Studies of organotin(IV)-orthoquinone systems

The primary process in the reaction of hexaphenylditin with various substituted orthoquinones (Q) is shown to involve attack by the quinone at a phenyl ligand. The intermediate thus formed decomposes to yield Ph₃Sn(SQ^·), where S(Q^·−) is the corresponding semiquinonate. Rearrangement of these species in solution gives rise to biradicals, while intramolecular electron transfer may lead to the formation and precipitation of Ph₂Sn(CAT), where CAT²⁻ is the corresponding substituted catecholate. The identification of these processes depends in part on electron paramagnetic resonance spectroscopy. The reaction of Ph₃SnCl or Ph₂SnCl₂ with Na(TBSQ^·) (TBSQ^·−=3,5-di-tert-butyl-orthobenzosemiquinonate) results in the formation of Ph₂Sn(TBSQ^·), which can undergo redistribution and intramolecular electron transfer, so that the solution chemistry of these latter systems is similar to that of the products of the Sn₂Ph₆+Q reaction.     

Kinetic and thermodynamic studies on ligand substitution reactions and base-on/base-off equilibria of cyanoimidazolylcobamide, a vitamin B12 analog with an imidazole axial nucleoside

Ligand substitution reactions of the vitamin B12 analog cyanoimidazolylcobamide, CN(Im)Cbl, with cyanide were studied. Cyanide substitutes imidazole (Im) in the alpha-position more slowly than it substitutes dimethylbenzimidazole in cyanocobalamin (vitamin B12). The kinetics of the displacement of Im by CN- showed saturation behaviour at high cyanide concentration; the limiting rate constant was found to be 0.0264 s(-1) at 25 degrees C and is characterized by the activation parameters: DeltaH(not =) = 111 +/- 2 kJ mol(-1), DeltaS(not =) = +97 +/- 6 J K(-1) mol(-1), and DeltaV(not =) = +9.3 +/- 0.3 cm3 mol(-1). These parameters are interpreted in terms of an I(d) mechanism. The equilibrium constant for the reaction of CN(Im)Cbl with CN- was found to be 861 +/- 75 M(-1), which is significantly less than that obtained for the reaction of cyanocobalamin with CN- (viz. 10(4) M(-1)). pKbase-off for the base-on/base-off equilibrium was determined spectrophotometrically and found to be 0.99 +/- 0.05, which is about 0.9 pH units higher than that obtained previously in the case of cyanocobalamin. In addition, the kinetics of the base-on/base-off reaction was studied using a pH-jump technique and the data obtained revealed evidence for an acid catalyzed reaction path. The results obtained in this study are discussed in reference to those reported previously for cyanocobalamin.     

Linear free energy relationship of the energy of the CTTS transition of Halide ions with the solvatochromic parameter α

A linear free energy relationship was found betweenv _max, the energy of the absorption maximum of chloride, bromide, or iodide ion in various solvents, and the solvatochromic parameter which is a measure of the hydrogen bond donor ability of the solvent. The relationships are: for chloride,v _max=6.99+50.16 kK; for bromide,v _max=5.52+45.20 kK; for iodide,v _max=5.02+40.33 kK. The correlation ofv _max for iodide ion with gave a larger correlation coefficient and smaller standard deviation than a correlation with the E _T (30) parameter of Dimroth. From the values ofv _max for iodide ion and the solvated electron in liquid ammonia at 25°C, these correlations indicate a preliminary value of 0.00 for the parameter of liquid ammonia. This had not been reported before and is lower than expected from a general knowledge of the physical and chemical properties of liquid ammonia but is consistent with a more detailed consideration and recent gas phase measurements of hydrogen bond donor strength.     

Evidence for the direct isomerization of a platinocyclobutane to an olefin complex

Dichloro-2,3,3-trimethyl-1-platinocyclobutane,

, prepared by the metathetical reaction of Zeise's dimer and 1,1,2-trimethylcyclopropane, reacts with pyridine in chloroform to produce a platinum complex of 2,3-dimethyl-1-butene

. Reaction of I with pyridine at low temperatures (ca. ?40° C) leads to a pyridine addition compound (III) in which the platinocyclobutane ring remains intact. The thermal isomerization of III, which may be conveniently studied using NMR, produces a mixture of II and the free olefin.     

Improved highly efficient synthesis of α,β-acetylenic ketones. Nature of the intermediate from the reaction of lithium acetylide with boron trifluoride etherate

A wide variety of α,β-acetylenic ketones were synthesized in very high yields via an exceptionally facile intermolecular reaction of lithium alkynyltrifluoroborates and carboxylic acid anhydrides.     

High-performance liquid chromatographic assay for acid and alkaline phosphatase in serum.

High-performance liquid chromatography was used to assay serum acid and alkaline phosphatase. Samples were incubated with adenosine-5'-monophosphoric acid (AMP) in a buffer of required pH, 5'-nucleotidase was inhibited with Ni2+ ions, and the phosphatase activity was determined by measuring the concentration of the reaction product, adenosine. The analysis time, after the incubation is terminated, is short (7 min), and the assay is quantitative and reproducible. Complete separation of the reaction product from the substrate and the naturally occurring serum constituents and the high sensitivity of the ultraviolet detection system eliminate some of the problems commonly encountered in spectrophotometric assays.     

Comments on the approximate calculation of lattice potential

The potential of a charge distribution due to a lattice of point charges may be evaluated by the classical multipole expansion method. The leading terms in the resultant expressions are just those used in some of our previous calculations [1–3]. In addition, for cases where the leading terms vanish because of the effect of orthogonality of the basis functions upon the Mulliken expansion (this being especially serious in the case of a one-centre charge distribution), we have derived the first nonvanishing term, involving |r|. In other cases it may be necessary to proceed to still higher multipole terms before a non-zero contribution is obtained. The entire procedure is formulated in such a way that it can be easily applied to LCAO-MO calculations for polyatomic ions in ionic lattices.     

Presentations for groups acting on simply-connected complexes

New expansions for global semigroup theory are developed. Many expansions have a left and a right version, each with specific (dual) properties; e.g., the Rhodes expansions ?^$\text{L}$, resp. ?^$\text{R}$, have unambiguous $\text{L}$-resp. $\text{R}$-order. In applications one sometimes needs expansions having both properties simultaneously; these can be constructed by alternately applying the left and the right expansion (possibly infinitely often) while keeping the same set of generators. Thus one obtains an expansion which is invariant under application of the old two expansions and thus has the properties of both (e.g., one obtains -+ with

, and so -+ has unambiguous $\text{L}$-and $\text{R}$-order). It is proved that, in the case of the Rhodes expansion, the new expansion is ‘close’ to the original semigroup; in particular (and this is the main result of the paper), ?⁺_A is finite (resp. finite $\text{J}$-above) if S is finite (resp. finite$\text{J}$-above).     

The stability of gold iodides in the gas phase and the solid state

The stability of gold iodides in the oxidation state +I and +III is investigated at the ab initio and density functional level using relativistic and nonrelativistic energy-adjusted pseudopotentials for gold and iodine. The calculations reveal that relativistic effects stabilize the higher oxidation state of gold as expected, that is Au2I6 is thermodynamically stable at the relativistic level, whilst at the nonrelativistic level the complex of two iodine molecules weakly bound to both gold atoms in Au2I2 is energetically preferred. The rather low stability of AuI3 with respect to dissociation into AuI and I2 will make it difficult to isolate this species in the solid state as (possibly) Au2I6 or detect it by matrix-isolation techniques. The monomer AuI3 is Jahn-Teller distorted from the ideal trigonal planar (D3h) form, but adopts a Y-shaped structure (in contrast to AuF3 and AuCl3), and in the nonrelativistic case can be described as I2 weakly bound to AuI. Relativistic effects turn AuI3 from a static Jahn-Teller system to a dynamic one. For the yet undetected gas-phase species AuI accurate coupled-cluster calculations for the potential energy curve are used to predict vibrational-rotational constants. Solid-state density functional calculations are performed for AuI and Au2I6 in order to predict cohesive energies.     

The absorption spectrum of the Ag2 molecule

The high dispersion absorption spectrum of the Ag₂ molecule has been photographed in the ～5300–1500-Å region. Observations include the previously reported A ← X, B ← X, C ← X, D ← X, and E ← X transitions and a new H ← X transition which occurs in the vacuum ultraviolet. Extensive spectral blending precluded detailed rotational analyses, but the band structures are consistent with $\text{ΔΩ}\text{= 0}$ and $\text{ΔΩ}\text{≥1}$ for D-X and C-X, respectively. The H state is perturbed and probably predissociated. The following molecular constants (in cm^?1) were obtained from fitting bandhead data to the usual expressions:

     

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State	Te	ωc	Xωt
X	0.0	192.0	0.58
B	35 838.6	151.8	0.87
C	37 631.6	171.0	0.84
D	39 014.5	168.2	1.20
E	40 159.9	146.1	1.58
H	58 273.1	165.9	2.46