Space groups and crystallographic symmetry: writing a multi-featured tutorial in a new style.

Knowledge of space groups and the implications of space group symmetry on the physical and chemical properties of solids are pivotal factors in all areas of crystalline solids. As Jerry Jasinski and I met to bring our ideas in teaching this subject to life, we both felt that 'early and often' - teaching the concepts with textual and visual reinforcement, is the key to providing a sound basis for students in this subject. The tutorial contains 200 PowerPoint 'slides', in five modules, arranged by crystal class; a sixth module covers special topics.

cis-Bis(L-DOPA-κN,O)copper(II) monohydrate: synthesis, crystal structure, and approaches to the analysis of pseudosymmetry.

The crystal structure of the cis isomer of cis-bis(L-DOPA-κN,O)copper(II) monohydrate (L-DOPA is 3,4-dihydroxy-L-phenylalanine) (CuLD), [Cu(CHNO)]·HO, is a singular example of a structurally characterized, homoleptic, crystalline metal L-DOPA complex. CuLD crystallizes in the space group P2, with Z' = 2. The two independent molecules are square planar, and are interconnected by a linear hydrogen-bonded chain containing 12 independent hydrogen bonds.

Δ-Tetrahydrocannabinolic acid A, the precursor to Δ-tetrahydrocannabinol (THC).

While Δ-tetrahydrocannabinolic acid A (THCA-A) has been reported to be difficult to crystallize and/or amorphous, we have obtained THCA-A in a pure crystalline form by extraction of marijuana and selective fractionation with liquid CO. THCA-A (systematic name: 1-hydroxy-6,6,9-trimethyl-3-pentyl-6a,7,8,10a-tetrahydro-6H-benzo[c]isochromene-2-carboxylic acid, CHO) crystallizes in the orthorhombic space group P222, with Z = 8 and Z' = 2. The two independent molecules are related by a pseudo-twofold axis centered between the two -COH groups, but the conformations of the two -CH chains are quite different (tgt and ttg; t is trans and g is gauche).

A Series of Dimeric Cobalt Complexes Bridged by N-Heterocyclic Phosphido Ligands.

A tridentate [PPP] ligand has been used to construct a series of dimeric cobalt complexes and explore cooperative multielectron redox processes that are both metal- and ligand-centered. Reduction of (PPP)CoCl () with excess magnesium affords the CoCo N-heterocyclic phosphido (NHP)-bridged symmetric dimer [(μ-PPP)Co] (). Two-electron oxidation of with FcPF generates an asymmetrically bridged dication [(μ-PPP)Co][PF] () in which the oxidation has occurred in a delocalized fashion throughout the CoP core.

Dimerization of terminal alkynes promoted by a heterobimetallic Zr/Co complex.

Enynes are important synthetic intermediates that are also found in a variety of natural products and other biologically relevant molecules. The most atom economical synthetic route to enynes is via the direct coupling of readily available terminal alkyne precursors. Towards this goal, we demonstrate the formation of 1,3-enynes from terminal alkynes facilitated by a reduced ZrIV/Co-I heterobimetallic complex.

O Activation by a Heterobimetallic Zr/Co Complex.

Oxygen reduction is a critical half reaction in renewable fuel cell development and a key step in the development of aerobic oxidation reactions. Herein, we report rapid two-electron O reduction by a d Zr center with an appended redox-active Co site serving as an electron reservoir. The early/late heterobimetallic Zr/Co complex (THF)Zr(MesNP Pr)CoCN Bu (1) reacts readily with O and O atom transfer reagents to generate reactive oxygenated species including terminal peroxo and oxo complexes, (O)Zr(MesNP Pr)CoCN Bu (2) and O≡Zr(MesNP Pr)CoCN Bu (3).

Cooperative activation of O-H and S-H bonds across the Co-P bond of an N-heterocyclic phosphido complex.

Metal-ligand cooperation has proven to be a viable concept for σ bond activation and catalysis, however there are few examples involving phosphorus as an active participant in bond cleavage. The reactivity of E-H bonds (E = S, O) across a metal-phosphorus bond of a cobalt(i) center ligated by a tridenate N-heterocyclic phosphido (NHP-) ligand with diphosphine sidearms, (PPP)-, has been explored. Addition of PhOH to (PPP)CoPMe3 (1) cleanly affords (PPOPhP)Co(H)PMe3 (2), in which the O-H bond was heterolytically cleaved across the M-PNHP bond.

Assessing the Metal-Metal Interactions in a Series of Heterobimetallic Nb/M Complexes (M = Fe, Co, Ni, Cu) and Their Effect on Multielectron Redox Properties.

A one-pot synthetic procedure for a series of bimetallic Nb/M complexes, Cl-Nb( PrNPPh)M-X (M = Fe (2), Ni (4), Cu (5)), is described. A similar procedure aimed at synthesizing a Nb/Co analogue instead affords PrN═Nb( PrNPPh)(μ-PPh)Co-I (3) through cleavage of one phosphinoamide P-N bond under reducing conditions. Complexes 4 and 5 are found to have short Nb-M distances, corresponding to unusual metal-metal bonds between Nb and these first row transition metals.

Origin of and a Solution for Uneven Efficiency by Cinchona Alkaloid-Derived, Pseudoenantiomeric Catalysts for Asymmetric Reactions.

Cinchona alkaloid-derived chiral catalysts represent one of the most widely applied classes of organocatalysts, which have been successfully utilized in the promotion of a wide variety of asymmetric reactions. Cinchona alkaloids exist in nature as pseudoenantiomers, which allow cinchona alkaloid-catalyzed reactions to provide high enantioselectivities and yields toward both enantiomers of interest in many reactions. On the other hand, the subtle structural difference between pseudoenantiomeric cinchona alkaloids could also lead to uneven efficiency that severely limits the applicability of some cinchona alkaloid-catalyzed reactions.

Absolute Configuration and Pharmacology of the Poison Frog Alkaloid Phantasmidine.

Phantasmidine, a rigid congener of the well-known nicotinic acetylcholine receptor agonist epibatidine, is found in the same species of poison frog ( Epipedobates anthonyi). Natural phantasmidine was found to be a 4:1 scalemic mixture, enriched in the (2a R,4a S,9a S) enantiomer by chiral-phase LC-MS comparison to the synthetic enantiomers whose absolute configurations were previously established by Mosher's amide analysis. The major enantiomer has the opposite S configuration at the benzylic carbon to natural epibatidine, whose benzylic carbon is R.

Zirconium Metal-Organic Frameworks Assembled from Pd and Pt PNP Pincer Complexes: Synthesis, Postsynthetic Modification, and Lewis Acid Catalysis.

Carboxylic acid-functionalized Pd and Pt PNP pincer complexes were used for the assembly of two porous Zr metal-organic frameworks (MOFs), 2-PdX and 2-PtX. Powder X-ray diffraction analysis shows that the new MOFs adopt cubic framework structures similar to the previously reported ZrO(OH)[(PCP)PdX], [PCP = 2,6-(OPAr)CH); Ar = p-CHCO, X = Cl, I] (1-PdX). Elemental analysis and spectroscopic characterization indicate the presence of missing linker defects, and 2-PdX and 2-PtX were formulated as ZrO(OH)(OAc)[M(PNP)X] [M = Pd, Pt; PNP = 2,6-(HNPAr)CHN; Ar = p-CHCO; X = Cl, I].

Addition of H Across a Cobalt-Phosphorus Bond.

Addition of H across the cobalt-phosphorus bond of (PPP)CoPMe (3) is demonstrated, where PPP is a monoanionic diphosphine pincer ligand with a central N-heterocyclic phosphido (NHP ) donor. The chlorophosphine Co complex (PP P)CoCl (2) can be generated through coordination of the chlorophosphine ligand (PP P, 1) to CoCl . Subsequent reduction of 2 with KC in the presence of PMe generates (PPP)CoPMe (3), in which both the phosphorus and cobalt centers have been reduced.

Electrochemical and structural investigation of the interactions between naphthalene diimides and metal cations.

The effects of Li and Mg on the electrochemical behaviour and photoreduction of N,N'-bis(2,6-diisopropylphenyl)naphthalene diimide (DippNDI) have been investigated using cyclic voltammetry and UV-vis spectroscopy. Strong cation-anion interactions between Li or Mg and [DippNDI] result in solvent-dependent anodic shifts of the NDI˙ redox couple. In organic solvents of moderate dielectric constant and donor ability, the two, one-electron redox processes typically observed for DippNDI merge into a single, two-electron process.

Heterobimetallic Complexes Comprised of Nb and Fe: Isolation of a Coordinatively Unsaturated Nb/Fe Bimetallic Complex Featuring a Nb≡Fe Triple Bond.

Heterometallic multiple bonds between niobium and other transition metals have not been reported to date, likely owing to the highly reactive nature of low-valent niobium centers. Herein, a C-symmetric tris(phosphinoamide) ligand framework is used to construct a Nb/Fe heterobimetallic complex Cl-Nb(PrNPPh)Fe-Br (2), which features a Fe→Nb dative bond with a metal-metal distance of 2.4269(4) Å.

Cobalt N-Heterocyclic Phosphenium Complexes Stabilized by a Chelating Framework: Synthesis and Redox Properties.

Two cobalt complexes containing coordinated N-heterocyclic phosphenium (NHP) ligands are synthesized using a bidentate NHP/phosphine chelating ligand, [PP]. Treatment of Na[Co(CO)] with the chlorophosphine precursor [PP]Cl (1) affords [PP]Co(CO) (2), which features a planar geometry at the NHP phosphorus center and a short Co-P distance [1.9922(4) Å] indicative of a Co═P double bond.

Exploring Trends in Metal-Metal Bonding, Spectroscopic Properties, and Conformational Flexibility in a Series of Heterobimetallic Ti/M and V/M Complexes (M = Fe, Co, Ni, and Cu).

To understand the metal-metal bonding and conformational flexibility of first-row transition metal heterobimetallic complexes, a series of heterobimetallic Ti/M and V/M complexes (M = Fe, Co, Ni, and Cu) have been investigated. The titanium tris(phosphinoamide) precursors ClTi(XylNPPr) (1) and Ti(XylNPPr) (2) have been used to synthesize Ti/Fe (3), Ti/Ni (4, 4), and Ti/Cu (5) heterobimetallic complexes. A series of V/M (M = Fe (7), Co (8), Ni (9), and Cu (10)) complexes have been generated starting from the vanadium tris(phosphinoamide) precursor V(XylNPPr) (6).

Multi-electron redox processes at a Zr(iv) center facilitated by an appended redox-active cobalt-containing metalloligand.

The reactivity of a reduced heterobimetallic Co(-I)/Zr(IV) complex, ((t)BuNC)Co((i)Pr2PNMes)3Zr(THF) (), with a series of azido and diazo reagents is explored to demonstrate the feasibility of facilitating two-electron redox processes at a formally d(0) Zr(iv) center using the appended Co fragment exclusively as an electron-reservoir. Addition of mesityl or adamantyl azide to affords the terminal ((t)BuNC)Co((i)Pr2PNMes)3Zr[triple bond, length as m-dash]NMes () and bridging ((t)BuNC)Co((i)Pr2PNMes)2(μ-NAd)Zr((i)Pr2PNMes) () Co(I)/Zr(IV) imido products, respectively. Similarly, diphenyldiazomethane reacts with to afford the terminal Ph2CN2(2-)-bound product ((t)BuNC)Co((i)Pr2PNMes)3Zr[triple bond, length as m-dash]N-N[double bond, length as m-dash]CPh2 () via a two-electron oxidation of the Co center.

Heterobimetallic Ti/Co Complexes That Promote Catalytic N-N Bond Cleavage.

Treatment of the tris(phosphinoamide) titanium precursor ClTi(XylNP(i)Pr2)3 (1) with CoI2 leads to the heterobimetallic complex (η(2)-(i)Pr2PNXyl)Ti(XylNP(i)Pr2)2(μ-Cl)CoI (2). One-electron reduction of 2 affords (η(2)-(i)Pr2PNXyl)Ti(XylNP(i)Pr2)2CoI (3), which can be reduced by another electron under dinitrogen to generate the reduced diamagnetic complex (THF)Ti(XylNP(i)Pr2)3CoN2 (4). The removal of the dinitrogen ligand from 4 under vacuum affords (THF)Ti(XylNP(i)Pr2)3Co (5), which features a Ti-Co triple bond.

N-heterocyclic phosphenium and phosphido nickel complexes supported by a pincer ligand framework.

A chelating diphosphine ligand with a central N-heterocyclic phosphenium cation (NHP(+)) has been used to explore the coordination chemistry of NHPs with nickel. Treatment of the chlorophosphine precursor [PPP]Cl (1) with stoichiometric Ni(COD)2 affords (PPP)NiCl (8), which is best described as a Ni(II)/NHP(-) phosphido complex formed via oxidative addition of the P-Cl bond. In contrast, treating [PPP]Cl (1) with excess Ni(COD)2 results in a mixture of the trimetallic complex (PPP)2Ni3Cl2 (9) and the reduced NHP-bridged dimer [(PPP)Ni]2 (10).

Use of a Bidentate Ligand Featuring an N-Heterocyclic Phosphenium Cation (NHP(+)) to Systematically Explore the Bonding of NHP(+) Ligands with Nickel.

A novel bidentate ligand featuring an N-heterocyclic phosphenium cation (NHP(+)) linked to a phosphine side arm is used to explore the coordination chemistry of NHP(+) ligands with nickel. Direct P-Cl bond cleavage from a chlorophosphine precursor [PP]-Cl (1) by Ni(COD)2 affords the asymmetric bimetallic complex [Cl2Ni(μ-PP)2Ni] (2) via a nonoxidative process. Abstraction of the halide with either NaBPh4 or K[B(C6F5)4] prior to metal coordination to form the free phosphenium ligand [PP](+) in situ, followed by coordination to Ni(COD)2, afforded the halide-free Ni(0) complexes [(PP)Ni(COD)] [B(C6F5)4] (4) and [(PP)Ni(COD)][BPh4] (5).

Triflyloxy-substituted carboranes as useful weakly coordinating anions.

New carborane anions carrying one or three triflyloxy substituents are described. The mono-triflyloxy substituted carborane can be halogenated to give pentabromo and decachloro derivatives with preservation of the B-OTf linkage. The use of [HCB11Cl10OTf](-) as a weakly coordinating anion is demonstrated.

A heterobimetallic complex featuring a Ti-Co multiple bond and its application to the reductive coupling of ketones to alkenes.

To explore metal-metal multiple bonds between first row transition metals, Ti/Co complexes supported by two phosphinoamide ligands have been synthesized and characterized. The Ti metalloligand ClTi(XylNPPr) () was treated with CoI under reducing conditions, permitting isolation of the Ti/Co complex [(μ-Cl)Ti(XylNPPr)CoI] (). One electron reduction of complex affords ClTi(XylNPPr)CoPMe (), which features a metal-metal triple bond and an unprecedentedly short Ti-Co distance of 2.

Comparison of the electronic properties of diarylamido-based PNZ pincer ligands: redox activity at the ligand and donor ability toward the metal.

This paper presents the synthesis and characterization of a series of pincer ligands and their Ni, Pd, Pt, and Rh complexes. The ligands under examination are based on a diarylamine which is modified either by two phosphino (-PR2) substituents in the ortho-positions (PNP ligands) or by a combination of a phosphino and an iminyl (-CH═NX) substituent (PNN ligands). The ligands can be broken down into three groups: (a) C2v-symmetric PNP ligands with identical side -PR2 donors, (b) Cs-symmetric PNP' ligands with different -PR2 side donors, and (c) PNN ligands containing a -P(i)Pr2 side donor.

Fitting the pieces of the puzzle: the δ bond.

The development of our understanding of the δ bond and its role in quadruple metal-metal bonding is described in terms of the conceptual advances and experimental and theoretical results achieved through a 50-year period beginning with the seminal report by Cotton and co-workers in 1964. The work behind the original discovery is described, along with the qualitative orbital description of the components of the quadruple bond. The effect of torsion about the metal-metal axis on the metal-metal bond length is described, together with the conclusion that this accords with a progressive loss of the δ component of the metal-metal bond.

Formation of heterobimetallic zirconium/cobalt diimido complexes via a four-electron transformation.

The reactivity of the reduced heterobimetallic complex Zr((i)PrNP(i)Pr2)3CoN2 (1) toward aryl azides was examined, revealing a four-electron redox transformation to afford unusual heterobimetallic zirconium/cobalt diimido complexes. In the case of p-tolyl azide, the diamagnetic C3-symmetric bis(terminal imido) complex 3 is formed, but mesityl azide instead leads to asymmetric complex 4 featuring a bridging imido fragment.