A stannylene strategy for regioselective acylation and phosphorylation of 1,2-cyclohexylidene-myo-inositol. Its convenient resolution and phosphatidylinositol synthesis

The bis(dibutylstannylene) derivative of 1,2-cyclohexylidene-myo-inositol reacted with (S)-O-acetylmandeloyl chloride and diphosphate tetraesters to give 3,6-dimandelate and 3-phosphate, respectively. Using the stannylene methodology for the optical resolution and regioselective phosphorylation of the ketal, a concise synthesis of phosphatidylinositol with the natural configuration was accomplished.     

Heavier Tetrylenes as Single Site Catalysts

An overview of the development of compounds with heavier low-valent group 14 elements (known as tetrylenes) as single component catalyst for organic transformation has been provided. Compounds with heavier group 14 elements possess stereochemically active lone pairs and energetically accessible π-antibonding orbitals, thereby resembling the electronic configuration of transition-metal compounds. Such compounds with low-valent group 14 elements has been known for small molecule activation since Power's report of dihydrogen activation by a digermyne, but their utilization in catalysis remained as a “Holy Grail” in main group chemistry. In recent years, numerous methodologies have been discovered epitomizing the use of Si(II), Ge(II) and Sn(II) compounds as single site catalysts for hydroboration of aldehydes, ketones, pyridines, cyanosilylation of aldehydes and ketones, N-formylations aromatic amines, dehydrocoupling reactions. This mini-review highlights these significant developments with an emphasis on the mechanistic investigation.     

Elimination of bis(trimethylsilyl)stannylene from tris(trimethylsilyl)stannylated zirconocene and hafnocene chlorides

Reactions of (Me₃Si)₃SnK with Cp₂MCl₂ (M = Zr, Hf) give the respective stannylated metallocene chlorides. These complexes display a tendency to eliminate bis(trimethylsilyl)-stannylene under Cp₂M(Cl)SiMe₃ formation.     

A ferrocenyl-bridged intramolecularly coordinated bis(diorganostannylene): Synthesis, molecular structure and reactivity of [4-t-Bu-2,6-{P(O)(O-i-Pr)2C6H2Sn}C5H4]2Fe

The intramolecularly coordinated heteroleptic stannylene [4-t-Bu-2,6-{P(O)(O-i-Pr)₂}₂C₆H₂]SnCl serves as synthon for the synthesis of the ferrocenyl-bridged bis(diorganostannylene) [4-t-Bu-2,6-{P(O)(O-i-Pr)₂}₂C₆H₂SnC₅H₄]₂Fe (1) which in turn reacts with W(CO)₆ and Cr(CO)₄(C₇H₈) to provide the corresponding transition metal complexes [4-t-Bu-2,6-{P(O)(O-i-Pr)₂}₂C₆H₂Sn{W(CO)₅}C₅H₄]₂Fe (2) and [4-t-Bu-2,6-{P(O)(O-i-Pr)₂}₂C₆H₂SnC₅H₄]₂Fe · Cr(CO)₄ (3), respectively. Reaction of compound 1 with sulphur and atmospheric moisture gave, under partial tin-carbon and oxygen-carbon bond cleavage, a tetranuclear organotin-oxothio cluster 5. All compounds were characterized by ¹H, ¹³C, ³¹P, and ¹¹⁹Sn NMR, and IR spectroscopy, as well as by single-crystal X-ray diffraction analysis. Compounds 1 and 3 were also investigated by Mössbauer spectroscopy. Cyclovoltametric studies reveal the influence of the organostannyl moieties on the redox-behaviour of compounds 1-3 in comparison with unsubstituted ferrocene.     

In search for a pentacoordinated monoorgano stannyl cation

Alkylation of Sn(OCH₂CH₂NMe₂)₂ (1) by MeI or MeOTf leads to a mixture of quaternary ammonium salts by alkylation of the NMe₂ moiety. Reaction of Sn(acac)₂ (2) with MeOTf gives unexpected redistribution product Sn(acac)OTf (3), which is a rare example of mono acetylacetonato tin (II) derivatives. Pentacoordinated monoorgano stannyl cation was generated by salt metathesis from PhSn(OCH₂CH₂NMe₂)₂Cl (5) and Ag[Al(OCH(CF₃)₂)₄] or Ag[B(C₆F₅)₄]. This cation was not isolated due to its strong electrophilic nature. It abstracts substituents from aluminate and borate weakly coordinating anions (WCAs) leading to redistribution products [Al[OCH(CF₃)₂]₂OCH₂CH₂NMe₂]₂ (6) and [Ph(C₆F₅)Sn(OCH₂CH₂NMe₂)₂][H₂OB(C₆F₅)₃] (9), respectively. Structures of 3 and 6 were established by single-crystal X-ray diffraction analysis.     

Heterocarbenoids of germanium and tin and their polyhedral oxidation products: The case for thermodynamic product control in Group 14 chalcogenides

The polycyclic Group 14 amides [P(μ-N^tBu)₂P(^tBuN)₂]M, M = Ge (4), Sn (5) were synthesized from cis-[P(μ-N^tBu)₂P(^tBuNLi · THF)₂] and GeCl₂ · dioxane or SnCl₂, respectively. Oxidation of these heterocarbenoids or of the analogous diazastannylene [MeSi(μ-^tBuN)₂SiMe(^tBuN)₂]Sn with O₂, S₈ and Se_n furnished the chalcogenides {[P(μ-N^tBu)₂P(^tBuN)₂]GeO}₂ (6), {[P(μ-N^tBu)₂P(^tBuN)₂]SnE}₂, E = O (7), S (8), Se (9), {[SP(μ-N^tBu)₂P(^tBuN)₂]SnS}₂ (10), and {[MeSi(μ-^tBuN)₂SiMe(^tBuN)₂]SnE}₂, E = S (11), Se (12), respectively. All products (6-12) were shown by single-crystal X-ray methods to consist of dimeric molecules with central (M-E)₂ rings, M = Group 14 element, E = chalcogen. The exclusive formation of dimeric compounds with bridging M-E-M bonds, vs. alternative monomeric structures with terminal ME bonds, is rationalized in terms of the thermodynamic favorability of the dimers. The case is made that most, if not all, currently known Group 14 chalcogenides, even those labeled “kinetically stabilized”, are really thermodynamic products.     

A Heteroleptic (E)-1,2-Diaryl-1,2-disilyldistannene without Donor Stabilization

The reaction of the stannylene R₂Sn : (R = 2-tBu-4,5,6-Me₃C₆H) with R′₂Sn (R′ = Si(SiMe₃)₃) proceeds with substituent exchange to afford the heteroleptic stannylene RR′Sn : which, in the solid state, forms the distannene RR′Sn = SnRR′ ( 7 ). The X-ray structure analysis of 7 reveals a trans-bent arrangement of the substituents with a large fold angle of 44.9° and an Sn–Sn double bond length of 279.14(4) pm.