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A mechanochemical strategy for the synthesis of N-heterocyclic carbene complexes is described, in which 1,3-dibenzylimidazole complexes of palladium and platinum are produced in a two-step process by grinding together the reactants with a mortar and pestle. Crystallographic characterization reveals that unlike the solution syntheses, which produce a mixture of products, the solid-state reactions occur under topochemical conditions affording isomerically and polymorphically pure products.

The two-step mechanochemical preparation of carbene-pyridine complexes of palladium and platinum is reported. The organometallic products, which represent a class of commercially available catalysts, are rapidly formed in excellent yield proving solvent-free synthesis to be a viable synthetic alternative even in the case of NHC-containing compounds.

The four isomers of 9-butylphosphabicyclo[3.3.1]nonane, s-PhobPBu, where Bu = n-butyl, sec-butyl, isobutyl, tert-butyl, have been prepared. Seven isomers of 9-butylphosphabicyclo[4.2.1]nonane (a5-PhobPBu, where Bu = n-butyl, sec-butyl, isobutyl, tert-butyl; a7-PhobPBu, where Bu = n-butyl, isobutyl, tert-butyl) have been identified in solution; isomerically pure a5-PhobPBu and a7-PhobPBu, where Bu = n-butyl, isobutyl, have been isolated. The σ-donor properties of the PhobPBu ligands have been compared using the JPSe values for the PhobP(═Se)Bu derivatives. The following complexes have been prepared: trans-[PtCl2(s-PhobPR)2] (R = nBu (1a), iBu (1b), sBu (1c), tBu (1d)); trans-[PtCl2(a5-PhobPR)2] (R = nBu (2a), iBu (2b)); trans-[PtCl2(a7-PhobPR)2] (R = nBu (3a), iBu (3b)); trans-[PdCl2(s-PhobPR)2] (R = nBu (4a), iBu (4b)); trans-[PdCl2(a5-PhobPR)2] (R = nBu (5a), iBu (5b)); trans-[PdCl2(a7-PhobPR)2] (R = nBu (6a), iBu (6b)). The crystal structures of 1a–4a and 1b–6b have been determined, and of the ten structures, eight show an anti conformation with respect to the position of the ligand R groups and two show a syn conformation. Solution variable-temperature 31P NMR studies reveal that all of the Pt and Pd complexes are fluxional on the NMR time scale. In each case, two species are present (assigned to be the syn and anti conformers) which interconvert with kinetic barriers in the range 9 to >19 kcal mol–1. The observed trend is that, the greater the bulk, the higher the barrier. The magnitudes of the barriers to M–P bond rotation for the PhobPR complexes are of the same order as those previously reported for tBu2PR complexes. Rotational profiles have been calculated for the model anionic complexes [PhobPR-PdCl3]− using DFT, and these faithfully reproduce the trends seen in the NMR studies of trans-[MCl2(PhobPR)2]. Rotational profiles have also been calculated for [tBu2PR-PdCl3]−, and these show that the greater the bulk of the R group, the lower the rotational barrier: i.e., the opposite of the trend for [PhobPR-PdCl3]−. Calculated structures for the species at the maxima and minima in the M–P rotation energy curves indicate the origin of the restricted rotation. In the case of the PhobPR complexes, it is the rigidity of the bicycle that enforces unfavorable H···Cl clashes involving the Pd–Cl groups with H atoms on the α- or β-carbon in the R substituent and H atoms in 1,3-axial sites within the phosphabicycle.

Previous work has shown that certain steroidal bis-(N-pheny)ureas, derived from cholic acid, form crystals in the P6(1) space group with unusually wide unidimensional pores. A key feature of the nanoporous steroidal urea (NPSU) structure is that groups at either end of the steroid are directed into the channels and may in principle be altered without disturbing the crystal packing. Herein we report an expanded study of this system, which increases the structural variety of NPSUs and also examines their inclusion properties. Nineteen new NPSU crystal structures are described, to add to the six which were previously reported. The materials show wide variations in channel size, shape, and chemical nature. Minimum pore diameters vary from similar to 0 up to 13.1 angstrom, while some of the interior surfaces are markedly corrugated. Several variants possess functional groups positioned in the channels with potential to interact with guest molecules. Inclusion studies were performed using a relatively accessible tris-(N-phenyl)urea. Solvent removal was possible without crystal degradation, and gas adsorption could be demonstrated. Organic molecules ranging from simple aromatics (e.g., aniline and chlorobenzene) to the much larger squalene (M-w = 411) could be adsorbed from the liquid state, while several dyes were taken up from solutions in ether. Some dyes gave dichroic complexes, implying alignment of the chromophores in the NPSU channels. Notably, these complexes were formed by direct adsorption rather than cocrystallization, emphasizing the unusually robust nature of these organic molecular hosts.

The reactions of [Ir(κ3N,N,H-Tai)(COD)] and [Ir(κ3N,N,H-PhBai)(COD)] (where Tai = HB(azaindolyl)3 and PhBai = Ph(H)B(azaindolyl)2) with carbon monoxide result in the formation of Z-type iridium–borane complexes supported by 7-azaindole units. Analysis of the reaction mixtures involving the former complex revealed the formation of a single species in solution, [Ir(η1-C8H13){κ3N,N,B-B(azaindolyl)3}(CO)2], as confirmed by NMR spectroscopy. In the case of the PhBai complex, a mixture of species was observed. A postulated mechanism for the formation of the new complexes has been provided, supported by computational studies. Computational studies have also focused on the reaction step involving the migration of hydrogen from boron (in the borohydride group) to the iridium center. These investigations have demonstrated a small energy barrier for the hydrogen migration step (ΔG298 = 10.3 kcal mol–1). Additionally, deuterium labeling of the borohydride units in Tai and PhBai confirmed the final position of the for...

The following unsymmetrical diphosphines have been prepared: o-C6H4(CH2PtBu2)(PR2) where R = PtBu2 (L3a3a3a); PCg (L3b3b); PPh2 (L3c3c3c); P(o-C6H4CH3)2 (L3d3d3d); P(o-C6H4OCH3)2 (L3e3e) and o-C6H4(CH2PCg)(PCg) (L3f3f) where PCg is 6-phospha-2,4,8-trioxa-1,3,5,7-tetramethyladamant-6-yl. Hydromethoxycarbonylation of ethene under commercially relevant conditions has been investigated in the presence of Pd complexes of each of the ligands L3a–f3a–f and the results compared with those obtained with the commercially used o-C6H4(CH2PtBu2)2 (L1a1a). The Pd complexes of the bulkiest ligands L3a3a3a, L3b3b and L3f3f are highly active catalysts but the Pd complexes of L3c3c3c, L3d3d3d and L3e3e are completely inactive. The crystal structures of the complexes [PtCl2(L1a1a)] (1a) and [PtCl2(L3a3a3a)] (2a) have been determined and show that the crystallographic bite angles and cone angles are greater for L1a1a than L3a3a3a. Solution NMR studies show that the seven-membered chelate in 1a is more rigid than the six-membered chelate in 2a. Treatment of [PtCl(CH3)(cod)] with L3a–f3a–f gave [PtCl(CH3)(L3a–f3a–f)] as mixtures of 2 isomers 3a–f and 4a–f. The ratio of the products 4 : 3 ranges from 100 : 1 to 1 : 20, the precise proportion is apparently governed by a balance of two competing factors, steric bulk and the antisymbiotic effect. The palladium complexes [PdCl(CH3)(L3b3b)] (5b/6b) and [PdCl(CH3)(L3c3c3c)] (5c/6c) react with labelled 13CO to give the corresponding acyl species [PdCl(13COCH3)(L3b3b)] (7b/8b) and [PdCl(13COCH3)(L3c3c3c)] (7c/8c). Treatment of [PdCl(13COCH3)(L)] with MeOH gave CH313COOMe rapidly when L = L3b3b but very slowly when L = L3c3c3c paralleling the contrasting catalytic activity of the Pd complexes of these two ligands.

We have expanded the ligand knowledge base for bidentate P,P- and P,N-donor ligands (LKB-PP, Organometallics 2008, 27, 1372-1383) by 208 ligands and introduced an additional steric descriptor (nHe(8)). This expanded knowledge base now captures information on 334 bidentate ligands and has been processed with principal component analysis (PCA) of the descriptors to produce a detailed map of bidentate ligand space, which better captures ligand variation and has been used for the analysis of ligand properties.

The bulky carboranyl monophosphine closo-1,2-B10H10C(H)C(PtBu2) (L) has been prepared in a one-pot procedure from o-carborane. The reaction of [PdCl2(NCPh)2] with L rapidly gave the binuclear B-cyclopalladate [Pd2(μ-Cl)2(κ2-L′)2] (L′ = L deprotonated at B3) as a mixture of two diastereoisomers, assigned structures 1a and 1a′. The Cl bridges of 1a/1a′ are cleaved by the addition of PEt3 to give the mononuclear [PdCl(κ2-L′)(PEt3)] (2) as a single isomer, with the P atoms mutually trans. The metalation occurs at boron positions 3 and 6 in the carborane cluster, and DFT calculations show that the 3,6-borometalate is lower in energy than the isomeric 4,5-borometalate and 2-carbometalate. Treatment of [Rh2Cl2(CO)4] with L led to the slow precipitation of the dirhodium(II) species [Rh2(μ-Cl)2(CO)2(κ2-L′)2] (3). The crystal structures of ligand L and complexes 1a, 2, and 3 have been determined.

The synthesis and properties of a series of unsymmetrical diphosphines o-C6H4(CH2PtBu2)(CH2PR2) are reported where R = C6H5 (La); p-CH3C6H4 (Lb); o-CH3C6H4 (Lc); o-CH3CH2C6H4 (Ld); o-CH3OC6H4 (Le); 2,4,6-(CH3)3C6H4 (Lf); CH(CH3)2 (Lg); or PR2 = PCg (Lh) where PCg is 6-phospha-2,4,8-trioxa-1,3,5,7-tetramethyladamant-6-yl. Hydromethoxycarbonylation of ethene under commercially relevant conditions is catalysed by the Pd complexes of each of the ligands La–ha–h to give methyl propanoate in >99% selectivity with catalytic activities comparable to those obtained with o-C6H4(CH2PtBu2)2 (L1) or o-C6H4(CH2PCg)2 (L55). The catalysts derived from Lc, Ld and Lh are more active than the catalyst derived from La or L1; these ligands have in common, a PR2 donor that is more bulky than the PPh2 present in La. Treatment of [PtCl(CH3)(cod)] with La–ha–h gave [PtCl(CH3)(L)] as mixtures of 2 isomers 1a–h and 2a–h. The major isomer in each case was 1a–h with the CH3 ligand trans to the PtBu2 group; the diastereoselectivity of this reaction for products 1a–h ranges from 88% to over 99%. The crystal structures of 1b, 1c and 1e have been determined. Fluxionality associated with chelate ring inversion has been detected for 1c by variable temperature 31P NMR spectroscopy. The 31P NMR data are compared for the complexes [PtCl(CH3)(L)], [Pt(CH3)2(L)] and [PtCl2(L)] where L = Lh, L1 or L55. The crystal structure of [Pt(CH3)2(Lh)] (4h) has been determined and shows that PCg is sterically less demanding than PtBu2 in this complex. Treatment of 4h with HCl gave a 1:1 mixture of 1h and 2h that equilibrated over 5 h to a 70:1 mixture. Treatment of an equilibrium mixture of 1h and 2h with isotopically labelled 13CO gas gave a single acyl complex [PtCl(13COCH3)(Lh)] (5h) with retention of configuration at Pt, i.e. the 13COCH3 is trans to the PtBu2 group. Mechanisms for the CO insertion are discussed which are consistent with the observed stereochemistry. The palladium complexes [PdCl(CH3)(Lh)] (7/8) also reacted with labelled 13CO to give a single acyl species [PdCl(13COCH3)(Lh)]. Treatment of [PdCl(13COCH3)(Lh)] with MeOH rapidly gave CH313COOMe.

The cage monophosphinites CgPOR {where CgP = 6-phospha-2,4,8-trioxa-adamantane and R = C6H5 (La); 2-C6H4CH3 (Lb); 2,4,6-C6H2(CH3)3 (Lc); 2,4-C6H3tBu2 (Ld); CH3 (Le); CH2CF3 (Lf)} and diphosphinites CgPZPCg {where ZH2 = 2,2′-biphenol (Lg) or 1,2-benzenedimethanol (Lh)} have been made from CgPBr and the corresponding alcohol or phenol. The cage phosphinites are remarkably stable to water. All the ligands La−h have been tested for nickel(0)-catalyzed hydrocyanation of 3-pentenenitrile in the presence of Lewis acids (ZnCl2, Ph2BOBPh2, or iBu2AlOAliBu2), and tentative structure−activity relationships are suggested. The hydrocyanation activities obtained with catalysts derived from monophosphinite Lf (with iBu2AlOAliBu2) and diphosphinite Lh (with ZnCl2) are comparable with the commercial catalyst based on P(OTol)3. The complexes trans-[PtCl2(L)2] where L = La (1a), Le (1e), and Lf (1f) and the chelate cis-[PtCl2(Lh)] (1h) are reported. From the νCO values for the complexes trans-[RhCl(CO)(La−f)2] (2a−f), it is...

para-Phenylenediamine (ppda) may be ground together with metal chloride salts MCl2 to produce the coordination network compounds [{(ppda)MCl2}n] {M = Zn (2), Cd (4), Cu (6)}. Its dihydrochloride salt [H2ppda]Cl2 can be ground with MCl2 to produce the layered salt structures [H2ppda][MCl4] {M = Zn (1), Cd (3), Cu (5)}, which (when M = Zn or Cd) may then be converted into 2 or 4 respectively by grinding with solid KOH. Alternatively, [H2ppda][MCl4] will react directly with appropriate basic metal compounds (hydroxides and/or carbonates) to give 2 or 4, which can then be converted back to the salts by reaction with gaseous HCl. The interconversion of 5 and 6 is more complicated, with different combinations of starting material giving different products. The crystal structure of 2 has been solved ab initio from the powder-diffraction data, and is shown to consist of zigzag polymeric chains containing alternating ppda and MCl2 units.

We have expanded the ligand knowledge base for monodentate P-donor ligands (LKB-P, Chem. Eur. J. 2006, 12, 291−302) by 287 ligands and added descriptors derived from computational results on a gold complex [AuClL]. This expansion to 348 ligands captures known ligand space for this class of monodentate two-electron donor ligands well, and we have used principal component analysis (PCA) of the descriptors to derive an improved map of ligand space. Potential applications of this map, including the visualization of ligand similarities/differences and trends in experimental data, as well as the design of ligand test sets for high-throughput screening and the identification of ligands for reaction optimization, are discussed. Descriptors of ligand properties can also be used in regression models for the interpretation and prediction of available response data, and here we explore such models for both experimental and calculated data, highlighting the advantages of large training sets that sample ligand space well.

Crystalline coordination compounds [MnCl(2)(Hpz)(2)] 3, [CdCl(2)(Hpz)(2)] 5, [MnCl(2)(Him)(2)] 9, and [CdCl(2)(Him)(2)] 13 (Him = imidazole; Hpz = pyrazole) can be synthesized in solid state reactions by grinding together the appropriate metal chloride and 2 equiv of the neutral ligand. Similarly, grinding together the metal chlorides with the ligand hydrochloride salts produces the halometallate salts [H(2)pz][MnCl(3)(OH(2))] 1, [H(2)pz][CdCl(4)] 4, [H(2)im](6)[MnCl(6)][MnCl(4)] 8, and [H(2)im](6)[CdCl(6)][CdCl(4)] 11. In contrast, reacting the metal chloride salt with the ligand in concentrated HCl solution yields a second set of salts [H(2)pz][MnCl(3)] 2, [H(2)im][MnCl(3)(OH(2))(2)] 7, and [H(2)im][CdCl(3)(OH(2))]·H(2)O 12. Compound 5 can be partly dehydrochlorinated by grinding with KOH to form an impure sample of the pyrazolate compound [Cd(pz)(2)] 6, while recrystallizing 9 from ethanol yielded crystals of solvated [Mn(4)Cl(8)(Him)(8)] 10. The crystal structure determinations of 1, 2, 4, 11, and 12 are reported.

The synthesis of the salt 3 and metallo-organic framework (MOF) [{(4,4 ′ -bipy)CoBr 2 } n ] 4 by a range of solid state (mechanochemical and thermochemical) and solution methods is reported; they are isostructural with their respective chloride analogues 1 and 2 . 3 and 4 can be interconverted by means of HBr elimination and absorption. Single phases of controlled composition and general formula [4,4 ′ -H 2 bipy][CoBr 4- x Cl x ] 5 x may be prepared from 2 and 4 by solid—gas reactions involving HBr or HCl respectively. Crystalline single phase samples of 5 x and [{(4,4 ′ -bipy)CoBr 2- x Cl x } n ] 6 x were prepared by solid-state mechanochemical routes, allowing fine control over the composition and unit cell volume of the product. Collectively these methods enable continuous variation of the unit cell dimensions of the salts [4,4 ′ -H 2 bipy][CoBr 4- x Cl x ] ( 5 x ) and the MOFs [{(4,4 ′ -bipy)CoBr 2- x Cl x } n ] ( 6 x ) by varying the bromide to chloride ratio and establish a means of controlling MOF composition and the lattice metrics, and so the physical and chemical properties that derive from it.

We have investigated the full catalytic cycle for the coupling of phenylbromide with morpholine (Buchwald–Hartwig amination), catalysed by the synthetically relevant Pd(PtBu3) complex, with computational methods. The experimentally observed utility of this catalyst can be related to the energetically accessible ligand dissociation from the initial Pd(0) species, combined with a low barrier to oxidative addition and sterically unfavourable dimer formation. Furthermore, the steric bulk of the PtBu3 ligand allows for a low-coordinate, dissociative pathway and facile reductive elimination over the competing, undesirable β-hydride elimination pathway. Evaluating the full catalytic cycle with one of the most versatile catalyst complexes used experimentally has allowed us to evaluate the most likely catalytic pathway and relate this to general ligand design criteria, as well as providing validation for the computational approach used.

The enantioselective hydrogenation catalyst [Rh(α-CgPH) 2 (cod)]BF 4 , (CgPH = 6-phospha-2,4,8-trioxa-adamantane) exists in solution as a mixture of two slowly interconverting rotamers, one with C 2 - and the other with C 1 -symmetry.

Rhodium(III) cyclopropenylidene complexes of the type [RhCl3(PPh3)2(2,3-di(aryl)cyclopropenylidene)] (Aryl = C6H5, 4-C6H4F) are synthesized via oxidative addition of 1,1-dichloro-2,3-diarylcyclopropene fragments to rhodium(I) precursors. The molecular structure of these complexes has been determined. Attempted hydroformylation of 1-hexene with these complexes leads to catalysis results which are strongly suggestive of decomposition of the carbene complex.

The d4 halide complexes [MX(CO)(η-RCCR)Tp′] {R = Me, M = W, X = F; R = Ph, M = Mo or W, X = F or Cl; Tp′ = hydrotris(3,5-dimethylpyrazolyl)borate} undergo two-electron oxidation in the presence of a halide source to give the d2 monocations [MX1X2(η-PhCCPh)Tp′]+ (R = Me, M = W, X1 = X2 = F; R = Ph, M = Mo, X1 = X2 = F or Cl; M = W, X1 = X2 = F or Cl; X1 = F, X2 = Cl). Each monocation (R = Ph) shows two reversible one-electron reductions (the second process was not detected for R = Me) corresponding to the stepwise formation of the neutral d3 and monoanionic d4 analogues, [MX1X2(η-PhCCPh)Tp′] and [MX1X2(η-PhCCPh)Tp′]− respectively; the potentials for the two processes can be ‘tuned’ over a range of ca. 1.0 V by varying M and X. Chemical one-electron reduction of [MX2(η-PhCCPh)Tp′]+ gave [MX2(η-PhCCPh)Tp′] (M = Mo or W, X = F or Cl). X-Ray structural studies on the redox pairs [WX2(η-PhCCPh)Tp′]z (X = F and Cl, z = 0 and 1+) show the alkyne to bisect the X–W–X angle in the d2 cations but align more closely with one M–X bond in the neutral d3 molecules, consistent with the anisotropic ESR spectra of the latter; the solution ESR spectrum of [MoF2(η-PhCCPh)Tp′] showed equivalent fluorine atoms, i.e the alkyne oscillates at room temperature. The successful isolation of [MX2(η-PhCCPh)Tp′]+ and [MX2(η-PhCCPh)Tp′] completes a series in which d6 to d2alkyne complexes are linked in a redox family tree by sequential one-electron transfer and substitution reactions. The implications for such trees in the production of new species and the selective synthesis of paramagnetic complexes acting as synthetically useful ‘alkyne radicals’ are discussed.

The binuclear cyclometalates [Pt2Cl2{2-CMe2C6H4P(C6H4(2-iPr))2}2] (1a) and [Pt2Cl2{2-CMe2C6H3(4-OMe)P(C6H3(2-iPr)(4-OMe))2}2] (1b) react with CHCl2CHCl2 to give the corresponding mononuclear phosphine-alkene chelates [PtCl2{2-CH2═CMeC6H4P(C6H4(2-iPr))2}] (2a) and [PtCl2{2-CH2═CMeC6H3(4-OMe)P(C6H3(2-iPr)(4-OMe))2}] (2b). The product 2a can also be formed directly from [PtCl2(NCtBu)2] and La in CHCl2CHCl2 or by addition of SO2Cl2 to 1a. Addition of an excess of SO2Cl2 to 1b gave [PtCl2{2-CH2═CMeC6H3(4-OMe)P(C6H2(2-iPr)(4-OMe)(5-Cl))2}] (3b), a derivative of 2b featuring meta-chlorine substituents on the terminal P groups as a result of electrophilic aromatic substitution. A mechanism for the conversion of 1a,b to 2a,b is proposed involving an electrophilic alkyl C−H activation by a coordinatively unsaturated platinum(IV) species. The mechanism is supported by the isolation of the diplatinum(IV) cyclometalate [Pt2Cl2{2-CH2C6H3(4-OMe)P(C6H3(2-Me)(4-OMe))2}] as a mixture of syn and anti isomers 5b and 5b′. The crystal structures of 2a and 3b have been determined.

International audience; Reduction of compound “Pd(bcope)(OTf)2” [bcope = (c-C8H14-1,5)PCH2CH2P(c-C8H14-1,5); OTf = O3SCF3] with H2/CO yields a mixture of Pd(I) compounds [Pd2(bcope)2(CO)2](OTf)2 (1) and [Pd2(bcope)2(μ-CO)(μ-H)](OTf) (2), whereas reduction with H2 or Ph3SiH in the absence of CO leads to [Pd3(bcope)3(μ3-H)2](OTf)2 (3). Exposure of 3 to CO leads to 1 and 2. The structures of 1 and 3 have been determined by X-ray diffraction. Complex [Pd2(bcope)2(CO)2]2+ displays a metal−metal bonded structure with a square planar environment for the Pd atoms and terminally bonded CO ligands and is fluxional in solution. DFT calculations aid the interpretation of this fluxional behavior as resulting from an intramolecular exchange of the two inequivalent P atom positions via a symmetric bis-CO-bridged intermediate. A cyclic voltammetric investigation reveals a very complex redox behavior for the “Pd(bcope)(OTf)2”/CO system and suggests possible pathways leading to the formation of the various observed products, as well as their relationship with the active species of the PdL22+/CO/H2-catalyzed oxo processes (L2 = diphosphine ligands).

The secondary phosphine CgPH (CgP = 6-phospha-2,4,8-trioxa-1,3,5,7-tetramethyladamantyl group) is made in 50% yield by a modification of the literature method (avoiding high pressures of PH3) by bubbling PH3 through an acidified solution of 2,4-pentanedione at 0 °C. Under similar conditions the ethyl analogue EtCgPH is formed from 3,5-heptanedione in 75% yield. The halophosphines CgPCl and CgPBr are made by treatment of CgPH with N-halosuccinimide. CgPBr is also made by treatment of CgPH with Br2. Three methods are described for the synthesis of CgPR, where R = alkyl: (a) the previously reported acid-catalyzed condensation reaction of RPH2 with 2,4-pentanedione, which has been extended to R = iPr; (b) treatment of CgP(BH3)Li with RX followed by borane deprotection with Et2NH, which has been used for R = iPr, benzyl, n-C20H41; (c) treatment of CgPBr with RMgX, which has been used for R = iPr, Me. The complexes [PtCl2(CgPH)2] (1), [PdCl2(CgPH)2] (2), [PdCl2(CgPR)2] (where R = iPr (3a), Cy (3b)), and [PtCl2(...

A series of copper(I) complexes containing bis(diarylphosphino)propane, bis(diarylphosphino)ethane, bis(diarylphosphino)methane, and N,N-bis(diarylphosphino)amine ligands (Aryl = Ph, 2-C6H4(Me) or 2-C6H4(i-Pr)) has been synthesized. Crystal structures of selected chloride derivatives are reported. The complex structures proved to be very sensitive to both the backbone and P-substituents of the chelating ligand. The complexes have been screened for catalytic amidation reactions. Although in most cases only very low activity is observed, comparable with simple copper halide salts, notable exceptions are catalysts based on N,N-bis(diphenylphosphino)amine ligands, where a significant improvement in catalyst efficiency is observed. We propose the unusual electronic properties of these ligands may be the cause of their distinctive performance in these and other catalytic reactions where hard donor ligands have previously been employed.

C 1-Symmetric phosphino/phosphonite ligands are prepared by the reactions of Ph 2P(CH 2) 2P(NMe 2) 2 with ( S)-1,1'-bi-2-naphthol (to give L A ) or ( S)-10,10'-bi-9-phenanthrol (to give L B ). Racemic 10,10'-bi-9-phenanthrol is synthesized in three steps from phenanthrene in 44% overall yield. The complexes [PdCl 2( L A,B )] ( 1a, b), [PtCl 2( L A,B )] ( 2a, b), [Rh(cod)( L A,B )]BF 4 ( 3a, b) and [Rh( L A,B ) 2]BF 4 ( 4a, b) are reported and the crystal structure of 1a has been determined. A (31)P NMR study shows that M, a 1:1 mixture of the monodentates, PMePh 2 and methyl monophosphonite L 1a (based on ( S)-1,1 '-bi-2-naphthol), reacts with 1 equiv of [Rh(cod) 2]BF 4 to give the heteroligand complex [Rh(cod)(PMePh 2)( L 1a )]BF 4 ( 5) and homoligand complexes [Rh(cod)(PMePh 2) 2]BF 4 ( 6) and [Rh(cod)( L 1a ) 2]BF 4 ( 7) in the ratio 2:1:1. The same mixture of 5- 7 is obtained upon mixing the isolated homoligand complexes 6 and 7 although the equilibrium is only established rapidly in the presence of an excess of PMePh 2. The predominant species 5 is a monodentate ligand complex analogue of the chelate 3a. When the mixture of 5- 7 is exposed to 5 atm H 2 for 1 h (the conditions used for catalyst preactivation in the asymmetric hydrogenation studies), the products are identified as the solvento species [Rh(PMePh 2)( L 1a )(S) 2]BF 4 ( 5'), [Rh(S) 2(PMePh 2) 2]BF 4 ( 6') and [Rh(S) 2( L 1a ) 2]BF 4 ( 7') and are formed in the same 2:1:1 ratio. The reaction of M with 0.5 equiv of [Rh(cod) 2]BF 4 gives exclusively the heteroligand complex cis-[Rh(PMePh 2) 2( L 1a ) 2]BF 4 ( 8), an analogue of 4a. The asymmetric hydrogenation of dehydroamino acid derivatives catalyzed by 3a, b is reported, and the enantioselectivities are compared with those obtained with (a) chelate catalysts derived from analogous diphosphonite ligands L 2a and L 2b , (b) catalysts based on methyl monophosphonites L 1a and L 1b , and (c) catalysts derived from mixture M. For the cinnamate and acrylate substrates studied, the catalysts derived from the phosphino/phosphonite bidentates L A,B generally give superior enantioselectivities to the analogous diphosphonites L 2a and L 2b ; these results are rationalized in terms of delta/lambda-chelate conformations and allosteric effects of the substrates. The rate of hydrogenation of acrylate substrate A with heterochelate 3a is significantly faster than with the homochelate analogues [Rh( L 2a )(cod)]BF 4 and [Rh(dppe)(cod)]BF 4. A synergic effect on the rate is also observed with the monodentate analogues: the rate of hydrogenation with the mixture containing predominantly heteroligand complex 5 is faster than with the monophosphine complex 6 or monophosphonite complex 7. Thus the hydrogenation catalysis carried out with M and [Rh(cod) 2]BF 4 is controlled by the dominant and most efficient heteroligand complex 5. In this study, the heterodiphos chelate 3a is shown to be more efficient and gives the opposite sense of optical induction to the heteromonophos analogue 5.

The ligand knowledge base approach has been extended to capture the properties of 108 bidentate P,P- and P,N-donor ligands. This contribution describes the design of the ligand set and a range of DFT-calculated descriptors, capturing ligand properties in a variety of chemical environments. New challenges arising from ligand conformational flexibility and donor asymmetry are discussed, and descriptors are related to other parameters, such as the ligand bite angle. A novel map of bidentate ligand space, potentially useful in catalyst design and discovery, has been derived from principal component analysis of the resulting LKB-PP descriptors. In addition, a range of multiple linear regression models have been derived for both experimental and calculated data, considering ligand bite angles in square-planar palladium complexes and ligand dissociation energies from octahedral chromium complexes, respectively. These data sets were fitted with models based on LKB descriptors to explore the transferability of des...

An NBO second-order perturbative energy analysis is used in a quantitative study of back-bonding toward YX3 (Y = P, N, C, Si; X = H, F, Me, Ph, OMe) ligands as well as pyridine and bipyridine. The pi acceptor character of these ligands in M-L, L'-M-L, and M(CO)(5)L complexes is studied at the B3LYP level of theory. All phosphine ligands are found to be pi acceptors, whereas the NH3 and NMe3 ligands are found to be sigma-only ligands. The NBO analysis also identifies competitive back-bonding and shows that even the carbon- and silicon-containing ligands have some pi-bonding character.

The d4 halide complexes [MX(CO)(η-RCCR)Tp′] {X = F, Cl, Br or I; R = Me or Ph; M = Mo or W; Tp′ = hydrotris(3,5-dimethylpyrazolyl)borate} undergo one-electron oxidation to the d3 monocations [MX(CO)(η-RCCR)Tp′]+, isolable for M = W, R = Me. X-Ray structural studies on the redox pairs [WX(CO)(η-MeCCMe)Tp′]z (X = Cl and Br, z = 0 and 1), the ESR spectra of the cations [WX(CO)(η-RCCR)Tp′]+ (X = F, Cl, Br or I; R = Me or Ph), and DFT calculations on [WX(CO)(η-MeCCMe)Tp′]z (X = F, Cl, Br and I; z = 0 and 1) are consistent with electron removal from a HOMO (of the d4 complexes) which is π-antibonding with respect to the W–X bond, π-bonding with respect to the W–C(O) bond, and δ-bonding with respect to the W–Calkyne bonds. The dependence of both oxidation potential and ν(CO) for [MX(CO)(η-RCCR)Tp′] shows an inverse halide order which is consistent with an ionic component to the M–X bond; the small size of fluorine and its closeness to the metal centre leads to the highest energy HOMO and the lowest oxidation potential. In the cations [MX(CO)(η-RCCR)Tp′]+ electronegativity effects become more important, leading to a conventional order for Cl, Br and I. However, high M–F π-donation is still facilitated by the short M–F distance.

Convenient syntheses are described for the five-, six-, and seven-membered phosphacycles PhP(CH2)x-1, where x = 5 (La5), 6 (La6), 7 (La7), and ButP(CH2)x-1 where x = 5 (Lb5), 6 (Lb6), 7 (Lb7). Treatment of [PtCl2(cod)] with La5-7 gives cis-[PtCl2(La5-7)2] (1a5-7), whereas with Lb5-7 a mixture of cis-[PtCl2(Lb5-7)2] (1b5-7) and trans-[PtCl2(Lb5-7)2] (2b5-7) is obtained. Metathesis of 1a7 with NaI gives a mixture of cis-[PtI2(La7)2] (3a7) and trans-[PtI2(La7)2] (4a7). The crystal structures of 1a5, 1a6, 1a7, and 4a7 have been determined. Comparison of the structures of 1a7 and 4a7 reveals that La7 has variable steric bulk, with the crystallographically determined cone angle ranging from 137° (smaller than La5) to 172° (larger than La6), depending on the particular twist-chair seven-membered-ring conformations adopted. The complex cis-[PtCl2(Lb6)] (1b6) is fluxional on the NMR time scale at ambient temperatures, as a result of restricted PtP rotation. Treatment of [Rh2Cl2(CO)4] with La5-7 or Lb5-7 gives the ...

The symmetrical diphosphanes R2P−PR2 {where R = Ph (1a), Cy (1b), or But (1c)} are made by the reaction of R2PLi with R2PCl. The unsymmetrical diphosphanes R2P−PR‘2 {where R = But and R‘ = Ph (2a); R = But and R‘ = o-Tol (2b); R = Cy and R‘ = Ph (2c); R = Cy and R‘ = o-Tol (2d); R = Cy and R‘ = But (2e)} are made by the reaction of R2P(BH3)Li with R‘2PCl followed by deprotection with Et2NH. Diphosphanes 1a,b and 2a−d react with ZC⋮CZ (Z = CO2Me) to give the corresponding R2PCZCZPR2 (3a,b) or R2PCZCZPR‘2 (4a−d). The reaction of 2a,b with HC⋮CZ give the corresponding R2PCHCZPR2 (5a,b). A mechanism is proposed that accounts for the cis stereospecificity and the regioselectivity of these diphosphinations. Treatment of [PtCl2(1,5-cod)] or [PdCl2(NCPh)2] with a selection of the diphosphines (3−5) gave the expected chelate complexes, four of which, [PtCl2(3b)], [PtCl2(4a)], [PtCl2(4c)], and [PdCl2(4a)], have had their crystal structures determined.

Reduction of [M(CO)2(η-RCCR′)Tp′]X {Tp′ = hydrotris(3,5-dimethylpyrazolyl)borate, M = Mo, X = [PF6]−, R = R′ = Ph, C6H4OMe-4 or Me; R = Ph, R′ = H; M = W, X = [BF4]−, R = R′ = Ph or Me; R = Ph, R′ = H} with [Co(η-C5H5)2] gave paramagnetic [M(CO)2(η-RCCR′)Tp′], characterised by IR and ESR spectroscopy. X-Ray structural studies on the redox pair [Mo(CO)2(η-PhCCPh)Tp′] and [Mo(CO)2(η-PhCCPh)Tp′][PF6] showed that oxidation is accompanied by a lengthening of the CC bond and shortening of the Mo–Calkyne bonds, consistent with removal of an electron from an orbital antibonding with respect to the Mo–alkyne bond, and with conversion of the alkyne from a three- to a four-electron donor. Reduction of [Mo(CO)(NCMe)(η-MeCCMe)Tp′][PF6] with [Co(η-C5H5)2] in CH2Cl2 gives [MoCl(CO)(η-MeCCMe)Tp′], via nitrile substitution in [Mo(CO)(NCMe)(η-MeCCMe)Tp′], whereas a similar reaction with [M(CO){P(OCH2)3CEt}(η-MeCCMe)Tp′]+ (M = Mo or W) gives the phosphite-containing radicals [M(CO){P(OCH2)3CEt}(η-MeCCMe)Tp′]. ESR spectroscopic studies and DFT calculations on [M(CO)L(η-MeCCMe)Tp′] {M = Mo or W, L = CO or P(OCH2)3CEt} show the SOMO of the neutral d5 species (the LUMO of the d4 cations) to be largely dyz in character although much more delocalised in the W complexes. Non-coincidence effects between the g and metal hyperfine matrices in the Mo spectra indicate hybridisation of the metal d-orbitals in the SOMO, consistent with a rotation of the coordinated alkyne about the M–C2 axis.

The industrially important mixture of sym- and asym-phobanes are separated efficiently by selective protonation of the sym isomer with hydrochloric acid; carbonylation catalysts generated from diphosphanes derived from the separated isomers have quite different activities and product selectivities.

The preparation and structures of the bismuth thiolato anions [Bi2(SC6F5)6(μ-SC6F5)]− and [Bi2(SC6F5)6(μ-SC6F5)2]2− and the halothiolato anions [Bi2(SC6F5)6(μ-Br)]−, [Bi2(SC6F5)6(μ-Cl)2]2− and [Bi3(SC6F5)9(μ-Br)2]2− are described. All compounds have been isolated from reactions between Bi(SC6F5)3 and ammonium or phosphonium halides. The basic structural units in the dinuclear species are of two types namely [Bi2(SR)6(μ-X)]− and [Bi2(SR)6(μ-X)2]2−, where X=thiolate or halide. In the former case the single bridging groups occupy an axial site within the disphenoidal (equatorially vacant, trigonal bipyramidal) geometry around the bismuth centres whereas in the latter the two bridging groups occupy cis basal sites in square based pyramidal bismuth environments. The trinuclear anion [Bi3(SC6F5)9(μ-Br)2]2− has features in common with the basic [Bi2(SC6F5)6(μ-Br)]− unit.

A series of perchlorometalate salts of the [1,3,5-tris(R)-2,4,6-triazine] 3+ trications, where R = 4-, 3-, or 2-pyridinium, have been prepared and structurally characterized. The supramolecular motifs in these salts show striking similarities despite differences in the local position of the pyridinium NH group, the metal atom used, and the incorporation of water molecules in the structure. A supramolecular motif in which the near-planar cations are surrounded by an octahedral array of six octahedral trianions is observed in the majority of the new salts. The crystal structures of [1,3,5-tris(4-pyridinium)-2,4,6-triazine] [SbCl 6 ] (4), [1,3,5-tris(4-pyridinium)-2,4,6-triazine] [BiCl 6 ] (5), [1,3,5-tris(3-pyridinium)-2,4,6-triazine] [SbCl 6 ] (8), [1,3,5-tris(3-pyridinium)-2,4,6-triazine] [BiCl 6 ] (9), and [1,3,5-tris(3-pyridinium)-2,4,6-triazine] [FeCl 6 ] (10) are essentially isostructural; [1,3,5-tris(4-pyridinium)-2,4,6-triazine] 2 -[FeCl 6 ][FeCl 4 ] 3 (6), [1,3,5-tris(2-pyridinium)-2,4,6-triazine][SbCl 6 ].3H 2 O (11), and [1,3,5-tris(2-pyridinium)-2,4,6-triazine] [BiCl 6 ].3H 2 O (12) show related supramolecular structural motifs. The crystal structures of all of 4, 5, 8, 9, 10, and 12 are of R3c or R3c symmetry and have similar cell dimensions (a = b = 14.6-15.2 A, c = 18.5-19.2 A) reflecting the planarity and 3-fold symmetry of the cations. The structures appear to be stabilized by complementary Cl...HN, Cl...HO, Cl...HC, and NH...O hydrogen bonding, shape, and electrostatic interactions and unanticipated triazine C...Cl interactions.

The preparation and structure determinations of the crystalline salts [3,3-H 2 bipy][PtCl 4 ] (2), [2,2'-H 2 bipy][PtCl 4 ] (3) and [1,4'-Hbipy] [PtCl 4 ] (4) and [3,3'-H 2 bipy][SbCl 5 ] (6) and [1,4'-Hbipy][SbCl 5 ] (8) are reported. In addition a redetermination of the structure of the metastable salt [4,4'-H 2 bipy][SbCl 5 ] (5b) in the corrected space group Phcm is described. These structures are compared to those of the known salt [4,4'-H 2 bipy][PtCl 4 ] (1), the stable triclinic form of [4.4'-H 2 bipy][SbCl 5 ] (5a) and [2,2'-H 2 bipy] [SbCl 5 ] (7). In the case of the salts of the rigid [PtCl 4 ] 2 - ion, structures 2, 3 and 4 are essentially isostructural despite the differing hydrogen-bonding capability of the cations. Similarly among the salts of [SbCl 5 ] 2 - ions, structures 7 and 8 are essentially isostructural. Structure 6 differs from these in having a differing pattern of aggregation of the [SbCl 5 ] 2 - ions to form polymeric rather than tetrameric units. It is evident that local hydrogen-bonding interactions, although significant, are not the only or even the decisive influence on the crystal structures formed by these salts. These observations are not in good accord with the heuristic "sticky tecton" or supramolecular synthon models for synthetic crystallography or crystal engineering.

Cationic nitrile complexes and neutral halide and cyanide complexes, with the general formula [MnL1L2(NO)(eta-C5H4Me)]z, undergo one-electron oxidation at a Pt electrode in CH2Cl2. Linear plots of oxidation potential, Eo', vs. nu(NO) or the Lever parameters, EL, for L1 and L2, allow Eo' to be estimated for unknown analogues. In the presence of TlPF6, [MnIL'(NO)(eta-C5H4Me)] reacts with [Mn(CN)L(NO)(eta-C5H4Me)] to give [(eta5-C5H4Me)(ON)LMn(mu-CN)MnL'(NO)(eta5-C5H4Me)][PF6] which undergoes two reversible one-electron oxidations; DeltaE, the difference between the potentials for the two processes, differs significantly for stable cyanide-bridged linkage isomers. Novel pentametallic complexes such as [Mn[(mu-NC)Mn(CNBut)(NO)(eta5-C5H4Me)]4(OEt2)][PF6]2 and [Mn[(mu-NC)Mn(CNXyl)(NO)(eta5-C5H4Me)]4(NO3-O,O')][PF6], containing a trigonal bipyramidal and a distorted octahedral Mn(II) centre, respectively, result either from slow decomposition of the binuclear cyanide-bridged species or from the reaction of anhydrous MnI2 with four equivalents of [Mn(CN)L(NO)(eta5-C5H4Me)] in the presence of TlPF6.

The nominally square-planar coordination of the d8 complexes [MClL1L2(p-XC6H4NNNHC6H4X-p)] (M = Rh, L1 = L2 = CO, X = H, Me, Et or F; M = Ir, L1 = L2 = CO, X = Me; M = Pd or Pt, L1 = Cl, L2 = PPh3, X = Me; M = Pd, L1L2 = η3-C3H5, X = Me), with the triazene N-bonded via the imine group, is supplemented by an axial M⋯H–N interaction involving the terminal amino group.

Propargyl alcohols HCCCR2OH (R=H, Me or Ph) react with [Ru2(CO)(MeCN)(μ-CO)(μ-CH2)(η-C5H5)2] (2) to form the allylidene complexes [Ru2(CO)(μ-CO){μ-η1,η3-C(CR2OH)CHCH2}(η-C5H5)2] (4a, R=H; 4b, R=Me; 4c, R=Ph). Treatment of complexes 4a–c with HBF4 removes the hydroxide group as water, giving the 2-butadienyl complexes [Ru2(CO)(μ-CO)(μ-η2,η3-CR2CCHCH2)(η-C5H5)2][BF4] (5a, R=H; 5b, R=Me; 5c, R=Ph). The reactivity of 5a–c towards nucleophiles and bases is described. With hydride, 5a–c undergo nucleophilic attack at the C(R2) carbon to give the allylidene complexes [Ru2(CO)(μ-CO){μ-η1,η3-C(CR2H)CHCH2}(η-C5H5)2] (6a, R=H; 7, R=Me; 11, R=Ph) and, in the case of 5c, the butadiene complex [Ru2(CO)2(μ-η2,η2-CPh2CHCHCH2)(η-C5H5)2] (12) and the allene complex [Ru2(CO)2(μ-η2,η2-CPh2CCHMe)(η-C5H5)2] (13), formally due to attack at the μ-C and CH2 carbons, respectively. The complexes 5a–c react with methyl lithium to undergo nucleophilic attack predominantly at the C(R2) carbon, giving methylated allylidene complexes [Ru2(CO)(μ-CO){μ-η1,η3-C(CR2Me)CHCH2}(η-C5H5)2] (6b, R=Me; 9, R=Me; 14, R=Ph). With 5b and 5c methyl lithium also acts as a base, abstracting protons to give the novel divinylcarbene complex [Ru2(CO)(μ-CO){μ-η1,η3-C(CMeCH2)CHCH2}(η-C5H5)2] (8) and the μ-butatriene complex [Ru2(CO)2(μ-η2,η2-CPh2CCCH2)(η-C5H5)2] (15), respectively. Complexes 8 and 15 are formed exclusively by treating 5b and 5c, respectively, with diazabicyclo[5.4.0]undec-7-ene (DBU). Complexes 8 and 9 were also prepared in good yield by reaction of complex 2 with 2-methyl-1-buten-3-yne {CH2C(Me)CCH} and t-butylacetylene, respectively. Treatment of complex 8 with HBF4 resulted in protonation at each of the methylene groups, affording 5b and isomeric [Ru2(CO)(μ-CO){μ-η2,η3-CH(Me)CC(Me)CH2}(η-C5H5)2][BF4] (10). The structures of 5b, 5c and 8 were established by X-ray diffraction.