Construction of [(eta5-C5Me5)WS3Cu3]-based supramolecular compounds from preformed incomplete cubane-like clusters [PPh4][(eta5-C5Me5)WS3(CuX)3] (X = CN, Br)

Approaches to the assembly of (eta5-C5Me5)WS3Cu3-based supramolecular compounds from two preformed incomplete cubane-like clusters [PPh4][(eta5-C5Me5)WS3(CuX)3] (X = CN, 1a; X = Br, 1b) have been investigated. Treatment of 1a with LiBr/1,4-pyrazine (1,4-pyz), pyridine (py), LiCl/py, or 4,4'-bipyridine (4,4'-bipy) and treatment of 1b with 4,4'-bipy gave rise to a new set of W/Cu/S cluster-based compounds, [Li[((eta5-C5Me5)WS3Cu3(mu3-Br))2(mu-CN)3].C6H6]infinity (2), [(eta5-C5Me5)WS3Cu3(mu-CN)2(py)]infinity (3), [[PPh4][(eta5-C5Me5)WS3Cu3(mu3-Cl)(mu-CN)(CN)].py]infinity (4), [PPh4]2[(eta5-C5Me5)WS3Cu3(CN)2]2(mu-CN)2.(4,4'-bipy) (5), and [[(eta5-C5Me5)WS3Cu3Br(mu-Br)(4,4'-bipy)].Et2O]infinity (6). The structures of 2-6 have been characterized by elemental analysis, IR spectra, and single-crystal X-ray crystallography. Compound 2 displays a 1D ladder-shaped chain structure built of square-like [[(eta5-C5Me5)WS3Cu3(mu3-Br)(mu-CN)]4](mu-CN)2(2-) anions via two pairs of Cu-mu-CN-Cu bridges. Compound 3 consists of a single 3D diamond-like network in which each (eta5-C5Me5)WS3Cu3 unit, serving as a tetrahedral node, interconnects with four other nearby units through Cu-mu-CN-Cu bridges. Compound 4 contains a 1D zigzag chain array made of cubane-like [(eta5-C5Me5)WS3Cu3(mu3-Cl)(mu-CN)(CN)]- anions linked by a couple of Cu-mu-CN-Cu bridges. Compound 5 contains a dimeric structure in which the two incomplete cubane-like [(eta5-C5Me5)WS3(CuCN)2(mu-CN)]- anions are strongly held together via a pair of Cu-mu-CN-Cu bridges. Compound 6 contains a 2D brick-wall layer structure in which dimers of [(eta5-C5Me5)WS3Cu3Br(4,4'-bipy)]2 are interconnected via four Cu-mu-Br-Cu bridges. The successful construction of (eta5-C5Me5)WS3Cu3-based supramolecular compounds 2-6 from the geometry-fixed clusters 1a and 1b may expand the scope of the rational design and construction of cluster-based supramolecular assemblies.     

Coupling of an aldehyde or ketone to pyridine mediated by a tungsten imido complex

The reactivity of W(NPh)(o-(Me3SiN)2C6H4)(py)2 and W(NPh)(o-(Me3SiN)2C6H4)(pic)2 (py=pyridine; pic=4-picoline) with unsaturated substrates has been investigated. Treatment of W(NPh)(o-(Me3SiN)2C6H4)(py)2 with diphenylacetylene or 2,3-dimethyl-1,3-butadiene generates W(NPh)(o-(Me3SiN)2C6H4)(eta2-PhCCPh) and W(NPh)(o-(Me3SiN)2C6H4)(eta4-CH2=C(Me)C(Me)=CH2), respectively, while the addition of ethylene to W(NPh)(o-(Me3SiN)2C6H4)(py)2 generates the known metallacycle W(NPh)(o-(Me3SiN)2C6H4)(CH2CH2CH2CH2). The addition of 2 equiv of acetone to W(NPh)(o-(Me3SiN)2C6H4)(pic)2 provides the azaoxymetallacycle W(NPh)(o-(Me3SiN)2C6H4)(OCH(Me)2)(OC(Me)2-o-C5H3N-p-Me), the result of acetone insertion into the ortho C-H bond of picoline. Similarily, the addition of 2 equiv of RC(O)H [R=Ph, tBu] to W(NPh)(o-(Me3SiN)2C6H4)(py)2 generates W(NPh)(o-(Me3SiN)2C6H4)(OCH2R)(OCHR-o-C5H4N) [R=Ph, tBu,]. In contrast, reaction between W(NPh)(o-(Me3SiN)2C6H4)(py)2 and 2-pyridine carboxaldehyde yields the diolate W(NPh)(o-(Me3SiN)2C6H4)(OCH(C5H4N)CH(C5H4N)O). The synthesis of W(NPh)(o-(Me3SiN)2C6H4)(PMe3)(py)(eta2-OC(H)C6H4-p-Me), formed by the addition of p-tolualdehyde to a mixture of W(NPh)(o-(Me3SiN)2C6H4)(py)2 and PMe3, suggests that an eta2-aldehyde intermediate is involved in the formation of the azaoxymetallacycle, while the isolation of W(NPh)(o-(Me3SiN)2C6H4)(Cl)(OC(Me)(CMe3)-o-C5H4N), formed by the reaction of pinacolone with W(NPh)(o-(Me3SiN)2C6H4)(py)2, in the presence of adventitious CH2Cl2, suggests that the reaction proceeds via the hydride W(NPh)(o-(Me3SiN)2C6H4)(H)(OC(Me)(CMe3)-o-C5H4N).     

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.     

Square-planar rhodium(I) complexes partnered with [arachno-6-SB(9)H(12)]- : a route toward the synthesis of new rhodathiaboranes and organometallic/thiaborane salts

Treatment of [RhCl(eta4-diene)]2 (diene = nbd, cod) with the N-heterocyclic ligands 2,2'-bipyridine (bpy), 4,4'-dimethyl-2,2'-bipyridine (Me2bpy), 1,10-phenanthroline (phen), and pyridine (py) followed by addition of Cs[arachno-6-SB9H12] affords the corresponding salts, [Rh(eta4-diene)(L2)][SB9H12] [diene = cod, L2 = bpy (1), Me2bpy (3), phen (5), (py)2 (7); diene = nbd, L2 = bpy (2), Me2bpy (4), phen (6), (py)2 (8)]. These compounds are characterized by NMR spectroscopy and mass spectrometry, and in addition, the cod-Rh species 1 and 3 are studied by X-ray diffraction analysis. These saltlike reagents are stable in the solid state, but in solution the rhodium(I) cations, [Rh(eta4-diene)(L2)]+, react with the polyhedral anion [SB9H12]- leading to a chemistry that is controlled by the d8 transition element chelates. The nbd-Rh(I) complexes react faster than the cod-Rh(I) counterparts, leading, depending on the conditions, to the synthesis of new rhodathiaboranes of general formulas [8,8-(L2)-nido-8,7-RhSB9H10] [L2 = bpy (9), Me2bpy (10), phen (11), (py)2 (12)] and [8,8-(L2)-8-(L')-nido-8,7-RhSB9H10] [L' = PPh3, L2 = bpy (13), Me2bpy (14), phen (15); L' = NCCH3, L2 = bpy (16), Me2bpy (17), phen (18)]. Compound 13 is characterized by X-ray diffraction analysis confirming the 11-vertex nido-structure of the rhodathiaborane analogues 14-18. In dichloromethane, 1 and 3 yield mixtures that contain the 11-vertex rhodathiaboranes 9 and 10 together with new species. In contrast, the cod-Rh(I) reagent 5 affords a single compound, which is proposed to be an organometallic rhodium complex bound exo-polyhedrally to the thiaborane cage. In the presence of H2(g) and stoichiometric amounts of PPh3, the cod-Rh(I) reagents, 1, 3, and 5, afford the salts [Rh(H)2(L2)(PPh3)2][SB9H12] [L2 = bpy (19), Me2bpy (20), phen (21)]. Similarly, in an atmosphere of CO(g) and in the presence of PPh3, compounds 1-6 afford [Rh(L2)(PPh3)2(CO)][SB9H12] (L2 = bpy (22), Me2bpy (23), phen (24)]. The structures of 19 and 24 are studied by X-ray diffraction analysis. The five-coordinate complexes [Rh(L2)(PPh3)2(CO)]+ undergo PPh3 exchange in a process that is characterized as dissociative. The observed differences in the reactivity of the nbd-Rh(I) salts versus the cod-Rh(I) analogues are rationalized on the basis of the higher kinetic lability of the nbd ligand and its faster hydrogenation relative to the cod diene.     

Novel reactions of phosphorus(III) azides and isocyanates: unusual modes of cycloaddition with dipolarophiles and an unexpected case of ring expansion

New modes of 1,3-dipolar cycloaddition are uncovered by the isolation of [CH2(6-t-Bu-4-Me-C6H2O)2]P(C(CO2Me)C(CO2Me)N[NP(N3)(OC6H2-6-t-Bu-4-Me)2CH2]N) (3) and [CH2(6-t-Bu-4-Me-C6H2O)2]P(C(CO2Me)C(CO2Me)C(O)N) (4) on treating [CH2(6-t-Bu-4-Me-C6H2O)2]P-X [X = N3 (1) and NCO (2)] with the dipolarophile MeO2CC identical to CCO2Me; compound 4 undergoes an unprecedented ring expansion upon addition of 2-(methylamino)ethanol to afford the spirocycle [CH2(6-t-Bu-4-Me-C6H2O)2]P(OCH2CH2N(Me)CH(CO2Me)CH(CO2Me)C(O)N) (5).     

Synthesis and characterization of pyridine amide cation radical complexes of iron: stabilization due to coordination with low-spin iron(III) center

We reported the synthesis and characterization of peptide complexes of low-spin iron(III) [Fe(bpb)(py)2][ClO4] (1) and Na[Fe(bpb)(CN)2] (2) [H2bpb = 1,2-bis(pyridine-2-carboxamido)benzene; py = pyridine], where iron is coordinated to four nitrogen donors in the equatorial plane with two amide nitrogen anions and two pyridine nitrogen donors (Ray, M.; Mukherjee, R.; Richardson, J. F.; Buchanan, R. M. J. Chem. Soc., Dalton Trans. 1993, 2451). Chemical oxidation of 2 and a new low-spin iron(III) complex Na[Fe(Me6bpb)(CN)2].H2O (4) [synthesized from a new iron(III) complex [Fe(Me6bpb)(py)2][ClO4] (3) (S = 1/2)] [H2Me6bpb = 1,2-bis(3,5-dimethylpyridine2-carboxamido)-4,5-dimethylbenzene) by (NH4)2Ce(NO3)6 afforded isolation of two novel complexes [Fe(bpb)-(CN)2] (5) and [Fe(Me6bpb)(CN)2].H2O (6). All the complexes have been characterized by physicochemical techniques. While 1-4 are brown/green, 5 and 6 are violet/bluish violet. The collective evidence from infrared, electronic, M?ssbauer, and 1H NMR spectroscopies, from temperature-dependent magnetic susceptibility data, and from cyclic voltammetric studies provides unambiguous evidence that 5 and 6 are low-spin iron(III) ligand cation radical complexes rather than iron(IV) complexes. Cyclic voltammetric studies on isolated oxidized complexes 5 and 6 display identical behavior (a metal-centered reduction and a ligand-centered oxidation) to that observed for complexes 2 and 4, respectively. The M?ssbauer data for 6 are almost identical with those of the parent compound 4, providing compelling evidence that oxidation has occurred at the ligand in a site remote from the iron atom. Strong antiferromagnetic coupling (-2J > or = 450 cm(-1)) of the S = 1/2 iron atom with the S = 1/2 ligand pi-cation radical leads to an effectively S = 0 ground state of 5 and 6. The oxidized complexes display 1H NMR spectra (in CDCl3 solution), characteristic of diamagnetic species.     

Chiral organometallic triangles with Rh-Rh bonds. 1. Compounds prepared from racemic cis-Rh2(C6H4PPh2)2(OAc)2

Reaction of racemic cis-Rh(2)(C(6)H(4)PPh(2))(2)(OAc)(2)(HOAc)(2) with excess Me(3)OBF(4) in CH(3)CN results in the formation of racemic cis-[Rh(2)(C(6)H(4)PPh(2))(2)(CH(3)CN)(6)](BF(4))(2).0.5H(2)O (1.0.5H(2)O), an ionic dirhodium complex which has two cisoid nonlabile orthometalated phosphine bridging anions and six labile CH(3)CN ligands in equatorial and axial positions. Reactions of 1 with tetraethylammonium salts of the linear dicarboxylates, oxalate, terephthalate, and 4,4'-biphenyl-dicarboxylate, in organic solvents, produced racemic crystals of the triangular compounds [Rh(2)(C(6)H(4)PPh(2))(2)](3)(C(2)O(4))(3)(py)(6).6MeOH.H(2)O (2.6MeOH.H(2)O), [Rh(2)(C(6)H(4)PPh(2))(2)](3)(O(2)CC(6)H(4)CO(2))(3)(DMF)(6).6.5DMF.0.5H(2)O (3.6.5DMF.0.5H(2)O), and [Rh(2)(C(6)H(4)PPh(2))(2)](3)(O(2)CC(6)H(4)C(6)H(4)CO(2))(3)(py)(6).4.5CH(3)OH.0.75H(2)O (4.4.5CH(3)OH.0.75H(2)O), respectively. All compounds are electrochemically active. The relative chiralities of the dirhodium units in each triangle have been established using a combination of data from X-ray crystallography and (31)P NMR spectroscopy.     

Phosphinito- and phosphonito-oxazoline Pd(II) complexes as CO/ethylene insertion intermediates: synthesis and structural characterization

The phosphinito-oxazoline ligand 4,4-dimethyl-2-[methoxy(diphenylphosphine)]-4,5-dihydrooxazole (2a) and the phosphonite-oxazoline ligand 4,4-dimethyl-2-[methoxy(6H-dibenz[c,e][1,2]oxaphosphorin)]-4,5-dihydrooxazole (8a) were prepared by deprotonation of (4,5-dihydro-4,4-dimethyloxazol-2-yl)methanol (1a) and reaction with the corresponding P-Cl function, similar to the ligands 2b (4,4-dimethyl-2-[1-oxy(diphenylphosphine)-1-methylethyl]-4,5-dihydrooxazole) and 8b (4,4-dimethyl-2-[1-oxy(6H-dibenz[c,e][1,2]oxaphosphorin)-1-methylethyl]-4,5-dihydrooxazole) reported previously. These ligands react with [PdClX(COD)] to give complexes of the type [PdClX(P,N)] (3a P,N = 2a, X = Cl; 4a P,N = 2a, X = Me; 4b P,N = 2b , X = Me; 9a P,N = 8a, X = Cl; 9b P,N = 8b, X = Cl; 10a P,N = 8a, X = Me; 10b P,N = 8b, X = Me). Complexes 4a,b and 10a,b reacted with AgCF(3)SO(3) to yield [PdMe(P,N)OSO(2)CF(3)] 5a,b and 11a,b, respectively. From the stepwise insertion reaction of CO and ethylene into the Pd-C bond of 5a and 11a,b, the alkyl ketone chelate complexes [Pd{CH(2)CH(2)C(O)Me}(P,N)]CF(3)SO(3) 7a and 14a,b respectively, have been isolated and spectroscopically characterized. Complexes 3a.CH(2)Cl(2), 5a, 9b, 10a,b, [PdMe(H(2)O)(P,N)]CF(3)SO(3) 12b, (P,N = 8b) and 14a,b have also been characterized by X-ray crystallography and the structures of 14a,b represent still rare examples of structurally characterized CO/ethylene coupling products.     

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).     

Carbonyl-carboxylato-ruthenium complexes incorporating diimine ligands and unexpected cyclometalation of carboxylate ligands

We report two new synthetic routes to the dinuclear Ru(I) complexes, [Ru(I)(2)(RCO(2))(CO)(4)(N( wedge )N)(2)](+) (N( wedge )N = 2,2'-bipyridine or 1,10-phenanthroline derivatives) that use RuCl(3).3H(2)O as a starting material. Direct addition of the bidentate diimine ligand to a methanolic solution of [Ru(CO)(2)Cl(2)](n) and sodium acetate yielded a mixture of [Ru(I)(2)(MeCO(2))(CO)(4)(N( wedge )N)(2)](+) (N( wedge )N = 4,4'-dmbpy, and 5,6-dmphen), and [Ru(II)(MeCO(2))(2)(CO)(2)(N( wedge )N)] (N( wedge )N = 4,4'-dmbpy and 5,5'-dmbpy). Single-crystal X-ray studies confirmed that the Ru(II) complexes had a trans-acetate-cis-carbonyl arrangement of the ligands. In contrast, the use of sodium benzoate resulted in the unexpected formation of a Ru-C bond producing ortho-cyclometalated complexes, [Ru(II)(O(2)CC(6)H(4))(CO)(2)(N( wedge )N)], where N( wedge )N = bpy or phen. A second approach used ligand exchange between a bidentate ligand (N( wedge )N) and the pyridine ligands of [Ru(I)(RCO(2))(CO)(2)(py)](2) to convert these neutral complexes into [Ru(I)(2)(RCO(2))(CO)(4)(N( wedge )N)(2)](+). This method, although it involved more steps, was applicable for a wider variety of diimine ligands (R = Me and N( wedge )N = 4,4'-dmbpy, 5,5'-dmbpy, 5,6-dmphen; R = Ph and N( wedge )N = bpy, phen, 5,6-dmphen).     

New 13-vertex metallacarborane sandwich compounds; synthetic and structural studies

Reduction of 1,12-closo-C2B10H12 followed by reaction with the appropriate metal halide and metathesis with either [K(18-crown-6)]Br or [BTMA]Cl ([BTMA] = [C6H5CH2N(CH3)3]+) affords isolable salts of the supraicosahedral metallacarborane sandwich anions [4,4-M-(1,10-closo-C2B10H12)2]n- in moderate to good yield. Compounds prepared are [BTMA][4,4-Co-(1,10-closo-C2B10H12)2] ( 1), [K(18-crown-6)][4,4-Co-(1,10-closo-C2B10H12)2] ( 2), [K(18-crown-6)]2[4,4-Ni-(1,10-closo-C2B10H12)2] ( 3), [K(18-crown-6)]2[4,4-Fe-(1,10-closo-C2B10H12)2] ( 4), [BTMA]2[4,4-Fe-(1,10-closo-C2B10H12)2] ( 5) and [K(18-crown-6)]2[4,4-Ti-(1,10-closo-C2B10H12)2] ( 6). Oxidation of the iron(II) species 4 and 5 with FeCl3 in THF generates the iron(III) analogues [K(18-crown-6)][4,4-Fe-(1,10-closo-C2B10H12)2] ( 7) and [BTMA][4,4-Fe-(1,10-closo-C2B10H12)2] ( 8), respectively. All diamagnetic compounds were characterised spectroscopically and the structures of 1, 3, 4, 6, 7 and 8 were established by single crystal X-ray diffraction. All anions have the anticipated cluster structures with two docosahedral 13-vertex cages joined at the central metal atom (the common degree-six vertex 4). Carbon atoms occupy the degree-four vertex 1 and the degree-five vertex 10. 11B NMR spectroscopy suggests the anions have, on the NMR timescale, C2h symmetry in solution at room temperature, consistent with free rotation, or at least substantial libration, of cage units about the long molecular axis. In the solid state the relative conformations of the two cages may be rationalised by simple bonding arguments, the single exception being the conformation of 4, in which both cages are subject to directional B-H...K+ interactions to the [K(18-crown-6)]+ counterion. The salts 3, 6 and 7 also show B-H...K+ interactions but involving one cage only.     

Titanium tert-butoxyimido compounds

The synthesis and molecular and electronic structures of the first tert-butoxyimido complexes of titanium (TiNO(t)Bu functional group) are reported, featuring a variety of mono- or poly-dentate, neutral or anionic N-donor ligands. Reaction of Ti(NMe(2))(2)Cl(2) with (t)BuONH(2) gave good yields of Ti(NO(t)Bu)Cl(2)(NHMe(2))(2) (1). Compound 1 serves as an excellent entry point into new tert-butoxyimido complexes by reaction with a variety of fac-N(3) donor ligands, namely, Me(3)[9]aneN(3) (trimethyl-1,4,7-triazacyclononane), HC(Me(2)pz)(3) (tris(3,5-dimethylpyrazolyl)methane), or Me(3)[6]aneN(3) (trimethyl-1,3,5-triazacyclohexane) to give Ti(NO(t)Bu)(Me(3)[9]aneN(3))Cl(2) (2), Ti(NO(t)Bu){HC(Me(2)pz)(3)}Cl(2) (3), or Ti(NO(t)Bu)(Me(3)[6]aneN(3))Cl(2) (4) in good yield. It was found that 4 could be converted into Ti(NO(t)Bu)Cl(2)(py)(3) (5) in very good yield by reaction with an excess of pyridine. Compound 5 is effective in a range of salt metathesis reactions with lithiated amide or pyrrolide ligands, and reacts with Li(2)N(2)N(py), Li(2)N(2)N(Me), LiN(pyr)N(Me(2)), or Li(2)N(2)(pyr)N(Me) to give Ti(N(2)N(py))(NO(t)Bu)(py) (6), Ti(N(2)N(Me))(NO(t)Bu)(py) (7), Ti(N(pyr)N(Me(2)))(NO(t)Bu)Cl(py)(2) (9), or Ti(N(2)(pyr)N(Me))(NO(t)Bu)(py)(2) (10) in moderate to good yields (N(2)N(py) = (2-NC(5)H(4))C(Me)(CH(2)NSiMe(3))(2); N(2)N(Me) = MeN(CH(2)CH(2)NSiMe(3))(2); N(pyr)N(Me(2)) = Me(2)NCH(2)(2-NC(4)H(3)); N(2)(pyr)N(Me) = MeN{CH(2)(2-NC(4)H(3))}(2)). Compounds 7, 9, and 10 reacted with 2,2'-bipyridyl by pyridine exchange reactions forming Ti(N(2)N(Me))(NO(t)Bu)(bipy) (8), Ti(N(pyr)N(Me(2)))(NO(t)Bu)Cl(bipy) (11), and Ti(N(2)(pyr)N(Me))(NO(t)Bu)(bipy) (12). Ten tert-butoxyimido compounds, namely, 1-6, 11, and 12, have been structurally characterized revealing approximately linear Ti-N-O(t)Bu linkages with Ti-N distances [range 1.686(2)-1.734(2) ?] that are generally intermediate between those in the homologous alkylimido and phenylimido analogues, and shorter than in the diphenylhydrazido counterparts. Density functional theory (DFT) studies on the model compounds Ti(NR)Cl(2)(NHMe(2))(2) (1_R; R = OMe, Me, Ph, NMe(2)) confirmed this trend and found that the destabilizing effect of the -OMe oxygen 2p(π) lone pair on one of the Ti-N π-bonds in 1_OMe is comparable to that of the occupied phenyl ring π orbitals in the phenylimido homologue 1_Ph but much less than for the -NMe(2) nitrogen lone pair in 1_NMe(2).     

General synthesis of (salen)ruthenium(III) complexes via N...N coupling of (salen)ruthenium(VI) nitrides

Reaction of [Ru (VI)(N)(L (1))(MeOH)] (+) (L (1) = N, N'-bis(salicylidene)- o-cyclohexylenediamine dianion) with excess pyridine in CH 3CN produces [Ru (III)(L (1))(py) 2] (+) and N 2. The proposed mechanism involves initial equilibrium formation of [Ru (VI)(N)(L (1))(py)] (+), which undergoes rapid N...N coupling to produce [(py)(L (1))Ru (III) N N-Ru (III)(L (1))(py)] (2+); this is followed by pyridine substituion to give the final product. This ligand-induced N...N coupling of Ru (VI)N is utilized in the preparation of a series of new ruthenium(III) salen complexes, [Ru (III)(L)(X) 2] (+/-) (L = salen ligand; X = H 2O, 1-MeIm, py, Me 2SO, PhNH 2, ( t )BuNH 2, Cl (-) or CN (-)). The structures of [Ru (III)(L (1))(NH 2Ph) 2](PF 6) ( 6), K[Ru (III)(L (1))(CN) 2] ( 9), [Ru (III)(L (2))(NCCH 3) 2][Au (I)(CN) 2] ( 11) (L (2) = N, N'-bis(salicylidene)- o-phenylenediamine dianion) and [N ( n )Bu 4][Ru (III)(L (3))Cl 2] ( 12) (L (3) = N, N'-bis(salicylidene)ethylenediamine dianion) have been determined by X-ray crystallography.     

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.     

Cyclophosphazene-supported tetranuclear copper assembly containing 15 contiguous inorganic rings

The cyclophosphazene hydrazide gem-N3P3Ph2[N(Me)NH2]4 was reacted with o-hydroxybenzaldehyde to afford the multisite coordination ligand gem-N3P3Ph2[N(Me)N=CHC6H4-2-OH]4 (LH4). The latter reacted with copper(II) salts to afford a novel tetranuclear copper assembly {N3P3Ph2[N(Me)N=CHC6H4-2-O]4Cu2}2, which contains, remarkably, 15 contiguous inorganic rings.     

Cadmium amido alkoxide and alkoxide precursors for the synthesis of nanocrystalline CdE (E = S, Se, Te)

The synthesis and characterization of a family of alternative precursors for the production of CdE nanoparticles (E = S, Se, and Te) is reported. The reaction of Cd(NR2)2 where NR2 = N(SiMe3)2 with n HOR led to the isolation of the following: n = 1 [Cd(mu-OCH2CMe3)(NR2)(py)]2 (1, py = pyridine), Cd[(mu-OC6H3(Me)(2)-2,6)2Cd(NR2)(py)]2 (2), [Cd(mu-OC6H3(CHMe2)(2)-2,6)(NR2)(py)]2 (3), [Cd(mu-OC6H3(CMe3)(2)-2,6)(NR2)(py)]2 (4), [Cd(mu-OC6H2(NH2)(3)-2,4,6)(NR2)(py)]2 (5), and n = 2 [Cd(mu-OC6H3(Me)(2)-2,6)(OC6H3(Me)(2)-2,6)(py)2]2 (6), and [Cd(mu-OC6H3(CMe3)(2)-2,6)(OC6H3(CMe3)(2)-2,6)(THF)]2 (7). For all but 2, the X-ray crystal structures were solved as discrete dinuclear units bridged by alkoxide ligands and either terminal -NR2 or -OR ligands depending on the stoichiometry of the initial reaction. For 2, a trinuclear species was isolated using four mu-OR and two terminal -NR2 ligands. The coordination of the Cd metal center varied from 3 to 5 where the higher coordination numbers were achieved by binding Lewis basic solvents for the less sterically demanding ligands. These complexes were further characterized in solution by 1H, 13C, and 113Cd NMR along with solid-state 113Cd NMR spectroscopy. The utility of these complexes as "alternative precursors" for the controlled preparation of nanocrystalline CdS, CdSe, and CdTe was explored. To synthesize CdE nanocrystals, select species from this family of compounds were individually heated in a coordinating solvent (trioctylphosphine oxide) and then injected with the appropriate chalcogenide stock solution. Transmission electron spectroscopy and UV-vis spectroscopy were used to characterize the resultant particles.     

Synthesis and structure of cyclic phosphate, phosphoramidate, phosphonates, and phosphonium salts. Phosphatrane formation

Reaction of tris(2-hydroxy-3,5-dimethylbenzyl)amine (6) with phosphorus reagents led to the formation of the phosphoramidate, N[CH2(Me2C6H2)O]2PO (1), the phosphate N[CH2(Me2C6H2)O]2[CH2(Me2C6H2)OH]P(O)(OPh) (2), the phosphonium salts N[CH2(Me2C6H2)O]3PMe+I- (3A) and N[CH2(Me2C6H2)O]3PMe+I3- (3B), and the phosphonates N[CH2(Me2C6H2)O]2[CH2(Me2C6H2)OH]P(O)Me (4) and N[CH2(Me2C6H2)O]2[CH2(Me2C6H2)OSiMe3]P(O)Me (5). X-ray analysis provided molecular structures for all of the compounds. The solid-state structural representations were supported in solution by an analysis of the NCH2 proton NMR patterns. The structures of 3A and 3B show the presence of phosphatranes with weak P-N donor interactions. These represent the first phosphatranes containing all six-membered rings. Variable temperature analysis of the 1H NMR spectra of 3A indicates fluxional behavior whereby a racemic mixture of the chiral phosphonium salt rapidly intraconverts at room temperature. The activation energy for the enantiomeric conversion of the clockwise and anticlockwise orientations of the propeller-like phosphatrane is 11.2 kcal/mol, which is compared to that of the isoelectronic silatrane N[CH2(Me2C6H2)O]3SiMe (E), 10.3 kcal/mol.     

Ditopic hexaazamacrocycles containing pyridine: synthesis, protonation and complexation studies

Structural studies of metal complexes of five ditopic hexaazamacrocycles containing two pyridine rings ([n]py2N4 n= 18, 20, 22, 24 and 26) have been carried out. The synthesis of macrocycles [22]- to [26]-py2N4 are also reported. The protonation constants of the last three compounds and the stability constants of their complexes with Ni2+, Cu2+, Zn2+, and Pb2+ were determined at 25 degrees C in 0.10 mol dm(-3) KNO3 in aqueous solution. Our results with [22]py2N4 show significant differences from those described previously, while [24]py2N4 has not been studied before and [26]py2N4 is a new compound. Mononuclear and dinuclear complexes of the divalent metal ions studied with [22]- to [26]-py2N4 were found in solution. The stability constants for the ML complexes of the three ligands follow the Irving-Williams order: NiL2+ < CuL2+ > ZnL2+ > PbL2+, however for the dinuclear complexes the values for Pb2+ complexes are higher than the corresponding values for the Ni2+ and the Zn2+ complexes. The X-ray single crystal structures of the supramolecular aggregates [Cu2([20]py2N4)(H2O)4][Cu(H2O)6](SO4)3 x 3H2O and [Cu(2)([20]py(2)N4)(CH3CN)4][Ni([20]py2N4)]2(ClO4)8 x H2O, which are composed of homodinuclear [Cu2([20]py2N4])(H2O)4]4+ and [Cu2([20]py2N4])(CH3CN))4]4+, and mononuclear species, [Cu(H2O)6]2+ and [Ni([20]py2N4)]2+, respectively, assembled by an extensive network of hydrogen bonds, are also reported. In both homodinuclear complexes the copper centres are located at the end of the macrocycle and display distorted square pyramidal coordination environments with the basal plane defined by three consecutive nitrogen donors and one solvent molecule, water in and acetonitrile in . The macrocycle adopts a concertina-type conformation leading to the formation of macrocyclic cavities with the two copper centres separated by intramolecular distances of 5.526(1) and 5.508(7) A in 1a and 2a, respectively. The mononuclear complex [Ni([20]py2N4])]2+ displays a distorted octahedral co-ordination environment with the macrocycle wrapping the metal centre in a helical shape. EPR spectroscopy of the copper complexes indicated the presence of mono- and dinuclear species.     

Reaction of vinyl chloride with late transition metal olefin polymerization catalysts

The reactions of vinyl chloride (VC) with representative late metal, single-site olefin dimerization and polymerization catalysts have been investigated. VC coordinates more weakly than ethylene or propylene to the simple catalyst (Me(2)bipy)PdMe(+) (Me(2)bipy = 4,4'-Me(2)-2,2'-bipyridine). Insertion rates of (Me(2)bipy)Pd(Me)(olefin)(+) species vary in the order VC > ethylene > propylene. The VC complexes (Me(2)bipy)Pd(Me)(VC)(+) and (alpha-diimine)Pd(Me)(VC)(+) (alpha-diimine = (2,6-(i)Pr(2)[bond]C(6)H(3))N[double bond]CMeCMe[double bond]N(2,6-(i)Pr(2)[bond]C(6)H(3))) undergo net 1,2 VC insertion and beta-Cl elimination to yield Pd[bond]Cl species and propylene. Analogous chemistry occurs for (pyridine-bisimine)MCl(2)/MAO catalysts (M = Fe, Co; pyridine-bisimine = 2,6-[(2,6-(i)Pr(2)[bond]C(6)H(3))N[double bond]CMe](2)-pyridine) and for neutral (sal)Ni(Ph)PPh(3) and (P[bond]O)Ni(Ph)PPh(3) catalysts (sal = 2-[C(H)[double bond]N(2,6-(i)Pr(2)-C(6)H(3))]-6-Ph-phenoxide; P[bond]O = [Ph(2)PC(SO(3)Na)[double bond]C(p-tol)O]), although the initial metal alkyl VC adducts were not detected in these cases. These results show that the L(n)MCH(2)CHClR species formed by VC insertion into the active species of late metal olefin polymerization catalysts undergo rapid beta-Cl elimination which precludes VC polymerization. Termination of chain growth by beta-Cl elimination is the most significant obstacle to metal-catalyzed insertion polymerization of VC.     

Iminoacylation. 3. Formation of platinum(IV)-based metallaligands due to facile one-end addition of vic-dioximes to coordinated organonitriles

The reaction of vic-dioximes with the organonitrile platinum(IV) complexes trans-[PtCl4(RCN)2] (R = Me, CH2Ph, Ph, vic-dioxime = dimethylglyoxime; R = Me, vic-dioxime = cyclohexa-, cyclohepta-, and cyclooctanedione dioximes) proceeds rapidly under relatively mild conditions and affords products of one-end addition of the dioximes to the nitrile carbon, i.e. [PtC4(NH=C(R)ON=[spacer]=NOH)2] (1-6) (R = Me, CH2Ph, Ph, spacer = C(Me)C-(Me) for dimethylglyoxime; R = Me, spacer = C[C4H8]C, C[C5H10]C, C[C6H12]C for the other dioximes), giving a novel type of metallaligand. All addition compounds were characterized by elemental analyses (C, H, N, C1, Pt), FAB mass spectrometry, and IR and 1H, 13C[1H], and 195Pt NMR spectroscopy. X-ray structure determination of the dimethylformamide bis-solvate [PtCl4(NH=C(Me)ON=C(Me)C(Me)=NOH)2] x 2DMF (la) disclosed its overall trans geometry with the dimethylglyoxime part in anti configuration and the amidine one-end (rather than N,N-bidentate) coordination mode of the N-donor ligands. When a mixture of cis- and trans-[PtC4(MeCN)2] in MeCN was treated with dimethylglyoxime, the formation of, correspondingly, cis- and trans-[PtCl4(NH=C(Me)ON=C(Me)C(Me)=NOH)2] (1) was observed and cis-to-trans isomerization in DMSO-d6 solution was monitored by 1H, 2D [1H,15N] HMQC, and 195Pt NMR spectroscopies. Although performed ab initio calculations give evidence that the trans geometry is the favorable one for the iminoacylated species [PtCl4-(ligand)2], the platinum(IV) complex [PtCl4(NH=C(Me)ON=C[C4Hs]C=NOH)2] (4) was isolated exclusively in cis configuration with the two metallaligand "arms" held together by intramolecular hydrogen bonding between the two peripheral OH groups, as it was proved by single-crystal X-ray diffractometry. The classic substitution products, e.g. [PtC12(N,N-dioximato)2] (12-15), are formed in the addition reaction as only byproducts in minor yield; two of them, [PtCl2(C7H11N2O2)2] (14) and [PtCl2(C8H13N2O2)2] (15), were structurally characterized. Complexes (12-15) were also prepared by reaction of the vic-dioximes with [PtCl4L(Me2SO)] (L = Me2SO, MeCN), but monoximes (Me2C=NOH, [C4H8]C=NOH, [C5H10]C=NOH, PhC(H)=NOH, (OH)C6H4C(H)= NOH) react differently adding to [PtCl4(MeCN)(Me2SO)] to give the corresponding iminoacylated products [PtCl4(NH=C(Me)ON=CRR')(Me2SO)](7-11).