John J. Harland

NEW RING SYSTEMS OF ELEMENTS OF MAIN GROUPS IV AND V

Abstract The synthesis of [PhSn(O)O2CC6H11]6 represents the first example of tin(IV) in a drum-shaped molecule. The formation of the dimeric composition, [(MeSn(O)O2CC6H11)2(MeSn(O2CC6H11)3]2, appears to be an intermediate hydrolysis product on the way to the drum composition. The X-ray structure reveals an “unfolded” drum array. The distannoxane unit which is represented as the sides of the drum is found in additional new dimeric compositions, [(SCH2CH2O)2SnCl]2[H][Et4N], [((CN)2C2S2)2SnOH]2, and [BuSnCl2(OH) · H2O]2. These all have six-coordinated tin atoms which contrasts to the dimeric aryl distannoxanes recently isolated, [Ph2(Cl)SnOSnPh2(X)]2, X = OH, Cl, containing five-coordinated tin. Also isolated are the new ring containing, five-coordinated tin derivatives, [(SCH2CH2S)2Sn]2[SCH2CH2S][Et3NH]2 and [(SC(CN)C(CN)S)2SnMe][Et4N]. The former has two trigonal bipyramidal tin atoms while the latter composition has a square pyramidal geometry. Related ring systems of new five-coordinated derivatives of ...

Sterically Hindered Pentacoordinated Phosphorus and Silicon Compounds

Abstract The synthesis and X-ray structures of the first examples of five-coordinated acyclic derivatives of phosphorus and silicon incorporating the bulky substituents, the 1-naphthyl and t-butyl ...

SYNTHESIS AND MOLECULAR STRUCTURE OF HYDROGEN-BONDED CYCLIC ANIONIC SILICATES ISOELECTRONIC WITH PHOSPHORANES. STRUCTURAL PRINCIPLES OF FIVE-COORDINATED SILICON

Abstract The new five-coordinated silicon compounds, pyridinium bis(2,3-naphthalenediolato)phenylsilicate(IV), [(C10H6O2)2SiPh][C5H6N], 11, pyridinium bis(1,2-benzenediolato)-1-naphthylsilicate(IV), [(C6H4O2)2SiC10H7][C5H6N], 12, and pyridinium bis(1,2-benzenediolato)(2- and 4-chlorophenyl)silicate(IV) (2-Cl, 0.85; 5-Cl, 0.15), [(C6H4O2)2SiC6H4Cl][C5H6N], 13, were synthesized and their X-ray structures determined. The structure of 11 is nearly an ideal rectangular pyramid (RP) and 12 is displaced about halfway between the RP and trigonal bipyramid (TBP), while 13 is closer to a TBP. A quantitative assessment of these and related pentacoordinated cyclic anionic silicate structures reveals a continuous change in ring Si[sbnd]O bond lengths that vary from 1.78 (axial) and 1.68 A (equatorial) for the idealized TBP to 1.73 A (basal) for the RP. The results for these compounds, all of which follow the Berry pseudorotational coordinate, suggest a structural nonrigidity at least as great as found for phosphoranes...

A PSEUDOROTATIONAL COORDINATE FOR FIVE-COORDINATED SILICON. SYNTHESIS AND MOLECULAR STRUCTURE OF CYCLIC ANIONIC SILICATES ISOELECTRONIC WITH PHOSPHORANES

Abstract Hexamethylenediammonium bis[bis(1,2-ethylenediolato)phenylsilicate(IV)], [H3N(CH2,)6NH3]0.5-[(C2H4O2)2SiPh], 4, and tetraethylammonium bis(3,4,5,6-tetrachloro-1,2-benzenediolato)phenylsilicate(IV), [Et4N][(C6Cl4O2)2SiPh], 5, were synthesized and their X-ray structures established. 4 has a structure displaced 72% from a trigonal bipyramid (TBP) to a rectangular pyramid (RP). 5 is nearly a rectangular pyramid (RP) being 90% so displaced. A quantitative assessment of structural distortion for 4 and 5 and related anionic silicates shows that these pentacoordinated compounds form a continuous series of structures, similar to phosphoranes, between the trigonal bipyramid and square or rectangular pyramid along the Berry pseudorotational pathway. It is shown that the idealized RP geometry is approached when two five-membered unsaturated rings are present with like ligands in any one ring attached directly to silicon. The existence of this low-energy coordinate indicates the presence of nonrigid character...