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Teaching the VSEPR (valence shell electron-pair repulsion) model can be a tedious process. Traditionally, Lewis structures are drawn and the number of “electron clouds” (groups) around the central atom are counted and related to the standard VSEPR table of possible geometries. A simpler method to deduce the VSEPR structure without first drawing Lewis structures is described. A sample lecture utilizing this methodology to determine VSEPR geometries is presented. Incorporated into the lecture are discussions of relevant topics including dipole moments, isomers, electron-pair repulsions, and bioinorganic chemistry. Although this lecture is aimed at first-year science majors, it can easily be modified and applied to nonscience-majors courses and advanced inorganic chemistry courses. A lab to accompany the lecture is available in the supporting material.

The kinetics of the substitution reaction [ML 7 ] 2+ +X - ⇔[ML 6 X] + +L (X=Cl, Br, or I; L=t-C 4 H 9 NC; M=Mo or W) have been investigated in both directions via conductance studies in acetonitrile. For M=Mo, the reaction is reversible. A dissociative process with participation of both ion-paired and non-ion-paired complexes is proposed as the mechanism of substitution

The metal N,N-diisopropyldithiocarbamate complexes NaL, NiL/sub 2/, CoL/sub 3/, AlL/sub 3/, InL/sub 3/, and ZrL/sub 4/ (L = S/sub 2/CN(i-Pr)/sub 2/) have been prepared and characterized by IR and /sup 1/H NMR spectroscopy. Low-temperature /sup 1/H NMR spectra of these compounds exhibit two equally intense isopropyl methyl doublets and two equally intense methine septets, attributed to a ligand conformation in which the methine protons of the inequivalent isopropyl groups are located in the plane of the liqand in environments that may be labeled ''inner'' or ''outer'' with respect to the quasi-twofold axis of the ligand. Between -50 and +15/sup 0/C the methyl doublets and methine septets coalesce to a single doublet and a single septet, respectively, owing to hindered rotation about the C-N single bonds. Rate constants (s/sup -1/) at -10/sup 0/C in CH/sub 2/Cl/sub 2/ solution vary from 1400 for CoL/sub 3/ to 8.3 for NaL; E/sub a/ = 10-12 kcal/mol and ..delta..S/sup + +/ = -7 to -13 eu. The rates increase with decreasing size, increasing charge, and increasing class by character of the metal ion and with decreasing SCS angle and increasing CNC angle in the analogous N,N-diethyldithiocarbamates. These trends can be understood in terms of amore » metal-induced variation in the amount of steric congestion in the N(i-Pr)/sub 2/ group. The methyl ester MeSC(S)N(i-Pr)/sub 2/ exists in CH/sub 2/Cl/sub 2/ solution as a 0.58:0.42 equilibrium mixture of two conformers that have the ''outer'' methine proton cis and trans, respectively, to the SMe group. Exchange of isopropyl methyl groups among the four inequivalent sites of the two conformers has been analyzed in terms of hindered rotation about (i) the C-N single bonds and (ii) the C-N partial double bond. Kinetic data are also reported for rotation about the C-N bond in the diisobutyl derivative MeSC(S)N(i-Bu)/sub 2/.« less