Synthesis and Structure of Alkali Bis(phosphinimino)methanides

The reaction of CH₂(PPh₂NSiMe₃)₂ with n‐butyllithium or potassium hydride in THF leads, after the recrystallization from toluene or n‐heptane/diglyme, to the corresponding alkali derivatives [Li(THF)][CH(PPh₂NSiMe₃)₂] ( 1 ), K[CH(PPh₂NSiMe₃)₂] ( 2 ), and [K(digylme)][CH(PPh₂NSiMe₃)₂] ( 3 ). Upon coordination to the metal center the ligand forms a six membered metallacycle in which both phosphinimine nitrogen atoms bind to the metal atom.     

Thio- and Seleno-Compounds of Main Group Elements—Novel Inorganic Oligomers and Polymers

During the last decade modern preparative and structural methods have led to novel and often unexpected oligomeric and polymeric main group element-sulfur compounds having remarkable bonding and structural properties and reactivities. Examples of important new developments in this area are: the discovery of boron sulfides B₈S₁₆ and (BS₂)_n and of ion-conducting air-stable thioborates with tetrahedrally coordinated boron; the successful use of boron sulfides in organic and inorganic syntheses; the preparation of different homologous series of molecular polynuclear thio- and selenoanions of Ga, In, Si, Ge and Sn, and of new polynuclear sulfide- and selenide-halides of Si and Ge as interesting reagents for inorganic and organic reactions; the synthesis of argyrodite(Ag₈GeS₆)-like phases with remarkable solid-state properties; and the characterization of the S? H…S type hydrogen bridge in thiocarbonic acid and thiophosphinic acids, which is of importance for an understanding of certain interactions in sulfur-containing biomolecules.     

[Me2AlBi(SiMe3)2]3—The First Structurally Characterized Organometallic Compound Containing a Bond between an Element of Group 13 and Bi

Dehydrosilylation of Bi(SiMe₃)₃ with Me₂AlH gave the title compound. This has a trimeric structure, the central unit of which is a six-membered Al₃Bi₃ ring (see structure). In agreement with the VSEPR model the angles are greater at the Al centers and smaller at the Bi centers.     

Homoatomic Bonding of Main Group Elements

Clusters of main group elements are not rare. On the contrary, it is becoming difficult to avoid the discovery of new substances of this type. Clusters are the natural intermediate stages between an element and its isolated atoms or ions. In the form of polycations and polyanions they offer models for the stepwise oxidation and reduction of an element and represent a bridge between the elements. The great majority of homonuclear bonded structures are already present in the solid phases of simple systems. Mobilization of these clusters as molecules represents a great challenge.     

Structurally Defined Allyl Compounds of Main Group Metals: Coordination and Reactivity

Organometallic allyl compounds are important as allylation reagents in organic synthesis, as polymerization catalysts, and as volatile metal precursors in material science. Whereas the allyl chemistry of synthetically relevant transition metals such as palladium and of the lanthanoids is well‐established, that of main group metals has been lagging behind. Recent progress on allyl complexes of Groups 1, 2, and 12–16 now provides a more complete picture. This is based on a fundamental understanding of metal–allyl bonding interactions in solution and in the solid state. Furthermore, reactivity trends have been rationalized and new types of allyl‐specific reactivity patterns have been uncovered. Key features include 1) the exploitation of the different types of metal–allyl bonding (highly ionic to predominantly covalent), 2) the use of synergistic effects in heterobimetallic compounds, and 3) the adjustment of Lewis acidity by variation of the charge of allyl compounds.     

Covalent versus Dative Bonds to Main Group Metals,a Useful Distinction

Textbooks of inorganic chemistry describe the formation of adducts by coordination of an electron donor to an electron acceptor, often using the amine-boranes, X₃N → BY₃, as examples. In the Lewis (electron dot) formulas of the compounds, the dative bond in H 3 N → BH₃ and the covalent bond in H₃C?CH₃ are both represented by a shared electron pair. In the simple molecular orbital or valence bond models the wave functions of both electron pairs would be constructed in the same manner from the appropriate sp³ type atomic orbitals on the bonded atoms; the difference between the covalent and the dative bond becomes apparent only after the orbital coefficients have been analyzed. This may be the reason why many structural chemists seem reluctant to distinguish between the two types of bonds. The object of this article is to remind the reader that the physiocochemical properties of covalent and dative bonds may be – and often are – quite different, and to show that a distinction between the two provides a basis for understanding the structures of a wide range of main group metal compounds.     

Some past vignettes of and future prospects for Main Group chemistry

The present article traces, from the author's perspective, some of the important developments in the chemistry of the Group 13 and 15 elements that have taken place over the past three decades. Included in the review are compounds that feature multiple bonding between heavier Main Group elements, the coordination chemistry of Group 13 and 15 carbene analogues, and novel ring systems involving these elements. Some materials science and medicinal aspects of this area of chemistry are also presented.     

Multiple Bonds between Transition Metals and “Bare” Main Group Elements: Links between Inorganic Solid State Chemistry and Organometallic Chemistry

The last two decades have seen a dramatic development in the study of metal-metal multiple bonds, particular successes being recorded in the field of organometallic chemistry. Syntheses designed to produce novel transition metal complexes with single, double, triple and quadruple metal-metal bonds occupy a most important place in such research, as also do reactivity studies. A striving to establish general principles has provided much of the motivation for such work, but one less obvious goal—the commercial application of the catalytic properties of metal-metal multiple bonding systems, in the medium and long term—should not be overlooked. All aspects of the investigations of metal-metal multiple bonds also apply to a particular class of compound that has, however, enjoyed little lime-light and thus deserves the present review: complexes with multiple bonds between transition metals and substituent-free (“bare”) main group elements. Although based mostly on accidental discoveries, the few noteworthy examples are now beginning to unfold general concepts of synthesis that are capable of being extended and thus are deserving of exploitation in preparative chemistry. The availability of further structural patterns exhibiting multiple bonds between transition metals and ligand-free main group elements might enable preparative organometallic chemistry to expand in a completely new direction (for instance by the stabilizing or activation of small molecules at the metal complex). This essay discusses the chemistry of complexes of bare carbon, nitrogen, and oxygen ligands (carbido-, nitrido-, and oxo-complexes) and their relationships to higher homologues from both a synthetic and a structural point of view.     

Palladium(II) Complexes of 1-Phosphaisoprene Molecules and Polymers: Reversible Cross-Linking of a Phosphorus-Containing Polymer

The anionic polymerization of 1-phosphaisoprene [Mes*P=C(Me)−CH=CH₂ (E- 1 )] affords poly(1-phosphaisoprene) 2 in high yield (75 %). Concentrated solutions of polymer 2 (M_n=21,800 g mol⁻¹; Đ=1.02) a P-analogue of natural rubber, undergo gelation upon treatment with [Pd(cod)Cl₂] (0.15 P equiv). Evidence for P-coordination of 2 to Pd^II was obtained by ³¹P and ¹H NMR spectroscopy. The gelation is reversed by the addition of PMe₃ and the reformation of recoverable 2 along with [Pd^II−PMe₃] complexes were confirmed by ³¹P NMR spectroscopy. The use of labile metal-ligand bonds to reversibly form gels is unprecedented and has relevance to self-healing materials. In contrast, coordination of 2 to [Pd(η³-C₃H₅)(μ-Cl)]₂ affords the well-defined complex 2 ⋅ [Pd(η³-C₃H₅)Cl] which was characterized by ³¹P, ¹H, ¹³C{¹H} NMR spectroscopy and GPC. This polymer chemistry was complemented by detailed molecular model studies of the coordination chemistry of monomer 1-phosphaisoprene E- 1 with [Pd(cod)Cl₂] and [Pd(η³-C₃H₅)(μ-Cl)]₂].     

以主族元素为桥的梯形化合物的光电性质

梯形化合物具有大的平面π共轭结构, 不会产生构象扭曲, 可以有效增加π共轭长度, 因而表现出非常好的光电性质. 将主族元素引入到梯形化合物骨架中作为桥接单元不仅可以固定其结构而且由于主族元素和π共轭骨架之间的轨道相互作用, 可以实现对这类化合物光电性质的调节. 采用密度泛函理论对一系列主族元素桥的梯形化合物的结构和光电性质进行了理论研究, 从而可更好地理解和预测这类化合物的性质. 研究发现, 这类化合物的电子结构可以通过引入主族元素进行调节. 由于具有更大的π共轭程度, 四主族元素桥化合物的吸收与双主族元素桥化合物相比有明显的红移, 而且荧光寿命较短. 另外, 通过计算离子化势(IPs)、电子亲和能(EAs)和重组能(λ)考察了这类化合物的电子和空穴注入及传输性质. 研究发现, 四主族元素桥化合物表现出更强的电子和空穴注入能力.     

Fluorescence Emission from Small Molecules Containing Amino Group

After the treatment of oxygen gas, the small molecules containing amine group could emit fluorescence. Oxidation was believed to play an important role in the formation of fluorescence centers. Compared to previous results, both small molecules and macromolecules might have the same fluorescence centers.     

Studien zur Reaktivität des viergliedrigen basenstabilisierten Iminoalans [(Me3N)HAlNDipp]2 mit elementarem Iod

Studies on the Reactivity of the Four‐membered Base‐stabilized Iminoalane [(Me₃N)HAlNDipp]₂ with Elemental Iodine The base‐stabilized iminoalane [(Me₃N)HAlNDipp]₂ (Dipp = 2, 6‐iPr₂C₆H₃) reacts with iodine under substitution of the hydridic H atom at the Al center and formation of HI, which subsequently protonates the Lewis basic imin nitrogen. A mixture of [DippN{AlI₂(NMe₃)}₂] ( 1 ), [DippN(H)AlI₂(NMe₃)] ( 2 ), [{DippN(H)}₂AlI(NMe₃)] ( 3 ) and DippNH₂ is formed. 1 ‐ 3 were identified by spectroscopic methods (¹H, ¹³C, IR, and mass spectroscopy), 1 and 2 also by single crystal X‐ray diffraction.     

Hydrotris(1,2,4‐triazolyl)borato Complexes with the Main Group Elements Ca,Sr, and Pb – Unexpectedly Bent ML2 Structures and a Stereochemically Inactive Lone Pair at Lead(II)

The coordination of the modified poly(azolyl)borato ligand hydrotris(1,2,4‐triazolyl)borato (L) with main group metals leads to complexes with coordination numbers of eight and the formula [CaL₂(H₂O)₂], [SrL₂(H₂O)₂], and [PbL₂(H₂O)₂]. The two L ligands coordinate in a “bent” arrangement to allow for the coordination of the two aqua ligands. This is in sharp contrast to six‐coordinated, pseudo‐octahedral CaTp₂ and PbTp₂ complexes [Tp = hydrotris(pyrazolyl)borato]. The calcium, strontium, and lead complexes are isostructural. No stereochemical lone pair activity is evident in [PbL₂(H₂O)₂]. Two additional water molecules of crystallization complete the crystal structure of [CaL₂(H₂O)₂] · 2 H₂O and [PbL₂(H₂O)₂] · 2 H₂O. In the synthesis of [PbL₂(H₂O)₂] an intermediate of the form [Pb(μ₃‐L)(NO₃)H₂O] could isolated and structurally characterized. There, the lead(II) center is seven coordinated with a presumably stereochemically active lone pair. Long M–L bonds argue for a more ionic bonding to the modified tris(triazolyl)borato ligand when compared to analogous M–Tp complexes.     

New Possible Applications of Heavy Main-Group Elements in Organic Synthesis

Aside from elements of the 2nd row, and one element of the 3rd row of the periodic system—Si, P, S, and Se, respectively, whose organoelement groups such as Me₃Si and Ph₃P^⊕ have proven useful in numerous organic syntheses—other elements of the 3rd as well as 4th and 5th row (Ge, As, Sn, Sb, Te, Pb, Bi) can also be used as components of synthetically useful organoelement groups, the elements As, Sn, and Pb, in particular, offering certain advntages over the others. Some of these organoelement groups are suitable equivalents for Li- or halogen-substituents attached to carbon; they stabilize carbanionic centers (minimum of this effect at the 3rd-row elements), and owing to their suitability as leaving groups in β-eliminations, also open up interesting synthetic possibilities. The thermally unduced syn- and silica-gel induced anti-elimination of Ph₃Sn, Ph₂Sb, Ph₃Pb, together with β-OH, are novel. With the newly synthesized compounds Ph_nEl—Ch₂—Li (El = Sn, Pb, As, Sb, Bi) and other α- and β-lithiated R_nEl- and Ph₂As(O)-reagents such organoelement groups can be introduced into organic compounds and exploited in organic and organoelement synthesis.     

主族金属氨基酸配合物的晶体学研究进展

主族金属配合物的研究是配位化学的重要主题之一. 相对于过渡金属和稀土金属配合物而言, 主族金属配合物的研究比较薄弱, 其主要原因在于: 主族金属的闭壳层电子层结构、有限的价电子数和较少的氧化态等特点, 使得主族金属与有机配体的相互作用较弱, 作用模式较为单一. 但近年来, 随着合成技术与分析检测技术的不断提升, 具有新颖结构并具有与过渡金属配合物相似的优良性能的主族金属配合物也不断地进入了人们的视野. 作为生物体的基本结构单元的氨基酸是一类良好的功能配体, 主族金属氨基酸配合物的研究具有重要的学术价值和应用价值, 也是化学、生物、医药和材料等众多学科领域中的共同的基本问题. 解决基本问题的一个切入点可能是研究这些新型主族金属氨基酸配合物的分子结构与物质结构. 因此, 本工作基于2000年以后发表的主族金属氨基酸配合物的晶体结构, 从X射线晶体学的研究视角, 分析了新型的主族金属氨基酸配合物的结构多样性, 包括当前热门的MOF类的结构; 综述了主族金属氨基酸配合物的研究进展; 展望了未来这一领域的发展方向; 提出了以功能为导向系统地开展主族金属氨基酸的配位化学和超分子化学的研究思路. 谨以此文献给2014年国际晶体学年.     

Mixed Ligands from Group 15/16 Elements: Interface of Solid-State and Molecular Chemistry

A wide range of chemical compounds is spanned by heteroatomic ligands from Group 15/16 elements, which in Nature extend from AsS (in realgar) to [AsS₂⁻]_∞ (in sulfosalt minerals). The stabilization of labile molecules or those that do not exist in the free state by incorporation into transition metal complexes like [Cp^*₂Fe₂(AsSe)₂] ( 1 ) and the oligomerization of molecular units under the influence of metal ions or complexes to form solids or hybrid clusters with inorganic cores and peripheral organometallic ligands are the main subjects of this article. Cp*=C₅Me₅.     

含活性基荧光素衍生物

介绍了近20年来含活性基荧光素衍生物的最新研究成果,重点介绍了含活性基的荧光素探针在生物分析中的应用及改进。     

Organometallic Compounds with Homonuclear Bonds between Bismuth Atoms, 70 Years after Paneth' Report on the Violet Dimethyl Bismuth Compound

The chemistry of organometallic compounds of the types (R₂Bi)₂, (RBi)_n (n = 2—5) and R₆Bi₈ is the objective of this report. Common features and differences between these bismuthanes and analogous compounds of lighter group 15 elements are discussed.