Syntheses, characterizations and crystal structures of new organoantimony(V) complexes with heterocyclic (S, N) ligand

Eight new organoantimony(V) complexes with 1-phenyl-1H-tetrazole-5-thiol [L¹H] and 2,5-dimercapto-4-phenyl-1,3,4-thiodiazole [L²H] of the type R_nSbL_5 − n (L = L¹: n = 4, R = n-Bu 1, Ph 2, n = 3, R = Me 3, Ph 4; L = L²: n = 4, R = n-Bu 5, Ph 6, n = 3, R = Me 7, Ph 8) have been synthesized. All the complexes 1-8 have been characterized by elemental, FT-IR, ¹H and ¹³C NMR analyses. Among them complexes 2, 6 and 8 have also been confirmed by X-ray crystallography. The structure analyses show that the antimony atoms in complexes 2 and 6 display a trigonal bipyramid geometry, while it displays a distorted capped trigonal prism in complex 8 with two intramolecular Sb?N weak interactions. Furthermore, the supramolecular structure of 2 has been found to consist of one-dimensional linear molecular chain built up by intermolecular C-H?N weak hydrogen bonds, while a macrocyclic dimer has been found in complex 6 linked by intermolecular C-H?S weak hydrogen bonds with head-to-tail arrangement. Interestingly, one-dimensional helical chain is recognized in complex 8, which is connected by intermolecular C-H?S weak hydrogen bonds.     

Palladium and platinum complexes of chiral and achiral calix[4]arene bisphosphite ligands

Chiral and achiral p-tert-butyl-calix[4]arene bisphosphites (L¹–L³) have been synthesized by the reaction of p-tert-butyl-calix[4]arene and the phosphorodichloridites, ROPCl₂ [R = (1S,2R,5R)-(+)-iso-menthyl (L¹), (1R,2S,5R)-(−)-menthyl (L²) or C₆H₄Bu^t-4 (L³)]. These bisphosphites function as chelating ligands in palladium(II) and platinum(II) complexes which are formed in good yields by the reaction of PdCl₂(PhCN)₂, MCl₂(COD) (M = Pd or Pt) or PdMeCl(COD) with the respective calix[4]arene bisphosphite. Single crystal X-ray diffraction studies performed on the complexes [PdCl₂(L¹)], [PdCl₂(L²)], [PdCl₂(L³)] and [PtCl₂(L³)] reveal a near square planar geometry around the metal with the two chloride ligands in a cis disposition. The crystal packing in the complexes [PdCl₂(L¹)] and [PdCl₂(L²)], which crystallize in the chiral (P6₁22) space group, shows different hydrophobic channels with intermolecular C–H?Cl hydrogen bonding. The complexes [PdCl₂(L³)] and [PtCl₂(L³)] are isostructural and the molecules in the crystal lattice are linked by intermolecular C–H?Cl and C–H?O hydrogen bonds.     

Structural diversity of di and triorganotin complexes with 4-sulfanylbenzoic acid: Supramolecular structures involving intermolecular Sn?O, O-H?O or C-H?X (X = O or S) interactions

Twelve new organotin complexes with 4-sulfanylbenzoic acid of two types: R_nSn[S(C₆H₄COOH)]_4−n (I) (n = 3: R = Me 1, n-Bu 2, Ph 3; PhCH₂4; n = 2: R = Me 5; n-Bu 6, Ph 7, PhCH₂8) and R₃Sn(SC₆H₄COO)SnR₃ · mEtOH (II) (m = 0: R = Me 9, n-Bu 10, PhCH₂12; m = 2: R = Ph 11), along with the 4,4′-bipy adduct of 9, [Me₃Sn(SC₆H₄COO)SnMe₃]₂(4,4-bipy) 13, have been synthesized. The coordination behavior of 4-sulfanylbenzoic acid is monodentate in 1-8 by thiol S atom but not carboxylic oxygen atom. While, in 9-13 it behaves as multidenate by both thiol S atom and carboxylic oxygen atoms. The supramolecular structures of 6, 11 and 13 have been found to consist of 1D molecular chains built up by intermolecular O-H?O, C-H?O or C-H?S hydrogen bonds. The supramolecular aggregation of 7 is 2D network determined by two C-H?O hydrogen bonds. Extended intermolecular C-H?O interactions in the crystal lattice of 9 link the molecules into a 2D network.     

Syntheses, crystal structures and coordination modes of tri- and di-organotin derivatives with 2-mercapto-4-methylpyrimidine

The organotin (IV) derivatives of 2-mercapto-4-methylpyrimidine (Hmpymt) R₃SnL (R = Ph 1, PhCH₂2, n-Bu 3), R₂SnCl_mL_n (m = 1, n = 1, R = CH₃4, Ph 5, n-Bu 6, PhCH₂7; m = 0, n = 2, R = CH₃8, n-Bu 9, Ph 10, PhCH₂11) were obtained by the reaction of the organotin(IV) chlorides R₃SnCl or R₂SnCl₂ with 2-mercapto-4-methylpyrimidine hydrochloride (HCl · Hmpymt) in 1:1 or 1:2 molar ratio. All complexes 1-11 were characterized by elemental analyses, IR, ¹H, ¹³C and temperature-dependent ¹¹⁹Sn NMR spectra. Except for complexes 3 and 6, the structures of complexes 1, 2, 4, 5, 7, 8-11 were confirmed by X-ray crystallography. Including tin-nitrogen intramolecular interaction, the tin atoms of complexes 1-7 are all five-coordinated and their geometries are distorted trigonal bipyramidal. While the tin atoms of complexes 8-11 are six-coordinated and their geometries are distorted octahedral. Besides, the ligand adopts the different coordination modes to bond to tin atom between the complexes 1, 6, 7 and 2, 3, 4, 5, 8-11. Furthermore, intermolecular Sn?N or Sn?S interactions were recognized in crystal structures of complexes 4, 7 and 11, respectively.     

Molecular structures and supramolecular association of chlorodiorganotin(IV) complexes with bis- and tris-dithiocarbamate ligand

Two series of di and trinuclear chlorodiorganotin(IV) complexes derived from bis- and tris-dithiocarbamate ligands have been prepared and structurally characterized. The dinuclear complexes 1-2 of the composition {(R₂SnCl)₂(bis-dtc)} (1, R = Me; 2, R = ⁿBu) have been obtained from R₂SnCl₂ (R = Me, ⁿBu) and the triethylammonium salt of N,N′-dibenzyl-1,2-ethylene-bis(dithiocarbamate). The trinuclear complexes 3-9 with the general formula {(R₂SnCl)₃(tris-dtc)} 3, R = Me, tris-dtc = tris-dtc-Me; 4, R = Me, tris-dtc = tris-dtc-ⁱPr; 5, R = Me, tris-dtc = tris-dtc-Bn; 6, R = ⁿBu, tris-dtc = tris-dtc-Me; 7, R = ⁿBu, tris-dtc = tris-dtc- ⁱPr; 8, R = ⁿBu, tris-dtc = tris-dtc-Bn; 9, R = ^tBu, tris-dtc = tris-dtc-Me) were prepared from R₂SnCl₂ (R = Me, ⁿBu, ^tBu) and the potassium dithiocarbamate salts of (tris[2-(methylamino)ethyl]amine) (tris-dtc-Me), (tris[2-(isopropylamino)ethyl]amine) (=tris-dtc-ⁱPr) and (tris[2-(benzylamino)ethyl]amine) (=tris-dtc-Bn). Compounds 1-9 have been analyzed as far as possible by elemental analysis, FAB⁺ mass spectrometry, IR and NMR (¹H, ¹³C, ¹¹⁹Sn) spectroscopy, and single-crystal X-ray diffraction analysis. The solid state and solution studies showed that the dtc ligands are coordinated to the tin atoms in the anisobidentate manner. In all cases the metal centers are five-coordinate. The coordination geometry is intermediate between square-pyramidal and trigonal-bipyramidal coordination polyhedra with τ-values in the range of 0.32-0.53. For the members of each series characterized in the solid state by X-ray diffraction analysis, different molecular conformations were found. The crystal structures show the presence of C-H?Cl, C-H?S, C-H?π, S?Cl, S?S, Cl?Sn and S?Sn contacts.     

Syntheses and crystal structures of diorganotin (IV) moieties with 3-hydroxy-2-pyridinecarboxylic acid

A series of new organotin (IV) complexes with 3-hydroxy-2-pyridinecarboxylic acid (3-OH-2-picH) of two types: R₂SnCl(3-OH-2-pic) (I) (R = Me 1, n-Bu 2, Ph 3, PhCH₂4) and R₂ Sn(3-OH-2-pic)₂ (II) (R = Me 5, n-Bu 6, Ph 7, PhCH₂8)have been synthesized by reactions of diorganotin (IV) dichloride with 3-hydroxy-2-pyridinecarboxylic acid in the presence of sodium ethoxide. All complexes are characterized by elemental analyses, IR spectra and NMR spectra analyses. Among them, complexes 1, 5, 6 and 7 are also characterized by X-ray crystallography diffraction analyses. Complex 1 is a 1D polymeric chain with six-coordinate tin atoms and the packing of complex 1 is stabilized by the C-H?Cl intermolecular weak interactions, thus a 2D network of 1 is formed. Complex 5 is also a 1D polymeric chain with seven-coordinate tin atoms. Complex 6 is a zigzag polymeric chain linked by Sn?O intermolecular weak interactions. Complex 7 is a monomeric complex with distorted octahedral geometry.     

Coordination behaviour in transition metal complexes of asymmetric NPN ligands

Two bicyclic, chiral aminophosphine ligands, namely 4R, 9R-1,3-bis(pyridin-2-ylmethyl)-2-(2-propyl)octahydro-1H-1,3,2-benzodiazaphosphole (1) and 4R, 9R-1,3-bis(pyridin-2-ylmethyl)-2-(2-ethoxy)octahydro-1H-1,3,2-benzodiazaphosphole (2) have been prepared from 1R, 2R-diaminocyclohexane and the appropriate dichlorophosphine and the nature of their coordination to a number of transition metals explored. Ligand 1 coordinates to Pd(II) and Pt(II) as a terdentate donor to give complexes of the type [M(κ³-N,P,N-1)Cl]⁺ whereas ligand 2 favours bidentate κ²-P,N coordination to give the complexes M(κ²-P,N-2)Cl₂. The study of the coordination chemistry of the NPN ligand 1 is frustrated by its ready decomposition to an unknown species which appears to be promoted by transition metals. The ligand 2 does not undergo such a transformation and its metal chemistry is more readily examined. Aside from the Pt(II) and Pd(II) complexes above, 2 has been coordinated to Cr(0) and Mo(0) in the octahedral complexes M(κ²-P,N-2)(CO)₄ and Au(I) in linear Au(κ¹-P-2)Cl. All the complexes have been fully characterised by spectroscopic and analytical techniques including a single-crystal X-ray structure analysis of [Pt(κ³-N,P,N-1)Cl]Cl, 3.     

Chiral self-assembly of triorganotin complexes: Syntheses, characterization, crystal structures and antitumor activity of organotin(IV) complexes containing (R)-(+)-methylsuccinic acid, (S)-(+)-methylglutaric acid and l-(−)-malic acid ligands

Six new chiral triorganotin(IV) complexes, {(R₃Sn)₂[C₃H₆(COO)₂]}_n (R = Me: 1; Bu: 2), {(R₃Sn)₂[C₄H₈(COO)₂]}_n (R = Me: 3; Bu: 4), and {(R₃Sn)₂[C₂H₄O(COO)₂]}_n (R = Me: 5; Bu: 6) have been prepared by treatment of (R)-(+)-methylsuccinic acid, (S)-(+)-methylglutaric acid and l-(−)-malic acid, with the corresponding R₃SnCl (R = Me, Bu) and sodium ethoxide in methanol. All the complexes were characterized by elemental analysis, FT-IR, NMR (¹H, ¹³C, ¹¹⁹Sn) spectroscopy and TGA. Except for 3, all of the complexes were also characterized by X-ray crystallography. The structural analyses reveal that complexes 1 and 5 have 2D network structures in which (R)-(+)-methylsuccinic acid and l-(−)-malic acid act as tetradentate ligands coordinated to trimethyltin(IV) ions. Complexes 2 and 4 have 3D metal-organic framework structures in which the deprotoned acids serve as tetradentate ligands. Complex 6 adopts a 1D zigzag chain structure and forms a 2D supramolecular framework through intermolecular C-H?O interactions. In addition, the antitumor activities of complexes 1-6 have been studied. We also have measured the specific rotation of the chiral dicarboxylic acids and the organotin derivatives.     

Hydrogen-bonded networks from η-semiquinone complexes of manganese tricarbonyl

The cationic manganese tricarbonyl complexes containing η⁶-2-methylhydroquinone (2a), η⁶-2,3-dimethylhydroquinone (3a), η⁶-2-t-butylhydroquinone (4a), η⁶-tetramethylhydroquinone (5a) and η⁶-4,4′-biphenol (6a) are readily deprotonated to the corresponding neutral (η⁵-semiquinone)Mn(CO)₃ (2b-6b) and anionic (η⁴-quinone)Mn(CO)₃⁻ (2c-5c) complexes. The X-ray structures of 2b-6b feature strong intermolecular hydrogen bonding interactions that result in the formation of supramolecular organometallic networks. Significantly, the substitution pattern at the semiquinone ring affects the stereochemistry of the hydrogen bonding interactions. NMR spectra of 2b, 3b and 5b reveal dynamic hydrogen bonding in solution.     

Self-assembly syntheses and crystal structures of triorganotin(IV) pyridinecarboxylate: 1D polymers and a 42-membered macrocycle

A series of new triorganotin(IV) pyridinecarboxylates with 6-hydroxynicotinic acid (6-OH-3-nicH), 5-hydroxynicotinic acid (5-OH-3-nicH) and 2-hydroxyisonicotinic acid (2-OH-4-isonicH) of the types: [R₃Sn (6-OH-3-nic)·L]_n (I) (R = Ph, L = Ph·EtOH, 1; R = Bn, L = H₂O·EtOH, 2; R = Me, L = 0, 3; R = n-Bu, L = 0, 4), [R₃Sn (5-OH-3-nic)]_n (II) (R = Ph, 5; R = Bn, 6; R = Me, 7; R = n-Bu, 8), [R₃Sn (2-OH-4-isonic·L)]_n (III) (R = Bn, 9, L = MeOH; R = Me, L = 0, 10; R = Ph, 11, L = 0.5EtOH) have been synthesized. All the complexes were characterized by elemental analysis, TGA, IR and NMR (¹H, ¹³C, ¹¹⁹Sn) spectroscopy analyses. Among them, except for complexes 5 and 6, all complexes were also characterized by X-ray crystallography diffraction analysis. Crystal structures show that complexes 1-10 adopt 1D infinite chain structures which are generated by the bidentate O, O or N, O and the five-coordinated tin centers. Significant O-H?O, and N-H?O intermolecular hydrogen bonds stabilize these structures. Complex 11 is a 42-membered macrocycle containing six tin atoms, and forms a 2D network by intermolecular N-H?O hydrogen.     

Synthesis and reactivity towards carbon monoxide of an optically active endo five-membered ortho-cyclopalladated imine: X-ray molecular structure of trans-(μ-Cl)2[Pd(κ-C,N-(R)-C6H4-CHN-CHMe-Ph)]2

(R)-1-Phenylethyl-benzylidene-amine (1) reacted with Pd(OAc)₂ in acetic acid at 60 °C under nitrogen affording the acetato-bridged dinuclear endo five-membered ortho-cyclopalladated compound (μ-OAc)₂[Pd(κ²-C,N-(R)-C₆H₄-CHN-CHMe-Ph)]₂ (2) in 65% yield. Compound 2 was converted by a metathesis reaction with LiCl into the corresponding chloro-bridged dinuclear cyclopalladated compound (μ-Cl)₂[Pd(κ²-C,N-(R)-C₆H₄-CHN-CHMe-Ph)]₂ (3). ¹H NMR of CDCl₃ solutions of compounds 2 and 3 treated separately with py-d₅, (R)-1-phenylethylamine and racemic 1-phenylethylamine were consistent with the endo cyclopalladated structure and the R absolute configuration of the chiral carbon atoms of compounds 2 and 3. Compounds 2 and 3 reacted with carbon monoxide in methanol affording, as major compounds, methyl 2-formylbenzoate (91% chemical yield) and the epimers of 3-methoxy-2-[(R)-1-phenylethyl]isoindolin-1-one (64% chemical yield) in ca. 20% diastereomeric excess, respectively. The trans isomer of compound 3 crystallized in the P2₁ monoclinic space group with a = 10.430(4) Å, b = 12.082(8) Å, c = 11.168(4) Å and β = 95.20(3)° and presented C-H?Cl intramolecular and C-H?Pd intermolecular non-conventional hydrogen bonds.     

Chiral organotin (IV) carboxylates complexes: Syntheses, characterization, and crystal structures with chiral (S)-(+)-6-methoxy-α-methyl-2-naphthaleneaceto acid ligand

Eight new organotin (IV) carboxylates, (R₃Sn)₄(nap)₄ (R = Me 1, n-Bu 2), [(R₃Sn) (nap)]_n (R = Ph 3, PhCH₂4), (R₂Sn) (nap)₂ (R = n-Bu 5, Ph 6, PhCH₂7) and {[R₂Sn(nap)]₂O}₂ (R = Me 8) (nap = (S)-(+)-6-methoxy-α-methyl-2-naphthaleneaceto anion) have been synthesized. All of the complexes have been characterized by elemental analysis, FT-IR, NMR (¹H, ¹³C and ¹¹⁹Sn) spectra. Among these complexes, complexes 1, 3, 5 and 8 were also characterized by X-ray crystallography diffraction analysis, and the data of X-ray crystallography diffraction indicated that complexes 1, 3 and 5 are new chiral organotin (IV) carboxylates complexes. The structural analyses show that complex 1 has a tetranuclear Sn₄O₈ macrocycle structure, complex 3 has a 1D spring-like chiral helical chain with a columnar channel, complex 5 possesses a dimer structure, and complex 8 has a supramolecular chainlike ladder structure through weak intermolecular non-covalent O^…O interactions.     

Synthesis, structure and electrochemical property of diphenylacetypene-substituted diiron azadithiolates as active site of Fe-only hydrogenases

The model complexes 1-3 of functionalized azadithiolate (ADT)-bridged Fe-only hydrogenases, [Fe₂(Co)₆(μ-ADT)C₆H₄CCR] [R = C₆H₄NO₂-4 (1), C₆H₅ (2), C₆H₄OCH₃-4 (3)] have been synthesized in high yields under mild conditions by using Sonogashira reaction. Spectroscopic study and X-ray crystal structural analysis of 1 demonstrate that the model complexes retain the butterfly structure of 2Fe2S model analogues. The intermolecular C-H?O, C-H?π hydrogen bonding and π-π interactions play important roles in molecular packing of 1. In the presence of HOAc, complex 1 features the catalytic electrochemical proton reduction.     

From bis(silylamino)tin dichlorides via di(1-alkynyl)-bis(silylamino)tin to new heterocycles by 1,1-organoboration

Bis(silylamino)tin dichlorides 1 [X₂SnCl₂ with X=N(Me₃Si)₂ (a), N(9-BBN)SiMe₃ (b), N(^tBu)SiMe₃ (c), and N(SiMe₂CH₂)₂ (d)] were prepared from the reaction of two equivalents of the respective lithium amides (Li-a-d) with tin tetrachloride, SnCl₄, or from the 1:1 reaction of the respective bis(amino)stannylene with SnCl₄. The compounds 1 react with two equivalents of lithium alkynides LiCCR¹ to give the di(1-alkynyl)-bis(silylamino)tin compounds X₂Sn(CCR¹)₂, 2 (R¹=Me), 3 (R¹=^tBu), and 4 (R¹=SiMe₃). Problems were encountered, mainly with LiCC^tBu as well as with 1b, since side reactions also led to the formation of 1-alkynyl-bis(silylamino)tin chlorides 5-7 and tri(1-alkynyl)(silylamino)tin compounds 8 and 9. 1,1-Ethylboration of compounds 2-4 led to stannoles 10, 11, and in the case of propynides, also to 1,4-stannabora-2,5-cyclohexadiene derivatives 12. The molecular structure of the stannole 11b (R¹=SiMe₃) was determined by X-ray analysis. The reaction of 2a and d with triallylborane afforded novel heterocycles, the 1,3-stannabora-2-ethylidene-4-cyclopentenes 14. These reactions proceed via intermolecular 1,1-allylboration, followed by an intramolecular 1,2-allylboration to give 14, and a second intramolecular 1,2-allylboration leads to the bicyclic compounds 15.     

Synthetic access to optically active isoflavans by using allylic substitution

A general approach to the (S)- and (R)-isoflavans was invented, and efficiency of the method was demonstrated by the synthesis of (S)-equol ((S)-3), (R)-sativan ((R)-4), and (R)-vestitol ((R)-5). The key step is the allylic substitution of (S)-6a (Ar¹=2,4-(MeO)₂C₆H₃) and (R)-6b (Ar¹=2,4-(BnO)₂C₆H₃) with copper reagents derived from CuBr·Me₂S and Ar²-MgBr (7a, Ar²=4-MeOC₆H₄; 7b, 2,4-(MeO)₂C₆H₃; 7c, 2-MOMO-4-MeOC₆H₃), furnishing anti S_N2′ products (R)-8a and (S)-8b,c with 93-97% chirality transfer in 60-75% yields. The olefinic part of the products was oxidatively cleaved and the Me and Bn groups on the Ar¹ moieties was then removed. Finally, phenol bromide 9a and phenol alcohols 9b,c underwent cyclization with K₂CO₃ and the Mitsunobu reagent to afford (S)-3 and (R)-4 and -5, respectively.     

C−H?Pd interactions and cyano-bridged heteronuclear polymeric complexes

Three new heterometallic complexes, [Cu(N-Meim)₄Pd(μ-CN)₂(CN)₂]_n (1), [Zn(N-Meim)₃Pd(μ-CN)₂(CN)₂]_n (2) and [Cd(N-Meim)₂Pd(μ-CN)₄]_n (3), have been isolated from the reactions of M[Pd(CN)₄] (M = Cu(II), Zn(II) or Cd(II)) and N-Meim (N-methylimidazole) with in different molar ratios. All complexes have been characterized by X-ray analyses, vibrational (FT-IR and Raman) spectra, thermal and elemental analyses. The crystallographic analysis reveals that the crystal structures of 1 and 2 are 1D coordination polymer, while 3 presents a 2D network. In the Cu(II) and Zn(II) complexes, two cyanide groups of [Pd(CN)₄]²⁻ coordinated to the adjacent M(II) ions and distorted octahedral and square pyramidal geometries of complexes are completed by four and three nitrogen atoms of N-Meim ligands, respectively. The Cd(II) ion is six-coordinate, completed with the two nitrogen atoms of N-Meim ligands in the axial positions and the four nitrogen atoms from bridging cyano groups in the equatorial plane. The most striking features of complexes 1-3 are the presence of obvious C-H?Pd hydrogen-bonding interactions between the Pd(II) and hydrogen atoms of N-Meim ligand. This weak hydrogen bonding plays a crucial role in the architecture of the network polymers. The adjacent chains are held together by C-H?Pd, C-H?π or π?π interactions, forming three-dimensional network.     

Supramolecular chemistry of half-sandwich organometallic building blocks based on RuCl2(p-cymene)Ph2PCH2Y

A new series of neutral organometallic building blocks based on piano-stool ruthenium(II) complexes, RuCl₂(p-cymene)Ph₂PCH₂Y [Y = -NHC₆H₄(2-CO₂H) (2a), -NHC₆H₄(3-CO₂H) (2b), -NHC₆H₃(3-CO₂H)(6-OCH₃) (2c), -NHC₆H₄(4-CO₂H) (2d), -NHC₆H₃(2-CO₂H)(4-OH) (2e), -NHC₆H₃(3-OH)(4-CO₂H) (2f), -NHC₆H₃(2-CO₂H)(5-CO₂H) (2g) and -OH (2h)], were synthesised in high yields (>88%) from {RuCl₂(p-cymene)}₂ and the appropriate phosphines 1a-1h. The new tertiary phosphine 1b was prepared by Mannich condensation of NH₂C₆H₄(3-CO₂H) with Ph₂PCH₂OH in MeOH. Solution NMR (³¹P{¹H}, ¹H), FT-IR and microanalytical data are in full agreement with the proposed structures. Single crystal X-ray studies confirm that, in each case, compounds 2a, 2b and 2d-2h have piano-stool arrangements with typical Ru-P, Ru-Cl and Ru-C_centroid bond lengths. From our crystallographic studies, factors that influence the supramolecular assemblies of these ruthenium(II) complexes include: (i) the type of functional group present, (ii) the geometric disposition of the -N(H)CH₂PPh₂, -CO₂H and -OH groups around the central benzene scaffold, and (iii) the solvents used in the recrystallisations. Hence in isomers 2a and 2b, molecules are associated into head-to-tail dimer pairs through classical intermolecular O-H?O hydrogen bonding. This feature is also observed in isomer 2d but dimer pairs are further associated to give a 1-D chain through assisted intermolecular N-H?Cl hydrogen bonding. The additional 4-hydroxo group in 2e promotes a ladder arrangement via intermolecular O-H?O and O-H?Cl hydrogen bonding. In contrast the isomeric compound 2f does not show head-to-tail O-H?O hydrogen bonding but instead O-H?Cl and N-H?O intermolecular hydrogen bonding is observed. Depending on the choice of solvent (MeOH or DMSO), 2g forms extended networks based on chains (2g · DMSO · 1.5MeOH) or tapes (2g · 3MeOH). In 2h, a single intramolecular O-H?Cl hydrogen bond is observed for each independent molecule. The X-ray structure of one representative tertiary phosphine, 1f, has also been determined.     

Introduction of a phosphorus ylide moiety into [η-(ω-hydroxy)alkenyl]chromium(0) carbene complexes with Ph3PCCO and consecutive Wittig alkenations with 2-alkynals. Part 12: the chemistry of metallacyclic alkenylcarbene complexes

Ketenylidenetriphenylphosphorane, Ph₃PCCO (2), reacts selectively with the ω-hydroxy group of the alkene-carbene complexes (OC)₄CrC(η²-NMeCH₂CHCHCH₂OH)R¹ (1) (R¹=Me: (1a); Ph: (1b)) to give the acyl ylide terminated complexes (OC)₄CrC[(4,5-η²)-NMeCH₂CHCHCH₂O(O)C-CHPPh₃]R¹ (3) (R¹=Me: (3a); Ph: (3b)). Complexes 3 undergo Wittig alkenation reactions with aldehydes such as 2-alkynals, R²-CC-CHO (R²=H, SiMe₃, Ph), to give the corresponding 4Z, 9E-dien-11-ynes (OC)₄CrC[(4,5-η²)-NMeCH₂CHCHCH₂O(O)C-CHCH-CC-R²]R¹ (4-6) (R¹=Me, R²=H, SiMe₃, Ph: (4a-6a); R¹=Ph, R²=H, SiMe₃, Ph: (4b-6b)). All complexes were characterized in solution by one- and two-dimensional NMR spectroscopy (¹H, ¹³C, ²⁹Si, ³¹P, ¹H/¹H COSY, ¹³C/¹H HETCOR, ³¹P/³¹P EXSY).     

Aluminum and zinc complexes supported by functionalized phenolate ligands: Synthesis, characterization and catalysis in the ring-opening polymerization of ε-caprolactone and rac-lactide

A series of aluminum and zinc complexes supported by functionalized phenolate ligands were synthesized and characterized. Reaction of 2-(3,5-R₂C₃N₂)C₆H₄NH₂ (R = Me, Ph) with salicylaldehyde or 3,5-di-tert-butylsalicylaldehyde afforded 2-((2-(1H-pyrazol-1-yl)phenylimino)methyl)phenol derivatives 2a-2d. Treatment of 2a-2d with an equiv. of AlR²₃ (R² = Me, Et) gave corresponding aluminum aryloxides 3a-3e, while reaction with an equiv. of ZnEt₂ afforded zinc aryloxides 4a-4d. Treatment of 2c with 0.5 equiv. of ZnEt₂ formed diphenolato zinc complex 5. All new compounds were characterized by ¹H and ¹³C NMR spectroscopy and elemental analyses. The structures of complexes 3a, 4a and 5 were further characterized by single crystal X-ray diffraction techniques. The catalytic activity of complexes 3-5 toward the ring-opening polymerization of ε-caprolactone was studied. The zinc complexes (4a-4d) exhibited higher catalytic activity than the aluminum complexes (3a-3e). The diphenolato zinc complex 5 showed lower catalytic activity than the ethylzinc complexes 4a-4d. The aluminum complex (3b) is inactive to initiate the ROP of rac-lactide, while the zinc complex (4d) is active initiator for the ROP of rac-lactide, giving atactic polylactide.     

Electron affinities of a homologous series of tertiary alkyl radicals and their C-H bond dissociation energies (BDEs)

Heats of formation have been derived from G3(MP2)//B3LYP and G3MP2B3(+) atomization energies for tert-butyl radical (6R), cubyl radical, bicyclooctyl radical (1R), and tricyclo[3.3.n.0^3,7]alk-3(7)-yl (n=0-3, 2R-5R) radicals, and their respective anions (1A-6A) and hydrocarbons (1H-6H). The electron affinity (EA) of 6R is estimated at 1.5±2 kcal/mol and tert-butyl anion (6A) is likely to be bound. In the homologous series 2R-5R the EAs range from 3.4±2 to 13.5±2 kcal/mol. The computed enthalpies of the acidities of the tricyclic hydrocarbons 1H-5H are in the range 407-411 kcal/mol. Their C-H bond dissociation energies (BDEs) are in the range 97-110 kcal/mol. The increase of the BDEs in the homologous series 2H-5H and the increase of EAs of 2A-5A is attributed to the enhanced pyramidalization induced in radicals 2R-5R by the shortening of the methylene chain connecting carbons C₃ and C₇.