Tetraarylpentaborates, [B(5)O(6)Ar(4)](-) (Ar = C(6)H(4)OMe-4, C(6)H(3)Me(2)-2,6): their formation from the reaction of arylboronic acids with an aryloxorhodium complex,structure, and chemical properties

The reactions of (4-methoxyphenyl)boronic acid (1a) and of (2,6-dimethylphenyl)boronic acid (1b) with (PMe(3))(3)Rh-(OC(6)H(4)Me-4) (2) in a 5:1 molar ratio result in the formation of cationic rhodium complexes with new tetraarylpentaborates [Rh(PMe(3))(4)](+)[B(5)O(6)Ar(4)](-) (3a, Ar = C(6)H(4)OMe-4; 3b, Ar = C(6)H(3)Me(2)-2,6). The characterization of 3a is as follows: orthorhombic space group P2(1)2(1)2(1), a = 14.7600(5) A, b = 17.1675(5) A, c = 19.8654(5) A; V = 5033.7(3) A(3); Z = 4. The characterization of 3b is as follows: orthorhombic space group Pnma, a = 23.704(6) A, b = 17.254(8) A, c = 13.304(2) A; V = 5441(2) A(3); Z = 4. An intermediate complex, [Rh(PMe(3))(4)](+)[Ph(3)B(3)O(3)(OC(6)H(4)Me-4)](-) (4), was isolated from the reaction of phenylboroxine, (PhBO)(3), with 2. The tetraarylpentaborates smoothly undergo hydrolysis to give [Rh(PMe(3))(4)](+)[B(5)O(6)(OH)(4)](-) (5).     

Diorganodiselenides and zinc(II) organoselenolates containing (imino)aryl groups of type 2-(RN=CH)C6H4

Several new diorganodiselenides containing (imino)aryl groups, [2-(RN[double bond, length as m-dash]CH)C(6)H(4)](2)Se(2) [R = Me(2)NCH(2)CH(2) (4), O(CH(2)CH(2))(2)NCH(2)CH(2) (5), PhCH(2) (6), 2',6'-(i)Pr(2)C(6)H(3) (7)] were obtained by reacting [2-{(O)CH}C(6)H(4)](2)Se(2) (3) with RNH(2). Treatment of the diselenides 6 and 7 with stoichiometric amounts of K-selectride or Na resulted in isolation of the selenolates K[SeC(6)H(4)(CH[double bond, length as m-dash]NCH(2)Ph)-2] (9) and Na[SeC(6)H(4)(CH[double bond, length as m-dash]NC(6)H(3)(i)Pr(2)-2',6')-2] (10), respectively. The reaction of potassium selenolates with anhydrous ZnCl(2) (2:1 molar ratio) gave Zn[SeC(6)H(4)(CH=NCH(2)Ph)-2](2) (11) and Zn[SeC(6)H(4)(CH[double bond, length as m-dash]NC(6)H(3)(i)Pr(2)-2',6')-2](2) (12). When the dark green solution obtained from diselenide 7 and an excess of Na (after removal of the unreacted metal) was reacted with anhydrous ZnCl(2) a carbon-carbon coupling reaction occurred and the 9,10-(2',6'-(i)Pr(2)C(6)H(3)NH)(2)C(14)H(10) (8) species was obtained. The compounds were investigated in solution by multinuclear NMR ((1)H, (13)C, (77)Se, including 2D and variable temperature experiments) and by mass spectrometry. The molecular structures of 6, 8, 11 and 12 were established by single-crystal X-ray diffraction. All compounds are monomeric in the solid state. In the diselenide 6 the (imino)aryl group acts as a (C,N)-ligand resulting in a distorted T-shaped coordination geometry of type (C,N)SeX (X = Se). For the zinc complexes 11 and 12 the (Se,N) chelate pattern of the selenolato ligands results in tetrahedral Zn(Se,N)(2) cores.     

Reactivity at the beta-diketiminate ligand Nacnac- on titanium(IV) (Nacnac- = [Ar]NC(CH3)CHC(CH3)N[Ar], Ar = 2,6-[CH(CH3)2]2C6H3). Diimine-alkoxo and bis-anilido ligands stemming from the Nacnac- skeleton

The reaction of ketene OCCPh(2) with the four-coordinate titanium(IV) imide (L(1))Ti[double bond]NAr(OTf) (L(1)(-) = [Ar]NC(CH(3))CHC(CH(3))N[Ar], Ar = 2,6-[CH(CH(3))(2)](2)C(6)H(3)) affords the tripodal dimine-alkoxo complex (L(2))Ti[double bond]NAr(OTf) (L(2)(-) = [Ar]NC(CH(3))CHC(O)[double bond]CPh(2)C(CH(3))N[Ar]). Complex (L(2))Ti[double bond]NAr(OTf) forms from electrophilic attack of the beta-carbon of the ketene on the gamma-carbon of the Nacnac(-) NCC(gamma)CN ring. On the contrary, nucleophiles such as LiR (R(-) = Me, CH(2)(t)Bu, and CH(2)SiMe(3)) deprotonate cleanly in OEt(2) the methyl group of the beta-carbon on the former Nacnac(-) backbone to yield the etherate complex (L(3))Ti[double bond]NAr(OEt(2)), a complex that is now supported by a chelate bis-anilido ligand (L(3)(2)(-) = [Ar]NC(CH(3))CHC(CH(2))N[Ar]). In the absence of electrophiles or nucleophiles, the robust (L(1))Ti[double bond]NAr(OTf) template was found to form simple adducts with Lewis bases such as CN(t)Bu or NCCH(2)(2,4,6-Me(3)C(6)H(2)). Complexes (L(2))Ti[double bond]NAr(OTf), (L(3))Ti[double bond]NAr(OEt(2)), and the adducts (L(1))Ti[double bond]NAr(OTf)(XY) [XY = CN(t)Bu and NCCH(2)(2,4,6-Me(3)C(6)H(2))] were structurally characterized by single-crystal X-ray diffraction studies.     

Ni(P(Ph)2N(C6H4X)2)2]2+ complexes as electrocatalysts for H2 production: effect of substituents, acids, and water on catalytic rates

A series of mononuclear nickel(II) bis(diphosphine) complexes [Ni(P(Ph)(2)N(C6H4X)(2))(2)](BF(4))(2) (P(Ph)(2)N(C6H4X)(2) = 1,5-di(para-X-phenyl)-3,7-diphenyl-1,5-diaza-3,7-diphosphacyclooctane; X = OMe, Me, CH(2)P(O)(OEt)(2), Br, and CF(3)) have been synthesized and characterized. X-ray diffraction studies reveal that [Ni(P(Ph)(2)N(C6H4Me)(2))(2)](BF(4))(2) and [Ni(P(Ph)(2)N(C6H4OMe)(2))(2)](BF(4))(2) are tetracoordinate with distorted square planar geometries. The Ni(II/I) and Ni(I/0) redox couples of each complex are electrochemically reversible in acetonitrile with potentials that are increasingly cathodic as the electron-donating character of X is increased. Each of these complexes is an efficient electrocatalyst for hydrogen production at the potential of the Ni(II/I) couple. The catalytic rates generally increase as the electron-donating character of X is decreased, and this electronic effect results in the favorable but unusual situation of obtaining higher catalytic rates as overpotentials are decreased. Catalytic studies using acids with a range of pK(a) values reveal that turnover frequencies do not correlate with substrate acid pK(a) values but are highly dependent on the acid structure, with this effect being related to substrate size. Addition of water is shown to dramatically increase catalytic rates for all catalysts. With [Ni(P(Ph)(2)N(C6H4CH2P(O)(OEt)2)(2))(2)](BF(4))(2) using [(DMF)H](+)OTf(-) as the acid and with added water, a turnover frequency of 1850 s(-1) was obtained.     

Yttrium complexes incorporating the chelating diamides [ArN(CH2)xNAr]2- (Ar = C6H3-2,6-iPr2, x= 2, 3) and their unusual reaction with phenylsilane

Novel yttrium chelating diamide complexes [(Y[ArN(CH(2))(x)NAr](Z)(THF)(n))(y)] (Z = I, CH(SiMe(3))(2), CH(2)Ph, H, N(SiMe(3))(2), OC(6)H(3)-2,6-(t)Bu(2)-4-Me; x = 2, 3; n = 1 or 2; y = 1 or 2) were made via salt metathesis of the potassium diamides (x = 3 (3), x = 2 (4)) and yttrium triiodide in THF (5,10), followed by salt metathesis with the appropriate potassium salt (6-9, 11-13, 15) and further reaction with molecular hydrogen (14). 6 and 11(Z = CH(SiMe(3))(2), x = 2, 3) underwent unprecedented exchange of yttrium for silicon on reaction with phenylsilane to yield (Si[ArN(CH(2))(x)NAr]PhH) (x = 2 (16), 3) and (Si[CH(SiMe(3))(2)]PhH(2)).     

Generation and coupling of [Mn(dmpe)2(C triple bond CR)(C triple bond C)]* radicals producing redox-active C4-bridged rigid-rod complexes

The symmetric d(5) trans-bis-alkynyl complexes [Mn(dmpe)(2)(C triple bond CSiR(3))(2)] (R = Me, 1 a; Et, 1 b; Ph, 1 c) (dmpe = 1,2-bis(dimethylphosphino)ethane) have been prepared by the reaction of [Mn(dmpe)(2)Br(2)] with two equivalents of the corresponding acetylide LiC triple bond CSiR(3). The reactions of species 1 with [Cp(2)Fe][PF(6)] yield the corresponding d(4) complexes [Mn(dmpe)(2)(C triple bond CSiR(3))(2)][PF(6)] (R = Me, 2 a; Et, 2 b; Ph, 2 c). These complexes react with NBu(4)F (TBAF) at -10 degrees C to give the desilylated parent acetylide compound [Mn(dmpe)(2)(C triple bond CH)(2)][PF(6)] (6), which is stable only in solution at below 0 degrees C. The asymmetrically substituted trans-bis-alkynyl complexes [Mn(dmpe)(2)(C triple bond CSiR(3))(C triple bond CH)][PF(6)] (R = Me, 7 a; Et, 7 b) related to 6 have been prepared by the reaction of the vinylidene compounds [Mn(dmpe)(2)(C triple bond CSiR(3))(C=CH(2))] (R = Me, 5 a; Et, 5 b) with two equivalents of [Cp(2)Fe][PF(6)] and one equivalent of quinuclidine. The conversion of [Mn(C(5)H(4)Me)(dmpe)I] with Me(3)SiC triple bond CSnMe(3) and dmpe afforded the trans-iodide-alkynyl d(5) complex [Mn(dmpe)(2)(C triple bond CSiMe(3))I] (9). Complex 9 proved to be unstable with regard to ligand disproportionation reactions and could therefore not be oxidized to a unique Mn(III) product, which prevented its further use in acetylide coupling reactions. Compounds 2 react at room temperature with one equivalent of TBAF to form the mixed-valent species [[Mn(dmpe)(2)(C triple bond CH)](2)(micro-C(4))][PF(6)] (11) by C-C coupling of [Mn(dmpe)(2)(C triple bond CH)(C triple bond C*)] radicals generated by deprotonation of 6. In a similar way, the mixed-valent complex [[Mn(dmpe)(2)(C triple bond CSiMe(3))](2)(micro-C(4))][PF(6)] [12](+) is obtained by the reaction of 7 a with one equivalent of DBU (1,8-diazabicyclo[5.4.0]undec-7-ene). The relatively long-lived radical intermediate [Mn(dmpe)(2)(C triple bond CH)(C triple bond C*)] could be trapped as the Mn(I) complex [Mn(dmpe)(2)(C triple bond CH)(triple bond C-CO(2))] (14) by addition of an excess of TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxy) to the reaction mixtures of species 2 and TBAF. The neutral dinuclear Mn(II)/Mn(II) compounds [[Mn(dmpe)(2)(C triple bond CR(3))](2)(micro-C(4))] (R = H, 11; R = SiMe(3), 12) are produced by the reduction of [11](+) and [12](+), respectively, with [FeCp(C(6)Me(6))]. [11](+) and [12](+) can also be oxidized with [Cp(2)Fe][PF(6)] to produce the dicationic Mn(III)/Mn(III) species [[Mn(dmpe)(2)(C triple bond CR(3))](2)(micro-C(4))][PF(6)](2) (R = H, [11](2+); R = SiMe(3), [12](2+)). Both redox processes are fully reversible. The dinuclear compounds have been characterized by NMR, IR, UV/Vis, and Raman spectroscopies, CV, and magnetic susceptibilities, as well as elemental analyses. X-ray diffraction studies have been performed on complexes 4 b, 7 b, 9, [12](+), [12](2+), and 14.     

Synthesis and X-ray crystal structure of an anionic heteronuclear metallamacrocyclic triangle

trans-[Pt(C[triple bond]C(Ar)C[triple bond]CH)2(PMe3)2](Ar = C(6)Me(4)-3,4,5,6) (1) reacts with PPN[Au(acac)(2)](Hacac = acetylacetone; 1 : 1.16 molar ratio; PPN = (Ph3P)2N) to give PPN[(Au[Pt(PMe3)2]2)(mu-Ar(C[triple bond]C)2)3] (2) the crystal structure of which showed the anions as quasi equilateral triangles stacked parallel to each other through C-HAu interactions, resulting in channels of rhombic cross-section.     

Chiral fluorous dialkoxy-diamino zirconium complexes: synthesis and use in stereospecific polymerization of 1-hexene

New catalysts for the isospecific polymerization of 1-hexene based on cationic zirconium complexes incorporating the tetradentate fluorous dialkoxy-diamino ligands [OC(CF(3))(2)CH(2)N(Me)(CH(2))(2)N(Me)CH(2)C(CF(3))(2)O](2-) [(ON(2)NO)(2-)] and [OC(CF(3))(2)CH(2)N(Me)(1R,2R-C(6)H(10))N(Me)CH(2)C(CF(3))(2)O](2-) [(ON(Cy)NO)(2-)] have been developed. The chiral fluorous diamino-diol [(ON(Cy)NO)H(2), 2] was prepared by ring-opening of the fluorinated oxirane (CF(3))(2)COCH(2) with (R,R)-N,N'-dimethyl-1,2-cyclohexanediamine. Proligand 2 reacts cleanly with [Zr(CH(2)Ph)(4)] and [Ti(OiPr)(4)] precursors to give the corresponding dialkoxy complexes [Zr(CH(2)Ph)(2)(ON(Cy)NO)] (3) and [Ti(OiPr)(2)(ON(Cy)NO)] (4), respectively. An X-ray diffraction study revealed that 3 crystallizes as a 1:1 mixture of two diastereomers (Lambda-3 and Delta-3), both of which adopt a distorted octahedral structure with trans-O, cis-N, and cis-CH(2)Ph ligands. The two diastereomers Lambda-3 and Delta-3 adopt a C(2)-symmetric structure in toluene solution, as established by NMR spectroscopy. Cationic complexes [Zr(CH(2)Ph)(ON(2)NO)(THF)(n)](+) (n=0, anion=[B(C(6)F(5))(4)](-), 5; n=1, anion=[PhCH(2)B(C(6)F(5))(3)](-), 6) and [Zr(CH(2)Ph)(ON(Cy)NO)(THF)](+)[PhCH(2)B(C(6)F(5))(3)](-) (7) were generated from the neutral parent precursors [Zr(CH(2)Ph)(2)(ON(2)NO)] (H) and [Zr(CH(2)Ph)(2)(ON(Cy)NO)] (3), and their possible structures were determined on the basis of (1)H, (19)F, and (13)C NMR spectroscopy and DFT methods. The neutral zirconium complexes H and 3 (Lambda-3/Delta-3 mixture), when activated with B(C(6)F(5))(3) or [Ph(3)C](+)[B(C(6)F(5))(4)](-), catalyze the polymerization of 1-hexene with overall activities of up to 4500 kg PH mol Zr(-1) h(-1), to yield isotactic-enriched (up to 74 % mmmm) polymers with low-to-moderate molecular weights (M(w)=4800-47 200) and monodisperse molecular-weight distributions (M(w)/M(n)=1.17-1.79).     

Syntheses and structures of structurally diverse potassium beta-diketiminates derived from the ligand [(N(SiMe3)C(Ph))2CH

The compounds [K((mu-N(SiMe3)C(Ph))2CH)(thf)2]infinity 1, [K(mu-N(SiMe3)C(Ph)C(H)C(Ph)NH)L]2 [L = (thf)2 2, tmen 3], [K(mu-NSi(Me)2C(Ph)C(H)C(Ph)N)(thf)3]2 4 and [K(N(H)C(Ph))2CH](thf)0.5 5 have been prepared from K[(N(SiMe3)C(Ph))2CH] and the X-ray structures of 1-4 are reported.     

The reactivity of gallium-(I), -(II) and -(III) heterocycles towards Group 15 substrates: attempts to prepare gallium-terminal pnictinidene complexes

The reactivity of a series of Ga(I), Ga(II) and Ga(III) heterocyclic compounds towards a number of Group 15 substrates has been investigated with a view to prepare examples of gallium-terminal pnictinidene complexes. Although no examples of such complexes were isolated, a number of novel complexes have been prepared. The reactions of the gallium(I) N-heterocyclic carbene analogue, [K(tmeda)][:Ga{[N(Ar)C(H)](2)}] (Ar = 2,6-diisopropylphenyl) with cyclo-(PPh)(5) and PhN[double bond, length as m-dash]NPh led to the unusual anionic spirocyclic complexes, [{kappa(2)P,P'-(PhP)(4)}Ga{[N(Ar)C(H)](2)}](-) and [{kappa(2)N,C-PhNN(H)(C(6)H(4))}Ga{[N(Ar)C(H)](2)}](-), via formal reductions of the Group 15 substrate. The reaction of the digallane(4), [Ga{[N(Ar)C(H)](2)}](2), with (Me(3)Si)N(3) afforded the paramagnetic, dimeric imido-gallane complex, [{[N(Ar)C(H) ](2)}Ga{mu-N(SiMe(3))}](2), via a Ga-Ga bond insertion process. In addition, the new gallium(III) phosphide, [GaI{P(H)Mes*}{[N(Ar)C(H)](2) }], Mes* = C(6)H(2)Bu(t)(3)-2,4,6; was prepared and treated with diazabicycloundecane (DBU) to give [Ga(DBU){P(H)Mes*}{[N(Ar)C(H)](2)}], presumably via a gallium-terminal phosphinidene intermediate, [Ga{[double bond, length as m-dash]PMes*}{[N(Ar)C(H)](2) }]. The possible mechanisms of all reactions are discussed, all new complexes have been crystallographically characterised and all paramagnetic complexes have been studied by ENDOR and/or EPR spectroscopy.     

Construction of a novel copper(I) chain polymer of hexanuclear Cu6(2-SC5H4NH)6I6 cores with a new (mu 3-S) mode of bonding of pyridine-2-thione and of an unusual triangular Cu3I3(dppe)3(2-SC5H4NH) cluster

The reactions of copper(I) iodide with pyridine-2-thione (2-SC(5)H(4)NH) in the presence of a series of diphosphane ligands, Ph(2)P[bond]X[bond]Ph(2)P [X = [bond](CH(2))(m)[bond], m = 1(dppm), 2 (dppe), 3 (dppp), 4 (dppb); [bond]CH[double bond]CH[bond] (dppen)], yielded an iodo-bridged hexanuclear Cu(I) linear polymer, [Cu(6)(mu(3)-SC(5)H(4)NH)(4)(mu(2)-SC(5)H(4)NH)(2)(I(4))(mu-I)(2)-](n).2nCH(3)CN (1). A similar reaction with 1,2-bis(diphenylphosphino)ethane (dppe) and 2-SC(5)H(4)NH yielded a triangular cluster, Cu(3)I(3)(dppe)(3)(2-SC(5)H(4)NH), 2. In the chain polymer 1, three Cu(I) iodide and three 2-SC(5)H(4)NH ligands combined via bridging S donor atoms to form a boat-shaped trinuclear Cu(3)S(3)I(3) core, and two such cores combined in an inverse manner via four S-donor atoms (mu(3)-S) to form a centrosymmetric hexanuclear repeat unit, Cu(6)S(6)I(4)(mu-I)(2-), which finally formed the iodo-bridged infinite linear chain polymer 1. Linear chains are separated by the nonbonded acetonitrile molecules. Polymer 1 is the first such example of a linear chain formed by the hexanuclear Cu(6)S(6)I(6) core in copper chemistry as well as in metal-heterocyclic thioamide chemistry. In addition, it has the first mu(3)-S mode of neutral pyridine-2-thione ever reported. In the moiety Cu(3)I(3)(dppe)(3) of 2, two copper(I) centers are bridged by the iodide ligands forming a Cu(mu-I)(2)Cu core, while a third copper(I) center is terminally bonded to another iodide ligand. Polymer 2 is also rare, and the first triangular cluster of Cu(I) with an heterocyclic thioamide.     

Rh(I) coordination chemistry of chiral alpha-aminophosphine(eta6-arene)chromium tricarbonyl ligands

The diastereoselective addition of Ph(2)PH to the chiral ortho-substituted eta(6)-benzaldimine complexes (eta(6)-o-X-C(6)H(4)CH=NAr)Cr(CO)(3) (1, X = MeO, Ar = p-C(6)H(4)OMe; 2, X = Cl, Ar = Ph) leads to the formation of the corresponding chiral aminophosphines (alpha-P,N) Ph(2)P-CH(Ar(1))-NHAr(2) (3, Ar(1) = o-C(6)H(4)(OCH(3))[Cr(CO)(3)], Ar(2) = p-C(6)H(4)OCH(3); 4, Ar(1) = o-C(6)H(4)Cl[Cr(CO)(3)], Ar(2) = Ph) in equilibrium with the starting materials. The uncomplexed benzaldimine (o-ClC(6)H(4)CH=NPh), 2', analogously produces an equilibrium amount of the corresponding aminophosphine Ph(2)P-CH(Ar(1))-NHAr(2) (4', Ar(1) = o-C(6)H(4)Cl, Ar(2) = Ph). Depending on the equilibrium constant, the subsequent addition of (1)/(2) equiv of [RhCl(COD)](2) (COD = 1,5-cyclooctadiene) leads to either Ph(2)PH oxidative addition in the case of 3 or to the corresponding [RhCl(COD)(alpha-P,N)] complexes [RhCl(COD)(Ph(2)P-CH[o-C(6)H(4)Cl[Cr(CO)(3)]]-NHPh)] (5) and [RhCl(COD)(Ph(2)P-CH(o-C(6)H(4)Cl)-NHPh)] (5') in the cases of the aminophosphines 4 and 4'. The addition of the latter ligands, as racemic mixtures, to (1)/(4) equiv of [Rh(CO)(2)Cl](2) leads to the [RhCl(CO)(alpha-P,N)(2)] complexes [RhCO(Ph(2)P-CH[o-C(6)H(4)Cl[Cr(CO)(3)]]-NHPh)(2)Cl] (7) or [RhCO(Ph(2)P-CH(o-C(6)H(4)Cl)-NHPh)(2)Cl] (7') as mixtures of (R(C),S(C))/(S(C),R(C)) and (R(C),R(C))/(S(C),S(C)) diastereomers. The rhodium complexes 5 and 7' have been fully characterized by IR and (31)P NMR spectroscopies and X-ray crystallography. These compounds exhibit intramolecular Rh-Cl.H-N interactions in the solid state and in solution. The stability of the new rhodium complexes has been studied under different CO pressures. Under 1 atm of CO, 5 is converted to an unstable complex [RhCl(CO)(2)(alpha-P,N)], 6, which undergoes ligand redistribution leading to 7 plus an unidentified complex. This reaction is inhibited under higher CO or syngas pressure, as confirmed by the observation of the same catalytic activity in hydroformylation when styrene was added to a catalytic mixture that was either freshly prepared or left standing for 20 h under high CO pressure.     

Probing stepwise reaction of NNP-ligand copper(I) complex with elemental sulfur by using N-heterocyclic carbene as a trapper

The dinuclear NNP-ligand copper(I) complex [o-N═CH(C(4)H(3)N)-PPh(2)C(6)H(4)](2)Cu(2) (1) has been synthesized by the reaction of (CuMes)(4) (Mes = 2,4,6-Me(3)C(6)H(2)) with N-((1H-pyrrol-2-yl)-methylene)-2-(diphenylphosphino)benzenamine under an elimination of MesH. Further reaction of 1 with an excess of S(8) produced a mononuclear Cu(II) complex [o-N═CH(C(4)H(3)N)-P(S)Ph(2)C(6)H(4)](2)Cu (5) and CuS. CuS was identified by Raman spectroscopy and 1 and 5 were clearly confirmed by X-ray crystallography. The N-heterocyclic carbene was employed to react with 1 to give a mononuclear [o-N═CH(C(4)H(3)N)-PPh(2)C(6)H(4)]Cu{C[N(iPr)CMe](2)} (2). The reactions of 2 were carried out with (1)/(8), (2)/(8), and (5)/(8) equiv of S(8), leading to compounds [o-N═CH(C(4)H(3)N)-P(S)Ph(2)C(6)H(4)]Cu{C[N(iPr)CMe](2)} (3), [o-N═CH(C(4)H(3)N)-P(S)Ph(2)C(6)H(4)]Cu (4), and 5 respectively, in which CuS was generated in the third reaction and S═C[N(iPr)CMe](2) in the latter two reactions. The clean confirmation of 2-4 demonstrates a stepwise reaction process of 1 with S(8) to 5 and CuS and the N-heterocyclic carbene acts well as a trapping agent.     

Synthesis and characterization of heterobimetallic oxo-bridged aluminum-rare earth metal complexes

Reaction of the aluminum hydroxide LAl(OH)[C(Ph)CH(Ph)] (1, L = HC[(CMe)(NAr)](2), Ar = 2,6-iPr(2)C(6)H(3)) with Y(CH(2)SiMe(3))(3)(THF)(2) yielded the oxo-bridged heterobimetallic yttrium dialkyl complex LAl[C(Ph)CH(Ph)](μ-O)Y(CH(2)SiMe(3))(2)(THF)(2) (2). Alkane elimination reaction of 2 with 2-(imino)pyrrole [NN]H ([NN]H = 2-(ArN═CH)-5-tBuC(4)H(2)NH) afforded the yttrium monoalkyl complex LAl[C(Ph)CH(Ph)] (μ-O)Y(CH(2)SiMe(3))[NN](THF)(2) (5). Alternatively, 5 can be prepared in high yield by reaction of 1 with [NN]Y(CH(2)SiMe(3))(2)(THF)(2) (3). The analogous samarium alkyl complex LAl[C(Ph)CH(Ph)](μ-O)Sm(CH(2)SiMe(3))[NN](THF)(2) (6) was prepared similarly. Reactions of 5 and 6 with 1 equiv of iPrOH yielded the corresponding alkoxyl complexes 7 and 8, respectively. The molecular structures of 3, 6, and 8 have been determined by X-ray single-crystal analysis. Complexes 2, 3, 5, 7, and 8 have been investigated as lactide polymerization initiators. The heterobimetallic alkoxyl 8 is highly active to yield high molecular weight (M(n) = 6.91 × 10(4)) polylactides with over 91% conversion at the lactide-to-initiator molar ratio of 2000.     

Syntheses, structures and magnetic properties of Mn(II) dimers [CpMn(micro-X)]2(Cp = C5H5; X = RNH, R1R2N, C[triple bond]CR)

Manganocene, Cp(2)Mn, has been employed as a precursor in the synthesis of a range of Mn(II) dimers of the type [CpMn(micro-X)](2)[X = 8-NHC(9)H(6)N (1), N(Ph)(C(5)H(4)N)(2), N(4-EtC(6)H(4))(C(5)H(4)N)(3) and C[triple bond]CPh (4)] as well as the bis-adduct [Cp(2)Mn[HN=C(NMe(2))(2)](2)](5). The solid-state structures of 1-5 are reported. Variable-temperature magnetic measurements have been used to assess the extent of Mn(micro-X)Mn communication within the dimers of 1-4 as a function of the bridging ligands (X).     

Studies of a series of [Ni(P(R)2N(Ph)2)2(CH3CN)]2+ complexes as electrocatalysts for H2 production: substituent variation at the phosphorus atom of the P2N2 ligand

A series of [Ni(P(R)(2)N(Ph)(2))(2)(CH(3)CN)](BF(4))(2) complexes containing the cyclic diphosphine ligands [P(R)(2)N(Ph)(2) = 1,5-diaza-3,7-diphosphacyclooctane; R = benzyl (Bn), n-butyl (n-Bu), 2-phenylethyl (PE), 2,4,4-trimethylpentyl (TP), and cyclohexyl (Cy)] have been synthesized and characterized. X-ray diffraction studies reveal that the cations of [Ni(P(Bn)(2)N(Ph)(2))(2)(CH(3)CN)](BF(4))(2) and [Ni(P(n-Bu)(2)N(Ph)(2))(2)(CH(3)CN)](BF(4))(2) have distorted trigonal bipyramidal geometries. The Ni(0) complex [Ni(P(Bn)(2)N(Ph)(2))(2)] was also synthesized and characterized by X-ray diffraction studies and shown to have a distorted tetrahedral structure. These complexes, with the exception of [Ni(P(Cy)(2)N(Ph)(2))(2)(CH(3)CN)](BF(4))(2), all exhibit reversible electron transfer processes for both the Ni(II/I) and Ni(I/0) couples and are electrocatalysts for the production of H(2) in acidic acetonitrile solutions. The heterolytic cleavage of H(2) by [Ni(P(R)(2)N(Ph)(2))(2)(CH(3)CN)](BF(4))(2) complexes in the presence of p-anisidine or p-bromoaniline was used to determine the hydride donor abilities of the corresponding [HNi(P(R)(2)N(Ph)(2))(2)](BF(4)) complexes. However, for the catalysts with the most bulky R groups, the turnover frequencies do not parallel the driving force for elimination of H(2), suggesting that steric interactions between the alkyl substituents on phosphorus and the nitrogen atom of the pendant amines play an important role in determining the overall catalytic rate.     

Synthesis, Structure, and Reactivity of [Zr(6)Cl(18)H(5)](2)(-), the First Paramagnetic Species of Its Class

Reaction of [Zr(6)Cl(18)H(5)](3)(-) (1) with 1 equiv of TiCl(4) yields a new cluster anion, [Zr(6)Cl(18)H(5)](2)(-) (2), which can be converted back into [Zr(6)Cl(18)H(5)](3)(-) (1) upon addition of 1 equiv of Na/Hg. Cluster 2 is paramagnetic and unstable in the presence of donor molecules. It undergoes a disproportionation reaction to form 1, some Zr(IV) compounds, and H(2). It also reacts with TiCl(4) to form [Zr(2)Cl(9)](-) (4) and a tetranuclear mixed-metal species, [Zr(2)Ti(2)Cl(16)](2)(-) (3). The oxidation reaction of 1 with TiCl(4) is unique. Oxidation of 1 with H(+) in CH(2)Cl(2) solution results in the formation of [ZrCl(6)](2)(-) (5) and H(2), while in py solution the oxidation product is [ZrCl(5)(py)](-) (6). There is no reaction between 1 and TiI(4), ZrCl(4), [TiCl(6)](2)(-), [ZrCl(6)](2)(-), or CrCl(3). Compounds [Ph(4)P](2)[Zr(6)Cl(18)H(5)] (2a), [Ph(4)P](2)[Zr(2)Ti(2)Cl(16)] (3a), [Ph(4)P](2)[Zr(2)Cl(9)] (4a), [Ph(4)P](2)[ZrCl(6)].4MeCN (5a.4MeCN), and [Ph(4)P][ZrCl(5)(py)] (6a) were characterized by X-ray crystallography. Compound 2a crystallized in the trigonal space group R&thremacr; with cell dimensions (20 degrees C) of a = 28.546(3) ?, b = 28.546(3) ?, c = 27.679(2) ?, V = 19533(3) ?(3), and Z = 12. Compound 3a crystallized in the triclinic space group P&onemacr; with cell dimensions (-60 degrees C) of a = 11.375(3) ?, b = 13.357(3) ?, c = 11.336(3) ?, alpha = 106.07(1) degrees, beta = 114.77(1) degrees, gamma = 88.50(1) degrees, V = 1494.8(7) ?(3), and Z = 1. Compound 4a crystallized in the triclinic space group P&onemacr; with cell dimensions (-60 degrees C) of a = 12.380(5) ?, b = 12.883(5) ?, c = 11.000(4) ?, alpha = 110.39(7) degrees, beta = 98.29(7) degrees, gamma = 73.12(4) degrees, V = 1572(1) ?(3), and Z = 2. Compound 5a.4MeCN crystallized in the monoclinic space group P2(1)/c with cell dimensions (-60 degrees C) of a = 9.595(1) ?, b = 19.566(3) ?, c = 15.049(1) ?, beta = 98.50(1) degrees, V = 2794.2(6) ?(3), and Z = 2. Compound 6a crystallized in the monoclinic space group P2(1)/c with cell dimensions (20 degrees C) of a = 10.3390(7) ?, b = 16.491(2) ?, c = 17.654(2) ?, beta = 91.542(6) degrees, V = 3026.4(5) ?(3), and Z = 4.     

The structure and chemistry of tris(pentafluorophenyl)borane protected mononuclear nitridotitanium complexes

Treatment of TiCl(NMe(2))(3) with H(3)N·B(C(6)F(5))(3) results in N-H activation and ligand exchange to yield the structurally characterised salt [TiCl(NMe(2))(2)(NMe(2)H)(2)](+)[Ti[triple bond]NB(C(6)F(5))(3)(Cl)(2)(NMe(2)H)(2)](-). Cation exchange with [Me(4)N]Cl, [Ph(4)P]Cl and [(PhCH(2))Ph(3)P]Cl yields the respective ammonium and phosphonium salts of the [Ti[triple bond]NB(C(6)F(5))(3)(Cl)(2)(NMe(2)H)(2)](-) anion. X-ray crystallography reveals that the essential trigonal bipyramidal geometry and composition of the anion is retained in each of these salts despite some minor variations in the Ti-N-B angle and the nature of the interionic interactions. Electronic investigation by DFT calculations confirmed the Ti-N triple bond character implied by the experimentally determined bond length, with the HOMO and HOMO-1 having Ti-N π-bonding character. The dimethylamine ligands of the anion resist substitution by moderate bases but can be displaced by pyridine to give a pentacoordinate anion. In contrast, addition of 2,2'-bipyridyl gives a neutral octahedral complex. Treatment of the pyridine complex with TlCp results in the formation of a four coordinate anionic cyclopentadienyl complex.     

Synthesis and structures of the [benzamidinato]3- complexes Li3(tmeda)(L1)]2 and [Li(thf)4][Li5(L2)(OEt2)2] [L1 = N(SiMe3)C(Ph)N(SiMe3) and L2 = N(SiMe3)C(C6H4-4)NPh

Reduction at ambient temperature of each of the lithium benzamidinates [Li(L(1))(tmeda)] or [{Li(L(2))(OEt(2))(2)}(2)] with four equivalents of lithium metal in diethyl ether or thf furnished the brown crystalline [Li(3)(L(1))(tmeda)] (1) or [Li(thf)(4)][Li(5)(L(2))(2)(OEt(2))(2)] (2), respectively. Their structures show that in each the [N(R(1))C(R(3))NR(2)](3-) moiety has the three negative charges largely localised on each of N, N' and R = Aryl); a consequence is that the "aromatic" 2,3- and 5,6-CC bonds of R(3) approximate to being double bonds. Multinuclear NMR spectra in C(6)D(6) and C(7)D(8) show that 1 and 2 exhibit dynamic behaviour. [The following abbreviations are used: L(1) = N(SiMe(3))C(Ph)N(SiMe(3)); L(2) = N(SiMe(3))C(C(6)H(4)Me-4)N(Ph); tmeda = (Me(2)NCH(2)-)(2); thf = tetrahydrofuran.] This reduction is further supported by a DFT analysis.     

Synthesis and structural characterisation of group 10 metal(II) gallyl complexes: analogies with platinum diboration catalysts?

Reactions of the anionic gallium(i) heterocycle, [:Ga{[N(Ar)C(H)](2)}](-) (Ar = C(6)H(3)Pr(i)(2)-2,6), with a variety of mono- and bidentate phosphine, tmeda and 1,5-cyclooctadiene (COD) complexes of group 10 metal dichlorides are reported. In most cases, salt elimination occurs, affording either mono(gallyl) complexes, trans-[MCl{Ga{[N(Ar)C(H)](2)}}(PEt(3))(2)] (M = Ni or Pd) and cis-[PtCl{Ga{[N(Ar)C(H)](2)}}(L)] (L = R(2)PCH(2)CH(2)PR(2), R = Ph (dppe) or cyclohexyl (dcpe)), or bis(gallyl) complexes, trans-[M{Ga{[N(Ar)C(H)](2)}}(2)(PEt(3))(2)] (M = Ni, Pd or Pt), cis-[Pt{Ga{[N(Ar)C(H)](2)}}(2)(PEt(3))(2)], cis-[M{Ga{[N(Ar)C(H)](2)}}(2)(L)] (M = Ni, Pd or Pt; L = dppe, Ph(2)CH(2)PPh(2) (dppm), tmeda or COD). The crystallographic and spectroscopic data for the complexes show that the trans-influence of the gallium(i) heterocycle lies in the series, B(OR)(2) > H(-) > PR(3) approximately [:Ga{[N(Ar)C(H)](2)}](-) > Cl(-). Comparisons between the reactivity of one complex, [Pt{Ga{[N(Ar)C(H)](2)}}(2)(dppe)], with that of closely related platinum bis(boryl) complexes indicate that the gallyl complex is not effective for the catalytic or stoichiometric gallylation of alkenes or alkynes. The phosphaalkyne, Bu(t)C[triple bond, length as m-dash]P, does, however, insert into one gallyl ligand of the complex, leading to the novel, crystallographically characterised P,N-gallyl complex, [Pt{Ga{[N(Ar)C(H)](2)}}{Ga{PC(Bu(t))C(H)[N(Ar)]C(H)N(Ar)}}(dppe)]. An investigation into the mechanism of this insertion reaction has been undertaken.