The Role of 2,6‐Diaminopyridine Ligands in the Isolation of an Unprecedented,Low‐Valent Tin Complex

Stabilization of the central atom in an oxidation state of zero through coordination of neutral ligands is a common bonding motif in transition‐metal chemistry. However, the stabilization of main‐group elements in an oxidation state of zero by neutral ligands is rare. Herein, we report that the transamination reaction of the DAMPY ligand system (DAMPY=2,6‐[ArNH‐CH₂]₂(NC₅H₃) (Ar=C₆H₃‐2,6‐iPr₂)) with Sn[N(SiMe₃)₂]₂ produces the DIMPYSn complex (DIMPY=(2,6‐[ArN?CH]₂(NC₅H₃)) with the Sn atom in a formal oxidation state of zero. This is the first example of a tin compound stabilized in a formal oxidation state of zero by only one donor molecule. Furthermore, three related low‐valent Sn^II complexes, including a [DIMPYSn^IICl]⁺[SnCl₃]^? ion pair, a bisstannylene DAMPY{Sn^II[N(SiMe₃)₂]₂}₂, and the enamine complex MeDIMPYSn^II, were isolated. Experimental results and the conclusions drawn are also supported by theoretical studies at the density functional level of theory and ¹¹⁹Sn Mössbauer spectroscopy.     

Synthesis of Structurally Complex Silicon Frameworks through the First Sila-Aldol Reaction

Herein, we report on the first sila-aldol reaction, which emphasizes the tight connection between silicon and carbon chemistry. This novel synthetic method provides straightforward access to 2-oxahexasilabicyclo[3.2.1]octan-8-ide, a structurally complex silicon framework, in quantitative yield. Its structure was confirmed by NMR spectroscopy and X-ray crystallography, and it displays a distinctive charge-transfer transition. The complete mechanism of this highly selective rearrangement cascade is outlined and supported by density functional theory (DFT) calculations, which highlight the thermodynamic driving force and the low activation barriers of this powerful silicon–carbon bond-forming strategy.     

Advances in alkaline earth-nitrogen chemistry

This article provides a concise summary of alkaline earth metal nitrogen chemistry. This important area of s-block metal chemistry is shedding important light on the recent development of alkaline earth metal chemistry, as the preparation of the target compounds utilizes a large variety of synthetic methodology. Further, the compounds have been utilized in a range of applications, including polymerization initiation, catalysis, as solid-state precursors, and even high energy materials.     

Porphyrin complexes containing coordinated BOB groups: synthesis, chemical reactivity and the structure of [BOB(tpClpp)]2+

The reactions of boron halides with free base porphyrins under conditions where partial hydrolysis of the boron halides can occur give diboron porphyrin complexes containing BOB moieties in which each boron is bonded to two porphyrin nitrogen atoms. BF(3).OEt(2) with H(2)(por) gives B(2)OF(2)(por) (por = tpp, ttp, tpClpp, oep) which has an asymmetric structure in which one boron lies in the porphyrin plane (B(ip)) while the other lies above it (B(oop)). BCl(3).MeCN with H(2)(por) gives B(2)O(2)(BCl(3))(2)(por) which contains a four-membered B(2)O(2) ring and is stable only in the presence of excess BCl(3). BBr(3) with Li(2)(tpClpp) gives the dicationic complex [B(2)O(tpClpp)](2+) as its [BBr(4)](-) salt, and is the first example of a boron porphyrin containing three-coordinate boron to be structurally characterised. B(2)O(2)(BCl(3))(2)(por) can be chromatographed on basic alumina to give the hydroxyboron complex B(2)O(OH)(2)(por), which is deduced from its NMR spectra and DFT calculations to have a structure analogous to B(2)OF(2)(por). The OH protons are shifted upfield to near delta -4 (B(oop)-OH) and -10 (B(ip)-OH) by the diamagnetic porphyrin ring current. The reaction of either B(2)O(2)(BCl(3))(2)(por) or B(2)O(OH)(2)(por) (por = ttp, tpClpp) with alcohols (ROH, R = Et, 4-C(6)H(4)CH(3)) gives B(2)O(OR)(2)(por), which can in turn be converted to B(2)O(OR)(OH)(por) by repeated chromatography. The reaction of PhBCl(2) with H(2)(por) (por = ttp, tpClpp) gives B(2)O(Ph)(OH)(por) which has been characterised by spectroscopy in concert with DFT calculations. It is a further example of the B(2)OF(2)(por) structural type, in which the phenyl group is coordinated to the out-of-plane boron and the OH group to the in-plane boron, as are its derivatives B(2)O(Ph)(X)(tpClpp) (X = F, OEt). Steric drivers for the facile hydrolysis of haloboron porphyrins relative to their dipyrromethene and expanded porphyrin counterparts are discussed.     

Synthesis of Mixed-Functionalized Tetraacylgermanes

Tetraacylgermanes are known as highly efficient photoinitiators. Herein, the synthesis of mixed tetraacylgermanes 4 a – c and 6 a – e with a nonsymmetric substitution pattern is presented. Germenolates are crucial intermediates of these new synthetic protocols. The synthesized compounds show increased solubility compared with symmetrically substituted tetraacylgermanes 1 a – d . Moreover, these mixed derivatives reveal broadened n–π* absorption bands, which enhance their photoactivity. Higher absorption of these new compounds at wavelengths above 450 nm causes efficient photobleaching when using an LED emitting at 470 nm. The quantum yields are in the range of 0.15–0.57, depending on the nature of the aroyl substituents. On the basis of these properties, mixed-functionalized tetraacylgermanes serve as ideal photoinitiators in various applications, especially in those requiring high penetration depth. The synthesized compounds were characterized by elemental analysis, IR spectroscopy, NMR and CIDNP spectroscopy, UV/Vis spectroscopy, photolysis experiments, and X-ray crystallography. The CIDNP data suggest that the germyl radicals generated from the new tetraacylgermanes preferentially add to the tail of the monomer butyl acrylate. In the case of 6 a – e only the mesitoyl groups are cleaved off, whereas for 4 a – c both the mesitoyl and the aroyl group are subject to α-cleavage.     

Toward the synthesis of thiadiazole-based therapeutic agents: synthesis,spectroscopic study,X-ray analysis,and cross-coupling reactions of the key intermediate 3,5-diiodo-1,2,4-thiadiazole

Research on Chemical Intermediates - The 1,2,4-thiadiazole moiety is an important component of several biologically active compounds, and varying substituents on this aromatic ring is one of the...     

s-Block organometallics: analysis of ion-association and noncovalent interactions on structure and function in benzyl-based compounds

The organometallic chemistry of alkali and alkaline-earth metals has been marred by synthetic setbacks because of their high reactivity. Advances in their synthesis and a better understanding of the stabilization effects of ligands and coligands have resulted in the revolution of s-block organometallics. Among those, benzyl-based derivatives have played a key role in developing this chemistry because factors such as the ligand size, charge delocalization, and introduction of electronic parameters along with metal effects can be analyzed. This article will focus on s-block benzylates and di- and triphenylmethanide derivatives with specific emphasis on the factors that stabilize the highly reactive metal species.     

Synthesis and characterization of cyano-substituted carborane-based compounds. Molecular structure of [1-(4-C7H7)-12-(C5H3-3-(CN)-3,4-(CH3)2)-C2B10H10

The reaction of cyanogen chloride with [1-(4-C(7)H(7))-12-(C(5)H(3)-3,4-(CH(3))(2))-C(2)B(10)H(10)] (7) was found to yield two new C(5)-substituted carborane cluster-based compounds, [1-(4-C(7)H(7))-12-(C(5)H(2)-3-(CN)-3,4-(CH(3))(2))-C(2)B(10)H(10)] (8) and [1-(4-C(7)H(7))-12-(C(5)H-2,4-(CN)(2)-3,4-(CH(3))(2))-C(2)B(10)H(10)] (9). This cyano-substitution pattern is in contrast to the known substitution for the analogous organic quinarene[5.6.7] system. The observed unique cluster-based products may be understood by a combination of steric and electronic effects. Compounds 8 and 9 were characterized by complete multinuclear NMR, (1)H-(1)H COSY NMR, (1)H-(13)C HMQC NMR, FTIR, UV-Vis, IR, MS data and a single crystal analysis for 8 [X-ray data for 8: C(17)H(25)B(10)N, monoclinic, space group P2(1)/n with cell constants a = 8.6794(17) ?, b = 11.021(2) ?, c = 43.175(9) ?, β = 91.00(3)°, V = 4129.2(14) ?(3), Z = 8, R(1) = 0.0729, wR(2) = 0.1464].     

Bis(chlorido)tin(IV)meso-substituted Porphyrins-Characterization and Solubility

Investigation of the solubility behavior of para-substituted (H, Me, t-Bu, n-Bu) meso-tetraarylporphyrins as well as meso-tetraalkylporphyrins (Me, n-Pr, n-Bu) were performed. An increase of solubility in chloroform and benzene is detected according to the higher functionality in para position of the phenyl ring for meso-tetraarylporphyrins or in meso position on meso-tetraalkylporphyrins. Furthermore, the series of bis(chlorido)tin(IV) meso-tetraarylporphyrin and bis(chlorido)tin(IV) meso-tetraalkylporphyrin was investigated via UV/Vis spectroscopy, ¹¹⁹Sn-NMR and single crystal X-ray diffraction.