Dilip V. Khasnis

2,2′-Bipyridine complexes of the lithium chalcogenolates Li(EPh) and Li(NC5H4E-2)(E = S or Se)

2,2′-Bipyridine (bipy) forms stable crystalline co-ordination complexes with lithium benzeneselenolate and lithium pyridine-2-selenolate. The compounds are insoluble in aromatic hydrocarbons, slightly soluble in pyridine, and extremely soluble in tetrahydrofuran, from which they can be crystallized in ca. 70% yield. Both complexes have been characterized by elemental analysis, NMR, IR, and single-crystal X-ray diffraction. Compound [{Li(bipy)(SePh)}2]1[space group p21/m, a= 9.493(4), b= 16.866(5), c= 10.112(9), β= 114.53(6)° and Z= 4] is a dimer containing two lithium ions bridged by a pair of symmetric benzeneselenolate ligands, with bidentate bipy ligands bound to each lithium ion. In compound [{Li(bipy)(NC5H4Se-2)}2]2[space group P21/n, a= 10.361(5), b= 13.521(4), c= 11.062(5)A, β= 117.21(4)° and Z= 4] each lithium ion is bound to a bidentate bipy ligand, one bridging selenium atom, and the nitrogen atom from the second bridging pyridine-2-selenolate ligand, thus forming an eight-membered Li–Se–C–N–Li–Se–C–N ring. The analogous lithium thiolates have also been prepared in 70% yield; they are not isostructural with the selenolates.

Main-Group Chemistry within Macrocyclic Rings and Baskets

Abstract The incorporation of main-group elements into macrocycles leads to stabilization of novel structures and control of reactivity. The tetraamino macrocycle cyclen appears to favor a pentacoordinate trigonal bipyramidal (tbp) geometry about phosphorus, even when phosphorus is bonded to transition-metals. The tbp geometry is also favored for arsenic. The tetraphenol macrocycle p-tert-butylcalix[4]arene appears to stabilize a hexacoordinate phosphorus geometry under certain conditions; however, pentacoordinate and tricoordinate structures are also found.

Two-fragment addition of borohydride to iron complexes: synthesis of dithioformate iron complexes with B–H–Fe bond interaction. X-Ray structural characterization of Fe[η3-HC(SMe)S → B(H)H2](CO)(PMe3)2

Reaction of Fe(X)(µ2CS2R)(CO)(PR3)2(X = Cl, I) complexes with NaBH4 leads to both hydride and BH3 addition with the formation of dithiofromate–iron(O) Fe[µ3-HC(SR)S → BH3](CO)(PR3)2 complexes (4) containing an agostic B–H–Fe interaction; the addition of pyridine to (4) liberates a 16 electron-iron(O) moiety by trapping of the BH3 unit.

Direct transformation of six- to three-coordinate phosphorus in p-tert-butylcalix[4]arene; the first X-ray crystal structure of a hypervalent main group atom bound to a calixarene

Removal of dimethylamine from the zwitterionic six-coordinate phosphorus species p-fert-butylcalix[4]areneP(H)NHMe21 leads to the three-coordinate derivative p-tert- butylcalix[4]arene(H)P 4; the X-ray structure of Li[p-tert-butylcalix[4]areneP(H)NMe2]3 gives an insight as to why no pentacoordinate species is observed.

Reactions of a Cyclenphosphoranide Platinum (II) Complex and the Role of Highly Nucleophilic Substituents at the Axial Positions of a Trigonal Bipyramid

Abstract (η2-cyclenP)Pt(Cl)PPh3 1 exhibits a large variety of selective reactions due to the platinum metal and cyclenphosphoranide ligand, cyclenP. Moreover, the cyclenP ligand is capable of altering many of the usual reactions and/or mechanisms at square planar platinum (II) complexes.

Lewis acid controlled tautomerization of a metallated cyclenphosphorane

The species HcyclenPMo(CO)5(2), which contains a trigonal bipyramidal phosphorus with a P ⋯ N transannular interaction, reacts with HBF4 or Me3OBF4 and leads to formation of phosphoranide (R4P:–) adducts, whereas reaction of (2) with THF·BH3(THF = tetrahydrofuran) yields the unexpected phosphine adduct H(BH3)cyclenP-Mo(CO)5(5), the X-ray structure of which reveals an unprecedented conformation of the cyclenP ring.