Group 15 pnictenium cations supported by a conjugated bithiophene backbone

Thiophene based polymers and oligomers have attracted considerable attention because they can be functionalized to alter the gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO), which enables the design of tunable light emitting materials. One area, which has been less explored, is the incorporation of low coordinate, low oxidation state main group elements into these systems. We have currently developed a novel π-conjugated ligand containing two contiguous thiophene rings in which we have demonstrated its ability to support both pnictogen cations and their metal complexes.     

Z4-Kerdock Codes, Orthogonal Spreads, and Extremal Euclidean Line-Sets

When m is odd, spreads in an orthogonal vector space of type⁺(2m + 2,2) are related to binary Kerdock codes and extremalline-sets in 2^{m + 1} with prescribed angles. Spreads in a 2m-dimensionalbinary symplectic vector space are related to Kerdock codesover Z₄ and extremal line-sets in with prescribed angles. These connections involve binary, realand complex geometry associated with extraspecial 2-groups.A geometric map from symplectic to orthogonal spreads is shownto induce the Gray map from a corresponding Z₄-Kerdock codeto its binary image. These geometric considerations lead tothe construction, for any odd composite m, of large numbersof Z₄-Kerdock codes. They also produce new Z₄-linear Kerdockand Preparata codes. 1991 Mathematics Subject Classification:primary 94B60; secondary 51M15, 20C99.     

Inhibited chelation in the new gamma-phosphino-beta-diketiminate to give phosphine --> arsine coordination

A gamma-diphenylphosphino-beta-diketimine has been synthesised and the 31P NMR handle allows for in situ analysis of reaction mixtures revealing unprecedented reactivity with AsCl3 to give a novel phosphinoarsine intramolecular coordination complex.     

Computational insights into the acceptor chemistry of phosphenium cations

Phosphines are traditionally considered as Lewis bases or ligands in transition metal and main group complexes. Despite their electron-rich (lone pair-bearing) nature, an extensive coordination chemistry for Lewis acidic phosphorus centers is being developed; such chemistry provides a new synthetic approach for phosphorus-element bond formation, leading to new types of structures and modes of bonding. Complexes of Ph2P+ with a variety of donor elements (P, N, C) give experimentally short donor-acceptor bond lengths, when compared to other cationic phosphorus Lewis acid complexes. We have calculated that the energy of the lowest unoccupied molecular orbital (LUMO) in Ph2P+ is lower than that of (Me2N)2P+, which partially explains the greater exothermicity of reactions of donors with the diaryl acceptor. Furthermore, the energies required to distort the diphenylphosphenium cation from its ground-state geometry are significantly smaller than those of the diamido cations and, thus, enhance the exothermicity of donor coordination. These computational data, in conjunction with evidence from experimental solid-state structures, indicate that Ph2P+ is a significantly better Lewis acid relative to the more common diaminophosphenium analogues (R2N)2P+ and are used to elucidate the nature of the bonding in donor-phosphenium complexes.     

Synthesis and structures of complexes demonstrating the coordinative versatility of the 2,4-diimino-3-phosphinopentene anion (gamma-phosphino-beta-diketiminate)

The synthesis and characterization of a 2,4-diimino-3-phosphinopentene anion (gamma-phosphino-beta-diketiminate) is reported and enables diversification of the beta-diketiminate ligand framework, which has been widely employed across the periodic table. Phosphines are observed to adopt the gamma-position of the ligand rather than the N,N' chelate. While aluminum and lithium adopt the familiar N,N' chelate arrangement with the new 2,4-diimino-3-phosphinopentene anion ligand, reactions with AsCl(3) or SbCl(3) result in substitution at the beta-methyl position on the ligand backbone, realizing novel P-->E (E = As or Sb) intramolecular coordination. The chemistry of the 2,4-diimino-3-phosphinopentene anion can be monitored by the (31)P NMR chemical shifts, which are distinctively diagnostic of the coordinative engagement of the ligand.