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The syntheses of the arylphosphonic esters 3-Br-5-tBu-1-{P(O)(OiPr)2}C6H3 (1), 5-tBu-1,3-{P(O)(OiPr)2}2C6H3 (2), of the heteroleptic intramolecularly coordinated organostannylenes [4-tBu-2,6-{P(O)(OiPr)2}2C6H2]SnX (3, X = Cl; 4, X = Br; 5, X = I; 6, X = SPh), the organoplumbylene [4-tBu-2,6-{P(O)(OiPr)2}2C6H2]PbCl (7), and the transition metal comp...
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... The difference between the latter compound and the heter- oleptic stannylenes 4 and 5 is (i) the formal replacement of one aryl substituent by a bromine respectively iodine atom and (ii) the presence of two strong intramolecular P=O→Sn inter- actions. The consequence of this is that there are dramatic dif- ferences in both the bond and torsion angles as it is illustrated in Figure 5. ...
Citations
... A 31 P NMR spectrum of compound 3 in C 6 D 6 showed a signal at δ 75.3 ppm being identical with that reported previously (Beck et al., 1994). (Henn et al., 2011). The second resonance is assigned to compound 1 (Wagner et al., 2013). ...
... A 1 H 13 C HMBC spectrum showed cross peaks to the C(1) carbon atoms at δ 170.4, 1, and δ 182.4 ppm, 4. The low field shift of the C(1) signal, which is assigned to compound 4, showed the absence of the transition metal fragment. A similar trend was observed for RSnCl [R = 4-tBu-2,6-{P(O)(OiPr) 2 } 2 C 6 H 2 ] (δ 186.7 ppm) compared with RSn(Cl)Cr(CO) 5 (δ 171.7 ppm) (Henn et al., 2011). The reaction according to Scheme 2 proceeds via nucleophilic attack of the kinetically labile triphenylphosphane at the chromium center (Scheme 2). ...
This chapter describes recent advances in the organometallic chemistry of tin and lead, a field which continues to develop at a rapid rate. Although many new tetravalent compounds have been reported, recent emphasis has been on the synthesis of compounds in which these elements are in low formal oxidation states. Such compounds frequently exhibit unusual structures and reactivities and are at the forefront of endeavours to replace expensive and rare transition metal catalysts with earth abundant alternatives. In this chapter emphasis is placed on isolated complexes which have been fully characterized, especially those which have been characterized by X-ray crystallography, although important examples of compound classes where this is not the case are also included for context.
α-Iminopyridine ligands L1 (2-(CHN(C6H2-2,4,6-Ph3))C5H4N), L2 (2-(CHN(C6H2-2,4,6-tBu3))C5H4N) and L3 (1,2-(C5H4N-2-CHN)2CH2CH2) differing by the steric demand of the substituent on the imine CHN group and by the number of donating nitrogen atoms were utilized to initiate a Lewis base mediated ionization of SnCl2 in an effort to prepare ionic tin(II) species [L1-3 → SnCl][SnCl3]. The reaction of L1 and L2 with SnCl2 led to the formation of neutral adducts [L1 → SnCl2] (2) and [L2 → SnCl2] (3). The preparation of the desired ionic compounds was achieved by subsequent reactions of 2 and 3 with an equivalent of SnCl2 or GaCl3. In contrast, ligand L3 containing four donor nitrogen atoms showed the ability to ionize SnCl2 and also Sn(OTf)2, yielding [L3 → SnCl][SnCl3] (7) and [L3 → Sn(H2O)][OTf]2 (8). The study thus revealed that the reaction is dependent on the type of the ligand. The prepared complexes 4-8 together with the previously reported [{2-((CH3)CN(C6H3-2,6-iPr2))-6-CH3O-C5H3N}SnCl][SnCl3] (1) were tested as catalysts for the ROP of L-lactide, which could operate via an activated monomer mechanism. Finally, a DFT computational study was performed to evaluate the steric and electronic properties of the ionic tin(II) species 1 and 4-8 together with their ability to interact with the L-lactide monomer.
A new bis‐sulfoxide derivative was isolated, characterized and used as ligand to obtain tin(II), silicon and phosphorus containing compounds. The unique structure of the bis‐sulfoxide, thanks to the strong ortho director effect of the two sulfinyl groups, facilitates selective deprotonation at the C(1)–H in presence of LDA. This particularity of the bis‐sulfoxide makes it a promising new ligand in the stabilisation of new organometallic and coordinative compounds. image John Wiley & Sons, Ltd.
Metal ion-linked multilayers offer an easily prepared and modular architecture for controlling energy and electron transfer events on nanoparticle, metal oxide films. However, unlike with planar electrodes, the mesoporous nature of the films inherently limits both the thickness of the multilayer and subsequent diffusion through the pores. Here, we systematically investigated the role of TiO2 nanoparticle film porosity and metal ion-linked multilayer thickness in surface loading, through-pore diffusion, and overall device performance. The TiO2 porosity was controlled by varying TiO2 sintering times. Molecular multilayer thickness was controlled through assembling ZnII-linked bridging molecules (B = p-terphenyl diphosphonic acid) between the metal oxide and the Ru(bpy)2((4,4'-PO3H2)2bpy)]Cl2 dye (RuP), thus producing TiO2-(B
n
)-RuP films. Using attenuated total reflectance infrared absorption and UV-vis spectroscopy, we observed that at least two molecular layers (i.e., TiO2-B2 or TiO2-B1-RuP) could be formed on all films but subsequent loading was dependent on the porosity of the TiO2. Rough estimates indicate that in a film with 34 nm average pore diameter, the maximum multilayer film thickness is on the order of 4.6-6 nm, which decreases with decreasing pore size. These films were then incorporated as the photoanodes in dye-sensitized solar cells with cobalt(II/III)tris(4,4'-di-tert-butyl-2,2'-bipyridine) as a redox mediator. In agreement with the surface-loading studies, electrochemical impedance spectroscopy measurements indicate that mediator diffusion is significantly hindered in films with thicker multilayers and less porous TiO2. Collectively, these results show that care must be taken to balance multilayer thickness, substrate porosity, and size of the mediator in designing and maximizing the performance of new multilayer energy and electron management architectures.
Pincer ligands have an important role in stabilizing group 14 metallylenes. The particular structure of the aryl pincer ligands makes them a unique ligand platform. This review is focused on presenting monoanionic metallylenes stabilized by aryl pincer‐type ligands, described so far in the literature, with focus on their synthesis, structural features, and reactivity. Throughout this work, the close correlation between structure and reactivity is highlighted, as well as the manner in which this influences the stability of the compounds and their potential applications.
In this contribution we report the synthesis of the novel unsymmetrical ferrocene‐based pincer‐type proligand η⁵‐CpFeη⁵‐C5H2‐1‐Br‐2‐PPh2‐5‐CH2NMe2 (1). Its reactivity is demonstrated by isolation of related organotin derivatives η⁵‐CpFeη⁵‐C5H2‐1‐SnR3‐2‐PPh2‐5‐CH2NMe2 (3, R = Ph; 4, R = Me). The reactions of compounds 3 and 4 with H2O2 and elemental sulfur gave the corresponding ferrocenylphosphane oxide (5) and the sulfides (6, 7), respectively. Most remarkably, an unprecedented reaction of the organotin derivative 3 with elemental iodine was observed, providing the ammonium salt [η⁵‐CpFeη⁵‐C5H2‐1‐SnPh2I‐2‐P(O)Ph2‐5‐CH2NHMe2]I (8). The compounds are characterized by elemental analyses, ¹H, ¹³C, ³¹P, ¹¹⁹Sn NMR spectroscopy, electrospray ionization mass spectrometry, and single‐crystal X‐ray diffraction analyses (3–8). Also reported are the solid‐state structures of the hydrolysis products [η⁵‐CpFeη⁵‐C5H2‐1‐SnPh2(OH)‐2‐P(O)Ph2‐5‐CH2NHMe2]·0.5H2O (9a) and [η⁵‐CpFeη⁵‐C5H2‐1‐SnPh(OH)‐2‐P(O)Ph2‐5‐CH2NMe2]2[I3]2 (9b) that were isolated by serendipity.
In this paper we present the synthesis and results of a high‐resolution single‐crystal X‐ray diffraction experiment on the O,N‐heterocyclic stannylene (tBuAPSn) (1) containing the chelate ligand 4,6‐di‐tert‐butyl‐N‐tert‐butyl‐o‐amidophenolate. The experimental work is accompanied by a charge density study based on a topological analysis according to quantum theory of atoms in molecules (QTAIM) together with a NBO calculation of the crystal packing fragment containing a Sn‐Sn bond. According to QTAIM, the Sn‐Sn interaction is covalent (∇²ρ(r)<0, he(r)<0). In the view of NBO analysis, there are two donor‐acceptor bonding interactions between the tin atoms of adjacent molecules. The Sn‐Sn bond energy evaluated by the Espinosa‐Molins‐Lecomte correlation is equal to ‐ 9.1 kcal/mol. We carried out the investigation of source function not only in CP(3,‐1) on the Sn‐Sn bond but also on NCI‐defined isosurface (λ2<0). The source function shows that the electron density from the Sn basins extensively contributes to the formation of this Sn–Sn bond in 1.
