0.3 (8)). Reactions of 5-8 with excess NaBO(3) in AcOH yield the corresponding ArI(OAc)(2) species 9-12 (9, 85 % as a 90:10 9/5 mixture; 10, 97 %; 11, 95 %; 12, 93 % as a 95:5 12/8 mixture). These rapidly oxidize 1,4-hydroquinones in MeOH. Subsequent additions of CF(3)C(6)F(11) give liquid biphase systems. Solvent removal from the CF(3)C(6)F(11) phases gives 5-8 in >99-98 % yields, and solvent removal from the MeOH phases gives the quinone products, normally in >99-95 % yields. The recovered compounds 5-8 are easily reoxidized to 9-12 and used again.     

Synthesis and structure of new carborane-substituted cyclotriphosphazenes

The reactions of [N(3)P(3)Cl(6)] with one, two, or three equivalents of the difunctional 1,2-closo-carborane C(2)B(10)H(10)[CH(2)OH](2) and K(2)CO(3) in acetone have been investigated. These reactions led to the new spiro-closo-carboranylphosphazenes gem-[N(3)P(3)Cl(6-2n)[(OCH(2))(2)C(2)B(10)H(10)](n)] (n=1 (1), 2 (2)) and the first fully carborane-substituted phosphazene gem-[N(3)P(3)[(OCH(2))(2)C(2)B(10)H(10)](3)] (3). A bridged product, non-gem-[N(3)P(3)Cl(4)[(OCH(2))(2)C(2)B(10)H(10)]] (4), was also detected. The reaction of the well-known spiro derivatives [N(3)P(3)Cl(2)(O(2)C(12)H(8))(2)] and [N(3)P(3)Cl(4)(O(2)C(12)H(8))] with the same carborane-diol and K(2)CO(3) in acetone gave the new compounds gem-[N(3)P(3)(O(2)C(12)H(8))(3-n)[(OCH(2))(2)C(2)B(10)H(10)](n)] (n=1 (5) or 2 (6), respectively), without signs of intra- or intermolecularly bridged species. Upon treatment with NEt(3) in acetone, compound 5 was converted into the corresponding nido-carboranylphosphazene. However, the reaction of gem-[N(3)P(3)(O(2)C(12)H(8))(2)[(OCH(2))(2)C(2)B(10)H(10)]] (5) with NEt(3) in ethanol instead of acetone proceeded in a different manner to give the new compound (NHEt(3))(2)[N(3)P(3)(O(2)C(12)H(8))(2)(O)[OCH(2)C(2)B(9)H(10)CH(2)OCH(2)CH(3)]] (7). For compounds with two 2,2'-dioxybiphenyl units, gem-[N(3)P(3)(O(2)C(12)H(8))(2)[(OCH(2))(2)C(2)B(10)H(10)]] (5), (NHEt(3))[N(3)P(3)(O(2)C(12)H(8))(2)[(OCH(2))(2)C(2)B(9)H(10)]] (8), and (NHEt(3))(2)[N(3)P(3)(O(2)C(12)H(8))(2)(O)[OCH(2)C(2)B(9)H(10)CH(2)OCH(2)CH(3)]] (7), a mixture of different stereoisomers may be expected. However, for 5 and 7 only the meso compounds seem to be formed, with the same (R,S)-configuration as in the precursor [N(3)P(3)Cl(2)(O(2)C(12)H(8))(2)]. The reaction of 5 to give 8 seems to proceed with a change of configuration at one phosphorus center, giving a racemic mixture. The crystal structures of the nido-carboranylphosphazenes 7 and 8 have been confirmed by X-ray diffraction methods.     

Solid state NMR characterization of individual compounds and solid solutions formed in Sc(2)O(3)--V(2)O(5)--Nb(2)O(5)--Ta(2)O(5) system

In this study, (51)V, (45)Sc and (93)Nb MAS NMR combined with satellite transition spectroscopy analysis were used to characterize the complex solid mixtures: VNb(9(1-x))Ta(9x)O(25), ScNb((1-x))Ta(x)O(4) and ScNb(2(1-x))Ta(2x)VO(9) (x = 0, 0.3, 0.5, 0.7, 1.0). This led us to describe the structures of Sc and V sites. The conclusions were based on accurate values for (51)V quadrupole coupling and chemical shift tensors obtained with (51)V MAS NMR/SATRAS for VNb(9)O(25), VTa(9)O(25) and ScVO(4). The (45)Sc NMR parameters have been obtained for Sc(2)O(3), ScVO(4), ScNbO(4) and ScTaO(4). On the basis of (45)Sc NMR and data available from literature, the ranges of the (45)Sc chemical shift have been established for ScO(6) and ScO(8). The gradual change of the (45)Sc and (51)V NMR parameters with x confirms the formation of solid solutions in the process of synthesis of VNb(9(1-x))Ta(9x)O(25) and ScNb((1-x))Ta(x)O(4), in contrast to ScNb(2(1-x))Ta(2x)VO(9). The cation sublattice of ScNb((1-x))Ta(x)O(4) is found to be in octahedral coordination. The V sites in VNb(9(1-x))Ta(9x)O(25) are present in the form of slightly distorted tetrahedra. The (93)Nb NMR parameters have been obtained for VNb(9)O(25).     

HP-Ca2Si5N8--a new high-pressure nitridosilicate: synthesis, structure, luminescence, and DFT calculations

HP-Ca(2)Si(5)N(8) was obtained by means of high-pressure high-temperature synthesis utilizing the multianvil technique (6 to 12 GPa, 900 to 1200 degrees C) starting from the ambient-pressure phase Ca(2)Si(5)N(8). HP-Ca(2)Si(5)N(8) crystallizes in the orthorhombic crystal system (Pbca (no. 61), a=1058.4(2), b=965.2(2), c=1366.3(3) pm, V=1395.7(7)x10(6) pm(3), Z=8, R1=0.1191). The HP-Ca(2)Si(5)N(8) structure is built up by a three-dimensional, highly condensed nitridosilicate framework with N([2]) as well as N([3]) bridging. Corrugated layers of corner-sharing SiN(4) tetrahedra are interconnected by further SiN(4) units. The Ca(2+) ions are situated between these layers with coordination numbers 6+1 and 7+1, respectively. HP-Ca(2)Si(5)N(8) as well as hypothetical orthorhombic o-Ca(2)Si(5)N(8) (isostructural to the ambient-pressure modifications of Sr(2)Si(5)N(8) and Ba(2)Si(5)N(8)) were studied as high-pressure phases of Ca(2)Si(5)N(8) up to 100 GPa by using density functional calculations. The transition pressure into HP-Ca(2)Si(5)N(8) was calculated to 1.7 GPa, whereas o-Ca(2)Si(5)N(8) will not be adopted as a high-pressure phase. Two different decomposition pathways of Ca(2)Si(5)N(8) (into Ca(3)N(2) and Si(3)N(4) or into CaSiN(2) and Si(3)N(4)) and their pressure dependence were examined. It was found that a pressure-induced decomposition of Ca(2)Si(5)N(8) into CaSiN(2) and Si(3)N(4) is preferred and that Ca(2)Si(5)N(8) is no longer thermodynamically stable under pressures exceeding 15 GPa. Luminescence investigations (excitation at 365 nm) of HP-Ca(2)Si(5)N(8):Eu(2+) reveal a broadband emission peaking at 627 nm (FWHM=97 nm), similar to the ambient-pressure phase Ca(2)Si(5)N(8):Eu(2+).     

Spectroelectrochemical studies on mixed-valence states in a cyanide-bridged molecular square, [Ru(II)(2)Fe(II)(2)(mu-CN)(4)(bpy)(8)](PF6)(4).CHCl(3).H(2)O

A cyanide-bridged molecular square of [Ru(II) (2)Fe(II) (2)(mu-CN)(4)(bpy)(8)](PF(6))(4).CHCl(3).H(2)O, abbreviated as [Ru(II) (2)Fe(II) (2)](PF(6))(4), has been synthesised and electrochemically generated mixed-valence states have been studied by spectroelectrochemical methods. The complex cation of [Ru(II) (2)Fe(II) (2)](4+) is nearly a square and is composed of alternate Ru(II) and Fe(II) ions bridged by four cyanide ions. The cyclic voltammogram (CV) of [Ru(II) (2)Fe(II) (2)](PF(6))(4) in acetonitrile showed four quasireversible waves at 0.69, 0.94, 1.42 and 1.70 V (vs. SSCE), which correspond to the four one-electron redox processes of [Ru(II) (2)Fe(II) (2)](4+) right arrow over left arrow [Ru(II) (2)Fe(II)Fe(III)] (5+) right arrow over left arrow [Ru(II) (2)Fe(III) (2)](6+) right arrow over left arrow [Ru(II)Ru(III)Fe(III) (2)](7+) right arrow over left arrow [Ru(III) (2)Fe(III) (2)](8+). Electrochemically generated [Ru(II) (2)Fe(II)Fe(III)](5+) and [Ru(II) (2)Fe(III) (2)](6+) showed new absorption bands at 2350 nm (epsilon =5500 M(-1) cm(-1)) and 1560 nm (epsilon =10 500 M(-1) cm(-1)), respectively, which were assigned to the intramolecular IT (intervalence transfer) bands from Fe(II) to Fe(III) and from Ru(II) to Fe(III) ions, respectively. The electronic interaction matrix elements (H(AB)) and the degrees of electronic delocalisation (alpha(2)) were estimated to be 1090 cm(-1) and 0.065 for the [Ru(II) (2)Fe(II)Fe(III) (2)](5+) state and 1990 cm(-1) and 0.065 for the [Ru(II) (2)Fe(III) (2)](6+) states.     

Half-sandwich bis(tetramethylaluminate) complexes of the rare-earth metals: synthesis, structural chemistry, and performance in isoprene polymerization

The protonolysis reaction of [Ln(AlMe(4))(3)] with various substituted cyclopentadienyl derivatives HCp(R) gives access to a series of half-sandwich complexes [Ln(AlMe(4))(2)(Cp(R))]. Whereas bis(tetramethylaluminate) complexes with [1,3-(Me(3)Si)(2)C(5)H(3)] and [C(5)Me(4)SiMe(3)] ancillary ligands form easily at ambient temperature for the entire Ln(III) cation size range (Ln=Lu, Y, Sm, Nd, La), exchange with the less reactive [1,2,4-(Me(3)C)(3)C(5)H(3)] was only obtained at elevated temperatures and for the larger metal centers Sm, Nd, and La. X-ray structure analyses of seven representative complexes of the type [Ln(AlMe(4))(2)(Cp(R))] reveal a similar distinct [AlMe(4)] coordination (one eta(2), one bent eta(2)). Treatment with Me(2)AlCl leads to [AlMe(4)] --> [Cl] exchange and, depending on the Al/Ln ratio and the Cp(R) ligand, varying amounts of partially and fully exchanged products [{Ln(AlMe(4))(mu-Cl)(Cp(R))}(2)] and [{Ln(mu-Cl)(2)(Cp(R))}(n)], respectively, have been identified. Complexes [{Y(AlMe(4))(mu-Cl)(C(5)Me(4)SiMe(3))}(2)] and [{Nd(AlMe(4))(mu-Cl){1,2,4-(Me(3)C)(3)C(5)H(2)}}(2)] have been characterized by X-ray structure analysis. All of the chlorinated half-sandwich complexes are inactive in isoprene polymerization. However, activation of the complexes [Ln(AlMe(4))(2)(Cp(R))] with boron-containing cocatalysts, such as [Ph(3)C][B(C(6)F(5))(4)], [PhNMe(2)H][B(C(6)F(5))(4)], or B(C(6)F(5))(3), produces initiators for the fabrication of trans-1,4-polyisoprene. The choice of rare-earth metal cation size, Cp(R) ancillary ligand, and type of boron cocatalyst crucially affects the polymerization performance, including activity, catalyst efficiency, living character, and polymer stereoregularity. The highest stereoselectivities were observed for the precatalyst/cocatalyst systems [La(AlMe(4))(2)(C(5)Me(4)SiMe(3))]/B(C(6)F(5))(3) (trans-1,4 content: 95.6 %, M(w)/M(n)=1.26) and [La(AlMe(4))(2)(C(5)Me(5))]/B(C(6)F(5))(3) (trans-1,4 content: 99.5 %, M(w)/M(n)=1.18).     

Construction of metal-organic frameworks: versatile behaviour of a ligand containing mono- and bidentate coordination sites

Five new coordination polymers based on a new 2,2'-bipyridine derived ligand N,N'-bis(pyridin-4-yl)-2,2'-bipyridine-5,5'-dicarboxamide (=L) are reported herein. Isostructural three-dimensional coordination polymers with a rare (4,6)-connected network of {4(4).6(2)}(3){4(6).8(9)}(2) topology were synthesised from Cu(NO(3))(2), Zn(NO(3))(2) or a mixture of Cu(NO(3))(2)/Fe(BF(4))(2) with L in complexes {[Cu(5)L(6)]·(NO(3))(10)·(H(2)O)(18)}(∞) (1), {[Zn(5)L(6)]·(NO(3))(10)·(H(2)O)(18)}(∞) (2) and {[Fe(x)Cu(y)L(6)]·(NO(3))(10)·(H(2)O)(18)}(∞) (3; where x+y=5). Complexes with two-dimensional grid structures resulted from treatment with CoCl(2) or Cd(NO(3))(2) with L in complexes {[CoLCl(2)]·DMF}(∞) (4) and {CdL(NO(3))(2)}(∞) (5).     

Unsymmetrically substituted 9,10-dihydro-9,10-diboraanthracenes as versatile building blocks for boron-doped π-conjugated systems

The targeted hydrolysis of the 9,10-dihydro-9,10-diboraanthracene adduct (Me(2)S)HB(C(6)H(4))(2)BH(SMe(2)) (1) with 0.5 equiv of H(2)O leads to formation of the borinic acid anhydride [(Me(2)S)HB(C(6)H(4))(2)B](2)O (2) and thereby provides access to the field of unsymmetrically substituted 9,10-dihydro-9,10-diboraanthracenes. Compound 2 reacts with tBuC≡CH to give the corresponding vinyl derivative in an essentially quantitative conversion. Subsequent cleavage of the B-O-B bridge by LiAlH(4) with formation of hydridoborate functionalities is possible but is accompanied by partial B-C(vinyl) bond degradation. This situation changes when the related mesityl derivative [MesB(C(6)H(4))(2)B](2)O (7) is employed, which can be synthesized from BrB(C(6)H(4))(2)BBr (6) by treatment with 1 equiv of MesMgBr and subsequent hydrolysis. The reaction of 7 with LiAlH(4) in tetrahydrofuran (THF) furnishes Li[MesB(C(6)H(4))(2)BH(2)] (8); hydride elimination with Me(3)SiCl leads to formation of the THF adduct MesB(C(6)H(4))(2)BH(THF) (9·THF). Alternatively, 7 can be transformed into the bromoborane MesB(C(6)H(4))(2)BBr (10) by treatment with BBr(3). A Br/H-exchange reaction between 10 and Et(3)SiH yields the donor-free borane MesB(C(6)H(4))(2)BH (9), which forms B-H-B bridged dimers (9)(2) in the solid state. The vinyl borane MesB(C(6)H(4))(2)BC(H)=C(H)Mes (14) is accessible from MesC≡CH and either 9·THF or 9. Compared with the related compound Mes(2)BC(H)=C(H)Mes, the electronic absorption and emission spectra of 14 reveal bathochromic shifts of Δλ(abs)=17 nm and Δλ(em)=74 nm, which can be attributed to the rigid, fully delocalized π framework of the [MesB(C(6)H(4))(2)B] chromophore.     

Coordination chemistry of the soluble metal oxide analogue [Mo5O13(OCH3)4(NO)]3- with manganese carbonyl species

The reactions of neutral or cationic manganese carbonyl species towards the oxo-nitrosyl complex [Na(MeOH)[Mo(5)O(13)(OCH(3))(4)(NO)]](2-) have been investigated in various conditions. This system provides an unique opportunity for probing the basic reactions involved in the preparation of solid oxide-supported heterogeneous catalysts, that is, mobility of transition-metal species at the surface and dissolution-precipitation of the support. Under nitrogen and in the dark, the reaction of in situ generated fac-[Mn(CO)(3)](+) species with (nBu(4)N)(2)[Na(MeOH)-[Mo(5)O(13)(OMe)(4)(NO)]] in MeOH yields (nBu(4)N)(2)[Mn(CO)(3)(H(2)O)[Mo(5)O(13)(OMe)(4)(NO)]] at room temperature, while (nBu(4)N)(3)[Na[Mo(5)O(13)(OMe)(4)(NO)](2)[Mn(CO)(3)](2)] is obtained under reflux. The former transforms into the latter under reflux in methanol in the presence of sodium bromide; this involves the migration of the fac-[Mn(CO)(3)](+) moiety from a basal kappa(2)O coordination site to a lateral kappa(3)O site. Oxidation and decarbonylation of manganese carbonyl species as well as degradation of the oxonitrosyl starting material and reaggregation of oxo(methoxo)molybdenum fragments occur in non-deareated MeOH, and both (nBu(4)N)(4)[Mn(H(2)O)(2)[Mo(5)O(16)(OMe)(2)](2)[Mn(CO)(3)](2)] and (nBu(4)N)(4)[Mn(H(2)O)(2)[Mo(5)O(13)(OMe)(4)(NO)](2)] as well as (nBu(4)N)(2)[MnBr[Mo(5)O(13)(OMe)(4)(NO)]] have been obtained in this way. The rhenium analogue (nBu(4)N)(2)[Re(CO)(3)(H(2)O)[Mo(5)O(13)(OMe)(4)(NO)]] has also been synthesized. The crystal structures of (nBu(4)N)(2)[Re(CO)(3)(H(2)O)[Mo(5)O(13)(OMe)(4)(NO)]], (nBu(4)N)(3)[Na[Mo(5)O(13)(OMe)(4)(NO)](2)[Mn(CO)(3)](2)], (nBu(4)N)(4)[Mn(H(2)O)(2)[Mo(5)O(16)(OMe)(2)](2)[Mn(CO)(3)](2)], (nBu(4)N)(4)[Mn(H(2)O)(2)[Mo(5)O(13)(OMe)(4)(NO)](2)] and (nBu(4)N)(2)[MnBr[Mo(5)O(13)(OMe)(4)(NO)]] have been determined.     

Diferratricarbaboranes of the subcloso-[(eta5-C5H5)2Fe2C3B8H11] type, the first representatives of the 13-vertex dimetallatricarbaborane series

Treatment of the [2-Cp-9-tBuNH-closo-2,1,7,9-FeC(3)B(8)H(10)] (1) ferratricarbollide (Cp = eta(5)-C(5)H(5) (-)) with Na(+) C(10)H(8) (-) in 1,2-dimethoxyethane (DME) at room temperature produced an air-sensitive transient anion with a tentatively identified nido-[tBuNH-CpFeC(3)B(8)H(10)](2-) constitution. In-situ reaction of this low-stability ion with [CpFe(CO)(2)I] or [CpFe(CO)(2)](2) generated three violet diferratricarbaboranes identified as paramagnetic subcloso complexes [4,5-Cp(2-)-4,5,1,6,7-Fe(2)C(3)B(8)H(11)] (2; yield 2 %), [4,5-Cp(2-)-4,5,1,7,12-Fe(2)C(3)B(8)H(11)] (3; yield 2 %), and [7-tBuNH-4,5-Cp(2-)-4,5,1,7,12-Fe(2)C(3)B(8)H(10)] (4; yield 14 %). These first representatives of the 13-vertex dimetallatricarbaborane family were characterized by EPR and IR spectroscopy, and mass spectrometry, and their structures were determined by X-ray diffraction analysis.