Manganese propane and manganese butane complexes derived from CpMn(CO)(3) were generated photochemically at 130-136 K with the alkane as solvent and characterized by FTIR spectroscopy and by (1)H NMR spectroscopy with in situ laser photolysis. Time-resolved IR spectroscopic measurements were performed at room temperature with the same laser wavelength. The ν(CO) bands in the IR spectra of the photoproducts in propane are shifted to low frequency with respect to CpMn(CO)(3), consistent with formation of CpMn(CO)(2)(propane). The (1)H NMR spectra conform to the criteria for alkane complexes: a high-field resonance for the η(2)-CH protons that shifts substantially on partial deuteration of the alkane and exhibits a coupling constant J(C-H) on (13)C-labeling of ca. 120 Hz. The NMR spectrum of each system exhibits two diagnostic product resonances in the high-field region for the η(2)-CH protons, corresponding to CpMn(CO)(2)(η(2)-C1-H-alkane) and CpMn(CO)(2)(η(2)-C2-H-alkane) isomers. Partial deuteration of the alkane at C1 results in characteristic strong isotopic perturbation of equilibrium of the η(2)-CH resonance of CpMn(CO)(2)(η(2)-C1-H-alkane). With propane-(13)C(1), the η(2)-CH resonance of CpMn(CO)(2)(η(2)-C1-H-alkane) isomer exhibits (13)C satellites with J(C-H) = 119 Hz. The corresponding resonance of CpMn(CO)(2)(η(2)-C2-H-alkane) is identified by use of propane-2,2-d(2). The lifetimes of the (η(2)-C1-H-alkane) isomers of the manganese complexes were determined by NMR spectroscopy as 22 ± 2 min at 134 K (propane) and 5.5 min at 136 K (butane). The corresponding spectra and lifetimes of the CpRe(CO)(2)(alkane) complexes were measured for reference (CpRe(CO)(2)(propane) lifetime ca. 60 min at 161 K; CpRe(CO)(2)(butane) 13 min at 171 K). The lifetimes determined by IR spectroscopy were similar to those determined by NMR spectroscopy, thereby supporting the assignments. These measurements extend the range of alkane complexes characterized by NMR spectroscopy from rhenium and rhodium derivatives to include less stable manganese derivatives.

Photolysis of solutions of M(CO)6 (M = Cr, Mo, and W) in the presence of Et3SiH affords the silane complexes Cr(CO)5(eta2-HSiEt3), Mo(CO)5(eta2-HSiEt3), and W(CO)5(eta2-HSiEt3). Observed values of J(SiH) in these complexes are consistent with modest elongation of the Si-H bond. With Ph3SiH, complexes of Cr(CO)5 and W(CO)5 were obtained, but no complex with Mo was observed. When Ph2SiH2 was employed, only one Si-H bond interacts with the metal center. A dynamic exchange process observable on the magnetic resonance time scale exchanges the pendant and coordinated Si-H bonds of the coordinated diphenylsilane. Silanes bound to M(CO)5 are activated with respect to reaction with nucleophiles. With methanol, catalytic methanolysis of HSiEt3 has been observed in the presence of Cr(CO)5(eta2-HSiEt3), affording Et3SiOMe.

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From the viewpoint of the fixation of atmospheric nitrogen, there is a long-term general interest in the identification and characterization of compounds that result from the reaction of transition metals with dinitrogen. In addition, the investigation of the interaction of N 2 with transition-metal compounds has intrinsic significance because of the isoelectronic, isolobal nature of dinitrogen and carbon monoxide. There is a voluminous amount of literature [1] on transition-metal carbonyl compounds, from which it is concluded that the nature of the generally strong bonding interaction of CO with the transition-metal center in such compounds is well-understood.Recently, a series of simple linear transition-metal carbonyl complexes of the type OCÀMÀX (M = Cu, [2] Ag, [3] or Au [4] ; X = F, Cl, or Br) were thoroughly investigated in the gas phase by means of their rotational spectra to give details of their geometry and electronic structure. Information about the electric-charge redistribution at the metal center is contained in the nuclear quadrupole coupling constants for M = Cu or Au. The interaction between CO and M was also found to be strong in these transient species. On the other hand, the hydrogen-bonded species OC···H À X, which may be envisaged, formally at least, as generated from OC À M À X by replacement of M by H, have been investigated extensively by rotational spectroscopy. [5][6][7] Such complexes are weakly bound (here depicted with ···) with intermolecular binding energies of only a few kJ mol À1 . The dinitrogen complexes N 2 ···HÀX have linear geometries similar to those of OC···H À X, but with slightly weaker hydrogen bonds. [8][9][10] The isostructural nature of OC···H À X and N 2 ···H À X can be understood by assuming that the electrophilic region of HX seeks the most nucleophilic region of CO or N 2 (namely, the axis of a nonbonding

In situ microwave activation of electrochemical processes in a novel electrochemical cell, in which intense microwave radiation is focused locally into the region at the electrode surface±solution interface, is shown to allow high-temperature voltammetry experiments at 100 mm Pt disk electrodes. Factors such as the cell geometry and the deposition of a thin ®lm of mercury are shown to in¯uence the microwave effect. The detection of trace metals or impurities by anodic stripping voltammetry is a routinely applied procedure with applications especially in rapid online monitoring, in remote place analysis, or for extremely dilute samples. For cadmium detection by anodic stripping voltammetry microwave radiation is demonstrated to strongly affect the accumulation process but not the stripping process. Calibration of the effects induced by microwave radiation on the experimentally observed voltammetric data, based on the equilibrium potentials for the FeCN 4Àa3À 6 and the RuNH 3 3a2 6 redox systems, demonstrates that the data obtained are consistent with a thermally enhanced process. The temperature achievable at the electrode±solution interface before boiling and cavitation occurs, is shown to be strongly dependent on the type of electrode material and surface morphology. At a mercury ®lm electrode deposited on platinum temperatures in excess of 150C can be applied in voltammetric experiments in a constant heating mode.