A remarkable inversion of structure-activity dependence on imido N-substituents with varying co-ligand topology and the synthesis of a new borate-free zwitterionic polymerisation catalyst

Ethylene polymerisation productivities of tris(pyrazolyl)methane-supported catalysts [Ti(NR){HC(Me2pz)3}Cl2] show a dramatically different dependence on the imido R-group compared to those of their TACN analogues, attributed to differences in fac-N3 donor topology; when treated with AliBu3, the zwitterionic tris(pyrazolyl)methide compound [Ti(N-2-C6H4tBu){C(Me2pz)3}Cl(THF)] also acts as a highly active, single site catalyst (TACN = 1,4,7-trimethyltriazacyclononane).     

Synthesis, structures, and DFT bonding analysis of new titanium hydrazido(2-) complexes

The reaction of 1,1-diphenylhydrazine with Ti(NMe2)2Cl2 produced the monomeric terminal titanium hydrazido(2-) species Ti(NNPh2)Cl2(HNMe2)2 (1) in near-quantitative yield. The reaction of Ti(NMe2)2Cl2 with the less sterically demanding ligand precursors 1,1-dimethylhydrazine or N-aminopiperidine gave the dimeric mu-eta2,eta1-bridged compounds Ti2(mu-eta2,eta1-NNMe2)2Cl4(HNMe2)2 (2) and Ti2[mu-eta2,eta1-NN(CH2)5]2Cl4(HNMe2)3 (3). The X-ray structures of 2 and 3 showed the formation of N-H...Cl hydrogen bonded dimers or chains, respectively. The reaction of 1 with an excess of pyridine formed [Ti(NNPh2)Cl2(py)2]n (4, n = 1 or 2). The reaction of the tert-butyl imido complex Ti(N(t)Bu)Cl2(py)3 with either 1,1-dimethylhydrazine or N-aminopiperidine again resulted in the formation of hydrazido-bridged dimeric complexes, namely Ti2(mu-eta2,eta1-NNMe2)2Cl4(py)2 (5, structurally characterized) and Ti2[mu-eta2,eta1-NN(CH2)5]2Cl4(py)2 (6). Compounds 1 and 4 are potential new entry points into terminal hydrazido(2-) chemistry of titanium. Compound 1 reacted with neutral fac-N3 donor ligands to form Ti(NNPh2)Cl2(Me3[9]aneN3) (7), Ti(NNPh2)Cl2(Me3[6]aneN3) (8), Ti(NNPh2)Cl2[HC(Me2pz)3] (9, structurally characterized), and Ti(NNPh2)Cl2[HC(n)Bupz)3] (10) in good yields (Me3[9]aneN3 = trimethyl-1,4,7-triazacyclononane, Me3[6]aneN3 = trimethyl-1,3,5-triazacyclohexane, HC(Me2pz)3 = tris(3,5-dimethylpyrazolyl)methane, and HC((n)Bupz)3 = tris(4-(n)butylpyrazolyl)methane). DFT calculations were performed on both the model terminal hydrazido compound Ti(NNPh2)Cl2[HC(pz)3] (I) and the corresponding imido compounds Ti(NMe)Cl2[HC(pz)3] (II) and Ti(NPh)Cl2[HC(pz)3] (III). The NNPh2 ligand binds to the metal center in an analogous manner to that of terminal imido ligands (metalligand triple bond), but with one of the Ti=N(alpha) pi components significantly destabilized by a pi interaction with the lone pair of the N(beta) atom. The NR ligand sigma donor ability was found to be NMe > NPh > NNPh2, whereas the overall (sigma + pi) donor ability is NMe > NNPh2 > NPh, as judged by fragment orbital populations, Ti-N atom-atom overlap populations, and fragment-charge analysis. DFT calculations on the hydrazido ligand in a mu-eta2,eta1-bridging mode showed involvement of the N=N pi electrons in donation to one of the Ti centers. This TiN2 interaction is best represented as a metallocycle.     

Half-sandwich o-N,N-dimethylaminobenzyl complexes over the full size range of group 3 and lanthanide metals. synthesis, structural characterization, and catalysis of phosphine P--H bond addition to carbodiimides

The acid-base reactions between the rare-earth metal (Ln) tris(ortho-N,N-dimethylaminobenzyl) complexes [Ln(CH2C(H4NMe2-o)3] with one equivalent of the silylene-linked cyclopentadiene-amine ligand (C5Me4H)SiMe2NH(C6H2Me3-2,4,6) afforded the corresponding half-sandwich aminobenzyl complexes [{Me2Si(C5Me4)(NC6H2Me3-2,4,6)}Ln(CH2C6H4NMe2-o)(thf)] (2-Ln) (Ln=Y, La, Pr, Nd, Sm, Gd, Lu) in 60-87 % isolated yields. The one-pot reaction between ScCl(3) and [Me2Si(C5Me4)(NC6H2Me3-2,4,6)]Li2 followed by reaction with LiCH2C6H4NMe2-o in THF gave the scandium analogue [{Me2Si(C5Me4)(NC6H2Me3-2,4,6)}Sc(CH2C6H4NMe2-o)] (2-Sc) in 67 % isolated yield. 2-Sc could not be prepared by the acid-base reaction between [Sc(CH2C6H4NMe2-o)3] and (C5Me4H)SiMe2NH(C6H2Me3-2,4,6). These half-sandwich rare-earth metal aminobenzyl complexes can serve as efficient catalyst precursors for the catalytic addition of various phosphine P--H bonds to carbodiimides to form a series of phosphaguanidine derivatives with excellent tolerability to aromatic carbon-halogen bonds. A significant increase in the catalytic activity was observed, as a result of an increase in the metal size with a general trend of La>Pr, Nd>Sm>Gd>Lu>Sc. The reaction of 2-La with 1 equiv of Ph2PH yielded the corresponding phosphide complex [{Me2Si(C5Me4)(NC6H2Me3-2,4,6)}La(PPh2)(thf)2] (4), which, on recrystallization from benzene, gave the dimeric analogue [{Me2Si(C5Me4)(NC6H2Me3-2,4,6)}La(PPh2)]2 (5). Addition of 4 or 5 to iPrN=C=NiPr in THF yielded the phosphaguanidinate complex [{Me2Si(C5Me4)(NC6H2Me3-2,4,6)}La{iPrNC(PPh2)NiPr}(thf)] (6), which, on recrystallization from ether, afforded the ether-coordinated structurally characterizable analogue [{Me2Si(C5Me4)(NC6H2Me3-2,4,6)}La{iPrNC(PPh2)NiPr}(OEt2)] (7). The reaction of 6 or 7 with Ph2PH in THF yielded 4 and the phosphaguanidine iPrN=C(PPh2)NHiPr (3a). These results suggest that the catalytic formation of a phosphaguanidine compound proceeds through the nucleophilic addition of a phosphide species, which is formed by the acid-base reaction between a rare-earth metal o-dimethylaminobenzyl bond and a phosphine P--H bond, to a carbodiimide, followed by the protonolysis of the resultant phosphaguanidinate species by a phosphine P--H bond. Almost all of the rare earth complexes reported this paper were structurally characterized by X-ray diffraction studies.     

The first observation of the [Cp3Mn]- anion; structures of hexagonal [(eta 2-Cp)3MnK.1.5thf] and ion-separated [(eta 2-Cp)3Mn]2[Mg(thf)6].2thf

Hexagonal [(eta 2-Cp)3MnK.1.5thf] 1 and ion-separated [(eta 2-Cp)3Mn]2[Mg(thf)6].2thf 2 are obtained from reactions of CpK and Cp2Mg, respectively, with manganocene, Cp2Mn; they are the first complexes to be structurally characterised containing the [Cp3Mn]- anion.     

Synthesis and structural characterization of unprecedented bis-asymmetric heteroscorpionate U(III) complexes: [U(kappa3-H2B(pztBu,Me)(pzMe,tBu))2I] and [U(kappa3-H2B(pztBu,Me)(pzMe2))2I

[UI(3)(THF)(4)] reacts at room temperature with 2 equiv of KBp(tBu,Me), in toluene, yielding [U(kappa(3)-H(mu-H)B(pz(tBu,Me))(pz(Me,tBu)))(2)I] (1). This unprecedented complex, stabilized by two asymmetric heteroscorpionate ligands, is formed due to an isomerization process promoted in situ by the metal center. To find a general method for preparing this type of compound, we synthesized the novel asymmetric K[H(2)B(pz(tBu,Me))(pz(Me2))], and by a straightforward salt metathesis with [UI(3)(THF)(4)] the novel bis-asymmetric complex [U(kappa(3)-H(mu-H)B(pz(tBu,Me))(pz(Me2)))(2)I] (2) was isolated and characterized in the solid state and in solution. As indicated by X-ray crystallographic analysis, the U(III) in 1 and 2 is seven-coordinated by two tridentate asymmetric dihydrobis(pyrazoly)borates and by an iodide. In both cases, the coordination geometry around the metal is very distorted, the pentagonal bipyramid being the one which better describes the arrangement of the atoms around the U(III). An approximate C(2) axis can be defined in the solid state, and is maintained in solution as indicated by the (1)H NMR spectrum of 1 and 2. In the course of attempting to crystallize some of the compounds, monocrystals of the dimer [U(kappa(3)-Bp(tBu,Me))(Hpz(tBu,Me))I(mu-I)](2) (3) were isolated. In this compound each U(III) atom is seven-coordinated by one kappa(3)-Bp(tBu,Me), by one terminal and by two bridging iodide ligands, and by a monodentate Hpz(tBu,Me), exhibiting a distorted 4:3 tetragonal base-trigonal geometry.     

A novel transformation of a zirconium imido compound and the development of a new class of N3 donor heteroscorpionate ligand

Reaction of the dimeric zirconium imido compound [Zr2(mu-NAr)2Cl4(THF)4] with tris(3,5-dimethylpyrazolyl)methyl silane very selectively gave [Zr{(Me2pz)2Si(Me)NAr}Cl3] (1), a highly active pre-catalyst for ethylene polymerisation; a more general and versatile route to N3 donor heteroscorpionate compounds was achieved via the protio ligand (Me2pz)2CHSi(Me)2N(H)iPr for which neutral and cationic organometallic Group 3 and 4 derivatives are reported (Ar = 2,6-C6H(3)iPr2).     

High tetraalkylaluminate fluxionality in half-sandwich complexes of the trivalent rare-earth metals

Steric factors govern the formation of half-sandwich complexes (C5Me4R)Ln[N(SiHMe2)2]2 according to acid-base reactions utilising Ln[N(SiHMe2)2)3(thf)2 and substituted cyclopentadienes. Subsequent trimethylaluminium-promoted silylamide elimination produces the first half-sandwich bis(tetramethylaluminate) complexes (C5Me4R)Ln(AlMe4)2.     

Highly efficient ethylene polymerisation by scandium alkyls supported by neutral fac-kappa3 coordinated N3 donor ligands

Reaction of [M(CH2SiMe3)3(THF)2] (M = Sc or Y) with the neutral fac-kappa3 N3 donor ligands (L) Me3[9]aneN3 or HC(Me2pz)3 gave the corresponding trialkyls [M(L)(CH2SiMe3)3]; activation of the scandium congeners with B(C6F5)3 in the presence of ethylene afforded highly active polymerisation catalysts (Me3[9]aneN3 = 1,4,7-trimethyltriazacyclononane).     

Synthesis and structures of a 3-sila-beta-diketiminatomagnesium bromide, ketenimide and triflate

The crystalline compounds [Mg(Br)(L)(thf)].0.5Et2O [L = {N(R)C(C6H3Me2-2,6)}2SiR, R = SiMe3] (1), [Mg(L){N=C=C(C(Me)=CH)2CH2}(D)2] [D = NCC6H3Me2-2,6 (2), thf (3)] and [{Mg(L)}2{mu-OSO(CF3)O-[mu}2] (4) were prepared from (a) Si(Br)(R){C(C6H3Me2-2,6)=NR}2 and Mg for (1), (b) [Mg(SiR3)2(thf)2] and 2,6-Me2C6H3CN (5 mol for (2), 3 mol for (3)), and (c) (2) + Me3SiOS(O)2CF3 for (4); a coproduct from (c) is believed to have been the trimethylsilyl ketenimide Me3SiN=C=C{C(Me)=CH}2CH2 (5).     

"Alkaline-earth metals in a box": structures of solvent-separated ion pairs

During our research on homoleptic organocalcium compounds, we found that fluorenylcalcium complexes show unusual solution behavior and precipitate from nonpolar solvents after addition of THF. Their solid-state structures reveal the unexpected rupture of both metal-carbanion bonds by the polar solvent THF. The crystal structures of five new Mg and Ca solvent-separated ion pairs are described. The compound [Ca(2+)(thf)(6)][Me(3)Si(fluorenyl(-))](2) is the first organometallic complex of a Group 2 element that crystallizes as a completely solvent-separated ion pair. The driving forces for its formation are: 1) the strong Ca-THF bond; 2) the stability of the free [Me(3)Si(fluorenyl)](-) ion; 3) encapsulation of [Ca(2+)(thf)(6)] in a "box", the walls of which consist of anionic fluorenyl ligands and benzene molecules; and 4) the presence of numerous (THF)C- H...pi interactions. The magnesium analogue [Mg(2+)(thf)(6)][Me(3)Si(fluorenyl(-))](2) is isostructural. Bis(7,9-diphenylcyclopenta[a]acenaphthadienyl)calcium also crystallizes as a completely solvent-separated ion pair and can likewise be described as a [Ca(2+)(thf)(6)] species in a box of delocalized anions and benzene molecules. In addition, the structures of two Ph(4)B(-) complexes of Mg and Ca are described. [Mg(2+)(thf)(6)][Ph(4)B(-)](2) crystallizes as a completely solvent-separated ion pair and also shows a solvated metal cation bonded via C-H.pi interactions in a cavity formed by Ph(4)B(-) ions. [(thf)(4)CaBr(+)][Ph(4)B(-)] has a structure in which one of the anionic ligands is still bonded to the Ca atom. Bridging bromide ligands result in the formation of the dimer [(thf)(4)CaBr(+)](2).     

Catalytic addition of amine N-H bonds to carbodiimides by half-sandwich rare-earth metal complexes: efficient synthesis of substituted guanidines through amine protonolysis of rare-earth metal guanidinates

Reaction of [Ln(CH(2)SiMe(3))(3)(thf)(2)] (Ln=Y, Yb, and Lu) with one equivalent of Me(2)Si(C(5)Me(4)H)NHR' (R'=Ph, 2,4,6-Me(3)C(6)H(2), tBu) affords straightforwardly the corresponding half-sandwich rare-earth metal alkyl complexes [{Me(2)Si(C(5)Me(4))(NR')}Ln(CH(2)SiMe(3))(thf)(n)] (1: Ln = Y, R' = Ph, n=2; 2: Ln = Y, R' = C(6)H(2)Me(3)-2,4,6, n=1; 3: Ln = Y, R' = tBu, n=1; 4: Ln = Yb, R' = Ph, n=2; 5: Ln = Lu, R' = Ph, n=2) in high yields. These complexes, especially the yttrium complexes 1-3, serve as excellent catalyst precursors for the catalytic addition of various primary and secondary amines to carbodiimides, efficiently yielding a series of guanidine derivatives with a wide range of substituents on the nitrogen atoms. Functional groups such as C[triple chemical bond]N, C[triple chemical bond]CH, and aromatic C--X (X: F, Cl, Br, I) bonds can survive the catalytic reaction conditions. A primary amino group can be distinguished from a secondary one by the catalyst system, and therefore, the reaction of 1,2,3,4-tetrahydro-5-aminoisoquinoline with iPrN==C==NiPr can be achieved stepwise first at the primary amino group to selectively give the monoguanidine 38, and then at the cyclic secondary amino unit to give the biguanidine 39. Some key reaction intermediates or true catalyst species, such as the amido complexes [{Me(2)Si(C(5)Me(4))(NPh)}Y(NEt(2))(thf)(2)] (40) and [{Me(2)Si(C(5)Me(4))(NPh)}Y(NHC(6)H(4)Br-4)(thf)(2)] (42), and the guanidinate complexes [{Me(2)Si(C(5)Me(4))(NPh)}Y{iPrNC(NEt(2))(NiPr)}(thf)] (41) and [{Me(2)Si(C(5)Me(4))(NPh)}Y{iPrN}C(NC(6)H(4)Br-4)(NHiPr)}(thf)] (44) have been isolated and structurally characterized. Reactivity studies on these complexes suggest that the present catalytic formation of a guanidine compound proceeds mechanistically through nucleophilic addition of an amido species, formed by acid-base reaction between a rare-earth metal alkyl bond and an amine N--H bond, to a carbodiimide, followed by amine protonolysis of the resultant guanidinate species.     

Modular approach to tridentate N,O,N' ligands using pyrazolylborate chemistry

Two anionic tridentate N,O,N' chelators, [pz(Ph)B(mu-pz)(mu-O)B(Ph)pz](-) (3(-)) and [pz(Ph)(Ph)B(mu-pz)(mu-O)B(Ph)pz(Ph)](-) (4(-)), as well as the corresponding complexes [Fe(3)(py)Cl], [Fe(3)Cl(2)] and [Cu(3)Cl], have been synthesised and structurally characterised by X-ray crystallography (pz: pyrazolyl, pz(Ph): 3-phenylpyrazolyl, py: pyridine). Since our synthesis approach takes advantage of the highly modular pyrazolylborate chemistry, inexpensive and relatively resistant N,O,N' ligands of varying steric demand are readily accessible. The complexes [Fe(3)(py)Cl] and [Fe(3)Cl(2)] possess a distorted trigonal-bipyramidal configuration with the pyrazolyl rings occupying equatorial positions and the oxygen donor being located at an apical position. The complex [Cu(3)Cl] crystallises as chloro-bridged dimers featuring Cu(II) ions with ligand environments that are intermediate between a square-planar and a trigonal-bipyramidal geometry.     

A series of [3 + 2] cycloaddition products from the reaction of rhenium oxo complexes with diphenyl ketene

The reaction of rhenium (VII) trioxo complexes containing the ligand sets scorpionate, [HB(pz)3]ReO3 (6), [Ph-B(pz)3]ReO3 (7), and [[HC(pz)3]ReO3][ReO4] (8) and pyridine/pyridine-type ligands [(4,7-diphenyl-1,10-phen)(Br)ReO3] (12), [(4,4'-di-tert-butyl-2,2'-dipyridyl)(Cl)ReO3] (13), and [(py)2Re(Cl)O3] (4), with diphenyl ketene, has led to the isolation of six novel [3 + 2] cycloaddition products. These air-stable solids 9-11 and 15-17 are the result of [3 + 2] addition of the O=Re=O motif across the ketene C=C double bond. Five of the six [3 + 2] cycloaddition products have been structurally characterized by single-crystal X-ray diffraction and in all cases by 13C NMR and IR spectroscopies.     

Heavy alkaline earth metal pyrazolates: synthetic pathways, structural trends, and comparison with divalent lanthanoids

Two series of heavy alkaline earth metal pyrazolates, [M(Ph(2)pz)(2)(thf)(4)] 1 a-c (Ph(2)pz=3,5-diphenylpyrazolate, M=Ca, Sr, Ba; THF=tetrahydrofuran) and [M(Ph(2)pz)(2)(dme)(n)] (M=Ca, 2 a, Sr, 2 b, n=2; M=Ba, 2 c, n=3; DME=1,2-dimethoxyethane) have been prepared by redox transmetallation/ligand exchange utilizing Hg(C(6)F(5))(2). Compounds 1 a and 2 b were also obtained by redox transmetallation with Tl(Ph(2)pz). Alternatively, direct reaction of the alkaline earth metals with 3,5-diphenylpyrazole at elevated temperatures under solventless conditions yielded compounds 1 a-c and 2 a-c upon extraction with THF or DME. By contrast, [M(Me(2)pz)(2)(Me(2)pzH)(4)] 3 a-c (M=Ca, Sr, Ba; Me(2)pzH=3,5-dimethylpyrazole) were prepared by protolysis of [M[N(SiMe(3))(2)](2)(thf)(2)] (M=Ca, Sr, Ba) with Me(2)pzH in THF and by direct metallation with Me(2)pzH in liquid NH(3)/THF. Compounds 1 a-c and 2 a-c display eta(2)-bonded pyrazolate ligands, while 3 a,b exhibit eta(1)-coordination. Complexes 1 a-c have transoid Ph(2)pz ligands and an overall coordination number of eight with a switch from mutually coplanar Ph(2)pz ligands in 1 a,b to perpendicular in 1 c. In eight coordinate 2 a,b the pyrazolate ligands are cisoid, whilst 2 c has an additional DME ligand and a metal coordination number of ten. By contrast, 3 a,b have octahedral geometry with four eta(1)-Me(2)pzH donors, which are hydrogen-bonded to the uncoordinated nitrogen atoms of the two trans Me(2)pz ligands. The application of synthetic routes initially developed for the preparation of lanthanoid pyrazolates provides detailed insight into the similarities and differences between the two groups of metals and structures of their complexes.     

Supramolecular networks of silver(I) and iron(II) complexes of the third generation tris(pyrazolyl)methane ligand Ph(2)(O)POCH(2)C(pz)(3) (pz = pyrazolyl ring)

The new ligand Ph(2)(O)POCH(2)C(pz)(3) (pz = pyrazolyl ring), prepared from the reaction of HOCH(2)C(pz)(3) and Ph(2)P(O)Cl in the presence of base, reacts with either AgBF(4) or Fe(BF(4))(2).6H(2)O in a 2/1 molar ratio to yield {[Ph(2)(O)POCH(2)C(pz)(3)](2)Ag}(BF(4)) () and {[Ph(2)(O)POCH(2)C(pz)(3)](2)Fe}(BF(4))(2) (), respectively. In the structure of , the silver is in an unusual planar geometry with each of the ligands in a kappa(2)-kappa(0) coordination mode. Slow evaporation of a thf solution of yields crystalline [Ph(2)(O)POCH(2)C(pz)(3)Ag](2)(thf)(2)}(BF(4))(2) (). In each cationic unit of , the two Ph(2)(O)POCH(2)C(pz)(3) ligands coordinate to the same two silver(i) centers in a kappa(2)-kappa(1) bonding mode, with a silver atom separation of 3.36 A. The supramolecular structure of both and is dominated by a pair of cooperative hydrogen bonding interactions between the Ph(2)P(O) secondary tecton and a hydrogen atom from a methylene group situated on a neighboring building block, which arranges the cations in chains. The reaction of HC(pz)(3) and AgO(3)SCF(3) (AgOTf) yields {[HC(pz)(3)](2)Ag(2)}(OTf)(2) (). The cationic unit in has a structure very similar to that of , but with a much shorter distance between the silver atoms at 2.86 A. The supramolecular structure of is dominated by an unusual pyrazolyl embrace interaction where the acceptor ring in the C-Hpi interaction is the pyrazolyl ring kappa(1)-bonded to silver in the adjacent dimeric unit rather than the other ring in a kappa(2)-bonded Cpz(2) unit. This interaction arranges the cations in chains which are further organized into sheets by the triflate anions that link the chains via combined AgO/CHO interactions. The iron in is octahedral with each tris(pyrazolyl)methane unit in the kappa(3)-tripodal coordination mode. The supramolecular structure is sheets formed by hydrogen bonding between the Ph(2)P(O) oxygen and a meta-position hydrogen on one of the diphenylphosphine rings from an adjacent cation.     

Syntheses of Cationic, Six-Coordinate Cadmium(II) Complexes Containing Tris(pyrazolyl)methane Ligands. Influence of Charge on Cadmium-113 NMR Chemical Shifts

Treating a thf (thf = tetrahydrofuran) suspension of Cd(acac)(2) (acac = acetylacetonate) with 2 equiv of HBF(4).Et(2)O results in the immediate formation of [Cd(2)(thf)(5)](BF(4))(4) (1). Crystallization of this complex from thf/CH(2)Cl(2) yields [Cd(thf)(4)](BF(4))(2) (2), a complex characterized in the solid state by X-ray crystallography. Crystal data: monoclinic, P2(1)/n, a = 7.784(2) ?, b = 10.408(2) ?, c = 14.632(7) ?, beta = 94.64(3) degrees, V = 1181.5(6) ?(3), Z = 2, R = 0.0484. The geometry about the cadmium is octahedral with a square planar arrangement of the thf ligands and a fluorine from each (BF(4))(-) occupying the remaining two octahedral sites. Reactions of [Cd(2)(thf)(5)](BF(4))(4) with either HC(3,5-Me(2)pz)(3) or HC(3-Phpz)(3) yield the dicationic, homoleptic compounds {[HC(3,5-Me(2)pz)(3)](2)Cd}(BF(4))(2) (3) and {[HC(3-Phpz)(3)](2)Cd}(BF(4))(2) (4) (pz = 1-pyrazolyl). The solid state structure of 3 has been determined by X-ray crystallography. Crystal data: rhombohedral, R&thremacr;, a = 12.236(8) ?, c = 22.69(3) ?, V = 2924(4) ?(3), Z = 3, R = 0.0548. The cadmium is bonded to the six nitrogen donor atoms in a trigonally distorted octahedral arrangement. Four monocationic, mixed ligand tris(pyrazolyl)methane-tris(pyrazolyl)borate complexes {[HC(3,5-Me(2)pz)(3)][HB(3,5-Me(2)pz)(3)]Cd}(BF(4)) (5), {[HC(3,5-Me(2)pz)(3)][HB(3-Phpz)(3)]Cd}(BF(4)) (6), {[HC(3-Phpz)(3)][HB(3,5-Me(2)pz)(3)]Cd}(BF(4)) (7), and {[HC(3-Phpz)(3)][HB(3-Phpz)(3)]Cd}(BF(4)) (8) are prepared by appropriate conproportionation reactions of 3or 4 with equimolar amounts of the appropriate homoleptic neutral tris(pyrazolyl)borate complexes [HB(3,5-Me(2)pz)(3)](2)Cd or [HB(3-Phpz)(3)](2)Cd. Solution (113)Cd NMR studies on complexes 3-8 demonstrate that the chemical shifts of the new cationic, tris(pyrazolyl)methane complexes are very similar to the neutral tris(pyrazolyl)borate complexes that contain similar substitution of the pyrazolyl rings.     

Amido-bridged double-cube nitrido complexes containing titanium and magnesium/calcium

Treatment of the single cube nitrido complexes [(thf)x((Me3Si)2N)M((mu3-N)(mu3-NH)2Ti3(eta5-C5Me5)3(mu3-N))](M = Mg, x= 0; Ca, x= 1) with one equivalent of anilines NH2Ar in toluene affords the arylamido complexes [(ArHN)M((mu3-N)(mu3-NH)2Ti3(eta5-C5Me5)3(mu3-N))]n[M = Mg (3), n= 1, Ar = 4-MeC6H4; Ca (4), n= 2, Ar = 2,4,6-Me3C6H2]. The magnesium complex 3 has a single-cube structure whereas the X-ray crystal structure of the analogous calcium derivative 4 shows two cube-type azaheterometallocubane moieties Ca((mu3-N)(mu3-NH)2Ti3(eta5-C5Me5)3(mu3-N)) held together by two mu-2,4,6-trimethylanilido ligands. Complexes 3 and 4 react with chloroform-d1 at room temperature to give the metal halide adducts [Cl2M((mu3-NH)3Ti3(eta5-C5Me5)3(mu3-N))](M = Mg, Ca). A solution of 3 in n-hexane gave complex [(Mg2(mu3-N)(mu3-NH)5[Ti3(eta5-C5Me5)3(mu3-N)]2)(mu-NHAr)3] which shows three mu-4-methylanilido ligands bridging two [MgTi3N4] cube type cores according to an X-ray crystal structure determination.     

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

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

Cu(I) dinuclear complexes with tripodal ligands vs monodentate donors: triphenylphosphine, thiourea, and pyridine. A 1H NMR titration study

Complexes [PPh3Cu(Tr(Mes,Me))] (1), [PPh3Cu(Tr(Me,o-Py))] (2), and [PPh3Cu(Br(Mes)pz(o-Py))] (3) (Tr(Mes,Me) = hydrotris[1,4-dihydro-3-methyl-4-mesityl-5-thioxo-1,2,4-triazolyl]borate; Tr(Me,o-Py) = hydrotris[1,4-dihydro-4-methyl-3-(2-pyridyl)-5-thioxo-1,2,4-triazolyl]borate; Br(Mes)pz(o-Py) = hydro[bis(thioxotriazolyl)-3-(2-pyridyl)pyrazolyl]borate; PPh3 = triphenylphosphine) were synthesized by the reaction of dinuclear complexes [Cu(Tr(Mes,Me))]2, [Cu(Tr(Me,o-Py))]2, [Cu(Br(Mes)pz(o-Py))]2, and PPh3. 1-3 were characterized by 1H, 13C, and 31P NMR spectroscopy and ESI-mass spectrometry. Crystal structure analyses were performed for 1 and 2. Both complexes crystallize in the triclinic P space group with the metal in a slightly distorted tetrahedral geometry (S3P coordination) bound by a kappa3-S3 ligand and a PPh3 molecule. The solution molecular structures were investigated by means of variable-temperature (210-310 K, CDCl3, 1-2; 200-310 K, CD2Cl2, 3) and NOESY NMR spectroscopy. The solution structures of 1-2 are in accordance with the X-ray structures, and the complexes do not exhibit fluxional behavior. On the other hand, 3 is subject to an equilibrium between two species with a coalescing temperature of approximately 260 K. DFT geometry optimizations suggest that the major species of 3 consists of the Br(Mes)pz(o-Py) ligand bound to Cu(I) in the kappa3-S2H fashion with two C=S groups and a [Cu...H-B] interaction. A PPh3 completes the copper coordination (S2HP coordination). The complex [TuCu(Tr(Mes,Me))] (4) (Tu = thiourea) was crystallized using an excess of Tu with respect to [Cu(Tr(Me,2-Py))]2 (approximately a 6:1 ratio). The metal adopts a distorted tetrahedral geometry with an overall S3H coordination determined by the bound kappa3-S2H ligand (two C=S groups and a [B-H...Cu] interaction) and by a Tu. The reactivity of dinuclear complexes [Cu(Tr(Mes,Me))]2, [Cu(Tr(Me,o-Py))]2, and [Cu(Br(Mes)pz(o-Py))]2 with monodentate ligands was investigated by means of NMR titrations with PPh3, Tu. and pyridine (Py), and formation constants for the adducts [DCu(L)] (D = monodentate donor, L = tripodal ligand) were determined.     

The first structural characterisation of a group 2 metal alkylperoxide complex: comments on the cleavage of dioxygen by magnesium alkyl complexes

A new high-yield synthesis of [(PhCH(2))(2)Mg(thf)(2)] and [[(PhCH(2))CH(3)Mg(thf)](2)] via benzylpotassium has allowed a simple entry into benzylmagnesium coordination chemistry. The syntheses and X-ray crystal structures of both [(eta(2)-Me(2)NCH(2)CH(2)NMe(2))Mg(CH(2)Ph)(2)] and [eta(2)-HC[C(CH(3))NAr'](2)Mg(CH(2)Ph)(thf)] (Ar'=2,6-diisopropylphenyl) are reported. The latter beta-diketiminate complex reacts with dioxygen to provide a 1:2 mixture of dimeric benzylperoxo and benzyloxo complexes. The benzylperoxo complex [[eta(2)-HC[C(CH(3))NAr'](2)Mg(mu-eta(2):eta(1)-OOCH(2)Ph)](2)] is the first example of a structurally characterised Group 2 metal-alkylperoxo complex and contains the benzylperoxo ligands in an unusual mu-eta(2):eta(1)-coordination mode, linking the two five-coordinate magnesium centres. The O[bond]O separation in the benzylperoxo ligands is 1.44(2) A. Reaction of the benzylperoxo/benzyloxo complex mixture with further [eta(2)-HC[C(CH(3))NAr'](2)Mg(CH(2)Ph)(thf)] results in complete conversion of the benzylperoxo species into the benzyloxo complex. This reaction, therefore, establishes the cleavage of dioxygen by this system as a two-step process that involves initial oxygen insertion into the Mg[bond]CH(2)Ph bond followed by O[bond]O/Mg[bond]C sigma-bond metathesis of the resulting benzylperoxo ligand with a second Mg[bond]CH(2)Ph bond. The formation of a 1:2 mixture of the benzylperoxo and benzyloxo species indicates that the rate of the insertion is faster than that of the metathesis, and this is shown to be consistent with a radical mechanism for the insertion process.