Conformationally rigid chelate rings in metal complexes of pyridyloxy-substituted 2,2'-dioxybiphenyl-cyclotetra- and cyclotriphosphazene platforms

Divalent metal halides react with pyridyloxy-substituted 2,2'-dioxybiphenyl-cyclotri- and cyclotetraphosphazene ligands to form the complexes, [MLX2] [M=Co or Cu; L=(2,2'-dioxybiphenyl)tetrakis(2-pyridyloxy)cyclotriphosphazene (L1) or (2,2'-dioxybiphenyl)tetrakis(4-methyl-2-pyridyloxy)cyclotriphosphazene (L2); X=Cl or Br], [ZnLCl2] [L=bis(2,2'-dioxybiphenyl)bis(2-pyridyloxy)cyclotriphosphazene (L3) or bis(2,2'-dioxybiphenyl)bis(4-methyl-2-pyridyloxy)cyclotriphosphazene (L4)], [MLCl2] [M=Cu or Hg; L=tris(2,2'-dioxybiphenyl)bis(2-pyridyloxy)cyclotetraphosphazene (L5)] and [Cu2LCl4] (L=trans-bis(2,2'-dioxybiphenyl)tetrakis(2-pyridyloxy)cyclotetraphosphazene (L6)]. Single-crystal X-ray structures show the L2 ligand complexes to have a N3Cl2 five-coordinate, trigonal-bipyramidal donor set with the phosphazene ring and pendant pyridyloxy nitrogens binding to the metal ions. The coordinated L2 ligand in the complex, [CoL2Cl2], slowly hydrolyses in acetonitrile with the loss of a pyridine pendant arm to form a dimetallic species, which has been characterized by crystallography as [{CoL2aCl}]2.4MeCN (L2a=[N3P3(biph)(OPy)3(O)]-, biph=2,2'-dioxybiphenyl, OPy=2-oxopyridine). The ligands, L3, L4, L5, and L6, bind to the metal halides via gem-substituted pyridyloxy nitrogens only. The resulting rigid eight-membered chelate rings all have distorted boat conformations, which force distorted-tetrahedral N2Cl2 coordination environments onto the metal ions. The spectroscopic (ESR and electronic) and magnetic properties of the complexes are reported.     

Synthesis and spectroscopy of N3P3X5OCH=CH2 (X = Cl, F, OCH3, OCH2CF3, N(CH3)2) and N3P3X4(OCH=CH2)2 (X = Cl, N(CH3)2). Correlations of ultraviolet photoelectron spectroscopy and nuclear magnetic resonance data to electronic and geometrical structure

The syntheses of the vinyloxycyclotriphosphazene derivatives N3P3X5OCH=CH2 (X = OMe, OCH2CF3) and the N3P3(NMe2)4(OCH=CH2)2 isomeric mixture along with improved preparations of N3P3X5OCH=CH2 (X = F, NMe2) are reported. The interactions between the vinyloxy function and the cyclophosphazene in these and the previously reported N3P3Cl5 (OCH=CH2) and N3P3F6-n(OCH=CH2)n (n = 1-4) have been examined by ultraviolet photoelectron spectroscopy (UPS) and NMR spectroscopy. The UPS data for the chloro and fluoro derivatives show a strong electron-withdrawing effect of the phosphazene on the olefin that is mediated with decreasing halogen substitution. The 1H and 13C NMR data for N3P3X5OCH=CH2 (X = F, Cl, OMe, OCH2CF3, NMe2) show significant changes as a function of the phosphazene substituent. There is a linear correlation between the beta-carbon chemical shift on the vinyloxy unit and the phosphorus chemical shift at the vinyloxyphosphorus centers. The chemical shifts of the different phosphorus centers on each ring are also related in a linear fashion. These relationships may be understood in terms of the relative electron donor-acceptor abilities of the substituents on the phosphazene ring. The 1H NMR spectra of the N3P3(NMe2)4(OCH-CH2)2 isomeric mixture allow for assignment of the relative amounts of cis and trans isomers. A model for the observed cis preference in the formation of N3P3Cl4(OCH=CH)2 is presented.     

Properties of cis- and trans-bis(crown ether)s for complexation and extraction of alkali metal picrates

The properties of cis- and trans-bis(crown ether)s containing benzo-15-crown-5 or benzo-18-crown-6 units as complexants and extractants for alkali metal picrates have been studied. The optical spectra suggest that the cis-bis(crown ether)s can form intramolecular 2:1 crown ether unit/cation complexes with particular metal cations easily, while the trans-bis(crown ether)s can form only 1:1 crown ether unit/cation complexes because of the unfavourable trans configuration for the formation of the 2:1 complexes. It was found that the cis isomer possesses much higher extractive power than the trans isomer for the metal cations, which also reflects their complexing properties. The extraction equilibrium constants and thermodynamic quantities have been also evaluated, and the effect of the stereochemical structure of the bis(crown ether) on the complexing and extractive properties is discussed.     

配合物[Mn(2,2''-bipy)(H2O)4]·(m-phth)的水热合成和晶体结构

A mononuclear manganese complex [Mn(2,2'-bipy)(H2O)4]·(m-phth) (2,2'-bipy=2,2'-bipyridine, m-phth=isophthalate) has been synthesized by hydrothermal methods. The crystal structure was determined by singlecrystal X-ray diffraction. The crystal is of orthorhombic, space group Pnna with a=0.766 8(8) nm, b =2.050 2(2)0.027 0, R=0.028 0 and wR=0.075 5. In the crystal the manganese atom is six-coordinated by two nitrogen atoms from 2,2'-bipyradine and four oxygen atoms from water molecules, completing an octahedral coordination geometry. The isophthalate molecules are included in the lattice and connected to Mn(2,2'-bipy)(H2O)4 by hydrogen bonding interactions to form a three-dimensional supramolecular structure. CCDC:286965.     

Nucleation, growth, and form in crystals of peptide helices

A model for the nucleation of crystallization in peptide helices is presented. The crystal structures of four polymorphic forms of a hydrophobic helical decapeptide Boc-Leu-Aib-Phe-Phe-Leu-Aib-Ala-Ala-Leu-Aib-OMe (I) exemplify alternative packing modes in cylindrical molecules. Three crystal forms of peptide I are monoclinic P2(1), while one is orthorhombic P22121. The five different helical molecules characterized have very similar backbone conformations over much of the peptide length. A survey of 117 helical peptide structures with a length >/=8 residues reveals a preponderance of the triclinic (P1), monoclinic (P2(1)), and orthorhombic (P2(1)2(1)2(1)) crystal forms. Models for the formation of critical nuclei are based on helix association driven by solvophobic forces, resulting in the formation of raftlike structures. Raft association can be further driven by the imperative of minimizing solvent accessible surface area with the formation of blocks, which can be subsequently fitted in Lego set fashion by multiple hydrogen bond interactions in the head-to-tail region. This model provides a rationalization for observed crystal formation based on a postulated structure for an embryonic nucleus, which is determined by aggregation patterns and unconstrained by the dictates of symmetry.     

Reactions of N-silylphosphoranimines with alcohols: synthesis and structure of cyclotriphosphazenes with nongeminal methyl and phenyl substituents

The reactions of Me(3)SiN=P(OR")RR'(R" = Ph, CH(2)CF(3); R, R' = Me, Ph) with alcohols were investigated. With nonequivalent amounts of CF(3)CH(2)OH, the reactions produced high yields of the cyclic phosphazene (Me(2)PN)(3) and both the cis and trans isomers of nongeminally substituted [(Ph)(Me)PN](3). The isomers of this new cyclic phosphazene were separated by column chromatography and characterized by NMR and IR spectroscopy, elemental analysis, and X-ray crystallography. Crystals of the cis isomer 6a have a monoclinic crystal system, while the trans isomer 6b has a triclinic crystal system with two different molecules in an asymmetric unit. The bond lengths and bond angles are very similar to those of the simpler cyclic trimers (Me(2)PN)(3) and (Ph(2)PN)(3.) A likely pathway for the formation of these compounds is discussed.     

Expedient synthesis of pseudo-Pro-containing peptides: towards constrained peptidomimetics and foldamers

The reaction of sulfonyl peptides containing L- or D-configured Ser or Thr with bis(succinimidyl) carbonate in the presence of a catalytic amount of a base affords, in solution or in the solid phase, the corresponding peptides with one or two, consecutive or alternate oxazolidin-2-ones (Oxd). The Oxd ring can be regarded to as a pseudo-Pro with an exclusively trans conformation of the preceding peptide bond; homochiral Oxd-containing peptides adopt extended conformations, while the presence of a D-configured Oxd favours folded conformations.     

Syntheses and Crystal Structures of Two Co(II) Coordination Polymers with 4,4'-(Hexafluoroisopropylidene)bis(benzoic acid)

Two new one-dimensional zigzag chain coordination polymers,[Co(hfipbb)(2,2'-bpy)(H2O)2]n 1 and [Co(hfipbb)(1,10-phen)(H2O)]n 2,have been synthesized under hydrother-mal reactions from CoCl2.6H2O,4,4'-(hexafluoroisopropylidene)bis(benzoic acid) and 2,2' -bipyridine or 1,10-phenanthroline ligands,respectively. Single-crystal X-ray analyses revealed that the zigzag chains of 1 and 2 are linked into three-dimensional supramolecular networks by both O-H···O hydrogen-bonds and π···π stacking interactions. Crystal data for 1:C27H20CoF6N2O6,Mr=641.38,orthorhombic,space group Pnna,a=9.3820(19),b=27.366(6),c=10.106(2) ,V=2594.8(9) 3,Z=4,Dc=1.642 g/cm3,F(000)=1300,μ=0.752 mm-1,R=0.0311 and wR=0.0924. Crystal data for 2:C29H18CoF6N2O5,Mr=647.38,monoclinic,space group P21/n,a=7.7626(16),b=29.446(6),c=11.281(2) ,β=93.98(3)°,V=2572.3(9) 3,Z=4,Dc=1.672 g/cm3,F(000)=1308,μ=0.757 mm-1,R=0.0403 and wR=0.0820.     

Stabilization of zwitterions in solution: GABA analogues

The solution-phase structures of a number of conformationally restricted gamma-aminobutyric acid (GABA) analogues are investigated at the MP2/6-31+G* level of theory, using both explicit water molecules and the conductor-like screening solvation model (COSMO) to model solvation. GABA analogues constrained in a cis conformation by either a double bond or cyclopropane ring have the potential to attain either folded, intramolecularly hydrogen-bonded, or partially folded conformations in solution. Systems constrained in a cis conformation by a cyclopentane or cyclopentene ring are more conformationally restricted and exist only in a folded, intramolecularly hydrogen-bonded form. GABA analogues constrained in a trans conformation by either a double bond or cyclopropane ring have the potential to adopt either partially folded or fully extended conformations in solution. Due to a lack of conformational flexibility, analogues that are constrained in a trans conformation by a cyclopentane or cyclopentene ring attain only partially folded conformations. Like GABA, conformationally flexible GABA analogues possess a large number of stable rotamers, and may exist in any or all of these conformations in aqueous solution. The structures of these analogues provide an essential foundation for subsequent structure-activity analysis of ligand binding at GABA receptors and transporters. This work is therefore expected to facilitate the design and development of new biologically active GABA analogues to treat GABA-related neurological disorders.     

Insertion of dipolar molecules in channels of a centrosymmetric organic zeolite: molecular modeling and experimental investigations on diffusion and polarity formation

The mechanism of insertion of p-nitroaniline (PNA) and its diffusion behavior in channels of the hexagonal host structure of tris(o-phenylenedioxy)cyclotriphosphazene (TPP) was investigated by means of molecular modeling tools. Strong preferential sites in the bulk were found to be due to pi-pi and NH-pi interactions between PNA and channel walls of TPP. MD simulations showed that diffusion can be characterized by jumps from one site to the next, occurring mainly because of the dynamic flexibility of the host structure. Calculations of host-guest interactions between the TPP surface and PNA approaching the entrance of channels with its terminal H2N-first or O2N-first revealed that the H2N-first insertion is clearly preferred. Preferential insertion of PNA is found to be the reason for polar effects, observed experimentally. Because of a distinct guest-host recognition at the surface, guest-guest interactions were found to have a minor influence on polarity.     

Synthesis of end‐functionalized polyethers by phosphazene base‐catalyzed ring‐opening polymerization of 1,2‐butylene oxide and glycidyl ether

For the living ring‐opening polymerization (ROP) of epoxy monomers, the catalytic activity of organic superbases, tert‐butylimino‐tris(dimethylamino)phosphorane, 1‐tert‐butyl‐2,2,4,4,4‐pentakis(dimethylamino)‐2Λ⁵,4Λ⁵‐catenadi(phosphazene), 2,8,9‐triisobutyl‐2,5,8,9‐tetraaza‐1‐phosphabicyclo[3.3.3]undecane, and 1‐tert‐butyl‐4,4,4‐tris(dimethylamino)‐2,2‐bis[tris(dimethylamino)phosphoranylidenamino]‐2Λ⁵,4Λ⁵‐catenadi(phosphazene) (t‐Bu‐P₄), was confirmed. Among these superbases, only t‐Bu‐P₄ showed catalytic activity for the ROP of 1,2‐butylene oxide (BO) to afford poly(1,2‐butylene oxide) (PBO) with predicted molecular weight and narrow molecular weight distribution. The results of the kinetic, post‐polymerization experiments, and MALDI‐TOF MS measurement revealed that the t‐Bu‐P₄‐catalyzed ROP of BO proceeded in a living manner in which the alcohol acted as the initiator. This alcohol/t‐Bu‐P₄ system was applicable to the glycidol derivatives, such as benzyl glycidyl ether (BnGE) and t‐butyl glycidyl ether, to afford well‐defined protected polyglycidols. The α‐functionalized polyethers could be obtained using different functionalized initiators, such as 4‐vinylbenzyl alcohol, 5‐hexen‐1‐ol, and 6‐azide‐1‐hexanol. In addition, the well‐defined cyclic‐PBO and PBnGE were successfully synthesized using the combination of t‐Bu‐P₄‐catalyzed ROP and click cyclization. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Preparation of new nitrogen-bridged heterocycles. 60. Syntheses and conformational analyses of bis(indolizin-1-yl) disulfides

Some bis(indolizin-1-yl) disulfides, readily obtainable from the treatment of 1-(benzoylthio)indolizines with piperidine, were prepared and their conformations were investigated. In comparison with those of 1-(benzoylthio)indolizines, the (1)H-NMR spectra of these disulfides showed considerable high field shifts (delta 0.13-0.82 ppm) on each pyridine ring proton and the UV spectra exhibited significant bathochromic and hyperchromic shifts. These results supported strongly the participation of an intramolecular pi-pi interaction between the two indolizine rings in these molecules and, hence, of a particular gauche (cis) conformation. However, the conformational considerations and molecular calculations (Mopac PM3) for some bis(indolizin-1-yl) disulfides showed the presence of four more stable gauche forms in which two are enantiomeric, resulting in three types of gauche structures. These three types of gauche structures were confirmed by X-ray analyses.     

Langmuir-Blodgett films of amphiphilic bis(tetrathiafulvalene) macrocycles with four alkyl chains

Amphiphilic bis(tetrathiafulvalene) [bis(TTF)] macrocycles with four alkyl chains were fabricated as novel electrically active Langmuir-Blodgett (LB) films. Two TTF units were linked via [24]crown-8, [21]crown-7, and [18]crown-6 macrocycles, forming charge-transfer (CT) salts with 2,3,5,6-tetrafluoro-7,7,8,8-tetracyano-p-quinodimethane (F4-TCNQ) at the air-water interface and on solid substrates. The CT salt of the amphiphilic bis(TTF)-macrocycle having a [24]crown-8 ring system formed a uniform surface morphology on mica. Using single-crystal X-ray structural analysis, the layer structure between the hydrophobic chains and the one-dimensional pi-pi stack of the CT salt was confirmed. Our results show that the bis(TTF)-macrocycle was folded at the flexible [24]crown-8 moiety, forming intramolecular pi-pi dimer structures and one-dimensional intermolecular pi-pi stacks with F4-TCNQ dimers. The open-shell electronic structure of the LB films was determined by electronic spectra, electrical conductivity, and electron spin resonance analyses. Asymmetry was introduced into the bis(TTF)-macrocycle by changing the ring size from [24]crown-8 to [21]crown-7. The surface morphology of the CT salts with F4-TCNQ was established as two-dimensional round-shape domains on mica. Further reduction of the macrocyclic ring from [21]crown-7 to [18]crown-6 resulted in a CT salt of the bis(TTF)-macrocycle with F4-TCNQ with a leaf-shape domain morphology and a typical dimension of approximately 1 microm2 on mica. In general, decreasing the macrocyclic ring size from [24]crown-8 to [21]crown-7 or [18]crown-6 affected the inter- and intramolecular interactions and the surface morphologies of LB films.     

Preparation and Characterization of Halogen-Boron-Phosphorus Compounds. X-ray Crystal Structures of X(3)B.P(SiMe(3))(3) and [X(2)BP(SiMe(3))(2)](2) (X = Cl, Br)

The 1:1 mole ratio reactions of boron trihalides (BX(3)) with tris(trimethylsilyl)phosphine [P(SiMe(3))(3)] produced 1:1 Lewis acid/base adducts [X(3)B.P(SiMe(3))(3), X = Cl (1), Br (2), I (5)]. Analogous 1:1 mole ratio reactions of these boron trihalides with lithium bis(trimethylsilyl)phosphide [LiP(SiMe(3))(2)] produced dimeric boron-phosphorus ring compounds {[X(2)BP(SiMe(3))(2)](2), X = Br (3), Cl (4)}. X-ray crystallographic studies were successfully conducted on compounds 1-4. Compound 1 crystallized in the orthorhombic space group Pbca, with a = 13.420(3) ?, b = 17.044(5) ?, c = 21.731(7) ?, V = 4970.6(25) ?(3), and D(calc) = 1.229 g cm(-3) for Z = 8; the B-P bond length was 2.022(9) ?, Compound 2 crystallized in the orthorhombic space group Pbca, with a = 13.581(6) ?, b = 17.106(7) ?, c = 22.021(9) ?, V = 5116(4) ?(3), and D(calc) = 1.540 g cm(-3) for Z = 8; the B-P bond length was 2.00(2) ?. Compound 3 crystallized in the monoclinic space group P2(1)/n, with a = 9.063(5) ?, b = 16.391(8) ?, c = 9.331(4) ?, V = 1379.2(12) ?(3), and D(calc) = 1.676 g cm(-3) for Z = 2; the B-P bond length was 2.023(10) ?. Compound 4 crystallized in the monoclinic space group P2(1)/n, with a = 9.143(5) ?, b = 16.021(8) ?, c = 9.170(4) ?, V = 1342.2(11) ?(3), and D(calc) = 1.282 g cm(-3) for Z = 2; the B-P bond length was 2.025(3) ?. Thermal decomposition studies were performed on compounds 1-4, yielding colored powders with boron:phosphorus ratios greater than 1:1 and significant C and H contamination indicated by elemental analyses.     

Synthesis,Spectroscopic Properties and Crystal Structure of 3,3＇-（Anthracene-9,10-diyl）bis（1-phenylpropan-1-one）

The compound 3,3'-(anthracene-9,10-diyl)bis(1-phenylpropan-1-one)(C32H26O2,Mr=442.55) has been synthesized by the reaction of 2,2'-(anthracene-9,10-diylbis(methy-lene))bis(1,3-diphenylpropane-1,3-dione) with CsCO3,and its structure was characterized by 1H NMR and single-crystal X-ray diffraction.The crystal of the title compound belongs to monoclinic,space group P21/c with a=9.154(3),b=5.2777(16),c=24.897(7) nm,β=107.337(10)°,Z=2 and V=1.1482 nm3.X-ray analysis indicates that an intermolecular hydrogen bond C(8)-H(8A)…O(1),weak C-H···π between H(9A) and the centre of anthracene rings and weak π-π interactions between two anthracene ring planes are observed.     

Preparation of hexacoordinated tris(bidentate) phosphorus compounds with 1,3,2-dioxaphosphorinane rings. NMR and X-ray crystallographic studies of their conformation

A series of new unstable tris(bidentate) hexacoordinated phosphorus compounds 1 with 1,3,2-dioxaphosphorinane rings was prepared and studied by NMR and X-ray crystallography. The X-ray crystal structures showed that the 1,3,2-dioxaphosphorinane ring adopts different conformations depending on the number and size of substituents at the carbon atom C14. Substituents are deployed around the phosphorus atom in a slightly deformed octahedral structure. Deviations in bond lengths around the phosphorus atom depend on the character of the bonds and the distribution of the negative charge. (1)H and (13)C NMR measurements showed that in solution the flexibility of 1,3,2-dioxaphosphorinane ring depends on the size of substituents at the carbon C14.     

Electrocatalytic properties of guanine, adenine, guanosine-5'-monophosphate, and ssDNA by Fe(II) bis(2,2':6',2'-terpyridine), Fe(II) tris(1,10-phenanthroline), and poly-Fe(II) tris(5-amino-1,10-phenanthroline)

The electrocatalytic oxidations of guanine, adenine, guanosine-5'-monophosphate(GMP) and ssDNA were performed in the presence of Fe(II) bis(2,2':6',2'-terpyridine) and Fe(II) tris(1,10-phenanthroline) complexes as homogeneous catalysts by cyclic voltammetric methods. The Fe(II/III) redox couple of these compounds is responsible for their catalytic properties. The electrocatalytic oxidation current of above substrates were developed from the anodic peak currents of Fe(II) bis(2,2':6',2'-terpyridine) and Fe(II) tris(1,10-phenanthroline) complexes at about +0.93 V and 0.97 V, respectively. The electrocatalytic oxidative properties of guanine by Fe(II) bis(2,2':6',2'-terpyridine) complex was measured by amperometry method using the rotating disk electrodes. Electropolymerization of Fe(II) tris(5-amino-1,10-phenanthroline) complex produced thin polymer films on gold and glassy carbon electrodes. The electrochemical quartz crystal microbalance (EQCM) and cyclic voltammetry were used to study the in situ growth of the polymer. The poly(FeII(5-NH(2)-1,10-phen)(3)) exhibited a good electrocatalytic oxidation towards guanine and also for the mixture of guanine and adenine too.     

Electrocatalytic reactions in organized assemblies: Part III. Reduction of allyl halides by bipyridyl derivatives of cobalt in anionic and cationic micelles

Reduction of allyl halides to 1,5-hexadiene at glassy carbon electrodes was catalyzed by tris(2,2'-bipyridyl) cobalt(II) and tris(4,4'-dimethyl-2,2'-bipyridyl)cobalt(II) in aqueous solutions of 0.1 M SDS or 0.1 M CTAB. An organocobalt(I) intermediate was observed by its separate voltammetric reduction peak in each system studied. This intermediate undergoes an internal redox reaction to form 1,5-hexadiene and Co(II). Small micellar enhancements of reaction rates found for tris(2,2'-bipyridyl) cobalt(II) in 0.1 M CTAB can be attributed to reactant compartmentalization in the micelles. Observed chemical rates followed the order CTAB > SDS = acetonitrile. For tris(4,4'-dimethyl-2,2'-bi-pyridyl) Co(II) in CTAB, catalysis was limited by adsorption of the Co(I) form at the electrode. Preliminary work with bis(2,2'-bipyridyl)-(4,4'-dihexadecyl-2,2'-bipyridyl)cobalt(II) showed that its catalytic utility in 0.1 M SDS was equivalent to that of the most efficient system studied, i.e. tris(2,2'-bipyridyl)Co(II) in 0.1 M CTAB.     

Synthesis and Spectroscopic Properties of Cyclotriphosphazenes Containing 6-(4-Hydroxyphenyl)-2,2''-bipyridine Side Groups

Two novel cyclotriphosphazene derivatives containing 6-(4-hydroxyphenyl)-2,2'-bipyridine(hopbp)side groups,N_3P_3(dobp)_2(hopbp)_2(1)and N_3P_3(dobp)(hopbp)_4(2)(dobp=2,2'-dioxybiphenyl),were synthesized and characterized.These compounds display strong fluorescent emission both in solution and in solid state.Their absorption and emission spectra are sensitive to proton:the addition of HBF4 to the methanol and dichloromethane solution(9∶1,volume ratio)of compound 1 led to a red-shift from 350 to 460 nm for the emission spectrum,and the process was also characterized by isosbestic points of absorption spectra at 267,287 and 313 nm.     

Two new dibenzobicyclic penta- and hexacoordinated tin compounds

Two new dibenzobicyclic penta- andhexacoordinated tin compounds ( 1–2 ) were prepared, derived from bis(2-hydroxy-3,5-di-tert-butyl-phenol)imine and dichloro-dimethylstannane and trichloro-n-butylstannane, respectively. Each compound is an example of two different coordination forms of the ligand. The crystalline complexes have been characterized by magnetic moment, infrared and mass spectrometry, elemental analysis, and X-ray diffraction studies. Compound 1 crystallized in the monoclinic system, space group P2₁/n; it contains a five-coordinated trigonal bipyramidal tin atom with methyl groups in equatorial positions and a planar dibenzobicyclic ring. It is a paramagnetic compound (μ_eff = 1.59 μ_B) due to the radical dianion nature of the ligand. Compound 2 crystallized also in the monoclinic system, space group P2₁/c; it contains a six-coordinated tin atom with an octahedral geometry; the dibenzobicyclic ring is planar, and the chlorine atoms are in trans positions. It is diamagnetic with a delocalized monoanion structure of the ligand. © 1998 John Wiley & Sons, Inc. Heteroatom Chem 9:321–326, 1998