A platinum-ruthenium dinuclear complex bridged by bis(terpyridyl)xanthene

4,5-Bis(terpyridyl)-2,7-di-tert-butyl-9,9-dimethylxanthene (btpyxa) was prepared to serve as a new bridging ligand via Suzuki coupling of terpyridin-4'-yl triflate and 2,7-di-tert-butyl-9,9-dimethylxanthene-4,5-diboronic acid. The reaction of btpyxa with either 1 equiv or an excess of PtCl(2)(cod) (cod = 1,5-cyclooctadiene) followed by anion exchange afforded mono- and dinuclear platinum complexes [(PtCl)(btpyxa)](PF(6)) ([1](PF(6))) and [(PtCl)(2)(btpyxa)](PF(6))(2) ([2](PF(6))(2)), respectively. The X-ray crystallography of [1](PF(6)).CHCl(3) revealed that the two terpyridine units in the ligand are nearly parallel to each other. The heterodinuclear complex [(PtCl)[Ru((t)Bu(2)SQ)(dmso)](btpyxa)](PF(6))(2) ([4](PF(6))(2)) (dmso = dimethyl sulfoxide; (t)Bu(2)SQ = 3,5-di-tert-butyl-1,2-benzosemiquinone) and the monoruthenium complex [Ru((t)Bu(2)SQ)(dmso)(trpy)](PF(6)) ([5](PF(6))) (trpy = 2,2':6',2' '-terpyridine) were also synthesized. The CV of [2](2+) suggests possible electronic interaction between the two Pt(trpy) groups, whereas such an electronic interaction was not suggested by the CV of [4](2+) between Pt(trpy) and Ru((t)Bu(2)SQ) frameworks.     

A study of M-X-BR3 (M = Pt, Pd or Rh; X = Cl or I) interactions in square planar ambiphilic ligand complexes: structural, spectroscopic, electrochemical and computational comparisons with borane-free analogues

Reaction of [PtCl(2)(COD)] and [PtI(2)(COD)] with 2,7-di-tert-butyl-5-diphenylboryl-4-diphenylphosphino-9,9-dimethylthioxanthene (TXPB) afforded square planar [PtCl(2)(TXPB)] (1B) and [PtI(2)(TXPB)] (4B), both of which were crystallographically characterized. Single-crystal X-ray quality crystals were also obtained for [PdCl(2)(TXPB)] (2B; Emslie et al., Organometallics, 2008, 27, 5317) as 2B·2CH(2)Cl(2) and solvent-free 2B. Both the chloro and iodo TXPB complexes exhibit metal-halide-borane bridging interactions similar to those in previously reported [RhCl(CO)(TXPB)] (3B) and [RhI(CO)(TXPB)] (5B) (Emslie et al., Organometallics, 2006, 25, 583 and Inorg. Chem., 2010, 49, 4060). To facilitate a more detailed analysis of M-X-BR(3) (X = Cl and I) interactions, a borane-free analogue of the TXPB ligand, 2,7-di-tert-butyl-4-diphenylphosphino-9,9-dimethylthioxanthene (TXPH), was prepared. Reaction with [PtX(2)(COD)] (X = Cl or I), [PdCl(2)(COD)] and 0.5 [{RhCl(CO)(2)}(2)] provided square planar [PtCl(2)(TXPH)] (1H), [PdCl(2)(TXPH)] (2H), [RhCl(CO)(TXPH)] (3H) and [PtI(2)(TXPH)] (4H). M-Cl-BR(3) and M-I-BR(3) bonding in 1B-5B was then probed through the use of structural comparisons, IR and NMR spectroscopy, cyclic voltammetry, and DFT calculations (Slater-type orbitals, Mayer bond orders, Hirshfeld charges, fragment analysis, SCF deformation density isosurfaces, and energy decomposition analysis).     

Synthesis and characterization of a novel tetranuclear 5f compound: a new synthon for exploring U(IV) chemistry

In the course of structurally characterizing previously reported complexes based on the 1,2-bis(dimethylphosphino)ethane)) (dmpe) ligand ([(dmpe)(2)UCl(4)] (1) and [(dmpe)(2)UMe(4)] (2)), we find that adjusting the U/dmpe ratio leads to an unprecedented species. Whereas the use of two or three equivalents of dmpe relative to UCl(4) produces 1 as a blue-green solid, the use of a 1:1 dmpe/UCl(4) stoichiometry yields [(dmpe)(4)U(4)Cl(16)]·2CH(2)Cl(2)·(3·2CH(2)Cl(2)) as a green solid. In turn, 3 is used to prepare a mixed-chelating ligand complex featuring the bidentate ligand 4,4'-dimethyl-2,2'-bipyridine (dmbpy), [(dmpe)(dmbpy)UCl(4)] (4). The measured magnetic susceptibilities for 1-4 trend toward nonmagnetic ground states at low temperatures.     

Alkylation reactions of [WS(4)](2)(-) and [(eta(5)-C(5)Me(5))WS(3)](-) with 2,6-bis(bromomethyl)pyridine: the first isolation of bisalkylated tetrathiometalate WS(2)[2,6-(SCH(2))(2)(C(5)H(3)N)

The trithio and tetrathio complexes of tungsten (PPh(4))[CpWS(3)] (Cp = eta(5)-C(5)Me(5)) and (PPh(4))(2)[WS(4)] undergo alkylation reactions with 2,6-bis(bromomethyl)pyridine to yield [(CpWS(2))(2)[2,6-(SCH(2))(2)(C(5)H(3)N)]].CH(3)CN (1.CH3CN) (73.1% yield) and WS(2)[2,6-(SCH(2))(2)(C(5)H(3)N)] (2) (76.0% yield), respectively. In the dinuclear complex 1, two CpWS(3) units are linked by a 2,6-dimethylenepyridine bridge, and the pyridine nitrogen is not coordinated at tungsten. Complex 2 is the first example of bisalkylated tetrathiometalates, the mononuclear structure of which is stabilized by coordination of the pyridine nitrogen.     

Cubane-type heterometallic sulfido clusters: incorporation of two metal fragments into a dinuclear ReS(mu-S)2ReS core affording bimetallic M2Re2(mu 3-S)4 clusters (M = Ru,Pt, Cu) or trimetallic MM'Re2(mu 3-S)4 clusters via incomplete cubane-type MRe2(mu 3-S)(mu 2-S)3 intermediates (M = Ru,Rh, Ir; M' = Mo,W, Pd,Ru, Rh)

Reactions of a dirhenium tetra(sulfido) complex [PPh(4)](2)[ReS(L)(mu-S)(2)ReS(L)] (L = S(2)C(2)(SiMe(3))(2)) with a series of group 8-11 metal complexes in MeCN at room temperature afforded either the cubane-type clusters [M(2)(ReL)(2)(mu(3)-S)(4)] (M = CpRu (2), PtMe(3), Cu(PPh(3)) (4); Cp = eta(5)-C(5)Me(5)) or the incomplete cubane-type clusters [M(ReL)(2)(mu(3)-S)(mu(2)-S)(3)] (M = (eta(6)-C(6)HMe(5))Ru (5), CpRh (6), CpIr (7)), depending on the nature of the metal complexes added. It has also been disclosed that the latter incomplete cubane-type clusters can serve as the good precursors to the trimetallic cubane-type clusters still poorly precedented. Thus, treatment of 5-7 with a range of metal complexes in THF at room temperature resulted in the formation of novel trimetallic cubane-type clusters, including the neutral clusters [[(eta(6)-C(6)HMe(5))Ru][W(CO)(3)](ReL)(2)(mu(3)-S)(4)], [(CpM)[W(CO)(3)](ReL)(2)(mu(3)-S)(4)] (M = Rh, Ir), [(Cp*Ir)[Mo(CO)(3)](ReL)(2)(mu(3)-S)(4)], [[(eta(6)-C(6)HMe(5))Ru][Pd(PPh(3))](ReL)(2)(mu(3)-S)(4)], and [(Cp*Ir)[Pd(PPh(3))](ReL)(2)(mu(3)-S)(4)] (13) along with the cationic clusters [(Cp*Ir)(CpRu)(ReL)(2)(mu(3)-S)(4)][PF(6)] (14) and [(Cp*Ir)[Rh(cod)](ReL)(2)(mu(3)-S)(4)][PF(6)] (cod = 1,5-cyclooctadiene). The X-ray analyses have been carried out for 2, 4, 7, 13, and the SbF(6) analogue of 14 (14') to confirm their bimetallic cubane-type, bimetallic incomplete cubane-type, or trimetallic cubane-type structures. Fluxional behavior of the incomplete cubane-type and trimetallic cubane-type clusters in solutions has been demonstrated by the variable-temperature (1)H NMR studies, which is ascribable to both the metal-metal bond migration in the cluster cores and the pseudorotation of the dithiolene ligand bonded to the square pyramidal Re centers, where the temperatures at which these processes proceed have been found to depend upon the nature of the metal centers included in the cluster cores.     

Synthesis and characterization of vanadium(V)-phosphinimide complexes

Synthetic routes to vanadium(V)-phosphinimide derivatives are addressed. Initial synthetic efforts afforded the known compound formulated as VCl(2)(NPPh(3))(3) which was crystallographically determined to be the salt [VCl(NPPh(3))(3)]Cl (1). Reactions of the vanadium-imide precursors VCl(3)(NAr) (Ar = Ph, C(6)H(3)-2,6-iPr(2)) with R(3)PNSiMe(3) (R = Ph, iPr, tBu) afforded VCl(2)(NPh)(NPPh(3)) (4), VCl(2)(NPh)(NPiPr(3)) (5), VCl(2)(NPh)(NPtBu(3)) (6), VCl(2)(NC(6)H(3)-2,6-iPr(2))(NPPh(3)) (7), VCl(2)(NC(6)H(3)-2,6-iPr(2))(NPiPr(3)) (8), and VCl(2)(NC(6)H(3)-2,6-iPr(2))(NPtBu(3)) (9) in yields ranging from 72% to 84%. Subsequent alkylation or arylation reactions resulted in VMe(2)(NC(6)H(3)-2,6-iPr(2))(NPtBu(3)) (10), VPh(2)(NPh)(NPtBu(3)) (11), VPh(2)(NC(6)H(3)-2,6-iPr(2))(NPiPr(3)) (12), and VPh(2)(NC(6)H(3)-2,6-iPr(2))(NPtBu(3)) (13) while substitution reactions with Li[N(SiMe(3))(2)] and Li[SBn] gave VCl(N(SiMe(3))(2))(NPh)(NPtBu(3)) (14) and V(SBn)(2)(NC(6)H(3)-2,6-iPr(2))(NPtBu(3)) (15) in yields ranging from 40% to 49% yield. Polarization of the N-P phosphinimide bond and V-N multiple bond character are evidenced by crystallographic data.     

Preparation, characterization, and magnetic behavior of the ln derivatives (ln = nd, la) of a 2,6-diiminepyridine ligand and corresponding dianion

An unprecedented Nd[2,6-[[2,6-(i-Pr)(2)C(6)H(5)]N=C(CH(3))](2)(C(5)H(3)N)]NdI(2)(THF) (1) complex was prepared by oxidizing metallic Nd with I(2) in THF and in the presence of 2,6-[[2,6-(i-Pr)(2)C(6)H(5)]N=C(CH(3))](2)(C(5)H(3)N). The magnetic behavior at variable T clearly indicated that the complex should be regarded as a trivalent Nd atom antiferromagnetically coupled to a radical anion. By using the doubly deprotonated form of the diimino pyridine ligand [[2,6-[[2,6-(i-Pr)(2)C(6)H(5)]N-C=CH(2)](2)(C(5)H(3)N)](2-) (2) the corresponding trivalent complexes [[2,6-[[2,6-(i-Pr)(2)C(6)H(5)]N-C=CH(2)](2)(C(5)H(3)N)]Ln (THF)](mu-Cl)(2)[Li(THF)(2)].0.5 (hexane) [Ln = Nd (3), La (4)] were obtained and characterized. Reduction of these species afforded electron transfer to the ligand system which gave ligand dimerization via C-C bond formation through one of the two ene-amido functions of each molecule. The resulting dinuclear [[([2,6-(i-Pr)(2)C(6)H(5)]N-C=(CH(2)))(C(5)H(3)N)([2,6-(i-Pr)(2)C(6)H(5)]N=CCH(2))]Ln(THF)(2)(mu-Cl)[Li(THF)(3)])(2).2(THF) [Ln = Nd (5), La (6)] were isolated and characterized.     

Synthesis, structural characterization, reactivity, and thermal stability of [eta(5):sigma-Me2C(C5H4)(C2B10H10)]Ti(R)(NMe2)

Reaction of [eta:(5)sigma-Me2C(C5H4)(C2B10H10)]TiCl(NMe2) (1) with 1 equiv of PhCH2K, MeMgBr, or Me3SiCH2Li gave corresponding organotitanium alkyl complexes [eta:(5)sigma-Me2C(C5H4)(C2B10H10)]Ti(R)(NMe2) (R = CH2Ph (2), CH2SiMe3 (4), or Me (5)) in good yields. Treatment of 1 with 1 equiv of n-BuLi afforded the decomposition product {[eta:(5)sigma-Me2C(C5H4)(C2B10H10)]Ti}2(mu-NMe)(mu:sigma-CH2NMe) (3). Complex 5 slowly decomposed to generate a mixed-valence dinuclear species {[eta:(5)sigma-Me2C(C5H4)(C2B10H10)]Ti}2(mu-NMe2)(mu:sigma-CH2NMe) (6). Complex 1 reacted with 1 equiv of PhNCO or 2,6-Me2C6H3NC to afford the corresponding monoinsertion product [eta:(5)sigma-Me2C(C5H4)(C2B10H10)]Ti(Cl)[eta(2)-OC(NMe2)NPh] (7) or [eta:(5)sigma-Me2C(C5H4)(C2B10H10)]Ti(Cl)[eta(2)-C(NMe2)=N(2,6-Me2C6H3)] (8). Reaction of 4 or 5 with 1 equiv of R'NC gave the titanium eta(2)-iminoacyl complexes [eta:(5)sigma-Me2C(C5H4)(C2B10H10)]Ti(NMe2)[eta(2)-C(R)=N(R')] (R = CH2SiMe3, R' = 2,6-Me2C6H3 (9) or tBu (10); R = Me, R' = 2,6-Me2C6H3 (11) or tBu (12)). The results indicated that the unsaturated molecules inserted into the Ti-N bond only in the absence of the Ti-C(alkyl) bond and that the Ti-C(cage) bond remained intact. All complexes were fully characterized by various spectroscopic techniques and elemental analyses. Molecular structures of 2, 3, 6-8, and 10-12 were further confirmed by single-crystal X-ray analyses.     

Group 6 imido complexes supported by diamido-donor ligands

Reactions of the lithiated diamido-pyridine or diamido-amine ligands Li(2)N(2)N(py) or Li(2)N(2)N(am) with [W(NAr)Cl(4)(THF)] (Ar = Ph or 2,6-C(6)H(3)Me(2); THF = tetrahydrofuran) afforded the corresponding imido-dichloride complexes [W(NAr)(N(2)N(py))Cl(2)] (R = Ph, 1, or 2,6-C(6)H(3)Me(2), 2) or [W(NAr)(N(2)N(am))Cl(2)] (R = Ph, 3, or 2,6-C(6)H(3)Me(2), 4), respectively, where N(2)N(py) = MeC(2-C(5)H(4)N)(CH(2)NSiMe(3))(2) and N(2)N(am) = Me(3)SiN(CH(2)CH(2)NSiMe(3))(2). Subsequent reactions of 1 with MeMgBr or PhMgCl afforded the dimethyl or diphenyl complexes [W(NPh)(N(2)N(py))R(2)] (R = Me, 5, or Ph, 6), respectively, which have both been characterized by single crystal X-ray diffraction. Reactions of Li(2)N(2)N(py) or Li(2)N(2)N(am) with [Mo(NR)(2)Cl(2)(DME)] (R = (t)Bu or Ph; DME = 1,2-dimethoxyethane) afforded the corresponding bis(imido) complexes [Mo(NR)(2)(N(2)N(py))] (R = (t)Bu, 7, or Ph, 8) and [Mo(N(t)Bu)(2)(N(2)N(am))] (9).     

Probing the 5f orbital contribution to the bonding in a U(V) ketimide complex

Reaction of UCl(4) with 5 equiv of Li(N═C(t)BuPh) generates the homoleptic U(IV) ketimide complex [Li(THF)(2)][U(N═C(t)BuPh)(5)] (1) in 71% yield. Similarly, reaction of UCl(4) with 5 equiv of Li(N═C(t)Bu(2)) affords [Li(THF)][U(N═C(t)Bu(2))(5)] (2) in 67% yield. Oxidation of 2 with 0.5 equiv of I(2) results in the formation of the neutral U(V) complex U(N═C(t)Bu(2))(5) (3). In contrast, oxidation of 1 with 0.5 equiv of I(2), followed by addition of 1 equiv of Li(N═C(t)BuPh), generates the octahedral U(V) ketimide complex [Li][U(N═C(t)BuPh)(6)] (4) in 68% yield. Complex 4 can be further oxidized to the U(VI) ketimide complex U(N═C(t)BuPh)(6) (5). Complexes 1-5 were characterized by X-ray crystallography, while SQUID magnetometry, EPR spectroscopy, and UV-vis-NIR spectroscopy measurements were also preformed on complex 4. Using this data, the crystal field splitting parameters of the f orbitals were determined, allowing us to estimate the amount of f orbital participation in the bonding of 4.     

Synthesis,characterization, and solution redox properties of (trimpsi)M(CO)(2)(NO) complexes [M = V,Nb, Ta; trimpsi = (t)BuSi(CH(2)PMe(2))(3)

Treatment of [Et(4)N][M(CO)(6)] (M = Nb, Ta) with I(2) in DME at -78 degrees C produces solutions of the bimetallic anions [M(2micro-I)(3)(CO)(8)](-). Addition of the tripodal phosphine (t)BuSi(CH(2)PMe(2))(3) (trimpsi) followed by refluxing affords (trimpsi)M(CO)(3)I [M = Nb (1), Ta (2)], which are isolable in good yields as air-stable, orange-red microcrystalline solids. Reduction of these complexes with 2 equiv of Na/Hg, followed by treatment with Diazald in THF, results in the formation of (trimpsi)M(CO)(2)(NO) [M = Nb (3), Ta (4)] in high isolated yields. The congeneric vanadium complex, (trimpsi)V(CO)(2)(NO) (5), can be prepared by reacting [Et(4)N][V(CO)(6)] with [NO][BF(4)] in CH(2)Cl(2) to form V(CO)(5)(NO). These solutions are treated with 1 equiv of trimpsi to obtain (eta(2)-trimpsi)V(CO)(3)(NO). Refluxing orange THF solutions of this material affords 5 in moderate yields. Reaction of (trimpsi)VCl(3)(THF) (6) with 4 equiv of sodium naphthalenide in THF in the presence of excess CO provides [Et(4)N][(trimpsi)V(CO)(3)] (7), (trimpsi)V(CO)(3)H, and [(trimpsi)V(micro-Cl)(3)V(trimpsi)][(eta(2)-trimpsi)V(CO)(4)].3THF ([8][9].3THF). All new complexes have been characterized by conventional spectroscopic methods, and the solid-state molecular structures of 2.(1)/(2)THF, 3-5, and [8][9].3THF have been established by X-ray diffraction analyses. The solution redox properties of 3-5 have also been investigated by cyclic voltammetry. Cyclic voltammograms of 3 and 4 both exhibit an irreversible oxidation feature in CH(2)Cl(2) (E(p,a) = -0.71 V at 0.5 V/s for 3, while E(p,a) = -0.55 V at 0.5 V/s for 4), while cyclic voltammograms of 5 in CH(2)Cl(2) show a reversible oxidation feature (E(1/2) = -0.74 V) followed by an irreversible feature (0.61 V at 0.5 V/s). The reversible feature corresponds to the formation of the 17e cation [(trimpsi)V(CO)(2)(NO)](+) ([5](+)()), and the irreversible feature likely involves the oxidation of [5](+)() to an unstable 16e dication. Treatment of 5 with [Cp(2)Fe][BF(4)] in CH(2)Cl(2) generates [5][BF(4)], which slowly decomposes once formed. Nevertheless, [5][BF(4)] has been characterized by IR and ESR spectroscopies.     

Synthesis and structural characterization of a series of lanthanide(II) amides: steric effect of amido ligand

The synthesis and structures of a series of lanthanide(II) and lanthanide(III) complexes supported by the amido ligand N(SiMe3)Ar were described. Several lanthanide(III) amide chlorides were synthesized by a metathesis reaction of LnCl3 with lithium amide, including {[(C6H5)(Me3Si)N]2YbCl(THF)}2.PhCH3 (1), [(C6H3-iPr2-2,6)(SiMe3)N]2YbCl(mu-Cl)Li(THF)3.PhCH3 (4), [(C6H3-iPr2-2,6)(SiMe3)N]YbCl2(THF)3 (6), and [(C6H3-iPr2-2,6)(SiMe3)N]2SmCl3Li2(THF)4 (7). The reduction reaction of 1 with Na-K alloy afforded bisamide ytterbium(II) complex [(C6H5)(Me3Si)N]2Yb(DME)2 (2). The same reaction for Sm gave an insoluble black powder. An analogous samarium(II) complex [(C6H5)(Me3Si)N]2Sm(DME)2 (3) was prepared by the metathesis reaction of SmI2 with NaN(C6H5)(SiMe3). The reduction reaction of ytterbium chloride 4 with Na-K alloy afforded monoamide chloride {[(C6H3-iPr2-2,6)(SiMe3)N]Yb(mu-Cl)(THF)2}2 (5), which is the first example of ytterbium(II) amide chloride, formed via the cleavage of the Yb-N bond. The same reduction reaction of 7 gave a normal bisamide complex [(C6H3-iPr2-2,6)(SiMe3)N]2Sm(THF)2 (8) via Sm-Cl bond cleavage. This is the first example for the steric effect on the outcome of the reduction reaction in lanthanide(II) chemistry. 5 can also be synthesized by the Na/K alloy reduction reaction of 6. All of the complexes were fully characterized including X-ray diffraction for 1-7.     

Protonation effect on catalytic water oxidation activity of a mononuclear Ru catalyst containing a free pyridine unit

Two efficient single-site Ru water oxidation catalysts [Ru(bda)(pic)(Ln)](bda = 2,2'-bipyridine-6,6'-dicarboxylic acid, pic = picoline, L1 = 4,5-bipyridine-2,7-di-tert-butyl-9,9-dimethylxanthene, L2 = 4-pyridine-5-phenyl-2,7-di-tert-butyl-9,9-dimethylxanthene) were only synthesized containing different xanthene ligands at the axial site. These complexes have been thoroughly characterized by spectroscopic(UV-vis, NMR) and electrochemical(CV and DPV) techniques. Kinetic analysis proved that the mechanism of water oxidation comprises the water nucleophilic attack process on high-valence ruthenium species.It is found that the catalyst 1 displayed higher activity than catalyst 2 on water oxidation, caused by the protonation of the axial ligand L1 with a free pyridine.     

Unique sigma-bond metathesis of silylalkynes promoted by an ansa-dimethylsilyl and oxo-bridged uranium metallocene

The tetrachloride salt of uranium reacts with 1 equiv of the lithium ligand Li2[(C5Me4)2SiMe2] in DME to form the complex [eta5-(C5Me4)2SiMe2]UCl2.2LiCl.2DME (1), which undergoes a rapid hydrolysis in toluene to yield the dimeric bridged monochloride, monooxide complex [{[eta5-(C5Me4)2SiMe2]UCl}2(mu-O)(mu-Cl)*Li*1/2DME]2 (2). Metathesis of 2 with BuLi in DME gives the mono-bridged dibutyl complex {[eta5-(C5Me4)2SiMe2]UBu}2(mu-O) (3). Complex 2 was characterized by solid-state X-ray analysis. Complex 3 was found to be an active catalyst for the disproportionation metathesis of TMSCCH (TMS = SiMe3) and the cross-metathesis of TMSCCH or TMSCCTMS with various terminal alkynes. The metathesis of TMSCCH gives TMSCCTMS and HCCH, whereas the cross-metathesis of TMSCCH or TMSCCTMS with terminal alkynes (RCCH) yields TMSCCTMS, TMSCCR, and HCCH. In addition, TMSCCCH3 also was found to react with tBuCCH, yielding TMSCCBut and CH3CCH. A plausible mechanism for the catalytic process is presented.     

Synthesis and structures of aluminum and magnesium complexes of tetraimidophosphates and trisamidothiophosphates: EPR and DFT investigations of the persistent neutral radicals {Me2Al[(mu-NR)(mu-NtBu)P(mu-NtBu)2]Li(THF)2}(*) (R = SiMe3, tBu)

Reactions of (RNH)(3)PNSiMe(3) (3a, R = (t)()Bu; 3b, R = Cy) with trimethylaluminum result in the formation of {Me(2)Al(mu-N(t)Bu)(mu-NSiMe(3))P(NH(t)()Bu)(2)]} (4) and the dimeric trisimidometaphosphate {Me(2)Al[(mu-NCy)(mu-NSiMe(3))P(mu-NCy)(2)P(mu-NCy)(mu-NSiMe(3))]AlMe(2)} (5a), respectively. The reaction of SP(NH(t)Bu)(3) (2a) with 1 or 2 equiv of AlMe(3) yields {Me(2)Al[(mu-S)(mu-N(t)Bu)P(NH(t)()Bu)(2)]} (7) and {Me(2)Al[(mu-S)(mu-N(t)()Bu)P(mu-NH(t)Bu)(mu-N(t)Bu)]AlMe(2)} (8), respectively. Metalation of 4 with (n)()BuLi produces the heterobimetallic species {Me(2)Al[(mu-N(t)Bu)(mu-NSiMe(3))P(mu-NH(t)()Bu)(mu-N(t)()Bu)]Li(THF)(2)} (9a) and {[Me(2)Al][Li](2)[P(N(t)Bu)(3)(NSiMe(3))]} (10) sequentially; in THF solutions, solvation of 10 yields an ion pair containing a spirocyclic tetraimidophosphate monoanion. Similarly, the reaction of ((t)BuNH)(3)PN(t)()Bu with AlMe(3) followed by 2 equiv of (n)BuLi generates {Me(2)Al[(mu-N(t)Bu)(2)P(mu(2)-N(t)Bu)(2)(mu(2)-THF)[Li(THF)](2)} (11a). Stoichiometric oxidations of 10 and 11a with iodine yield the neutral spirocyclic radicals {Me(2)Al[(mu-NR)(mu-N(t)Bu)P(mu-N(t)Bu)(2)]Li(THF)(2)}(*) (13a, R = SiMe(3); 14a, R = (t)Bu), which have been characterized by electron paramagnetic resonance spectroscopy. Density functional theory calculations confirm the retention of the spirocyclic structure and indicate that the spin density in these radicals is concentrated on the nitrogen atoms of the PN(2)Li ring. When 3a or 3b is treated with 0.5 equiv of dibutylmagnesium, the complexes {Mg[(mu-N(t)()Bu)(mu-NH(t)()Bu)P(NH(t)Bu)(NSiMe(3))](2)} (15) and {Mg[(mu-NCy)(mu-NSiMe(3))P(NHCy)(2)](2)} (16) are obtained, respectively. The addition of 0.5 equiv of MgBu(2) to 2a results in the formation of {Mg[(mu-S)(mu-N(t)()Bu)P(NH(t)Bu)(2)](2)} (17), which produces the hexameric species {[MgOH][(mu-S)(mu-N(t)()Bu)P(NH(t)Bu)(2)]}(6) (18) upon hydrolysis. Compounds 4, 5a, 7-11a, and 15-17 have been characterized by multinuclear ((1)H, (13)C, and (31)P) NMR spectroscopy and, in the case of 5a, 9a.2THF, 11a, and 18, by X-ray crystallography.     

Reduction of benzophenone and 9(10H)-anthracenone with the magnesium complex [(2,6-iPr2C6H3-bian)Mg(thf)3

The reduction of benzophenone with the magnesium complex [(2,6-iPr(2)C(6)H(3)-bian)Mg(thf)(3)] (1), containing the 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene dianion, affords the pinacolato complex [(2,6-iPr(2)C(6)H(3)-bian)Mg(thf)](2)[micro-O(2)C(2)Ph(4)].(C(6)H(6))(4) (2). The reaction of 1 with 9(10H)-anthracenone yields the 9-anthracenolato complex [(2,6-iPr(2)C(6)H(3)-bian)Mg(OC(14)H(9))(thf)(2)] (3). Complexes 2 and 3 were characterized by elemental analyses, UV/Vis, IR, and ESR spectroscopy, as well as by single crystal X-ray diffraction. Complex 2 dissociates in solution with splitting of the bridging pinacolato unit, forming the biradical diimino/ketyl complex [(2,6-iPr(2)C(6)H(3)-bian)Mg(thf)(OCPh(2))].     

Vanadium complexes of the N(CH2CH2S)3(3-) and O(CH2CH2S)2(2-) ligands with coligands relevant to nitrogen fixation processes

Vanadium(III) and vanadium(V) complexes derived from the tris(2-thiolatoethyl)amine ligand [(NS3)3-] and the bis(2-thiolatoethyl)ether ligand [(OS2)2-] have been synthesized with the aim of investigating the potential of these vanadium sites to bind dinitrogen and activate its reduction. Evidence is presented for the transient existence of (V(NS3)(N2)V(NS3), and a series of mononuclear complexes containing hydrazine, hydrazide, imide, ammine, organic cyanide, and isocyanide ligands has been prepared and the chemistry of these complexes investigated. [V(NS3)O] (1) reacts with an excess of N2H4 to give, probably via the intermediates (V(NS3)(NNH2) (2a) and (V(NS3)(N2)V(NS3) (3), the V(III) adduct [V(NS3)(N2H4)] (4). If 1 is treated with 0.5 mol of N2H4, 0.5 mol of N2 is evolved and green, insoluble [(V(NS3))n] (5) results. Compound 4 is converted by disproportionation to [V(NS3)(NH3)] (6), but 4 does not act as a catalyst for disproportionation of N2H4 nor does it act as a catalyst for its reduction by Zn/HOC6H3Pri2-2,6. Compound 1 reacts with NR1(2)NR2(2) (R1 = H or SiMe3; R2(2) = Me2, MePh, or HPh) to give the hydrazide complexes [V(NS3)(NNR2(2)] (R2(2) = Me2, 2b; R2(2) = MePh, 2c; R2(2) = HPh, 2d), which are not protonated by anhydrous HBr nor are they reduced by Zn/HOC6H3Pri2-2,6. Compound 2b can also be prepared by reaction of [V(NNMe2)(dipp)3] (dipp = OC6H3Pri2-2,6) with NS3H3. N2H4 is displaced quantitatively from 4 by anions to give the salts [NR3(4)][V(NS3)X] (X = Cl, R3 = Et, 7a; X = Cl, R3 = Ph, 7b; X = Br, R3 = Et, 7c; X = N3, R3 = Bu(n), 7d; X = N3, R3 = Et, 7e; X = CN, R3 = Et, 7f). Compound 6 loses NH3 thermally to give 5, which can also be prepared from [VCl3(THF)3] and NS3H3/LiBun. Displacement of NH3 from 6 by ligands L gives the adducts [V(NS3)(L)] (L = MeCN, nu CN 2264 cm-1, 8a; L = ButNC, nu NC 2173 cm-1, 8b; L = C6H11NC, nu NC 2173 cm-1, 8c). Reaction of 4 with N3SiMe3 gives [V(NS3)(NSiMe3)] (9), which is converted to [V(NS3)(NH)] (10) by hydrolysis and to [V(NS3)(NCPh3)] (11) by reaction with ClCPh3. Compound 10 is converted into 1 by [NMe4]OH and to [V(NS3)NLi(THF)2] (12) by LiNPri in THF. A further range of imido complexes [V(NS3)(NR4)] (R4 = C6H4Y-4 where Y = H (13a), OMe (13b), Me (13c), Cl (13d), Br (13e), NO2 (13f); R4 = C6H4Y-3, where Y = OMe (13g); Cl (13h); R4 = C6H3Y2-3,4, where Y = Me (13i); Cl (13j); R4 = C6H11 (13k)) has been prepared by reaction of 1 with R4NCO. The precursor complex [V(OS2)O(dipp)] (14) [OS2(2-) = O(CH2CH2S)2(2-)] has been prepared from [VO(OPri)3], Hdipp, and OS2H2. It reacts with NH2NMe2 to give [V(OS2)(NNMe2)(dipp)] (15) and with N3SiMe3 to give [V(OS2)(NSiMe3)(dipp)] (16). A second oxide precursor, formulated as [V(OS2)1.5O] (17), has also been obtained, and it reacts with SiMe3NHNMe2 to give [V(OS2)(NNMe2)(OSiMe3)] (18). The X-ray crystal structures of the complexes 2b, 2c, 4, 6, 7a, 8a, 9, 10, 13d, 14, 15, 16, and 18 have been determined, and the 51V NMR and other spectroscopic parameters of the complexes are discussed in terms of electronic effects.     

Chiral bisphosphinite metalloligands derived from a P-chiral secondary phosphine oxide

Interaction of PdCl(2)(MeCN)(2) with 2 equiv of (S(P))-(t)BuPhP(O)H (1H) followed by treatment with Et(3)N gave [Pd((1)(2)H)](2)(micro-Cl)(2) (2). Reaction of 2 with Na[S(2)CNEt(2)] or K[N(PPh(2)S)(2)] afforded Pd[(1)(2)H](S(2)CNEt(2)) (3) or Pd[(1)(2)H)[N(PPh(2)S)(2)] (4), respectively. Treatment of 3 with V(O)(acac)(2) (acac = acetylacetonate) and CuSO(4) in the presence of Et(3)N afforded bimetallic complexes V(O)[Pd(1)(2)(S(2)CNEt(2))](2) (5) or Cu[Pd(1)(2)(S(2)CNEt(2))](2) (6), respectively. X-ray crystallography established the S(P) configuration for the phosphinous acid ligands in 3 and 6, indicating that 1H binds to Pd(II) with retention of configuration at phosphorus. The geometry around Cu in 6 is approximately square planar with the average Cu-O distance of 1.915(3) A. Treatment of 2 with HBF(4) gave the BF(2)-capped compound [Pd((1)(2)BF(2))](2)(micro-Cl)(2) (7). The solid-state structure of 7 containing a PdP(2)O(2)B metallacycle has been determined. Chloride abstraction of 7 with AgBF(4) in acetone/water afforded the aqua compound [Pd((1)(2)BF(2))(H(2)O)(2)][BF(4)] (8) that reacted with [NH(4)](2)[WS(4)] to give [Pd((1)(2)BF(2))(2)](2)[micro-WS(4)] (9). The average Pd-S and W-S distances in 9 are 2.385(3) and 2.189(3) A, respectively. Treatment of [(eta(6)-p-cymene)RuCl(2)](2) with 1H afforded the phosphinous acid adduct (eta(6)-p-cymene)RuCl(2)(1H) (10). Reduction of [CpRuCl(2)](x)() (Cp = eta(5)-C(5)Me(5)) with Zn followed by treatment with 1H resulted in the formation of the Zn(II) phosphinate complex [(CpRu(eta(6)-C(6)H(5)))(t)BuPO(2))](2)(ZnCl(2))(2) (11) that contains a Zn(2)O(4)P(2) eight-membered ring.     

Investigation of the electronic, photosubstitution, redox, and surface properties of new ruthenium(II)-containing amphiphiles

A series of pyridine- and phenol-based ruthenium(II)-containing amphiphiles with bidentate ligands of the following types are reported: [(L(PyI))Ru(II)(bpy)(2)](PF(6))(2) (1), [(L(PyA))Ru(II)(bpy)(2)](PF(6))(2) (2), [(L(PhBuI))Ru(II)(bpy)(2)](PF(6)) (3), and [(L(PhClI))Ru(II)(bpy)(2)](PF(6)) (4). Species 1 and 2 are obtained by treatment of [Ru(bpy)(2)Cl(2)] with the ligands L(PyI) (N-(pyridine-2-ylmethylene)octadecan-1-amine) and L(PyA) (N-(pyridine-2-ylmethyl)octadecan-1-amine). The imine species 3 and 4 are synthesized by reaction of [Ru(bpy)(2)(CF(3)SO(3))(2)] with the amine ligands HL(PhBuA) (2,4-di-tert-butyl-6-((octadecylamino)methyl)phenol), and HL(PhClA) (2,4-dichloro-6-((octadecylamino)methyl)phenol). Compounds 1-4 are characterized by means of electrospray ionization (ESI(+)) mass spectrometry, elemental analyses, as well as electrochemical methods, infrared and UV-visible absorption and emission spectroscopies. The cyclic voltammograms (CVs) of 1-2 are marked by two successive processes around -1.78 and -2.27 V versus Fc(+)/Fc attributed to bipyridine reduction. A further ligand-centered reductive process is seen for 1. The Ru(II)/Ru(III) couple appears at 0.93 V versus Fc(+)/Fc. The phenolato-containing 3 and 4 species present relatively lower reduction potentials and more reversible redox behavior, along with Ru(II/III) and phenolate/phenoxyl oxidations. The interpretation of observed redox behavior is supported by density functional theory (DFT) calculations. Complexes 1-4 are surface-active as characterized by compression isotherms and Brewster angle microscopy. Species 1 and 2 show collapse pressures of about 29-32 mN·m(-1), and are strong candidates for the formation of redox-responsive monolayer films.     

Tetra- to dodecanuclear oxomolybdate complexes with functionalized bisphosphonate ligands: activity in killing tumor cells

We report the synthesis and characterization of five novel Mo-containing polyoxometalate (POM) bisphosphonate complexes with nuclearities ranging from 4 to 12 and with fully reduced, fully oxidized, or mixed-valent (Mo(V), Mo(VI)) molybdenum, in which the bisphosphonates bind to the POM cluster through their two phosphonate groups and a deprotonated 1-OH group. The compounds were synthesized in water by treating [Mo(V)(2)O(4)(H(2)O)(6)](2+) or [Mo(VI)O(4)](2-) with H(2)O(3)PC(C(3)H(6)NH(2))OPO(3)H(2) (alendronic acid) or its aminophenol derivative, and were characterized by single-crystal X-ray diffraction and (31)P NMR spectroscopy. (NH(4))(6)[(Mo(V)(2)O(4))(Mo(VI)(2)O(6))(2)(O(3)PC(C(3)H(6)NH(3))OPO(3))(2)]·12H(2)O (1) is an insoluble mixed-valent species. [(C(2)H(5))(2)NH(2)](4)[Mo(V)(4)O(8)(O(3)PC(C(3)H(6)NH(3))OPO(3))(2)]·6H(2)O (2) and [(C(2)H(5))(2)NH(2)](6)[Mo(V)(4)O(8)(O(3)PC(C(10)H(14)NO)OPO(3))(2)]·18H(2)O (4) contain similar tetranuclear reduced frameworks. Li(8)[(Mo(V)(2)O(4)(H(2)O))(4)(O(3)PC(C(3)H(6)NH(3))OPO(3))(4)]·45H(2)O (3) and Na(2)Rb(6)[(Mo(VI)(3)O(8))(4)(O(3)PC(C(3)H(6)NH(3))OPO(3))(4)]·26H(2)O (5) are alkali metal salts of fully reduced octanuclear and fully oxidized dodecanuclear POMs, respectively. The activities of 2-5 (which are water-soluble) against three human tumor cell lines were investigated in vitro. Although 2-4 have weak but measurable activity, 5 has IC(50) values of about 10 μM, which is about four times the activity of the parent alendronate molecule on a per-alendronate basis, which opens up the possibility of developing novel drug leads based on Mo bisphosphonate clusters.