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Treatment of Mes*P=C(Si(CH3)3)Br with CH2=CHMgBr in the presence of Pd(0) affords 1-phosphabutadiene Mes*P=C(Si(CH3)3)–CH=CH2 (1) selectively as the Z isomer. Remarkably, treatment of Z-1 with n-BuLi (0.1 equiv.) resulted in quantitative formation of E-1. The exact role of the n-BuLi is unknown; however, it appears to be required to promote the isomerization in the absence of light. The isomerization of Z-1 to E-1 was also mediated by sunlight with the reaction mixture consisting of a ca. 1:9 ratio of Z-1 to E-1. DFT calculations were consistent with the thermodynamic favorability of the isomerization of Z-1 to E-1.

Syntheses are reported for: nine 2-nitroimidazoles, the abbreviated names all beginning with E, based on derivation from Etanidazole); five 2-methyl-5-nitroimidazoles (M compounds, derived from Metronidazole); and five 2-methyl-4-nitroimidazoles (labelled 2M4N compounds). The nitroimidazoles all have an amide side-chain at the N1 atom of the imidazole, with 17 of them containing one to five halogen atoms. The aim is to study compounds for comparison with EF5 (the number showing the presence of five F-atoms), a previously reported, pentafluoropropylacetamide derivative of 2-nitroimidazole that is currently used as a hypoxia marker drug to detect cancerous tumours. The new compounds are characterized by standard methods, including X-ray structural data for the fluorinated MF5, 2M4NF5, and 2M4NF1(−1) species, with the “–1” indicating two C-atoms in an alkylamide chain rather than the three C-atoms in the propylacetamide of EF5. Intra- and inter-molecular H-bonding is seen in the solid state structures, likely an important property in biological use; another key property of the nitroimidazoles is their reduction potentials, and the measured CV data confirm that 2NO2Im compounds with longer side-chains and more F-atoms (like EF5) are worth investigating for possible activity as hypoxia-selective, bioreductive agents.

The Lewis acceptor chemistry of Me3SiOTf with p-block Lewis bases has been explored and a library of complexes has been characterized by spectroscopic and, where possible, crystallographic methods. Compounds with the generic formula [Me3Si(L)][OTf] (L = 4-dmap, pyr, imz, OPMe3, OPCy3, OPPh3, OpyrMe, dmso, PMe3) were isolated from 1:1 mixtures of Me3SiOTf and the respective ligand in CH2Cl2. Characterization by NMR spectroscopy confirmed the solution stability of all but [Me3Si(PMe3)][OTf], with indications that the latter dissociates into PMe3 and Me3SiOTf. Solid-state structures of [Me3Si(4-dmap)][OTf], [Me3Si(pyr)][OTf], [Me3Si(OPCy3)][OTf], [Me3Si(OPPh3)][OTf], [Me3Si(OpyrMe)][OTf], and [Me3Si(PMe3)][OTf] were elucidated by single crystal X-ray diffraction, confirming the envisaged ionic formulations resulting from the displacement of the OTf anion from the silicon center of Me3SiOTf by the incoming ligand. Mixtures of Me3SiOTf with other related donors, including ChPPh3 (Ch = S or Se), NEt3, SMe2, PPh3, 2,2′-bipy, or Me2CO, show no evidence of reaction under ambient conditions, reflecting the lower basicity and (or) greater steric encumbrance of these ligands. Reactions of Me3SiOTf with bis-donor ligands yielded complexes of the generic formulae [Me3Si(L–L)SiMe3][OTf]2 (L–L = 4,4′-bipy, tmeda, dmpe) and [Me3Si(L–L)][OTf] (L–L = 4,4′-bipy, tmeda, dmpe). The tmeda and dmpe complexes, however, were found to dissociate in solution, with complexes only prevailing in the solid phase. X-ray diffraction studies of [Me3Si(4,4′-bipy)SiMe3][OTf]2 and [Me3Si(dmpe)SiMe3][OTf]2 confirmed the expected connectivities and ionic formulations, with Si–ligand bond lengths comparable to those observed in [Me3Si(pyr)][OTf] and [Me3Si(PMe3)][OTf], respectively.

A series of titanium and zirconium bis(amidate) complexes of the type L2MX2, where L is an amidate ligand, and X is either –NMe2 or –Cl, were prepared in 60%–83% yield and fully characterized. Multiple binding motifs are observed as the amidate ligand can bind in κ1- and κ2-modes. These complexes were then subjected to screening the catalytic polymerization of ethylene. All catalysts, after reaction with suitable co-catalyst, were functional for ethylene polymerization, though not for the copolymerization of ethylene and longer linear 1-alkenes. Polyethylene was formed in the range of 1000–4000 kDa, and with PDI values as low as 1.3. These long polymeric chains are considered as ultra-high molecular weight polyethylene (UHMWPE).

Three series of phosphine chalcogenide complexes of the antimony(III) halides SbX3 (X = F, Cl, Br, or I) have been synthesized and characterized by spectroscopic and crystallographic methods. Complexes of the generic formulae (Cy3PO)SbX3 (X = F (1a), Cl (1b), or Br (1c)), (Cy3PO)2SbX3 (X = F (2a), Cl (2b), or Br (2c)), and (Cy3PS)SbX3 (X = Cl (3b), Br (3c), or I (3d)) were synthesized via the treatment of solutions of SbX3 with OPCy3 and SPCy3, respectively. Derivatives of (Cy3PO)SbX3 were characterized by single crystal X-ray diffraction for 1a and 1b and crystallize as dimers through symmetry related intermolecular Sb–X interactions, providing the first structurally characterized examples of this class of complex. Derivatives of (Cy3PS)SbX3 (3b–3c) adopt analogous dimeric structures in the solid state. The solid-state structure of (Cy3PO)2SbCl3 (2b) is consistent with the previously reported structures of bis-phosphine oxide complexes of antimony(III), with a square pyramidal Sb center and cis-configured OPCy3 ligands. The phosphine chalcogenide complexes of SbX3 display configurations that are consistent with the perceived trans-labilizing properties of the ligands/substituents.

Reactions of [RhCl(COE)(IPr)]2 (1) and [RhCl(COE)(IMes)]2 (2) (COE = cyclooctene; IPr = N,N′-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene; IMes = N,N′-bis(2,4,6-trimethylphenyl)imidazolin-2-ylidene) with the diphosphines Ph2P(CH2)nPPh2 and 1,2-bis(diphenylphosphino)benzene (dppbz) give the N-heterocyclic carbene (NHC) – diphosphine – rhodium(I) complexes: RhCl(NHC)[Ph2P(CH2)nPPh2] [NHC = IPr, n = 1 (3); NHC = IMes, n = 1 (4); NHC = IPr, n = 2 (5); NHC = IMes, n = 2 (6); NHC = IPr, n = 4 (7); NHC = IMes, n = 4 (8)] and RhCl(NHC)(dppbz) [NHC = IPr (9); NHC = IMes (10)]. All the complexes are characterized by 1H, 31P{1H}, and 13C{1H} NMR spectroscopy, elemental analysis, and mass spectrometry. Complexes 3, 7, and 9 are also characterized crystallographically. In benzene solution, the complexes decompose in the presence of O2 with formation of the diphosphine dioxide, whereas reaction with CO leads to replacement of the NHC ligand to give known carbonyl–diphosphine complexes.

Oxidation of 2,5-bis(diphenylphosphino)-1,4-hydroquinone (8) with iodobenzene diacetate produces the corresponding bis(phosphine) substituted benzoquinone (9), the first phosphine-substitued quinone. Cyclic voltammetry studies reveal that the redox functionality of the quinone unit in 9 is retained, and the reduction potentials render this compound slightly more easily reduced than the parent p-benzoquinone. Reaction of the precursor hydroquinone 8 with Pd(hfac)2 affords a binuclear complex 10 with the hydroquinonate ligand bridging two Pd(hfac) substrates. The redox activity of the bridging dioxolene ligand is retained in complex 10, although there are significant changes in the redox potentials relative to those of the free quinone 9. Chemical oxidation of 10 with AgPF6 yields a persistent cationic complex 11, which, based on EPR and electronic spectroscopy, can be formulated as containing a bridging semiquinone ligand.Key words: p-quinones, phosphines, bridging ligands, redox properties.

A new family of rhodium-diene based complexes has been developed that incorporates an N-heterocyclic carbene ligand with an N-donor tether. The ligand is denoted Mes[CNH] 2 (where Mes[CNH] is 2,4,6-Me3C6H2NC3H2NCH2CH2NH-2,4,6-Me3C6H2) and Mes[CN] for the amido form. The synthesis of the Mes[CNH] ligand involves reaction of N-mesitylimidazole with 2-chloroethyl-N-mesitylamine under melt conditions, followed by deprotonation with KN(SiMe3)2. The reaction of Mes[CNH] with [(diene)RhCl]2 results in the formation of the monodentate complexes, Mes[CNH]Rh(diene)Cl (where diene = 1,5-cyclooctadiene (COD): 3a; diene = 2,5-norbornadiene (NBD): 3b). Bidentate variants could be isolated as either a neutral species, Mes[CN]Rh(diene) 4a–4b, via deprotonation, or an ionic analogue such as [Mes[CNH]Rh(diene)]BF4 5a–5b by reaction with NaBF4. Compounds 4–5 are the first examples of rhodium compounds that contained a bidentate NHC ligand with a pendant amino or amido donor. Complexes 3–5 were characterized fully and the solid-state single crystal X-ray structures of 3a, 4a, and 5b are discussed. The utility of these complexes as catalyst precursors for hydrogenation reactions was examined and it was determined that these systems are not significantly more active than colloidal rhodium when parallel reactions were run. Various methods of transfer hydrogenations were also investigated with 3a, which did not yield an appreciable conversion of either benzophenone or N-benzylideneaniline as substrates.Key words: rhodium, N-heterocyclic carbene, catalysis, hydrogenation.

Reactions of cis,trans,cis-[Ir(H)2(PPh3)2(solv)2]PF6 (solv = MeOH or Me2CO) with the imines HN=CPh2, (o-HOC6H4)C(Me)=NCH2Ph, and PhC(H)=N(p-F-C6H4) in MeOH or acetone under Ar give the complexes [IrH{NH=C(Ph)(o-C6H4)}(NH=CPh2)(PPh3)2]PF6 (3), [IrH{PhCH2N=C(Me)(o-C6H3OH)}(solv)(PPh3)2]PF6, where solv = MeOH (4) or Me2CO (4a), and [IrH{N(p-F-C6H4)=CH(o-C6H4)}(Me2CO)(PPh3)2]PF6 (5a), which have been isolated and characterized. The imine (C6F5)C(H)=NPh is unreactive toward the Ir precursors. The X-ray structures of 3, 4·2MeOH, and 5a·1/2Me2CO show an η2-N,C-imine moiety coordinated via the N atom and an orthometallated-C atom. Complex 3, which contains both an orthometallated imine and an η1-imine, is the first structurally characterized hydrido-(η1-imine)-Ir complex. Comparisons are made with data for the corresponding Rh systems.Key words: iridium, hydride complexes, imines, fluoroimines, phosphine complexes, orthometallation, crystallography, NMR spectroscopy.

Diastereoselective syntheses of the unusual dimers, 4-heptyl-2-(2′-hydroxy-binaphthyl)hydrogen phosphonate (5) and the cyclohexyl analogue (7), are achieved by hydrolysis of 4-(3,5-dioxa-4-phosphacyclohepta[2,1-α;3,4-α′]-dinaphthalene-4-yloxy)heptane (4) and the cyclohexane analogue (6), respectively. Two out of eight possible pairs of monomers units are involved in the stereoselective formation of the dimer 5a of configuration BINOLR-PS:BINOLR-PS; this is determined by X-ray crystallographic data, which reveal a centrosymmetric, 18-membered ring structure with Ci symmetry, consisting of two monomers strongly hydrogen-bonded between the oxygen of P=O units and hydroxyl hydrogen atoms. Mass spectrometric, melting point, and thermal decomposition point data, as well as NMR data, support the presence of strong, quasi-covalent hydrogen bonds. Computational analysis suggests that the diastereoselectivity is controlled by molecularly constrained geometry of the monomer. Compound 7, although not characterized crystallographically, appears to be analogous to 5.Key words: 18-membered ring, phosphonate dimer, diastereoselectivity, hydrogen-bonds, computational analysis.

A series of Pt(II) and Pd(II) complexes containing diphenylphosphino-substituted oligothiophene ligands ranging from 1 to 3 thiophene rings in length have been prepared. Crystal structures of four of these complexes were determined via single X-ray crystal diffraction and the solid-state packing arrangements found to vary with both the metal and the thiophene-containing ligand. In some cases, π-stacking between thiophene rings are found for the oligothiophene ligands. Solution and solid-state absorption spectra of these complexes are reported.Key words: oligothiophenes, metal complexes, structural properties, electronic spectra.

Oxidative addition of H2S to MoRu(CO)6(µ-dppm)2 (1) at ~20 °C in toluene yields an isolable complex formulated as Mo(CO)3(µ-SH)(µ-CO)(µ-dppm)2RuH(CO) (2) via the possible intermediate Mo(CO)3(µ-H)(µ-CO)(µ-dppm)2Ru(SH)(CO) (4) (dppm = Ph2PCH2PPh2) that is detectable at lower temperatures. Over 2 days, species 2 in toluene loses H2 (and CO) to yield the bridged-sulfide product, Mo(CO)2(µ-CO)(µ-S)(µ-dppm)2Ru(CO) (5) that is also formed directly from the reaction of 1 with elemental sulfur. The solid-state molecular structure of 5 is determined by X-ray crystallography. A further hydrido-sulfhydryl species, possibly Mo(CO)3(µ-SH)(µ-H)(µ-dppm)2Ru(CO)2 (3), is in equilibrium with 2 at ambient temperature.Key words: molybdenum, ruthenium, bis(diphenylphosphino)methane, hydrogen sulfide, hydrido-sulfhydryl species, carbonyl complexes, bridged-sulfide complex.

Perfluorinated 9-phenyl-9-borafluorene, 1, is an antiaromatic analog of the well-known tris(pentafluorophenyl)borane. Spectroscopic, structural, and electrochemical studies have been performed on 1 and its Lewis base adducts with MeCN, THF, and PMe3 with a view to assessing its comparative Lewis acid strength relative to B(C6F5)3. For the sterically undemanding Lewis base MeCN, 1 and B(C6F5)3 have comparable LA strengths, while for more sterically prominent THF, 1 is clearly the stronger Lewis acid (LA) based on competition experiments. We conclude that steric factors, rather than antiaromaticity, are the most important determinants in the LA strength differences between 1 and B(C6F5)3.Key words: boranes, Lewis acids, fluorinated compounds, heterocycles.

A photo and thermally stable bis(amidate)–dibenzyl complex of Hf ([DMP(NO)Ph]2Hf(CH2Ph)2(THF) (2a) was formed as a monosolvated THF adduct in near quantitative yield from Hf(CH2Ph)4 and N-2,6-dimethylphenyl(phenyl)amide (1). Isomerization between the THF-bound product and the THF-free product can be observed visually by the conversion from a red-orange product at low temperatures to a pale yellow product at high temperatures. Solid-state crystallographic characterization of the orange product confirmed its constitution as a monosolvated species. Kinetic parameters for the exchange of the THF moiety were determined from variable-temperature NMR experiments. The product of the hydrolysis of the Hf dibenzyl species by water was characterized by X-ray crystallography, and was found to be a rare tetrametallic Hf oxo cluster species (3).Key words: hafnium, protonolysis, amidate, coordination chemistry, organometallic chemistry, exchange processes.

The reaction of the side-on, end-on ditantalum dinitrogen complex ([NPN]Ta)2(µ-η1:η2-N2)(µ-H)2 (where NPN = PhP(CH2SiMe2NPh)2) with a variety of secondary and primary boranes is reported. With 9-BBN, hydroboration of the Ta2N2 unit occurs via B-H addition, which in turn triggers a cascade of reactions that result in N—N bond cleavage, ancillary ligand rearrangement involving silicon group migration, and finally elimination of benzene from the N-Ph group and a B-H moiety to generate the imide–nitride derivative. In the presence of excess 9-BBN, the Lewis acid – base adduct of the imide–nitride ([NPµ–N]Ta(=NBC8H14)(µ-NB(H)C8H14)Ta[NPN]) is formed. A similar set of reactions is observed for dicyclohexylborane (Cy2BH), which hydroborates the dinitrogen complex to generate [NPN]Ta(H)(µ-η1:η2-NNBCy2)(µ-H)2Ta[NPN], followed by loss of H2 and silicon group migration to yield the imide–nitride [NPµ–N]Ta(=NBCy2)(µ-N)(Ta[NPN]. With thexyl borane (H2BCMe2CHMe2), a similar sequence of reactions is suggested starting with hydroboration to generate [NPN]Ta(H)(µ-η1:η2-NNB(H)C6H13)(µ-H)2Ta[NPN], followed by loss of H2 and ancillary ligand rearrangement. When bis(pentafluorophenyl)borane (HB(C6F5)2) is used, no hydroboration of coordinated N2 is observed, rather simple adduct formation to give ([NPN]Ta)2(µ-η1:η2-NN-B(H)(C6F5)2)(µ-H)2 occurs. Key words: dinitrogen, tantalum, hydroboration, N—N bond cleavage.

The thermal decarboxylation of 2-methoxycarbonyl-5-(4′-nitrophen-oxy)tetrazole (1a) with the electron-rich, aromatic compounds (anisole, N,N-dimethylaniline, 1,4-dimethoxybenzene, and 1,3,5-trimethoxybenzene), neat or in polar solvents (DMSO, DMF, and CH3CN), is investigated. The solid phase thermal decomposition of a mixture of 1a, 1,3,5-trimethoxybenzene, and a Lewis acid (AlCl3) produces methyl-2,4-dimethoxysalicylate (8) in good yield, instead of the expected 2,4,6-trimethoxybenzoic acid. The X-ray structure of 8 shows intramolecular hydrogen bonds between the carbonyl oxygen and hydrogens of Me and OH groups. A measured pKa value of 6.8 compares well with a value of 6.4 estimated using the [C=O···H···O] hydrogen bond distances.Key words: anti–tumor, novel synthesis, X-ray structure, hydrogen bonds, computational analysis.

The monomeric trinitrosyl complex, W(NO)3Cl3, can be prepared by the treatment of WCl6 in CH2Cl2 with NO gas, and its identity has been unambiguously confirmed by a single-crystal X-ray diffraction analysis. The complex crystallizes in the space group Pmn21 as a three-component twin (a = 10.4280(4) Å, b = 6.3289(2) Å, c = 5.6854(2) Å, Z = 2, R1 = 0.065, wR2 = 0.176). Its solid-state molecular structure consists of a tungsten centre bound to three chloride ligands and three linear nitrosyl ligands in a fac-octahedral stereochemistry. In addition, the structure contains a crystallographically imposed mirror plane. The two independent W—N linkages are 1.88(2) and 1.92(1) Å long, while the two corresponding N—O bond lengths are 1.13(2) and 1.16(2) Å. DFT calculations on fac-W(NO)3Cl3 at the B3LYP/LANL2DZ level of theory afford optimized intramolecular metrical parameters that match the X-ray crystallographically determined bond lengths and bond angles quite well. In addition, they provide a rationale for the nearly linear W-N-O linkages extant in the complex. Solutions of fac-W(NO)3Cl3 in CH2Cl2 lose ClNO under ambient conditions and deposit the well-known [W(NO)2Cl2]n polymer, and this conversion is fully reversible.Key words: nitrosyl, tungsten, structure, bonding.

When crystals of 9-tricyclo[4.4.1.0]undecalyl-4-(carbomethoxy)phenyl ketone (1) were allowed to stand in the dark for extended periods of time at room temperature, the compound underwent a thermal reaction — the enolene rearrangement — to afford enol 2. The crystals remained transparent and appeared unchanged in shape as the reaction proceeded. X-ray diffraction data were collected on single crystals containing 17%, 25%, 66%, and 100% of the enol. The crystal structure of a simple enol was obtained via this novel single-crystal-to-single-crystal enolene rearrangement.Key words: single crystal, thermal, rearrangement, enol, enolene.

The tridentate ligand precursors R′P(CH2SiMe2NR′′)2 (R′R′′[NPN]: R′ = Cy, Ph; R′′ = Ph, Mes, Me) were prepared from metathesis reactions of a lithiated amine, chloro(chloromethyl)dimethylsilane, the appropriate 1° phosphine, and n-butyl lithium and were isolated as solvent adducts. Metathesis between CyPh[NPN]Li2(OEt2), 2, and VCl3(THF)3 afforded (CyPh[NPN]VCl)2, 7, whose solid-state structure was established by X-ray crystallography. Reduction attempts of the (R′R′′[NPN]VCl)2 species with KC8 incorporated molecular nitrogen but were complicated by imide formation and ligand decomposition. Metathesis of 2 with NbCl2Me3 afforded the highly unstable complex CyPh[NPN]NbMe3, 15. Attempts to hydrogenate this species were unsuccessful.Key words: vanadium, niobium, metathesis, coordination chemistry, reduction, hydrogenation.

The synthesis and complete characterization of the family of tetra(amine)bisphosphine ligands (o-NMe2C6H4)2P-(X)-P(o-NMe2C6H4)2, where X = CH2 (dmapm), (CH2)2 (dmape), and [Formula: see text] (dmapcp), are described. Crystal structure data are compared with known, analogous bisphosphines containing o-pyridyl or phenyl substituents in place of the o-dimethylanilinyl groups. Several short, intramolecular C-H···N distances in the anilinyl derivatives may represent the presence of weak hydrogen bonds. Key words: phosphine, amine, polydentate, hydrogen-bonding to N atoms.

The phenolic OH moiety in lignin is one of the key functional groups responsible for the photo-induced yellowing of mechanical wood pulps and papers. To evaluate new protective groups for the stabilization of lignin phenols, the model compounds, 2-methoxy-4-propylphenol (1) and 4-hydroxy-3-methoxyacetophenone (2) were reacted with 5-chloro-1-phenyl-1H-tetrazole to give the corresponding tetrazole ethers 1' and 2', respectively, that were then studied for their photostability. The synthesis of these ethers was more efficient than that of alkyl ethers because of less hydrolysis of the alkylating agent under the reaction conditions. Compounds 1' and 2' were fully characterized, including X-ray crystal structure analyses. Crystals of 1' and 2' were monoclinic of space groups P21/c and P21/a, respectively. For 1': a = 9.8679(6), b = 16.708(1), c = 10.2841(6) Å, β = 109.732(5)°, Z = 4. For 2': a = 7.7212(2), b = 27.350(5), c = 14.569(3) Å, β = 101.30(2)°, Z = 8. The structures were solved by direct methods and refined by full-matrix least-squares procedures to R = 0.039 (Rw = 0.046) for 2029 reflections with I [Formula: see text] 3σ(I) (for 1'), and to R = 0.055 (Rw = 0.073) for 3634 reflections with I [Formula: see text] 3σ(I) (for 2'). Compound 2' was much more photostable than the precursor phenol on exposure to strong fluorescent light, while 1' was only slightly more stable than the precursor phenol.Key words: alkylation, ethers, lignin model compounds, methylation, phenols, yellowing inhibition.

The reaction of the dilithiodiamidophosphine ligand precursor PhP(CH2SiMe2NPh)2Li2(THF)2([NPN]Li2(THF)2) with LnCl3(THF)3 (Ln = Y, Sm, Ho, Yb, Lu; THF = tetrahydrofuran) in refluxing toluene generates the mononuclear complexes [NPN]LnCl(THF) in good yield. The molecular structures have been shown to be five-coordinate in the solid state and in solution. Attempts to prepare alkyl derivatives have only met with partial success; the reaction of MeMgCl with [NPN]YCl(THF) generates the partially characterized mixed-metal derivative [NPN]YMe2MgCl. The reaction with LiAlH4 results in complete ligand exchange and the formation of the tetranuclear lithium aluminum hydride derivative {[NPN]AlH2Li(THF)}2. Reduction of the lutetium derivative with KC8 and naphthalene generated the dinuclear naphthalene-bridged species {[NPN]Lu}2(µ-η4:η4-C10H8) wherein each Lu centre engages in η4-coordination to opposite sides of the arene moiety. X-ray crystallography was used to characterize the four complexes.Key words: lanthanides, yttrium, mixed-donor ligands, aluminum, lithium, naphthalene.

Second-harmonic generation in the solid state is restricted to materials that crystallize in non-centrosymmetric space groups. Unfortunately, the vast majority of solids crystallize in centrosymmetric space groups and are therefore SHG-inactive. The requirement for solid-state asymmetry is addressed in a new series of organic salts. The acid p-nitrophenylglycine, SHG-inactive due to its centrosymmetric (P1) packing, was coupled to six optically pure amines to form salts and (or) complexes that, by virtue of their chiral counterion, crystallized in non-centrosymmetric space groups. The 1064 nm output from a Nd:YAG laser produced 532 nm second-harmonic generation from each of the six salts, with three of the salts producing second-harmonic intensities at least an order of magnitude greater than that of our standard, urea. X-ray crystallographic analysis was carried out on five of the six salts, and an attempt was made to rationalize the second-harmonic intensity of each of these five salts based on the orientation of its molecular charge-transfer axis in the unit cell and on its chromophore density.Key words: second-harmonic generation, nonlinear optics, chiral organic salts, crystal structures.

The reaction of CrCl3 with three equivalents of the lithium salt of [R-(R*,R*)]-(+)-bis(α-methylbenzyl)amine produces the trigonal planar Cr(III) tris(amido) complex. The X-ray structure of Cr[N{CH(Me)Ph}2]3 is reported.Key words: chromium, X-ray crystal structure, amido ligands, chiral ligands.