Imide Complexes Research Articles

Sc[N(SO 2C 8F 17) 2] 3 catalyzed condensation of β-naphthol and aldehydes in fluorous solvent: One-pot synthesis of 14-substituted-14 H-dibenzo[ a, j]xanthenes

A facile synthesis of 14-substituted-14 H-dibenzo[ a, j]xanthenes was proposed by one-pot condensation of β-naphthol with aryl or alkyl aldehydes by using Scandium bis(perfluorooctanesulfonyl)imide complex as catalyst and perfluorodecalin as sole solvent.

Synthesis, Structural Characterization, and Quantitative Basicity Studies of Lithium Zirconimidate Complexes

Synthesis, Structural Characterization, and Quantitative Basicity Studies of Lithium Zirconimidate Complexes

Dinitrogen Cleavage by a Diniobium Tetrahydride Complex: Formation of a Nitride and Its Conversion into Imide Species

Breaking up isn't hard to do: When a solution of the hydride complex [K(dme)]2[{Nb}2(μ-H)4] (see scheme) is exposed to N2, the nitride complex [K(thf)2]2[{Nb}2(μ-N)2] and H2 form with concomitant cleavage of the dinitrogen triple bond. The nitride ligands undergo alkylation with MeI in a stepwise fashion, resulting in formation of a bis(imide) complex via a nitride imide complex.

Synthesis, Structure, and Computational Studies of the Tetrameric Magnesium Imides [2,4,6-Cl3C6H2NMg·S]4 (S = 1,4-Dioxane and Tetrahydrofuran)

The magnesium imide complexes [(ArNMg.diox)4.3(diox)] (4) and [(ArNMg.THF)4.tol] (5) (where Ar=2,4,6-Cl3C6H2, diox=1,4-dioxane, and THF=tetrahydrofuran) were prepared by the equimolar reaction of Bu2Mg with the primary amine in suitable solvent mixtures. The successful synthesis of the halide-substituted imides is notable because similar reactions with the less acidic organo-substituted anilines cease upon monodeprotonation. Both 4 and 5 form unusual Mg4N4 cubane aggregates in the solid state. Computational studies (HF/6-31G*) indicate that a combination of sterics and metal solvation determines the aggregation state adopted.

Electrochemical investigation of polymer electrolytes based on lithium 2-(phenylsulfanyl)-1,1,2,2-tetrafluoro-ethansulfonate

The salt PhSCF 2CF 2SO 3Li appears promising for lithium-polymer batteries. Its poly(oxyethylene) complexes, although less conductive than lithium imide complexes, provided cationic transference numbers ranging between 0.45 and 0.5, enabling high cationic conductivities to be obtained. Thanks to its double substitution by aryl and perfluorinated moieties, the thioether function is stable enough to be used with positive electrodes, such as vanadium oxide and perhaps cobalt oxide.

Poly(oxyethylene) electrolytes based on lithium pentafluorobenzene sulfonate

Lithium pentafluorobenzene sulfonate was synthesized by a protocol whereby pollution by aromatic nucleophilic substitutions on the perfluorinated ring was avoided. Its poly(oxyethylene) complexes, although less conductive than lithium imide complexes, provided cationic transference numbers higher than 0.5. Surprisingly, even at fairly low concentrations, this salt markedly increased the mechanical properties of the polymer electrolyte. This effect was attributed to telechelic interactions of the ion pairs with distinct polyether chains and is in agreement with the high cationic transference numbers.

Homoleptic Alkaline Earth Metal Bis(trifluoromethanesulfonyl)imide Complex Compounds Obtained from an Ionic Liquid

The first homoleptic alkaline earth bis(trifluoromethanesulfonyl)imide (Tf2N) complexes [mppyr]2[Ca(Tf2N)4], [mppyr]2[Sr(Tf2N)4], and [mppyr][Ba(Tf2N)3] were crystallized from a solution of the respective alkaline earth bis(trifluoromethanesulfonyl)imide and the ionic liquid [mppyr][Tf2N] (mppyr = 1,1-N-methyl-N-propylpyrrolidinium). In the calcium and strontium compounds, the alkaline earth metal (AE) is coordinated by four bidentately chelating Tf2N ligands to form isolated (distorted) square antiprismatic [AE(Tf2N)4]2- complexes which are separated by N-methyl-N-propylpyrrolidinium cations. In contrast, the barium compound, [mppyr][Ba(Tf2N)3], forms an extended structure. Here the alkaline earth cation is surrounded by six oxygen atoms belonging to three Tf2N- anions which coordinate in a bidentate chelating fashion. Three further oxygen atoms of the same ligands are linking the Ba2+ cations to infinite (infinity)(1)[Ba(Tf2N)3] chains.

Lithium ion conductive polymer electrolyte by side group rotation

Ionic conductive materials are of much interest as an electrolyte for solid-state lithium batteries. Poly(alkylene oxide) and lithium salt complex exhibits high ionic conductivity in terms of its high solubility for lithium salts. However, the temperature dependency of its ionic conductivity is quite large and non-linear, the ionic conductivity drops down at low temperature, especially below glass transition temperature of the polymer. Because its ionic conductive mechanism is derived from its segmental motion of polymer main chain. A novel ionic conductive material, poly[2,6-dimethoxy- N-(4-vinylphenyl)benzamide] is synthesized and confirm ionic conductivity even below glass transition temperature. Ionic conductivity of the polymer with lithium ditrifluoromethylsulfonate imide complex shows 10 −5 S cm −1 from 0 to 60 °C. Its temperature dependency is linear, namely Arrehnius type dependency. Evaluating from these data, activation energy of ionic conductivity for temperature region from 20 to 60 °C is calculated as 31 kJ mol −1 and that for temperature region from −20 to 20 °C is 11 kJ mol −1. Judging from these results, we conclude that the ionic conductivity of the polymer salt complex derived from 2,6-dimethoxyphenyl group rotation, instead of segmental motion of the polymer.

Ground-State Singlet L3Fe-(μ-N)-FeL3 and L3Fe(NR) Complexes Featuring Pseudotetrahedral Fe(II) Centers

Pseudotetrahedral iron(II) coordination complexes that contain bridged nitride and terminal imide linkages, and exhibit singlet ground-state electronic configurations, are described. Sodium amalgam reduction of the ferromagnetically coupled dimer, {[PhBP(3)]Fe(mu-1,3-N(3))}(2) (2) ([PhBP(3)] = [PhB(CH(2)PPh(2))(3)](-)), yields the diamagnetic bridging nitride species [{[PhBP(3)]Fe}(2)(mu-N)][Na(THF)(5)] (3). The Fe-N-Fe linkage featured in the anion of 3 exhibits an unusually bent angle of approximately 135 degrees , and the short Fe-N bond distances (Fe-N(av) approximately equal to 1.70 A) suggest substantial Fe-N multiple bond character. The diamagnetic imide complex {[PhBP(3)]Fe(II)(triple bond)N(1-Ad)}{(n)()Bu(4)N} (4) has been prepared by sodium amalgam reduction of its low-spin iron(III) precursor, [PhBP(3)]Fe(III)(triple bond)N(1-Ad) (5). Complexes 4 and 5 have been structurally characterized, and their respective electronic structures are discussed in the context of a supporting DFT calculation. Diamagnetic 4 provides a bona fide example of a pseudotetrahedral iron(II) center in a low-spin ground-state configuration. Comparative optical data strongly suggest that dinuclear 3 is best described as containing two high-spin iron(II) centers that are strongly antiferromagnetically coupled to give rise to a singlet ground-state at room temperature.

Synthesis of a Vanadium(III) Tris(arylthiolato) Complex and Its Reactions with Azide and Azo Compounds: Formation of a Sulfenamide Complex via Cleavage of an Azo NN Bond

The tris(arylthiolate) vanadium(III) complex (1) has been synthesized in good yield. This complex is found to undergo CH activation across a V-S bond in the presence of TMEDA to give a cyclometalated species along with free arylthiol. Complex 1 behaves as a two-electron reductant toward Ad-N(3), yielding an imide complex. Treatment of 1 with azobenzene produces an imide-sulfenamide compound, in which an azo N=N bond cleavage takes place concomitant with formation of a V=N and an S-N bond.

New Rhenium(I) and Rhenium(II) Species Assembled by Stereospecific Azopyridine Chelation

AbstractThe spontaneous reaction of [ReO(OEt)I2(PPh3)2] with 2,2′‐azobipyridine (L) in acetonitrile, and of [ReOCl3(PPh3)2] with L in toluene, proceeds stereospecifically furnishing the green tris‐chelate [ReIL3]I (1) and the red bis‐chelate [ReIICl2L2] (2), respectively. A structure determination reveals that the coordination geometry of 1 is facial and that of 2 is cis(Cl,Cl)‐trans(Np,Np)‐cis(Na,Na) (Np is a pyridine nitrogen and Na is an azo nitrogen). The isomer preference is exclusive in both cases and no other isomer has been observed. The average N−N distance in both compounds is about 1.35 Å, signifying the presence of strong d(Re)‐π*(azo) back‐bonding which plays a crucial role in controlling isomer specificity. The bis‐chelate 2 is a one‐electron paramagnet and displays a six‐line EPR spectrum in fluid solution with g = 2.080 and A = 320 G. The 1H NMR spectrum of diamagnetic 1 is consistent with the facial geometry. In acetonitrile solution 1 displays an ReII/ReI couple and 2 an ReIII/ReII couple, the reduction potentials being 0.60 and 0.50V vs. SCE respectively. The violet‐coloured imide complex [ReVCl3(NC6H4Cl‐p)L] (3) is also reported; it displays an ReVI/ReV redox wave at 1.33 V vs. SCE. The stabilization of the lower rhenium oxidation states in 1 and 2 is consistent with the decrease of metal reduction potential with progressive L chelation. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

Neighbouring group participation reactions in nitrile- and amido-N-bonded pentaamminecobalt(III) complexes in which the unique ligand contains a remote amide group

The [(NH 3) 5CoNCCH 2CONH 2] 3+ ion hydrates in aqueous base to form [(NH 3) 5CoNHCOCH 2CONH 2] 2+ (33%) and a cobalt(II) species. The kinetics have been measured: k obsd=(( k OH+ Kk e − )[OH −])/(1+ K[OH −]) where K=7.9×10 3 (p K a=9.9), k OH=50 M −1 s −1 and k e − =1.4×10 −2 s −1 . In liquid ammonia the complex is unreactive while in aqueous acid it solvolyzes slowly. The [(NH 3) 5CoNCC 6H 42-CONH 2] 3+ complex cyclizes rapidly in aqueous base, liquid ammonia and dimethyl sulfoxide/Cs 2CO 3 to form only pentaammine(3-imino-1-oxo-isoindolino- exo- N)cobalt(III). The reaction also occurs in aqueous acid, with a spontaneous path identified: k obsd= k 0+ k 1/[H +], where k 0=1.1×10 −5 s −1 and k 1= k OH/ K w=4.3×10 −8 M s −1 (25 °C, I=1 M, LiClO 4), whence k OH=2.5×10 6 M −1 s −1. These data remove an anomaly in the literature. In Me 2SO, but not water, the reaction is acid catalyzed, a reaction pathway new in coordinated nitrile chemistry. The aliphatic analogue [(NH 3) 5CoNC(CH 2) 2CONH 2] 3+ also cyclizes in aqueous base to form pentaammine(5-imino-2-oxo-pyrrolidino- exo- N)cobalt(III) (90%), but here OH − addition to the bound nitrile is competitive, yielding [(NH 3) 5CoNHCO(CH 2) 2CONH 2] 2+ (10%). The kinetics of the reactions were measured: k obsd=[OH −]{ k OH+ Kk cyc}, [OH −]=(1–40)×10 −5 M, where k OH=40 M −1 s −1, approximately 10 4-fold slower than the o-phenylene analogue. The [(NH 3) 5CoNC(CH 2) 2CONH 2] 3+ ion solvolyzes slowly in aqueous acid, while in liquid ammonia it cyclizes, and only pentaammine(2-oxo-5-iminopyrrolidino- exo- N)cobalt(III) is formed. Amido-N-bonded pentaamminecobalt(III) complexes of malonamide, succinamide and glutaramide were synthesized from their free ligands. The malonamido- N and succinamido- N complexes react slowly in aqueous base and the products are the amido-N-bonded complexes of malonamic and succinamic acids. The intermediate imide complexes, one of which has been synthesized independently, were not detected. The glutaramido- N complex undergoes only slow solvolysis. Attempts to synthesize the phthalamido- N complex from the free ligand yielded only pentaammine (phthalimido- N)cobalt(III); the intermediate diamide complex cyclizes rapidly as soon as it is formed. In acid solution all diamide complexes are protonated on the coordinated amide and undergo slow rearrangement to their amide- O forms with parallel and subsequent solvolysis in both water and dimethylsulfoxide.

New Group 4 Metallocene and Niobocene Complexes Containing Phosphane-Functionalizedansa-Ligands

The asymmetric ansa-ligand precursors Me2Si(C5Me4H)(C5H4R) [R = CH2CH2PPh2 (1), PPh2 (2)] and their lithium derivatives Li2{Me2Si(C5Me4)(C5H3R)} [R = CH2CH2PPh2 (3), PPh2 (4)] have been prepared. The group 4 metal ansa complexes [M{Me2Si(η5-C5Me4)(η5-C5H3R)}Cl2] [M = Ti, R = CH2CH2PPh2 (5), PPh2 (6); M = Zr, R = CH2CH2PPh2 (7), PPh2 (8); M = Hf, R = CH2CH2PPh2 (9), PPh2 (10)] were obtained by the reaction of [TiCl4(THF)2] or MCl4 (M = Zr or Hf) and the corresponding lithiated ansa derivative. The reaction of complexes 7 and 8 with two equivalents of MgMeCl led to the formation of the alkyl complexes [Zr{Me2Si(η5-C5Me4)(η5-C5H3R)}Me2] [R = CH2CH2PPh2 (11), PPh2 (12)]. Methyl abstraction from 11 and 12 with B(C5F6)3 gave the cationic species [Zr{Me2Si(η5-C5Me4)(η5-C5H3R)}Me]+ [R = CH2CH2PPh2 (13), PPh2 (14)]. The insertion reaction of the isocyanide reagent CNC6H3Me2-2,6 into the Zr−Me bond of complex 12 giving the corresponding η2-iminoacyl compound [Zr{Me2Si(η5-C5Me4)(η5-C5H3PPh2)}{η2-MeC=N(C6H3Me2-2,6)}(Me)] (15) is described. The ansa-niobocene imide [Nb(=NtBu){Me2Si(η5-C5Me4)(η5-C5H3PPh2)}Cl] (16) and the niobocene imide complexes [Nb(=NtBu)(η5-C5H4PPh2)2Cl] (17) were synthesised by the reaction of [Nb(=NtBu)Cl3(py)2] with Li2{Me2Si(C5Me4)(C5H3PPh2)} (4) or two equivalents of Li(C5H4PPh2), respectively. Preliminary results for the catalytic activity of 7 and 8 in the polymerization of ethylene are presented. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

Synthesis and Reactivity of Amidoaluminum Hydride Compounds as Potential Precursors to AlN

A new series of amidoaluminum hydride complexes H n Al[N(SiHMe2)2]3−n⋅NMe3 (1, n=2; 2, n=1), Al[N(SiHMe2)2]3 (3), and [H2AlN(SiHMe2)2]2 (4) were prepared by the metallation of tetramethyldisilazane (Me2HSi)2NH with either H3Al⋅NMe3 or H3Al⋅2OEt2. The molecular structures of 1 and 2 were shown by X-ray crystal structure determination to be monomeric Lewis acid-base adducts with four coordinate aluminum centers and terminal amido groups. The molecular structure of 4 was found to be a dimer with bridging disilylamides in the solid state. Attempts to obtain crystals of [H2AlN(SiMe3)2]2, a bulkier analogue of 4, led to the isolation of the unusual alumoxane μ2-(Me3Si)2 N-(AlH2)2-μ3-O-Al(H)N(SiMe3)2⋅OEt2 (6) in moderate yields. Thermolysis of 1 and 2 resulted only in the formation of ligand exchange and decomposition products, whereas thermolysis of 4 at 80°C afforded 1 equivalent of Me2SiH2 and a new species formulated as the imide complex [HAlNSiMe2H] n (7). Thermolysis of 4 in the presence of AlH3⋅NMe3 gave Me2SiH2 and 7 at a higher reaction rate even at a lower temperature.

A study of ortho- and para-siloxyanilines for the synthesis of mono-, bi-, and tetra-nuclear early transition metal–imido complexes

The siloxyanilines o-Me 3SiOC 6H 4NH 2 ( 1) and p-RMe 2SiOC 6H 4NH 2 (R=H ( 2); R=Me ( 3)), and their N-silylated derivatives p-Me 3SiOC 6H 4NHSiMe 3 ( 4) and p-Me 3SiOC 6H 4N(SiMe 3) 2 ( 5) have been prepared from ortho- or para-aminophenol and used in the synthesis of imido complexes. Thus, binuclear [{Ti(η 5-C 5H 5)Cl}{μ-NC 6H 4( p-OSiMe 3)}] 2 ( 6) and mononuclear [TiCl 2{NC 6H 4( p-OSiMe 3)}(py) 3] ( 7) imido complexes have been obtained from the reaction of 3 and [Ti(η 5-C 5H 5)Cl 3] or [TiCl 2(N t Bu)(py) 3], respectively. In contrast, the reaction of 1 with TiCl 4 and t Bupy affords the titanocycle [TiCl 2{OC 6H 4( o-NH)N,O}( t Bupy) 2] ( 8). Compound 5 has also been used to prepare the niobium imide complex [NbCl 3{NC 6H 4( p-OSiMe 3)}(MeCN) 2] ( 9), by its reaction with NbCl 5 in CH 3CN. These findings have been applied to the synthesis of polynuclear systems. Thus, chlorocarbosilane Si[CH 2CH 2CH 2Si(Me) 2Cl] 4 (CS–Cl) has been functionalized with the ortho- and para-aminophenoxy groups to give 10 and 11, respectively. The use of 11 has allowed the formation of the tetranuclear compound 12. Attempts to synthesize terminal imido titanium complexes from 10 and TiCl 4 in the presence of t Bupy and Et 3N, give complex 8 and carbosilane CS–Cl.

Electrochemical Reduction of a Bridging Imide: Generation of Ammonia at a Dimolybdenum Tris(μ-thiolate) Site

The electrochemical reduction of the imide complex [Mo2(cp)2(mu-SMe)3(mu-NH)]+ (1+) has been investigated in THF and MeCN electrolytes by cyclic voltammetry, controlled-potential electrolysis and coulometry. In the absence of free protons, the electrochemical reduction produces the amide derivative [Mo2(cp)2(mu-SMe)3(mu-NH2)] (2) after consumption of 1 Fmol(-1) of 1+. In THF in the presence of acid, the reduction of 1+ occurs through a two-electron process. The presence of acid also results in the shift of the equilibrium between 1+ and amide dication 2(2+) (MeCN electrolyte) or induces an isomerisation of the imide ligand (THF electrolyte). This allows the electrolysis to be conducted at a potential 600 mV less negative than the reduction potential of 1+. Controlled-potential electrolyses in the presence of acid (2 equiv HTsO) produce the ammine derivative. Ammonia is released from these compounds either by coordination of the solvent (MeCN electrolyte) or by the binding of chloride to the ammine-tosylate complex (electrolyses in THF in the presence of acid and chloride). The final products, isolated almost quantitatively (>95%), are [Mo2(cp)2(mu-SMe)3(MeCN)2]+ and [Mo2(cp)2(mu-SMe)3(mu-Cl)], respectively.

X‐Ray Diffraction and Vibrational Spectroscopic Studies on PAN‐LiTFSI Polymer Electrolytes

Polyacrylonitrile(PAN)‐lithium bis(trifluoromethane sulfone)imide (LiTFSI) complex has been investigated by X‐ray diffraction (XRD) and vibrational spectroscopy. Two kinds of amorphous complexes are found in the salt‐in‐polymer and polymer‐in‐salt regime, respectively. Phase transition is observed by XRD as the content of lithium salt increases from to . It is also evidenced by Fourier Transform infrared (FTIR) and Raman spectroscopic studies. Interactions between the ion and host polymer are clarified by comparing the spectral evolution of the −C≡N group before and after LiTFSI was complexed with PAN. However, the LiTFSI addition has no obvious influence on the group of PAN, evidently different from that observed with PEO. ions coordinate also with O and/or N of anions, probed by the spectral changes of ‐SNS and groups. © 2000 The Electrochemical Society. All rights reserved.

Electrochemical Reduction of Nitrogenous Ligands at a Conserved Dinuclear Metal-Sulfur Site: Cleavage of the N=N Bond of Phenyldiazene and Reduction of an Imide to NH(3).

The electrochemical reduction of the phenyldiazene complex [Mo2(cp)2(μ-SMe)3(μ-η2-HNNPh)]+ in the presence of HX (X = TsO, CF3CO2) produces aniline and an ammino derivative. This may involve [Mo2(cp)2(μ-SMe)3(μ-NH)]+ as an intermediate since the imide complex also reduces to the ammino derivative in the presence of HX. These electrochemical steps complete a cycle whereby a phenyldiazenido ligand coordinated to the {Mo2(cp)2(μ-SMe)3+} core is cleaved to PhNH2 and NH3 by successive proton- and electron-transfer steps.

Reactions of N,N′-dicarboxamido-N,N′-dicarboxymethyl-1,2-diaminoethane (EDTA–diamide) with hydrated ruthenium(III) chloride and potassium tetrachloroplatinate(II). Crystal and molecular structures of the pentadentate EDTA–H complex NH4[Ru(EDTA–H)Cl] · 2H2O and the EDTA–imide complex PtCl 2[ 2(HOOCCH 2)NCH 2CH 2NCH 2CONHCOCH 2] · 2H2O

Treatment of ruthenium (III) chloride hydrate with N, N′-dicarboxamido- N, N′-dicarboxymethyl-1,2-diaminoethane (1) (EDTA–diamide) in refluxing HCl solution followed by cooling afforded the crystalline complex NH 4[Ru(EDTA–H)Cl] · 2H 2O (2), the EDTA–H ligand and the +NH 4 cation resulting from the hydrolysis of the amide groups in 1. The crystal and molecular structure confirms that in this complex EDTA–H acts as a pentadentate ligand, bonded to the metal through the tertiary nitrogen atoms and three carboxylate oxygens. A chloride ligand completes octahedral geometry around the metal ion. Reaction of K 2[PtCl 4] with the same ligand in hot basic solution followed by acidification initially gave PtCl 2[HOOCCH 2( 2HNOCCH 2)NCH 2CH 2.

Variable-Valent Re&tbd1;NAr Species. A Family of Re(VI)NAr Amide Complexes and Their Re(V)NAr Imine Precursors Related by Oxygen Atom Transfer.

Imide complexes of type Re(V)Cl(3)(X-SB)(NC(6)H(4)Y(p)), with X, Y= H, Me, OMe, Cl have been synthesized where X-SB is the Schiff base of pyridine-2-carboxaldehyde (the corresponding complex is 4), 2-acetylpyridine (5), 2-benzoylpyridine (6), and anilines, p-XC(6)H(4)NH(2). Treatment of 4 or 5 (but not 6) with aqueous nitric acid in acetonitrile afforded Re(VI)Cl(3)(X-PA)(NC(6)H(4)Y(p)), 7, via oxygen atom transfer (X-PA = monoanionic picolinamide). In the structures of 5(X=Cl,Y=Cl), 6(OMe,OMe), and 7(Me,Me), the chlorine atoms are meridionally disposed in a ReCl(3)N(3) coordination sphere. The trans influence of the imide nitrogen considerably lengthens the Re-N(pyridine) bond. The ReNC(6)H(4)Y(p) group has the triple-bonded linear moiety, Re&tbd1;N-C. The amide group in 7(Me,Me) is planar. In 6(OMe,OMe) the two aryl rings on the imine function block water attack and hence amide formation. The rhenium(VI)-rhenium(V) E(1/)(2) values for 4-6 (0.7-1.0 V vs SCE) are much higher than that for 7 (E(1/2) approximately 0.15 V), which displays the rhenium(VII)-rhenium(VI) couple near 1.6 V. Six EPR hyperfine lines are observed for solutions of 7 at room temperature (g(iso) approximately 1.91; A(av) approximately 490 G). Crystal data for the complexes are as follows: 5(Cl,Cl), empirical formula C(19)H(15)Cl(5)N(3)Re, crystal system monoclinic, space group P2(1)/c, a = 13.360(6) Å, b = 12.110(3) Å, c = 14.954(9) Å, beta = 111.41(4) degrees, V = 2252.4(1.7) Å(3), Z = 4; 6(OMe,OMe), empirical formula C(26)H(23)Cl(3)N(3)O(2)Re, crystal system orthorhombic, space group Pbca, a= 12.079(5) Å, b = 17.083(9) Å, c = 26.049(9) Å, V = 5375.4(4.0) Å(3), Z = 8; 7(Me,Me), empirical formula C(20)H(18)Cl(3)N(3)ORe, crystal system monoclinic, space group P2(1)/c, a = 7.071(2) Å, b = 17.541(6) Å, c = 16.857(8) Å, beta = 100.59(3) degrees, V = 2055.3(1.3) Å(3), Z = 4.