Reduction of C,O-chelated organotin(IV) dichlorides and dihydrides leading to protected polystannanes

Hypercoordination by Multiple Dangling Benzylmethoxy Ligands in Highly Crowded Triaryltin Bromide [(2-MeOCH2 C6 H4 )]3 SnBr and Diaryltin Mixed Halides [(2-MeOCH2 C6 H4 )]2 SnBrCl, and a related Distannane and Distannoxane

The reaction between the Grignard reagent formed from Mg and 2-bromobenzylmethyl ether and SnCl4 produced four products: [2-(MeOCH2 )C6 H4 ]3 SnBr (1), [2-(MeOCH2 )C6 H4 ]2 SnX2 (2, X2 =Br2 (a) and BrCl (b)), [{2-(MeOCH2 )C6 H4 }3 Sn]2 (3), and [{2-(MeOCH2 )C6 H4 }2 SnBr]2 O (4). In the case of 1, two of the three dangling arm O atoms coordinate to the central tin atom with O-Sn internuclear distances of 2.53 (O1) and 2.91 (O2) Å, the shorter interaction being trans to the Br atom, the other trans to a phenyl carbon atom. In the case of 2a the resulting hexacoordinate structure exhibits two very short O-Sn interactions of 2.42 and 2.50 Å, well below the sum of the VdW radii of O and Sn, 3.69 Å. The sterically crowded ditin compound 3 was obtained in trace amounts and the structure demonstrates no dangling O-Sn interactions. General changes in structure compared to other distannane systems are reflective of the great steric crowding. Distannoxane 4, has a Sn-O-Sn bond angle of 148.1(2)° which is larger compared to other distannoxane structures. The intermolecular interactions between Sn-O 2.470(3) and 2.521(3)Å and 2.665(3) and 2.629(3)Å for Sn1 and Sn2 respectively are responsible for a distorted octahedral geometry around the two tin atoms. The various 119 Sn, 13 C and 1 H NMR spectra are in accord with their structural analysis for 1 and 2, and in the solid state 13 C NMR spectrum of 1 the dangling methylene group is observable whereas is solution there is a rapid dynamic equilibrium resulting in a single resonance for all methylene groups.

Molecular Main Group Metal Hydrides

This review serves to document advances in the synthesis, versatile bonding, and reactivity of molecular main group metal hydrides within Groups 1, 2, and 12-16. Particular attention will be given to the emerging use of said hydrides in the rapidly expanding field of Main Group element-mediated catalysis. While this review is comprehensive in nature, focus will be given to research appearing in the open literature since 2001.

Preparation and DFT Studies of κ2C,N-Hypercoordinated Oxazoline Organotins: Monomer Constructs for Stable Polystannanes

Tetraorganotin tin(IV) compounds containing a flexible or rigid (4: Ph3Sn-CH2-C6H4-R; 7: Ph3SnC6H4-R, R = 2-oxazolinyl) chelating oxazoline functionality were prepared in good yields by the reaction of lithiated oxazolines and Ph3SnCl. Reaction of 7 with excess HCl resulted in the isolation of the tin monochlorido compound, 9 (ClSn[Ph2]C6H4-R). Conversion of the triphenylstannanes 7 and 4 into their corresponding dibromido species was successfully achieved from the reaction with Br2 to yield 10 (Br2Sn[Ph]C6H4-R) and 11 (Br2Sn[Ph]-CH2-C6H4-R), respectively. X-ray crystallography of 4, 7, 9, 10, and 11 reveal that all structures adopt a distorted trigonal bipyramidal geometry around Sn in the solid state. Compound 4, with an additional methylene spacer group, displays a comparatively long Sn–N bond distance compared to the dibromido tin species, 11. Several DFT methods were compared for accuracy in predicting the solid-state geometries of compounds 4, 7, 9–11. Compounds 10 and 11 were further converted into the corresponding dihydrides (12: H2Sn[Ph]C6H4-R, 13: H2Sn[Ph]-CH2-C6H4-R), via Br–H exchange, in high yield by reaction with NaBH4. Polymerization of 12 or 13 with a late transition metal catalyst produced a low molecular weight polystannane (14: –[Sn[Ph]C6H4-R]n–, Mw = 10,100 Da) and oligostannane (15: –[Sn[Ph]-CH2-C6H4-R]n–, Mw = 3200 Da), respectively.

“Push–push and push–pull” polystannanes

Alternating “Push–pull” and “push–push” polystannanes prepared by condensation of tin diamides and tin dihydrides are described.

Polystannanes: processible molecular metals with defined chemical structures

Polystannanes are a unique class of materials as those inorganic polymers (more precisely organometallic polymers) appear to be hitherto the only characterized polymers with a backbone of covalently bound metal atoms.

Polymers and the p-block elements

A survey of the state-of-the-art in the development of synthetic methods to incorporate p-block elements into polymers is given. The incorporation of main group elements (groups 13-16) into long chains provides access to materials with fascinating chemical and physical properties imparted by the presence of inorganic groups. Perhaps the greatest impedance to the widespread academic and commercial use of p-block element-containing macromolecules is the synthetic challenge associated with linking inorganic elements into long chains. In recent years, creative methodologies have been developed to incorporate heteroatoms into polymeric structures, with perhaps the greatest advances occurring with hybrid organic-inorganic polymers composed of boron, silicon, phosphorus and sulfur. With these developments, materials are currently being realized that possess exciting chemical, photophysical and thermal properties that are not possible for conventional organic polymers. This review focuses on highlighting the most significant recent advances whilst giving an appropriate background for the general reader. Of particular focus will be advances made over the last two decades, with emphasis on the novel synthetic methodologies employed.