Selective complexation of uranium(III) over lanthanide(III) triflates by 2,2':6',2"-terpyridine. X-Ray crystal structures of [M(OTf)3(terpy)2] and [M(OTf)2(terpy)2(py)][OTf](M = Nd, Ce, U) and of polynuclear mu-oxo uranium(IV) complexes resulting from hydrolysis

Reactions of Ln(OTf)3(Ln = Ce, Nd) or [U(OTf)3(dme)2](OTf = OSO2CF3, dme = dimethoxyethane) with 2 mol equivalents of 2,2':6',2"-terpyridine (terpy) in pyridine or acetonitrile led to the quantitative formation of the bis(terpy) complexes which crystallized as the discrete cation-anion pairs [M(OTf)2(terpy)2(py)][OTf] x 0.5py from pyridine or neutral derivatives [M(OTf)3(terpy)2] x nMeCN from acetonitrile (M = Ce, Nd, U). The crystal structures of these complexes show the differences in the M-O bond lengths to follow the variation of the ionic radii of the metals, while the U-N(terpy) and U-N(py) bonds are shorter than those expected from a purely ionic bonding model. The better affinity of terpy for U(III) over Ce(III) and Nd(III) was evidenced by the thermodynamic parameters (K, DeltaH, DeltaS) corresponding to the equilibrium between the bis- and tris(terpy) complexes in acetonitrile. Hydrolysis of the bis(terpy) compounds followed different courses; whereas the aquo compound [Ce(OTf)2(terpy)2(H2O)][OTf] crystallized readily from pyridine, the uranium complexes [UX2(terpy)2(py)]X (X = I, OTf) were oxidized into the tri- and tetranuclear mu-oxo U(IV) compounds [{UI(terpy)2(mu-O)}2{UI2(terpy)}]I4 x 2MeCN x H2O and [{U(OTf)(terpy)2(mu-O)(mu-OTf)U(terpy)}2(mu-OTf)2(mu-O)][OTf]4 x py x MeCN. The crystal structures of these first examples of uranium(IV) compounds with terpy ligands show the almost linear arrangement of the metal atoms.     

Synthesis of the stable UO2I2, the last of the uranyl dihalides. X-ray crystal structure of [UO2I2(py)3

Treatment of UO2(OTf)2 with pure Me3SiI led to the quantitative formation of UO2I2 (1). This compound dissolved in pyridine and thf to give the red adducts [UO2I2L3][L = py (2) or thf (3)], which were also obtained from the metathetical reaction of UO2(OTf)2 and KI. The crystal structure of has been determined. The uranyl diiodide complexes - are thermally quite stable, providing that strictly anhydrous conditions are employed.     

Sterically congested uranyl complexes with seven-coordination of the UO2 unit: the peculiar ligation mode of nitrate in [UO2(NO3)2(Rbtp)] complexes

Addition of 1 or 2 molar equiv of Rbtp [Rbtp = 2,6-bis(5,6-dialkyl-1,2,4-triazin-3-yl)pyridine; R = Me, Pr ( n )] to UO 2(OTf) 2 in anhydrous acetonitrile gave the neutral compounds [UO 2(OTf) 2(Rbtp)] [R = Me ( 1), ( n )Pr ( 2)] and the cationic complexes [UO 2(Rbtp) 2][OTf] 2 [R = Me ( 3), Pr ( n ) ( 4)], respectively. No equilibrium between the mono and bis(Rbtp) complexes or between [UO 2(Rbtp) 2][OTf] 2 and free Rbtp in acetonitrile was detected by NMR spectroscopy. The crystal structures of 1 and 3 resemble those of their terpyridine analogues, and 3 is another example of a uranyl complex with the uranium atom in the unusual rhombohedral environment. In the presence of 1 molar equiv of Rbtp in acetonitrile, UO 2(NO 3) 2 was in equilibrium with [UO 2(NO 3) 2(Rbtp)] and the formation of the bis adduct was not observed, even with an excess of Rbtp. The X-ray crystal structures of [UO 2(NO 3) 2(Rbtp)] [R = Me ( 5), Pr ( n ) ( 6)] reveal a particular coordination geometry with seven coordinating atoms around the UO 2 fragment. The large steric crowding in the equatorial girdle forces the bidentate nitrate ligands to be almost perpendicular to the mean equatorial plane, inducing bending of the UO 2 fragment. The dinuclear oxo compound [U(CyMe 4btbp) 2(mu-O)UO 2(NO 3) 3][OTf] ( 7), which was obtained fortuitously from a 1:2:1 mixture of U(OTf) 4, CyMe 4btbp, and UO 2(NO 3) 2 [CyMe 4btbp = 6,6'-bis-(3,3,6,6-tetramethyl-cyclohexane-1,2,4-triazin-3-yl)-2,2'-bipyridine] is a very rare example of a mixed valence complex involving covalently bound U (IV) and U (VI) ions; its crystal structure also exhibits a seven coordinate uranyl moiety, with one bidentate nitrate group almost parallel to the UO 2 fragment. The distinct structural features of [UO 2(kappa (2)-NO 3) 2(Mebtp)], with its high coordination number and a noticeable bending of the UO 2 fragment, and of [UO 2(kappa (2)-NO 3)(kappa (1)-NO 3)(terpy)], which displays a classical geometry, were analyzed by Density Functional Theory, considering the bonding energy components and the molecular orbitals involved in the interaction between the uranyl, nitrate, and Mebtp or terpy moieties. The unusual geometry of the Mebtp derivative with the seven coordinating atoms around the UO 2 fragment was found very stable. In both the Mebtp and terpy complexes, the origin of the interaction appears to be primarily steric (Pauli repulsion and electrostatic); this term represents 62-63% of the total bonding energy while the orbital term contributes to about 37-38%.     

Cation-cation complexes of pentavalent uranyl: from disproportionation intermediates to stable clusters

Three new cation-cation complexes of pentavalent uranyl, stable with respect to the disproportionation reaction, have been prepared from the reaction of the precursor [(UO(2)py(5))(KI(2)py(2))](n) (1) with the Schiff base ligands salen(2-), acacen(2-), and salophen(2-) (H(2)salen = N,N'-ethylene-bis(salicylideneimine), H(2)acacen = N,N'-ethylenebis(acetylacetoneimine), H(2)salophen = N,N'-phenylene-bis(salicylideneimine)). The preparation of stable complexes requires a careful choice of counter ions and reaction conditions. Notably the reaction of 1 with salophen(2-) in pyridine leads to immediate disproportionation, but in the presence of [18]crown-6 ([18]C-6) a stable complex forms. The solid-state structure of the four tetranuclear complexes, {[UO(2)(acacen)](4)[μ(8)-](2)[K([18]C-6)(py)](2)} (3) and {[UO(2)(acacen)](4)[μ(8)-]}?2?[K([222])(py)] (4), {[UO(2)(salophen)](4)[μ(8)-K](2)[μ(5)-KI](2)[(K([18]C-6)]}?2?[K([18]C-6)(thf)(2)]?2?I (5), and {[UO(2)(salen)(4)][μ(8)-Rb](2)[Rb([18]C-6)](2)} (9) ([222] = [222]cryptand, py = pyridine), presenting a T-shaped cation-cation interaction has been determined by X-ray crystallographic studies. NMR spectroscopic and UV/Vis studies show that the tetranuclear structure is maintained in pyridine solution for the salen and acacen complexes. Stable mononuclear complexes of pentavalent uranyl are also obtained by reduction of the hexavalent uranyl Schiff base complexes with cobaltocene in pyridine in the absence of coordinating cations. The reactivity of the complex [U(V)O(2)(salen)(py)][Cp*(2)Co] with different alkali ions demonstrates the crucial effect of coordinating cations on the stability of cation-cation complexes. The nature of the cation plays a key role in the preparation of stable cation-cation complexes. Stable tetranuclear complexes form in the presence of K(+) and Rb(+), whereas Li(+) leads to disproportionation. A new uranyl-oxo cluster was isolated from this reaction. The reaction of [U(V)O(2)(salen)(py)][Cp*(2)Co] (Cp* = pentamethylcyclopentadienyl) with its U(VI) analogue yields the oxo-functionalized dimer [UO(2)(salen)(py)](2)[Cp*(2)Co] (8). The reaction of the {[UO(2)(salen)(4)][μ(8)-K](2)[K([18]C-6)](2)} tetramer with protons leads to disproportionation to U(IV) and U(VI) species and H(2)O confirming the crucial role of the proton in the U(V) disproportionation.     

Synthesis, structures and reactivity of ruthenium nitrosyl complexes containing Kläui's oxygen tripodal ligand

Ruthenium nitrosyl complexes containing the Kl?ui's oxgyen tripodal ligand L(OEt)(-) ([CpCo{P(O)(OEt)(2)}(3)](-) where Cp = η(5)-C(5)H(5)) were synthesized and their photolysis studied. The treatment of [Ru(N^N)(NO)Cl(3)] with [AgL(OEt)] and Ag(OTf) afforded [L(OEt)Ru(N^N)(NO)][OTf](2) where N^N = 4,4'-di-tert-butyl-2,2'-bipyridyl (dtbpy) (2·[OTf](2)), 2,2'-bipyridyl (bpy) (3·[OTf](2)), N,N,N'N'-tetramethylethylenediamine (4·[OTf](2)). Anion metathesis of 3·[OTf](2) with HPF(6) and HBF(4) gave 3·[PF(6)](2) and 3·[BF(4)](2), respectively. Similarly, the PF(6)(-) salt 4·[PF(6)](2) was prepared by the reaction of 4·[OTf](2) with HPF(6). The irradiation of [L(OEt)Ru(NO)Cl(2)] (1) with UV light in CH(2)Cl(2)-MeCN and tetrahydrofuran (thf)-H(2)O afforded [L(OEt)RuCl(2)(MeCN)] (5) and the chloro-bridged dimer [L(OEt)RuCl](2)(μ-Cl)(2) (6), respectively. The photolysis of complex [2][OTf](2) in MeCN gave [L(OEt)Ru(dtbpy)(MeCN)][OTf](2) (7). Refluxing complex 5 with RNH(2) in thf gave [L(OEt)RuCl(2)(NH(2)R)] (R = tBu (8), p-tol (9), Ph (10)). The oxidation of complex 6 with PhICl(2) gave [L(OEt)RuCl(3)] (11), whereas the reduction of complex 6 with Zn and NH(4)PF(6) in MeCN yielded [L(OEt)Ru(MeCN)(3)][PF(6)] (12). The reaction of 3·[BF(4)](2) with benzylamine afforded the μ-dinitrogen complex [{L(OEt)Ru(bpy)}(2)(μ-N(2))][BF(4)](2) (13) that was oxidized by [Cp(2)Fe]PF(6) to a mixed valence Ru(II,III) species. The formal potentials of the RuL(OEt) complexes have been determined by cyclic voltammetry. The structures of complexes 5,6,10,11 and 13 have been established by X-ray crystallography.     

Formation of double cubanes [Sn(7)(NR)(8)] in the reactions of pyridyl and pyrimidinyl amines with Sn(NMe(2))(2): a synthetic and theoretical study

In contrast to the reactions of Sn(NMe(2))(2) with unfunctionalized primary amines (RNH(2)), which yield the simple imido Sn(II) cubanes [SnNR](4), the reactions of 2-pyridyl or 2-pyrimidinyl amines give the mixed-oxidation-state Sn(II)/Sn(IV) double cubanes [Sn(7)(NR)(8)]. In addition to [Sn(7)[2-N(5-Mepy)](8)] x 2thf (1 x 2thf) (py = pyridine) and [Sn(7)[2-N(pm)](8)] x 0.33thf (2 x 0.33thf) (pm = pyrimidine), which were communicated previously, the syntheses and structures of the new complexes [Sn(7)[2-N(4-Mepm)](8)] x 2thf (3 x 2thf), [Sn(7)[2-N(4,6-Me(2)pm)](8)] x 4thf (4 x 4thf), [Sn(7)[2-N(4-Me-6-MeO-pm)](8)] (5), and [Sn(7)[2-N(4-MeO-6-MeO-pm)](8)] (6) are reported. Model DFT calculations on the reactions of Sn(NMe(2))(2) with 2-pmNH(2) or PhNH(2), producing the cubanes [Sn[2-N(pm)]](4) and [SnNPh](4) (respectively), and the corresponding double cubanes [Sn(7)[2-N(pm)](8)] and [Sn(7)(NPh)(8)], show that the presence of intramolecular Sn...N bonding which spans the cubane halves of the complexes is crucial to the formation of the double-cubane structure.     

Factors affecting the solid-state structure and dimensionality of mercury cyanide/chloride double salts, and NMR characterization of coordination geometries

In the reaction of organic monocationic chlorides or coordinatively saturated metal-ligand complex chlorides with linear, neutral Hg(CN)(2) building blocks, the Lewis-acidic Hg(CN)(2) moieties accept the chloride ligands to form mercury cyanide/chloride double salt anions that in several cases form infinite 1-D and 2-D arrays. Thus, [PPN][Hg(CN)(2)Cl].H(2)O (1), [(n)Bu(4)N][Hg(CN)(2)Cl].0.5 H(2)O (2), and [Ni(terpy)(2)][Hg(CN)(2)Cl](2) (4) contain [Hg(CN)(2)Cl](2)(2-) anionic dimers ([PPN]Cl = bis(triphenylphosphoranylidene)ammonium chloride, [(n)Bu(4)N]Cl = tetrabutylammonium chloride, terpy = 2,2':6',6' '-terpyridine). [Cu(en)(2)][Hg(CN)(2)Cl](2) (5) is composed of alternating 1-D chloride-bridged [Hg(CN)(2)Cl](n)(n-) ladders and cationic columns of [Cu(en)(2)](2+) (en = ethylenediamine). When [Co(en)(3)]Cl(3) is reacted with 3 equiv of Hg(CN)(2), 1-D [[Hg(CN)(2)](2)Cl](n)(n-) ribbons and [Hg(CN)(2)Cl(2)](2-) moieties are formed; both form hydrogen bonds to [Co(en)(3)](3+) cations, yielding [Co(en)(3)][Hg(CN)(2)Cl(2)][[Hg(CN)(2)](2)Cl] (6). In [Co(NH(3))(6)](2)[Hg(CN)(2)](5)Cl(6).2H(2)O (7), [Co(NH(3))(6)](3+) cations and water molecules are sandwiched between chloride-bridged 2-D anionic [[Hg(CN)(2)](5)Cl(6)](n)(6n-) layers, which contain square cavities. The presence (or absence), number, and profile of hydrogen bond donor sites of the transition metal amine ligands were observed to strongly influence the structural motif and dimensionality adopted by the anionic double salt complex anions, while cation shape and cation charge had little effect. (199)Hg chemical shift tensors and (1)J((13)C,(199)Hg) values measured in selected compounds reveal that the NMR properties are dominated by the Hg(CN)(2) moiety, with little influence from the chloride bonding characteristics. delta(iso)((13)CN) values in the isolated dimers are remarkably sensitive to the local geometry.     

A remarkable anion effect on palladium nanoparticle formation and stabilization in hydroxyl-functionalized ionic liquids

Pd nanoparticles (NPs) with a small size and narrow size distribution were prepared from the decomposition of Pd(OAc)(2) in a series of hydroxyl-functionalized ionic liquids (ILs) comprising the 1-(2'-hydroxylethyl)-3-methylimidazolium cation and various anions, viz. [C(2)OHmim][OTf] (2.4 ± 0.5 nm), [C(2)OHmim][TFA] (2.3 ± 0.4 nm), [C(2)OHmim][BF(4)] (3.3 ± 0.6 nm), [C(2)OHmim][PF(6)] (3.1 ± 0.7 nm) and [C(2)OHmim][Tf(2)N] (4.0 ± 0.6 nm). Compared with Pd NPs isolated from the non-functionalized IL, [C(4)mim][Tf(2)N] (6.2 ± 1.1 nm), it would appear that the hydroxyl group accelerates the formation of the NPs, and also helps to protect the NPs from oxidation once formed. Based on the amount of Pd(OAc)(2) that remains after NP synthesis (under the given conditions) the ease of formation of the Pd NPs in the [C(2)OHmim](+)-based ILs follows the trend [Tf(2)N](-), [PF(6)](-) > [BF(4)](-) > [OTf](-) > [TFA](-). Also, the ability of the [C(2)OHmim](+)-based ILs to prevent the Pd NPs from undergoing oxidation follows the trend [Tf(2)N](-) > [PF(6)](-) > [TFA](-) > [OTf](-) > [BF(4)](-). DFT calculations were employed to rationalize the interactions between Pd NPs and the [C(2)OHmim](+) cation and the various anions.     

Synthesis and crystal structure of uranium(IV) complexes with calix[n]arenes (n = 4, 6 and 8): mononuclear, polynuclear and 1D polymeric species

Reactions of UCl4 with calix[n]arenes (n = 4, 6) in THF gave the mononuclear [UCl2(calix[4]arene - 2H)(THF)2].2THF (.2THF) and the bis-dinuclear [U2Cl2(calix[6]arene - 6H)(THF)3]2.6THF (.6THF) complexes, respectively, while the mono-, di- and trinuclear compounds [Hpy]2[UCl3(calix[4]arene - 3H)].py (.py), [Hpy](4)[U2Cl6(calix[6]arene - 6H)].3py (.3py), [Hpy]3[U2Cl5(calix[6]arene - 6H)(py)].py (.py) and [Hpy]6[U3Cl11(calix[8]arene - 7H)].3py (.3py) were obtained by treatment of UCl4 with calix[n]arenes (n = 4, 6, 8) in pyridine. The sodium salt of calix[8]arene reacted with UCl4 to give the pentanuclear complex [U{U2Cl3(calix[8]arene - 7H)(py)5}2].8py (.8py). Reaction of U(acac)4 (acac = MeCOCHCOMe) with calix[4]arene in pyridine afforded the mononuclear complex [U(acac)2(calix[4]arene - 2H)].4py (.4py) and its treatment with the sodium salt of calix[8]arene led to the formation of the 1D polymer [U2(acac)6(calix[8]arene - 6H)(py)4Na4]n. The sandwich complex [Hpy]2[U(calix[4]arene - 3H)2][OTf].4py (.4py) was obtained by treatment of U(OTf)4 (OTf = OSO2CF3) with calix[4]arene in pyridine. All the complexes have been characterized by X-ray diffraction analysis.     

A convenient synthetic route to half-sandwich rhodium(III) complexes of the tripodal ligand tris(3,5-dimethylpyrazolyl)methane

The synthesis of the complex [RhCl3tpm*], (1), (tpm*= tris(3,5-dimethylpyrazolyl)methane) is reported. This complex is a suitable starting material for the synthesis of heteroleptic half-sandwich complexes: it has been used to synthesise the complexes; [RhCl(bpy)tpm*][(PF6)2][2][(PF6)2](bpy = 2,2'-bipyridyl), [RhCl(phen)tpm*][(PF6)2][3][(PF6)2]. (phen = 1,10-phenanthroline), [RhCl2(py)tpm*][(PF6)], [4][(PF6)2], (py = pyridine), and[RhCl(py)2tpm*][(PF6)2], [5][(PF6)2]. The structures of [2][(PF6)2], [33][(PF6)2], [4][(PF6)2], and [5][(PF6)2] have been determined by X-ray crystallography. The electrochemical and photophysical properties of these new compounds have also been investigated.     

Synthesis and characterization of several dicopper(I) complexes and a spin-delocalized dicopper(I,II) mixed-valence complex using a 1,8-naphthyridine-based dinucleating ligand

The synthesis of dicopper(I) complexes [Cu2(BBAN)(MeCN)2](OTf)2 (1), [Cu2(BBAN)(py)2](OTf)2 (2), [Cu2(BBAN)(1-Me-BzIm)2](OTf)2 (3), [Cu2(BBAN)(1-Me-Im)2](OTf)2 (4), and [Cu2(BBAN)(mu-O2CCPh3)](OTf) (5), where BBAN = 2,7-bis((dibenzylamino)methyl)-1,8-naphthyridine, py = pyridine, 1-Me-Im = 1-methylimidazole, and 1-Me-BzIm = 1-methylbenzimidazole, are described. Short copper-copper distances ranging from 2.6151(6) to 2.7325(5) A were observed in the solid-state structures of these complexes depending on the terminal ligands used. The cyclic voltammogram of compound 5 dissolved in THF exhibited a reversible redox wave at E1/2 = -25 mV vs Cp2Fe+/Cp2Fe. When complex 5 was treated with 1 equiv of silver(I) triflate, a mixed-valence dicopper(I,II) complex [Cu2(BBAN)(mu-O2CCPh3)(OTf)](OTf) (6) was prepared. A short copper-copper distance of 2.4493(14) A observed from the solid-state structure indicates the presence of a copper-copper interaction. Variable-temperature EPR studies showed that complex 6 has a fully delocalized electronic structure in frozen 2-methyltetrahydrofuran solution down to liquid helium temperature. The presence of anionic ligands seems to be an important factor to stabilize the mixed-valence dicopper(I,II) state. Compounds 1-4 with neutral nitrogen-donor terminal ligands cannot be oxidized to the mixed-valence analogues either chemically or electrochemically.     

The distinct affinity of cyclopentadienyl ligands towards trivalent uranium over lanthanide ions. Evidence for cooperative ligation and back-bonding in the actinide complexes

The mono and bis(cyclopentadienyl) compounds [M(C5H4Bu t)I2] and [M(C5H4Bu t)2I](M = U, La, Ce, Nd) were formed in thf by comproportionation reactions of [M(C5H4Bu t)3] and LnI3 or [UI3(L)4](L = thf or py) in the molar ratio of 1 : 2 and 2 : 1, respectively, while treatment of [UI(3)(py)(4)] or LnI(3)(Ln = La, Ce, Nd) with 1 or 2 mol equivalents of LiC5H4Bu t in thf afforded the [M(C5H4Bu t)I2] and [M(C5H4Bu t)2I2]- compounds, respectively. The X-ray crystal structures of [M(C5H4Bu t)I2(py)3](M = U, La, Ce, Nd), [{Ce(C5H4Bu t)2(mu-I)}2] and [M(C5H4Bu t)2I(py)2](M = U, Nd) have been determined; the differences between the average M-C distances in the mono(cyclopentadienyl) complexes correspond to the variation in the ionic radii of the trivalent uranium and lanthanide ions while the U-N and U-I bond lengths seem to be smaller than those predicted from a purely ionic bonding model. The distinct affinity of the cyclopentadienyl ligands towards Ln(III) and U(III) was revealed by two series of competing reactions: the ligand exchange reactions between [Ln(C5H4Bu t)(n')I(3-n')](Ln = La, Ce, Nd) and [U(C5H4Bu t)(n')I(3-n')] species (1 < or = n'+n' =n < or = 5), and the addition of n mol equivalents of LiC(5)H(4)Bu(t)(1 [less-than-or-equal]n[less-than-or-equal] 5) to a 1 : 1 mixture of LnI3 and [UI3(thf)4] or [UI3(py)4]. The stability of the [M(C5H4Bu t)I2] species was found to vary in the order Nd > Ce > U > La, a trend which is in accord with an electrostatic bonding model. However, the bis and tris(cyclopentadienyl) complexes of uranium are more stable than their lanthanide analogues. This difference can be accounted for by a higher degree of covalency in the U-C5H4Bu t bond, resulting from the late appearance of back-bonding which would emerge only after the first cyclopentadienyl ligand is bound.     

A neutral organometallic fluoro complex can be a good ligand

The reaction of the complex [Mo(OTf)(eta(3)-C(3)H(4)-Me-2)(CO)(2)(phen)] (1) (OTf = trifluoromethylsulfonate; phen = 1,10-phenanthroline) with tetrabutylammonium fluoride trihydrate afforded the fluoride complex [MoF(eta(3)-C(3)H(4)-Me-2)(CO)(2)(phen)] (2). The IR spectrum and the oxidation potential of 2 reflect the fact that its metal center is more electron-rich than that of the chloro analogue [MoCl(eta(3)-C(3)H(4)-Me-2)(CO)(2)(phen)]. Compound 2 reacted with 1 affording the homobinuclear complex [[Mo(eta(3)-C(3)H(4)-Me-2)(CO)(2)(phen)](2)(mu-F)][OTf] (3), with a fluoride bridge. Compound 2 also reacts with the species generated in situ by triflate abstraction from [M(OTf)(CO)(3)('N-N')] (M = Mn, Re; 'N-N' = 2,2'-bipyridine (bipy), phen) using NaBAr'(4) (Ar' = 3,5-bis(trifluoromethyl)phenyl), affording the heterobinuclear complexes [[Mo(eta(3)-C(3)H(4)-Me-2)(CO)(2)(phen)](mu-F)[M(CO)(3)('N--N')]][BAr'(4)] (M = Mn, 'N-N' = bipy (4); M = Re, 'N-N' = phen (5)). All new compounds have been characterized by spectroscopic methods (IR and NMR) and, in the case of 1, 2, 3, and 4, also by means of X-ray diffraction analysis.     

Synthesis, crystal structure and reactivity of uranium(IV) complexes with p-tert-butylcalix[4]arene ligands

Reactions of UCl4 with 25,27-dimethoxy-5,11,17,23-tetra-tert-butylcalix[4]arene (H2Me2calix) in THF or pyridine at 80 degrees C gave [UCl2(Me2calix)L2] [L = THF (1) or pyridine (2)]. Similar treatment of U(acac)(4) (acac = MeCOCHCOMe) with H2Me2calix in THF or pyridine afforded [U(acac)2(Me2calix)] (3). The bis-calixarene compound [U(Me2calix)(H2calix)] (4) was obtained by reaction of U(OTf)4 or U(OTf)3 with H2Me2calix in pyridine at 110 degrees C. Treatment of UCl4 with H2Me2calix in pyridine at 110 degrees C gave [Mepy][UCl2(Hcalix)(py)2] (5) resulting from demethylation and acid cleavage of the methoxy groups of the calixarene ligand of 2. Adventitious traces of air were responsible for the formation of [Hpy][Mepy]4[{UCl(calix)}3(mu3-O)][UCl6] (6) during the reaction of UCl4 and H2Me2calix, and of [{U(Me2calix)(mu3-O)LiCl(THF)}2] (7) during the reaction of 2 with tBuLi. The X-ray crystal structures of 1.2THF, 2.2py, 3.0.25L (L = THF and py), 4.2py, 5, 6.3py and 7.THF have been determined.     

Mononuclear and dinuclear complexes with a [Ru(tBu2PCH2CH2PtBu2)(CO)] core

Thermolysis of solid [Ru(d(t)bpe)(CO)2Cl2](2, d(t)bpe =(t)Bu2PCH2CH2P(t)Bu2) under vacuum affords the five-coordinate complex [Ru(d(t)bpe)(CO)Cl2] (4), which was shown by X-ray crystallography to contain a weak remote agostic interaction. In solution, 4 can be readily trapped by CO, CH3CN or water to give [Ru(d(t)bpe)(CO)(L)Cl2](L = CO, 2; L = CH3CN, 6; L = H2O, 7). Reaction of 4 with AgOTf/H2O yields the tris-aqua complex [Ru(d(t)bpe)(CO)(H2O)3](OTf)2 (8), which has been structurally characterised and probed in solution by pulsed-gradient spin echo (PGSE) NMR spectroscopy. The water ligands in 8 are labile and easily substituted to give [Ru(d(t)bpe)(CO)(NCCH3)3](OTf)2 (10) and [Ru(d(t)bpe)(CO)(DMSO)3](OTf)2 (11). In the presence of CO, the tris-aqua complex undergoes water-gas shift chemistry with formation of the cationic hydride species [Ru(d(t)bpe)(CO)3H](OTf) (12) and CO2. X-Ray crystal structures of complexes 2, 4, 6, 8 and 11-12 are reported along with those for [{Ru(d(t)bpe)(CO)}2(mu-Cl)2(mu-OTf)](OTf) (3), [{Ru(d(t)bpe)(CO)}2(mu-Cl)3][Ru(d(t)bpe)(CO)Cl3](5) and [Ru(d(t)bpe)(CO)(H2O)2(OTf)](OTf)(9).     

Low-valent molecular plutonium halide complexes

Treatment of plutonium metal with 1.5 equiv of bromine in tetrahydrofuran (thf) led to isolation of PuBr3(thf)4 (1), which is a new versatile synthon for exploration of non-aqueous Pu(III) chemistry. Adventitious water in the system resulted in structural characterization of the eight-coordinate complex [PuBr2(H2O)6][Br] (2). The crystal structure of PuI3(thf)4 (3) has been determined for the first time and is isostructural with UI3(thf)4. Attempts to form a bis(imido) plutonyl(VI) moiety ([Pu(NR)2](2+)) by oxidation of PuI3(py)4 with iodine and (t)BuNH2 resulted in crystallization of the Pu(III) complex [PuI2(thf)4(py)][I3] (4). Dissolution of a Pu(IV) carbonate with a HCl/Et2O solution in thf gave the mixed valent (III/IV) complex salt [PuCl2(thf)5][PuCl5(thf)] (5) as the only tractable product. Oxidation of Pu[N(SiMe3)2]3 with TeCl4 afforded the Pu(IV) complex Pu[N(SiMe3)2]3Cl (6), which may prove to be a useful entry route for investigation of organometallic/non-aqueous tetravalent plutonium chemistry.     

Structure and magnetism of heptanuclear complexes formed on encapsulation of hexacyanoferrate(II) with the Mn(II) and Ni(II) complexes of 1,4-bis(2-pyridylmethyl)-1,4,7-triazacyclononane

The reaction of [Mn(dmptacn)OH(2)](2+) and [Ni(dmptacn)OH(2)](2+) (dmptacn = 1,4-bis(2-pyridylmethyl)-1,4,7-triazacyclononane) with each cyano ligand on ferricyanide results in the assembly of heteropolynuclear cations around the cyanometalate core and reduction of Fe(III) to Fe(II). In [[Mn(dmptacn)CN](6)Fe][ClO(4)](8) x 5H(2)O (1) and [[Ni(dmptacn)CN](6)Fe][ClO(4)](8) x 7H(2)O (2), ferrocyanide is encapsulated by either six Mn(II) or Ni(II) dmptacn moieties. These same products are obtained when ferrocyanide salts are used in the synthesis instead of ferricyanide. A binuclear complex, [[Mn(dmptacn)](2)CN][ClO(4)](3) (3), has also been formed from KCN and [Mn(dmptacn)OH(2)](2+). For both Mn(II) and Ni(II), the use of the pentadentate dmptacn ligand facilitates the formation of discrete cations in preference to networks or polymeric structures. 1 crystallizes in the trigonal space group R3 macro (No. 148) with a = 30.073(3) A, c = 13.303(4) A, and Z = 3 and is composed of heptanuclear [[Mn(dmptacn)CN](6)Fe](8+) cations whose charge is balanced by perchlorate counteranions. Weak H-bonding interactions between neighboring heptanuclear cations and some perchlorate counterions generate an infinite 1D chain of alternating [[Mn(dmptacn)CN](6)Fe](8+) and ClO(4)(-) ions running along the c-axis. Complex 3 crystallizes in the orthorhombic space group Pbcn (No. 60) with a = 16.225(3) A, b = 16.320(2) A, c = 18.052(3) A, and Z = 8 and is composed of binuclear [[Mn(dmptacn)](2)CN](3+) cations in which the cyano-bridged Mn(II) centers are in a distorted trigonal prismatic geometry. Variable temperature magnetic susceptibility measurements have revealed the presence of a weak ferromagnetic interaction between the paramagnetic Mn(II) centers in 1, mediated either by the -NC-Fe-CN- bridging units or by Mn-NH...ClO(4-)...NH-Mn intercluster pathways.     

Syntheses, structures, and redox properties of dimeric triruthenium clusters bridged by bis(diphenylphosphino)acetylene and -ethylene

Reactions of oxo-centered triruthenium acetate complexes [Ru3O(OAc)6(py)2(CH3OH)](PF6) (py = pyridine, OAc = CH3COO-) (1) with nearly equimolar amounts of dppa [bis(diphenylphosphino)acetylene] or dppen [trans-1,2-bis(diphenylphosphino)ethylene] gave [Ru3O(OAc)6(py)2(L)](PF6) (L = dppa, 2; dppen, 3). With 2.4 equiv of 1, the reactions provided diphosphine-linked triruthenium dimers, [[Ru3O(OAc)6(py)2]2(L)](PF6)2 (L = dppa, 4; L = dppen, 5), respectively. Similarly, the reactions of [Ru3O(OAc)6(L')2(MeOH)]+ [L' = dmap (4-(dimethylamino)pyridine), 1a; L' = abco (1-azabicyclo[2.2.2]octane), 1b] with dppen gave dppen-linked dimers, [[Ru3O(OAc)6(dmap)2]2(dppen)](SbF6)2 (6) and [[Ru3O(OAc)6(abco)2]2(dppen)](BF4)2 (7), respectively. The chemical reduction of 2, 4, and 5 by hydrazine afforded one- or two-electron-reduced, neutral products, Ru3O(OAc)6(py)2(dppa) (2a), [Ru3O(OAc)6(py)2]2(dppa) (4a), and [Ru3O(OAc)6(py)2]2(dppen) (5a), respectively. The complexes were characterized by elemental analyses, ES-MS, UV-vis, IR, and 31P NMR spectroscopies, and cyclic and differential-pulse voltammetries. The molecular structures of compounds 2, 4, 5, 5a, 6, and 7 were determined by single-crystal X-ray diffraction. In 0.1 M (Bu4N)PF6-acetone, the monomers and dimers of triruthenium clusters show reversible and multistep redox responses. The two triruthenium cluster centers in dimers undergo stepwise reductions and oxidations due to the identical redox processes of the individual Ru3O cluster cores, suggesting the presence of electronic communications between them through the conjugated diphosphine spacer. The redox wave splitting mediated by dppa containing an ethynyl group (C triple bond C) is found to be more extensive than that by dppen containing an ethenyl (C=C) one. It appears that the redox wave splitting is enhanced by the introduction of electron-donating substituents on the auxiliary pyridine rings.     

Diverse heteroleptic ytterbium(III) thiocyanate complexes by oxidation from bis(thiocyanato)ytterbium(II)

The new ytterbium(II) thiocyanate complex [Yb(NCS)2(thf)2] (1), synthesised by redox transmetallation between [Hg(SCN)2] and ytterbium metal in THF at room temperature, gave monomeric, eight coordinate [Yb-(NCS)2(dme)3] (2, dme = 1,2-dimethoxyethane) on crystallisation from DME, and is a powerful, synthetically useful reductant. Thus, oxidation of 1 with Hg(SCN)2, Hg(C6F5)2/HOdpp (HOdpp = 2,6-diphenylphenol), TlCp (Cp = C5H5 or CH3C5H4), Tl(Ph2pz) (Ph2pz = 3,5-diphenylpyrazolate) and CCl3CCl3 in THF yielded the ytterbium(II) complexes [Yb(NCS)3(thf)4] (3), [Yb-(NCS)2(Odpp)(thf)3](4), [Yb(NCS)2Cp-(thf)3] (Cp = C5H5 (5), CH3C5H4 (6)), [Yb(NCS)2(Ph2pz)(thf)4] (7) and [Yb(NCS)2Cl(thf)4] (8). In the solid state, complexes 4, 6 and 7 were shown by X-ray crystallography to be six, eight and eight coordinate monomers, respectively. Exclusively terminal, N-bound transoid thiocyanate bonding is observed with eta1-Odpp (4), eta5/-C5H4Me (6) and eta2-Ph2Pz (7) ligands attached approximately perpendicular to the N...N vector. The chloride complex 8 is not a molecular species, but consists of discrete, seven coordinate [YbCl2(thf)5] cations and [Yb(NCS)4(thf)3] anions. By contrast, oxidation of 1 with TlO2CPh gave a mixture of [[Yb(NCS)-(O2CPh)2(thf)2]2] (9) and 3 through rearrangement of an initially formed [Yb(NCS)2(O2CPh)] species. The X-ray structure of 9 indicates a dimeric complex with a (Yb(mu-O2CPh)4Yb] core that contains both bridging bidentate and bridging tridentate benzoate groups, and with a terminal N-bound thiocyanate and two THF ligands on each ytterbium. Reduction of Ph2CO with 1 in THF yielded the dinuclear complex [[Yb(NCS)2(thf)3]2(mu-OC(Ph)2C(Ph)2O)] (10), in which two octahedral Yb centres are bridged by a 1,1,2,2-tetraphenylethane-1,2-diolate ligand, derived from reductive coupling of the benzophenone reagent.     

Coordination solids derived from Cp*M(CN)3- (M = Rh,Ir)

Solutions of Rh2(OAc)4 and Et4N[Cp*Ir(CN)3] react to afford crystals of the one-dimensional coordination solid [Et4N[Cp*Ir(CN)3][Rh2(OAc)4]]. This reaction is reversed by coordinating solvents such as MeCN. The structure of the polymer consists of helical anionic chains containing Rh2(OAc)4 units linked via two of the three CN ligands of Cp*Ir(CN)3-. Use of the more Lewis acidic Rh2(O2CCF3)4 in place of Rh2(OAc)4 gave purple [(Et4N)2[Cp*Ir(CN)3]2[Rh2(O2CCF3)4]3], whose insolubility is attributed to stronger Rh-NC bonds as well as the presence of cross-linking. The species [[Cp*Rh(CN)3][Ni(en)n](PF6)] (n = 2, 3) crystallized from an aqueous solution of Et4N[Cp*Rh(CN)3] and [Ni(en)3](PF6)2; [[Cp*Rh(CN)3][Ni(en)2](PF6)] consists of helical chains based on cis-Ni(en)(2)2+ units. Aqueous solutions of Et4N[Cp*Ir(CN)3] and AgNO3 afforded the colorless solid Ag-[Cp*Ir(CN)3]. Recrystallization of this polymer from pyridine gave the hemipyridine adduct [Ag[Ag(py)][Cp*Ir(CN)3]2]. The 13C cross-polarization magic-angle spinning NMR spectrum of the pyridine derivative reveals two distinct Cp* groups, while in the pyridine-free precursor, the Cp*'s appear equivalent. The solid-state structure of [Ag[Ag(py)][Cp*Ir(CN)3]2] reveals a three-dimensional coordination polymer consisting of chains of Cp*Ir(CN)3- units linked to alternating Ag+ and Ag(py)+ units. The network structure arises by the linking of these helices through the third cyanide group on each Ir center.