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The reaction mechanisms on the palladium-catalyzed oxidative carbocyclization of enallenes assisted by weak coordination hydroxyl groups have been computationally investigated by employing density functional theory (DFT) calculations. The allyl C-H activation is the rate-determining step and the olefin insertion is the diastereoselectivity-determining step. The calculated results can explain the lower diastereoselectivity obtained in the experiment when the OH group was replaced by OAc or OMe.

New preparative methods for halogenation of the cage producing the corresponding [2-NH3-B10X9]- species (2- to 4-, X = Cl, Br, I) have been developed using halogenations by elemental halogens in a glass pressure vessel. Compared to similar icosahedral species of formulation [1-H3N-B12X11]- (X = Cl, Br), the N-alkylation reactions in 10-vertex series proceed significantly more easily. The reason for this difference is conceivably due to the two orders of magnitude lower basicity of the amino group, with pKa values in the interval from 9.27 to 8.37, and slightly lower steric strain around the reaction centre. Thus methylations with MeI under mild conditions provided the whole series of corresponding quarternary amines of the formulation [2-Me3N-B10X9]- (5- to 7-, X = Cl, Br, I). The effect of the steric strain of the surrounding halogens on the reactivity at the NH3- centre could then be better seen from reactions with bulkier benzyl bromide. Under comparable conditions, these reactions resulted in the ready formation of disubstituted compounds in case of X = Cl (8-), mixture of mono and disubstituted derivatives for X = Br (9-, 10-) or in monosubstited product for X = I (11-) only. Dibenzyl derivative of the nonaiodinated products (12-) could be still obtained, however only under more forcing conditions. The single-crystal X-ray diffraction structures of all three polyhalogenated derivatives 2- to 4- are presented along with that for benzyl derivative 10-, spectral and physicochemical properties of these polyhalogenated systems are outlined along with specific insights into specific properties of the NH3 group.

The reaction of sterically hindered benzylic telluride bearing 2,4,6-tris[bis(trimethylsilyl)methyl]phenyl (Tbt) group with 2.0 eq. of n-BuLi and HSi(OMe)3 afforded a 1,4-silicon rearrangement product. This rearrangement is made possible by the intermediacy of a 5-membered silicate. The product may be exploited as a potential motif for the synthesis of numerous multiply bonded systems containing heavier group 14 elements.

NMR chemical shifts of d0 transition metal compounds show the following trends: (1) For single-bonded ligands such as M-H, M-CR3, M←NR3, M-SiR3 and M←PR3, 1H, 13C, 15N, 29Si and 31P shifts of these α atoms in the complexes of both first- and third-row transition metals are typically downfield from (or at higher frequencies than) those of second-row analogs with a “V-shape” (Trend 1). (2) For multiple-bonded ligands including those with d-p π bonds, such as M=CHR, M≡CR, M=NR, M=O and M F, 13C, 15N, 17O and 19F shifts of the α atoms in the complexes of first-, second- and third-row transition metals move consecutively upfield (or to lower frequencies) (Trend 2). NMR shifts of lanthanum(III) complexes help interpret Trend 1 in Group 3 congeners. Scandide (d-block) and lanthanide (f-block) contractions and relativistic effects are believed to contribute to the NMR shifts, leading to the observed trends. Comparisons are made with NMR chemical shifts of dn complexes and organic compounds. Since many chemical properties of the second- and third-row congeners such as Zr and Hf are similar, as a result of lanthanide contraction, the NMR chemical shifts are a rare property to distinguish compounds of the otherwise nearly identical congeners. The current paper points out the trends with our narrative interpretations of the trends.

Acid-catalyzed condensation of fluorenylacetaldehyde diethylacetal (1) or indenylacetaldehyde diethylacetal (2) with 3-methylindole yields fluorenylbis(3-methylindolyl)ethane (3) or indenylbis(3-methylindolyl)ethane (4), respectively. Compounds 3 and 4 were used to demonstrate the coordination modes of this new class of ligands to zirconium. Transamination of Zr(NEt2)4 with 3 (H3L) yields (HL)Zr(NEt2)2(THF) (5) in which doubly deprotonated 3 chelates zirconium via two N-indolide moieties. The fluorenyl group remains protonated and uncoordinated. Transamination of Zr(NEt2)4 with 4 (H3L´) yields L´Zr(NEt2) (6) in which triply deprotonated 4 coordinates to zirconium via an η5-indenyl and both N-indolide moieties in a constrained geometry fashion. The molecular structures of 3·THF, 5·3THF, and 6·0.5C7H8 were confirmed by X-ray crystallography.

A review is given of the chemistry of compounds containing platinum-metal bonds, focussed on the research developed in the author's group. The synthetic methods, structures and bonding, and reactivity are treated, as well as the ability of some compounds to mimic the reactivity of platinum-containing bimetallic catalysts, which are widely used in petroleum reforming.

A post-modification strategy is used to synthesize a new class of diimine-amido PN3P-pincer group-10 transition metal complexes. The coordination chemistry and the thermal stabilities of their organometallic derivatives are characterized and investigated.

The first N-heterocyclic carbene 1 featuring a cyclic sulfonamide structural motif has been prepared from 1,2,4-benzothiadiazine-1,1-dioxide. Within the six-membered heterocycle the carbene C atom is bound to an amino and a sulfonamido group. The (COD)Rh and (CO)2Rh complexes of the new NHC have been prepared and fully characterised including X-ray diffraction studies. Spectroscopic and structural data indicate that 1 is a poor overall donor (TEP: 2063 cm−1) and it has donor/acceptor properties that are close to those of related cyclic carboxamide substituted carbenes.

The molecular structures of the transition metal cyclohexasilyl complexes M(CO) 5 Si 6 Me 11 * 0.5 n -C 5 H 12 (M = Mn, Re) were determined by single crystal X-ray diffraction. The two compounds are isomorphous. Their silicon-silicon bond lengths are compared with those of the parent cyclohexasilane and of other cyclohexasilyl complexes (comprising group 6, 7, 8, and 10 as well as row 3, 4, and 5 transition metals) with respect to silicon-silicon bond activation.

We report the synthesis and structural characterization of moderately air stable metal rich metallaboranes of iridium. Treatment of [Cp*IrCl2]2 with BH3·thf at high temperature led to the isolation of a trimetallic [nido-5-(Cp*Ir)3B7H11], 1. Compound 1 is isoelectronic and isostructural with decaborane-14 where three BH units in [B10H14] have been replaced by Cp*Ir fragments. As far as we are aware, 1 is the first example of a iridadecaborane having three metals. In addition to the formation of 1, a change in the reaction conditions enabled us to isolate a 7 sep [(Cp*Ir)3B4H4], 2. The geometry of 2 can be viewed as a condensed polyhedron composed of Ir3B3 octahedron capped by a BH unit. All the compounds have been characterized by IR and 1H, 11B, and 13C NMR spectroscopy in solution, and the solid-state structures were established by X-ray crystallographic analysis. Quantum-chemical calculations by DFT methods for compounds 1 and 2 showed reasonable agreement with the experimentally observed structural parameters. The large HOMO–LUMO gaps are consistent with the high stabilities of the iridium clusters compared to their known Rh and Co analogues.

Organic selenides were efficient regioselective synthesized by palladium-catalyzed switchable mono- and diselenylation of arenes sp 2 C–H bonds through simply tuning the DMSO to water ratio. The present protocol was also successfully extended to the monoselenylation of 2-phenoxypyridines, which bore a removable directing group, in modest yields.

Para- and meta-substituted o-carboranes with a dimesityl(phenyl)borane (dmpb) group, namely, p-1, p-2, m-1, and m-2, were prepared and their electronic natures were evaluated by steady-state photophysical methods. It was found that excited states were greatly influenced by the linking position of the dimesityl-borane group(s) at the phenyl unit of diphenyl-o-carboranes. While intramolecular charge-transfer (ICT) prevails in both para- and meta-regioisomers, para-isomers show much enhanced ICT character, as evidenced by observation of a new emission band at λmax ≈ 570 nm in dichloromethane (DCM) solution. Furthermore, the solvatochromic shifts, Δυf, from n-hexane to DCM were significantly different for para- and meta-isomers, which showed 8105, 8184, 1834, and 1895 cm−1 for p-1, p-2, m-1, and m-2, respectively. The difference in dipole moment between ground and excited states for para- (∼31.8 D) and meta-isomers (∼15.0 D) by using Mataga–Lippert plot confirmed that the ICT occurs from dimesityl-borane to o-carborane in para-isomers while the ICT occurs only from dimesityl-borane to the bridged phenyl group in meta-isomers. Excited state estimation by electrochemical and DFT studies corroborated well to the ICT character, and even with engagement of the strong electron withdrawing dimesityl-borane group o-carborane unit still acts as an electron accepter as found in the para-isomers, p-1 and p-2.

Since the first isolation of an N-heterocyclic carbene (NHC) in the early 1990s, these species have been identified as valuable tools for the stabilization of main-group elements in unusual oxidation states and allowed for the isolation of novel types of compounds. While bis(NHC)s, i.e., compounds in which two NHC units are framed within one molecule by using suitable linker groups, found numerous application in rare-earth and transition-metal chemistry, this does not hold true for main-group elements. Although examples are found throughout the s- and p-block, their potential still needs to be realized. This review summarizes the syntheses of the related bis(NHC)s and gives an overview of mono-, di- and polynuclear complexes incorporating main-group elements and bis(NHC)s.

Phosphine functionalized imidazolium precursors were reacted with triiron(0)- resp. triruthenium(0)dodecacarbonyl in order to compare the reactivity of the Group VIII metals. Furthermore, [(η6-cymene)RuCl2]2 was treated in a transmetallation reaction with the silver(I) resp. copper(I) complexes of the corresponding imidazolylidenes possessing sterically largely different substituents at the NHC site, in order to evaluate the influence of these substituents on the catalytic activity of the ruthenium complexes.

Methylation of 3-amino-1,2,4-triazole and 1-methyl-3-nitro-1,2,4-triazole provides access to three NHC-precursors. For the nitro compound only a monomethylation to the triazolium salt 3(OTf) is observed. The aminotriazole could be subsequently converted to mono- and dicationic carbene precursors 1I and 2(OTf)2, respectively. The nitro group on NHC 3 leads to a decrease of donor strength and a slightly enhanced acceptor character as compared to a related NHC lacking the nitro group. The cationic NHC 2 is the poorest donor within the series and shows a TEP value of 2072 cm−1. The properties of this species are dominated by its cationic nature while the influence of the NMe2 group is surprisingly small. X-ray diffraction studies suggest a guanidinium-like character for the NMe2 substituted compounds.

The review discusses the structures, properties and applications of ortho-substituted phenylboronic acids. The compounds were compared with meta- and para-isomers, indicating differences resulting from the presence of a substituent in close proximity to the boron group. The effect of an individual substituent on the electron density on boron atom and, as a result, on the acidity constant of these compounds were discussed. Geometric parameters for compounds with known crystal structures were collected and their relationships with the possibility of forming intramolecular hydrogen bonds were evaluated. The most important groups of ortho-substituted boronic acids were evaluated from the point of view of their use in synthesis, analytical chemistry as well as their biological activity.

Stable mono- and dicarboxylate phosphabetaines with α-location of the phosphonium center relative to the carboxylate group on the basis of methyldiphenylphosphine, triphenylphosphine, 3-(diphenylphosphino)propionic acid, various bisdiphenylphosphines and glyoxylic acid have been synthesized.

A narrow area of macrocyclic ligands, including N-heterocyclic carbene (NHC) groups and their metal complexes, is reported in the review. This review highlights recent perspectives in the fields of synthesis and structures of mononuclear macrocyclic NHC metal complexes and their catalytic applications. The review covers some transition metals (Cr, Fe, Co, Ni, Rh, Ru, Pd, Pt and Au) and group 13 and 14 metals (Sn, In and Al) with a limited number of macrocyclic tetra-NHC ligands.

The reaction of di-iron nonacarbonyl with triphenyl stannane yielded the bow-tie structured Fe4(CO)16(μ4-Sn), 1. 1 reacted with LPh3 to afford the corresponding derivatives Fe4(CO)15(LPh3)(μ4-Sn), (L = P, 2, L = Sb, 3) by CO substitution on Fe. 2 and 3 were characterized crystallographically by single-crystal X-ray diffraction techniques.

By carrying out B3LYP calculations, we have performed a detailed mechanism study on the reaction of platinum catalyzed rearrangements of homopropargylic alcohols derivatives into isomeric polysubstituted furans in THF and toluene solutions, respectively. The reaction steps include α,β-unsaturated carbene complex formation, and H atom or Si (Si = tert-butyldimethylsilyl) group migration. In the step of α,β-unsaturated carbene complex formation, the methoxy group is the optimal leaving group. Our calculations are consistent with the experimental results that Si-migration is favored in toluene while H-migration is favored in THF. Based on the Cl-aided H-migration mechanism postulated by Ferreira et al., we proposed a H 2 O and Cl co-aided H-migration mechanism in THF, in which H 2 O and Cl both act as the medium to transfer H.

The lowest singlet and triplet potential energy surfaces for all group 15 HSbXH (X = N, P, As, Sb, and Bi) systems have been explored through ab initio calculations. The geometries of the various isomers were determined at the QCISD/LANL2DZdp level and confirmed to be minima by vibrational analysis. Our model calculations indicate that the relativistic effect on heavier group 15 elements should play an important role in determining the geometries as well as the stability of HSbXH molecules. The results obtained are in good agreement with the available experimental data and allow a number of predictions to be made.

DFT calculation of cluster shapes and their related boron-vertex 11B nuclear shieldings for a range of substituted 12-vertex metalladicarbaborane cluster compounds [3,1,2-R2-3-(η6-C6H6)-3,1,2-RuC2H9H9] confirms that the array of experimentally observed C–C distances in the group of progressively more open closo, ‘semipseudocloso’ and ‘pseudocloso’ clusters results from the inherent propensity of the [(η6-C6H6)RuC2H9H9R2] cluster to occupy, in the absence of steric drivers, either closo-structured or so-called ‘pseudocloso’-structured fundamental local minima on the overall potential energy surface. The shallow profiles of the potential wells, together with the electronic and steric influences of substituents on the cluster carbon vertices, alter the relative energies of the closo and ‘pseudocloso’ minima, and alter the energy profile between them, thereby accounting for the observed variations in the distances in the crystallographically measured C–C separations. We propose that these differ fundamentally due to either the closo or ‘pseudocloso’ configuration being electronically preferred, with some instances of the ‘pseudocloso’ configuration being compressed towards closo by packing forces, or stretched further beyond ‘pseudocloso’ by steric effects of bulky substituents on carbon. This contrasts with one view postulated in the literature which holds that steric repulsion between the C-bound substituents is the sole driver that forces an inherently fundamental closo cluster to open into an anomalous ‘pseudocloso’ configuration. In two reported cases, the cluster flexibility is evident in solution and, in these cases, GIAO calculation of the 11B chemical shieldings explains the measured 11B chemical shifts, which can be interpreted in terms of the dynamic interchange of the closo and ‘pseudocloso’ species. A currently held view is that the ‘weighted average’ of 11B chemical shifts reflects the inherent degree of electronic ‘pseudocloso’ character in a particular cluster can therefore often equally be rationalised in terms of lability between similarly stable fundamentally closo and ‘pseudocloso’ forms.

The reaction of the trans-cyclo-[2,6-Mes2C6H3Sn(O)(OH)]3 with the dimeric pnictogen(III) oxides [2,6-(Me2NCH2)2C6H3EO]2 (E = Sb, Bi) proceeds with mutual ring-opening and provided the novel tetranuclear metallastannoxanes [2,6-(Me2NCH2)2C6H3E](2,6-Mes2C6H3Sn)3O3(OH)5 (1, E = Sb; 2, E = Bi) that were fully characterized by X-ray crystallography.

Three (PR)2-bridged [2]ferrocenophanes (R = tBu (10a), nBu (10b), and Ph (10c)) in which the two C5H4 rings of the ferrocene unit were bridged with a P(III)—P(III) bond were synthesized via Mg-mediated reductive coupling between the phosphorus centers of corresponding [Fe{C5H4P(Cl)R}2]. The P(Cl)R groups of [Fe{C5H4P(Cl)R}2] were derived from the P(NEt2)2 groups of [Fe{C5H4P(NEt2)2}2] as follows: the P(NEt2)2 group was first converted to P(Cl)NEt2 by HCl, and then R (R = tBu, nBu, and Ph) was introduced to give P(R)NEt2, which was again allowed to react with HCl to form the P(Cl)R group. Of the three diphospha[2]ferrocenophanes, (PtBu)2-bridged [2]ferrocenophane (10a) could be isolated as free diphosphine, while because of difficulty in their isolations as free ligands, the nBu and Ph analogs (10b and 10c, respectively) were characterized as bis(pentacarbonylmetal) complexes (μ-10b)-[W(CO)5]2 (11) and (μ-10c)-[Cr(CO)5]2 (12), in which the respective phosphorus centers were coordinated to the pentacarbonylmetal fragments. X-ray analysis was performed for the three diphospha[2]ferrocenophanes, 10a, 11, and 12, demonstrating that their P—P bond lengths are 2.3093(7), 2.261(5), and 2.2502(8) A, respectively. Because these tether P—P lengths are smaller than an ideal distance between the two parallel C5H5 rings of ferrocene, the two C5H4 rings of each of 10a, 11, and 12 are inclined from the parallel by 12.9°, 9.7°, and 13.6°, respectively. DFT calculations were performed on (PH)2-bridged [2]ferrocenophane as a model-compound, and showed that there are two conformational isomers. One, named the parallel form, features a P—P bond that is almost parallel to the axis passing through the centers of the two C5H4 rings, while the P—P bond of the other, named the twist form, leans with the two C5H4 rings twisted. The smaller inclined angle of 9.7° observed for 11 was found to result from its parallel-form conformation, while the C5H4 rings of 10a and 12 were more inclined due to adoption of the twist-form conformation.

Three new IrRuAu trimetallic cluster complexes: IrRu3(CO)13AuPPh3, 1, HIrRu3(CO)12(AuPPh3)2, 2 and IrRu3(CO)12(AuPPh3)3, 3 were obtained in low yields from the reaction of HIrRu3(CO)13 with [(AuPPh3)3O][BF4]. Compounds 1 and 3 were subsequently obtained in much better yields (82%) and (84%) from the reactions of [AuPPh3][NO3] and [(AuPPh3)3O][BF4] with [PPN][IrRu3(CO)13], respectively. The molecular structures of all three compounds were established by single crystal x-ray diffraction methods. Compounds 1 and 2 contain an Au(PPh3) group that bridges one triangular face of a tetrahedral IrRu3 cluster. Compound 2 contains a second Au(PPh3) capping group that bridges an Ir–Ru–Au triangle. Compound 3 consists of a pentagonal bipyramidal Au3IrRu3 cluster that has three gold atoms and two of the ruthenium atoms in the equatorial plane. There is a bond between the apical Ir and Ru atoms. Compounds 2 and 3 exhibit dynamical activity in the metal skeleton that leads to a rapid averaging of the inequivalent Au(PPh3) groups on the NMR timescale at room temperature.

Alkyl aluminum-, gallium-, and indium oxamidates Me4Al2(dpoa) (1), Me4Al2(dboa) (2), Me4Ga2(dpoa) (3), Me4Ga2(dboa) (4), t Bu4Ga2(dpoa) (5) and Me4In2(dboa) (6) (dpoa-H2 ¼ N,N 0 -diphenyloxamide, dboa-H2 ¼ N,N

Two novel mono- and bi-functionalized organoimido derivatives of hexamolybdates bearing the strong electron-withdrawing nitro group, (Bu4N)2[Mo6O17( NAr)2] (1) and (Bu4N)2[Mo6O18( NAr)] (2) (Ar o-NO2–C6H4) have been synthesized for the first time via the reaction of hexamolybdate ions and 2 equivalent of aromatic amines with an excessive dehydrating agent N,N′-dicyclohexylcarbodiimide (DCC). By controlling the amount of DCC, such two derivatives can be selectively prepared in reasonable yields, which have been characterized with UV/vis, IR, 1H NMR, ESI-mass spectrometry and single-crystal X-ray diffraction techniques. The influences of [NAr] ligands and [NAr] incorporation number on properties and supermolecular assembly of such two derivatives have been systematically investigated.

Radiochemical studies of nucleogenic trivalent cations of the 14th group elements (silicon and germanium) generated by the β-decay of tritium atoms incorporated into organometallic molecules are reviewed. The radiochromatographic analysis of the neutral labeled products of reactions of these cations with various nucleophiles combined with quantum chemical data allowed us to obtain new information about the reactivity and rearrangements of silylium and germylium cations.

Desulfurizative titanation of group 14 metal compounds bearing two or four bis(phenylthio)methyl groups with the low-valent titanium reagent Cp 2 Ti[P(OEt) 3 ] 2 produced phenylthio groups substituted 1-metalla-3-titanacyclobutanes stereoselectively. The molecular structures of the titanacycles were unambiguously confirmed by X-ray diffraction analysis.

A computational study with Becke3LYP of DFT was carried out to investigate the ligand exchange reaction mechanisms of Cp(CO)FeH(EEt3)(E′Et3) with (HEEt3) (E, E′ = Si, Ge, Sn). The full ligand exchange reactions were computed, starting from the reductive elimination and then followed by the oxidative addition. The reductive elimination of HEEt3 from the Fe(IV) center takes place more readily in the order Et3Si–H > Et3Ge–H ≫ Et3Sn–H. There are several reasons for the order: (i) the thermodynamic stability of the corresponding products, (ii) the order of bond binding energy: Et3Si–H > Et3Ge–H > Et3Sn–H, (iii) the order of the interaction of E–H: Et3Si–H > Et3Ge–H > Et3Sn–H.

The saturated, four-membered rings of the type [XP(μ-NR)] 2 containing alternating phosphorus(III) and nitrogen atoms are known as cyclodiphosphazanes or diazadiphosphetidines. The current interest in these well-known heterocycles is due to their catalytic and biological applications besides their excellent synthetic utility as scaffolds to design interesting macrocycles with or without involving main group or transition metals. Although the rigid and nearly-planar neutral P 2 N 2 rings resemble [Cu(μ-X)] 2 (X = Cl, Br or I) rhombic units ([Cu(μ-X)] 2 are known for giving a variety of structures with suitable ligands), their utility in designing the high-nuclearity clusters, cages or coordination polymers is scarce. In this context, we fine tuned the coordinating ability of these ligands by incorporating pendant hemi-labile functionalities on phosphorus centers which resulted in the isolation of several interesting molecules. The details are described.

The oxidative addition of selenol, HhfSeH ( 2 , Hhf = 9,10,11,12,14,15-hexahydro-9,10[3′,4′]-furanoanthracenyl) with [Pt(η 2 -nb)(Ph 3 P) 2 ] (nb = norbornene) in toluene afforded the corresponding hydrido(selenolato) Pt(II) complex [ cis -PtH(SeHhf)(Ph 3 P) 2 ] ( 3 ) as a stable compound. Refluxing a xylene solution of 3 produced two isomers of five-membered selenaplatinacycles 4 in moderate yield as an inseparable mixture. In addition, the molecular structures of HhfSeH 2 and the minor selenaplatinacycle 4a were determined by X-ray crystallography.

The synthesis of a series of azolium salts such as azolium iodides and chlorides having both N-anionic functional group and N-alkyl group have been developed. Reaction of azolium iodides or chlorides with Ag2O gave the corresponding NHC–Ag complexes. It was found that the resulting NHC–Ag complexes derived from azolium iodides or chlorides differ in their physical properties. The azolium chlorides as well as azolium iodides were successfully converted into the NHC–Ag complexes, which subsequently reacted with PdCl2(CH3CN)2 to give the anionic amidate/NHC–Pd complexes. Thus, a variety of the NHC–Pd complexes could be obtained from benzimidazolium and imidazolium salts.

We wish to report the synthesis and characterization of Group 9 metal complexes with the novel P , P ′-diphenyl-1,4-diphospha-cyclohexane (dpdpc) ligand. The complexes are readily prepared by direct ligand substitution reactions from the dichloro-bridged binuclear complexes, [{η 5 -Cp*M(Cl) 2 } 2 ]. The complexes include: [η 5 -Cp*Rh(Cl) 2 ] 2 (μ-dpdpc) ( 1 ), [η 5 -Cp*Ir(Cl) 2 ] 2 (μ-dpdpc) ( 2 ), and [η 5 -Cp*Rh(Cl)(dpdpc)]PF 6 ( 3 ). The structures for all three complexes are supported by 1 H, 13 C{ 1 H}, and 31 P{ 1 H} NMR spectroscopy as well as elemental analysis. The molecular structures of 1 and 3 have also been established by single-crystal X-ray analysis.

Six compounds of cyclic hypervalent organobismuth(III) chlorides and triphenylgermylpropionates bearing a nitrogen or sulfur atom as intramolecular coordination atom have been synthesized and characterized. The results of single-crystal X-ray analysis reveal that the eight-membered tetrahydroazabismocine rings are highly flexible. The Bi–S or Bi–N bond lengths in the thiabismocine or azabismocine derivatives are dependent on how the substituted groups are acting on the Bi, S or N atom. The replacement of the chlorine atom in azabismocine and thiabismocine with the triphenylgermylpropionic group (Ph3GeCH2CH2COO ) leads to the lengthening of Bi–N and Bi–S bond. The substituents connected with the nitrogen atom also have an effect on the Bi–N bond length of azabismocine. For example, a cyclohexyl group has electron-donating ability higher than a phenyl group; the replacement of the former by the latter would lead to the decline of Bi–N bond length and increase of CAr–Bi–CAr angle in the eight-membered ring. The in vitro antiproliferative activities of the fabricated materials were compared on gastric carcinoma cells by means of the 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl tetrazolium bromide (MTT) method. It was found that the compounds show antiproliferative activity on gastric carcinoma cells (MGC-803) much higher than that of cisplatin. Moreover, there is enhancement of antiproliferative activity when the chlorine atom of the bismocine compounds is replaced by the triphenylgermylpropionic group, giving a low IC50 value of 0.7 μM for thiabismocine triphenylgermylpropionate.

Seven group 14 element(IV) compounds 2–7 have been prepared, derived either (2–5) from the potassium β-diketiminate K(L) [L = {N(Ar)C(Me)}2CH, Ar = C6H3Pri2-2,6] (1) or the known lithium β-dialdiminate Li(L′)] [L′ = {N(Ar)C(H)}2CPh, Ar = C6H3Pri2-2,6]. Treatment of 1 with ButC(O)Cl, Me3SiCl, Ph3SnCl, or Me3SnCl afforded {N(Ar)C(Me)}2C(H)C(O)But (2), [ArNC(Me)C(H)C(Me)N(Ar)SiMe3] (3), [HN(Ar)C(Me)C(H)C(CH2SnPh3)N(Ar)] (4), or (5), respectively. Compounds 4 and 5 are remarkable as they have arisen from a tautomer of 1; crystalline centrosymmetric 5 has a fused tricyclic structure, a central eight-membered ring flanked by two six-membered rings. The compounds [GeCl2(L′)(OGeCl3)] (6) or [SnCl(L′)Me2] (7), the first group 14 metal β-dialdiminates, were obtained from Li(L′) and (GeCl3)2O or Me2SnCl2, respectively. The Sn(II) compound SnCl(L′) (8) was prepared from SnCl2 and K(L′). The molecular structures of the crystalline compounds 3–8 are reported.

A series of gold chloride {AuCl} adducts of the sterically demanding phosphines DmpPR2 (Dmp = 2,6-dimesitylphenyl; R = H (1); Me (2); Cl (3)) have been prepared. The adducts are readily formed by the reaction of Au(tht)Cl and DmpPR2, yielding [(DmpPR2)AuCl] (R = H (4); Me (5); Cl (6)) in moderate to excellent yields. All three new compounds have been structurally characterized. The structures demonstrate little or no significant intermolecular Au⋯Au or intramolecular Au⋯arene interactions. In addition, the new difluoroarylphosphine DmpPF2 (7) has been prepared and structurally characterized.

Photolysis of Group VIII complexes of the form M(CO) 2 X 2 L 2 and chelated ruthenium compounds, Ru(CO) 2 Cl 2 (κ 2 -L) in frozen matrices results in CO-loss. In the case of Fe(CO) 2 Br 2 (PMe 3 ) 2 evidence is presented for photochemical bromide ion elimination.

The Group 6 metal tetracarbonyl complexes [Cr(CO) 4 {FcTe(CH 2 ) 3 TeFc}], [Mo(CO) 4 {FcE(CH 2 ) 3 E′Fc}] (E = E′ = Se; E = Se, E′ = Te; E = E′ = Te), and [W(CO) 4 {FcTe(CH 2 ) 3 TeFc}] (Fc = [Fe(η 5 -C 5 H 5 )(η 5 -C 5 H 4 )]) have been prepared and fully characterised. Electronic communication between the ferrocenyl groups is observed in the case of [Mo(CO) 4 {FcSe(CH 2 ) 3 SeFc}], where the through-bond Fe⋯Fe distance is 13.17 A, but in the other four complexes the longer through-bond Fe⋯Fe distances (⩾13.56 A) preclude it.

Pyridylimine ligands of general formula CS-{O-4-(2,5-C6H2R2)-NCH-2-Py}n, where CS is a trimethylsilyl group (n = 1, R = H, Ia or Me, Ib) or a carbosilane dendritic framework (IIa,b, n = 4; IIIa, n = 8), have been coordinated to platinum(II) and molybdenum(0) centers to give the mononuclear [(Ia,b){PtCl2}], tetranuclear [(IIb){PtCl2}4] and [(IIa){Mo(CO)3(MeCN)}4], and octanuclear [(IIIa){Mo(CO)3(MeCN)}8] complexes. The poor solubility of the polymetallic platinum compounds impedes the preparation of higher-generation dendrimers, although such a limitation is not found in the case of the more soluble molybdenum dendrimers.

Density functional theory (DFT) at the generalized gradient approximation (GGA) level has been applied for the analysis of the bond between group 10 metals and N-heterocyclic carbene (NHC) in complexes [MX3(NHC)] � (M = Ni, Pd, Pt, X = H, Cl, I). For comparative purposes, similar calculations have been performed for analogous pyridine complexes [MX3(py)] � (py = pyridine). Full geometry optimizations have been performed for all complexes. The role of the M–L p interaction was investigated by the aid of respectively, energy decomposition analysis, Hirshfeld atomic charge variation, molecular orbital considerations and bond order decomposition analysis. The p-bonding contribution increases in the order I < Cl < H, and Pt < Pd < Ni. Most significantly, the absolute p-acceptor ability of the NHC in these complexes is larger than that of pyridine. However, due to the dominant r donor interactions, the relative contribution, that is the p/r ratio, is predicted to be smaller.

An efficient route for the preparation of Mes2HSiCH2CN (1) and (Mes2HSi)2CHCN (2) is reported (Mes = 2,4,6-trimethylphenyl). Although the X-ray analyses for 1 and 2 reveal the CHnCN functionality (n = 1, 2) to be shielded by the Mes2HSi group, hydrolysis under basic conditions gave exclusively Mes2HSiOH (3), as a result of hydroxide-induced Si–C bond cleavage. In the solid state 3 is a tetramer forming an eight membered ring by H-bond interactions.

The nickel–molybdenum complex [(η5-C5Me5)Ni Mo(CO)3(η5-C5H4Me)] can be considered to contain a partially dative nickel–molybdenum double bond. This complex reacts with the bulky terminal alkyne HC CCPh2(OMe) (DPMP) to afford the alkyne–carbonyl coupled metallacyclic product (3c, R = CPh2(OMe), Ni–Mo) regioselectively and exclusively. No traces of a nickel–molybdenum μ-alkyne complex, analogous to similar complexes isolated with less bulky alkynes, were observed. The structure of complex 3c was established via a single crystal X-ray diffraction study. It exhibits the same connectivity as that observed with a related complex formed with the smaller but-2-yne, but some significant differences are observed between the two structures. Reactions of the nickel–molybdenum and -tungsten species [(η5-C5Me5)Ni M(CO)3(η5-C5H5)] (M = Mo, W) with DPMP proceeded analogously and afforded similar products.

In attempts to form group 15 heteroalkynes, the reactions of Ar′C(O)Cl ( Ar ′ = C 6 H 3 ( C 6 H 2 Pr 3 i - 2 , 4 , 6 ) 2 - 2 , 6 ) or Ar″C(O)Cl (Ar″ = C6H3(C6H2Me3-2,4,6)2-2,6) with [LiE(SiMe3)2] (E = P, As or Sb) have been carried out. No reactions occurred with the bulkier acid chloride, Ar′C(O)Cl, whilst reactions only occurred with Ar″C(O)Cl at elevated temperatures. One of these afforded the first terphenyl substituted phosphaalkyne, P CAr″, as an air stable, crystalline solid. The X-ray crystal structure of this compound was obtained.

The 18e Cp-containing silene tungsten complex, Cp2W(η2-Me2Si CH2), can break H–H bond to afford the product, Cp2WH(SiMe3). The mechanisms on reaction of Cp2W(η2-Me2Si CH2) with H2 are investigated in this paper by using density functional theory (DFT). On the basis of the features of the reaction and experimental proposal for the reaction mechanisms, three possible pathways are proposed, which are related to the migration of silicon group, Cp ring slippage, and σ-bond metathesis, respectively. Our results of calculations indicate that the pathway involving migration of silicon group is the most favored, supporting the experimental observations. The other two paths are quite unfavorable kinetically.

The combined use of theoretical and mathematical methods in the analysis of electron paramagnetic resonance data has greatly increased the ability to interpret even the most complex spectra reported for doublet state inorganic main group radicals. This personal account summarizes the theoretical basis of such an approach and provides an in-depth discussion of some recent illustrative examples of the utilization of this methodology in practical applications. The emphasis is on displaying the enormous potential embodied within the approach. peerReviewed

In the reaction of oxiranes and cobalt-containing early–late heterobimetallic (ELHB) compounds isolated or prepared in situ, acyl-cobalt complexes, Y 3 M E OCHRCH 2 C(O)Co(CO) 4 ( 1 , M E = Ti, Zr, Hf), were obtained. Some of the complexes 1 were isolated in form of their derivatives substituted on the cobalt atom with PPh 3 . We have demonstrated that the ELHB compounds containing Group 4 metals and silyl-cobalttetracarbonyls are analogous concerning their reactivity against oxiranes. The studied heterobimetallic systems mediated the rearrangement of terminal oxiranes to ketones.

Group 4 metallocene complexes can form adducts or condensation products with a variety of typical biogenic molecules. In this account, examples are presented and discussed for the reactions of zirconocene or titanocene complexes with suitably protected/deprotected carbohydrate derivatives. Some methodological developments are shown for the attachment of aminoacid or peptide derived functional groups at the Cp-rings of the Group 4 bent metallocenes. Eventually, the reactions of methylzirconocene- and methyltitanocene cations with a series of short oligopeptides are discussed that lead to the formation of primary κO-adducts followed by O,N,O-chelate complex formation with methane evolution. The dynamic features of some such systems are discussed.

Reactions of incomplete cubane-type clusters [(Cp°RuCl)2(μ-SH)(μ-SM′Cl2)] (M′ = Sb (2a), Bi; Cp° = η5-C5Me4Et) with 0.5 equiv of [PdCl2(cod)] (cod = 1,5-cyclooctadiene) afforded the corner-shared double cubane-type clusters [{(Cp°Ru)(Cp°RuCl)(μ-SM′Cl2)}2(μ3-S)2(μ-Cl)2Pd] (3a: M′ = Sb, 3b: M′ = Bi) in moderate yields, whereas treatment of 2a with 0.75 equiv of [PdCl2(cod)] gave the corner-shared triple cubane-type cluster [{(Cp°Ru)(Cp°RuCl)(μ-SSbCl2)(μ3-S)2(μ-Cl)2Pd}2(Cp°Ru)2] (4). Single-crystal X-ray analyses have disclosed the detailed structures of novel heptanuclear and decanuclear mixed-metal cores for 3a and 4, respectively.

Allylation of chlorosilanes has been achieved with allylsamarium bromide, especially in a controlled manner. Thus allylation of trisubstituted chlorosilanes (R 3 SiCl) afforded a variety of aryl, aralkyl, and alkenyl substituted allylsilanes. Dichlorosilanes (R 2 SiCl 2 ) can either afford monoallylated silanes or diallylated silanes depending on the amount of allylsamarium bromide used. Similarly, trichlorosilanes (RSiCl 3 ) can selectively afford mono-, di-, and tri-allylation products. Finally, perchlorosilane (SiCl 4 ) was allylated stepwise and the corresponding silanes containing one, two, three or four allylic groups, respectively, were obtained in satisfactory yields.