Some chemical properties of monochlorogallane: decomposition to gallium(I) trichlorogallate(III), Ga(+)[GaCl3H](-), and other reactions.

Thermal decomposition of monochlorogallane, [H2GaCl]n, at ambient temperatures releases H2 and results in the formation of gallium(I) species, including the new compound Ga[GaHCl3], which has been characterized crystallographically at 100 K (monoclinic P2(1)/n, a = 5.730(1), b = 6.787(1), c = 14.508(1) A, beta = 97.902(5) degrees ) and by its Raman spectrum. The gallane suffers symmetrical cleavage of the Ga(mu-Cl)2Ga bridge in its reaction with NMe3 but unsymmetrical cleavage, giving [H2Ga(NH3)2](+)Cl(-), in its reaction with NH3. Ethene inserts into the Ga-H bonds to form first [Et(H)GaCl]2 and then [Et2GaCl]2.

Preparation and properties of gallaborane, GaBH(6): structure of the gaseous molecule H(2)Ga(mu-H)(2)BH(2) as determined by vibrational, electron diffraction, and ab initio studies, and structure of the crystalline solid at 110 K as determined by X-ray diffraction.

Gallaborane (GaBH(6), 1), synthesized by the metathesis of LiBH(4) with [H(2)GaCl](n) at ca. 250 K, has been characterized by chemical analysis and by its IR and (1)H and (11)B NMR spectra. The IR spectrum of the vapor at low pressure implies the presence of only one species, viz. H(2)Ga(mu-H)(2)BH(2), with a diborane-like structure conforming to C(2v) symmetry. The structure of this molecule has been determined by gas-phase electron diffraction (GED) measurements afforced by the results of ab initio molecular orbital calculations. Hence the principal distances (r(alpha) in A) and angles ( angle(alpha) in deg) are as follows: r(Ga.B), 2.197(3); r(Ga-H(t)), 1.555(6); r(Ga-H(b)), 1.800(6); r(B-H(t)), 1.189(7); r(B-H(b)), 1.286(7); angleH(b)-Ga-H(b), 71.6(4); and angleH(b)-B-H(b), 110.0(5) (t = terminal, b = bridging). Aggregation of the molecules occurs in the condensed phases. X-ray crystallographic studies of a single crystal at 110 K reveal a polymeric network with helical chains made up of alternating pseudotetrahedral GaH(4) and BH(4) units linked through single hydrogen bridges; the average Ga.B distance is now 2.473(7) A. The compound decomposes in the condensed phases at temperatures exceeding ca. 240 K with the formation of elemental Ga and H(2) and B(2)H(6). The reactions with NH(3), Me(3)N, and Me(3)P are also described.

Matrix photochemistry of syn-(chlorocarbonyl)sulfenyl bromide, syn-ClC(O)SBr: precursor to the novel species anti-ClC(O)SBr, syn-BrC(O)SCl, and BrSCl.

The vapor of (chlorocarbonyl)sulfenyl bromide, ClC(O)SBr, was isolated in solid Ar, Kr, N(2), and Ar doped with 5% CO at 15 K, and the matrix was subsequently irradiated with broad-band UV--visible light (200 < or = lambda < or = 800 nm), the changes being followed by reference to the IR spectrum of the matrix. The initial spectrum showed the vapor of ClC(O)SBr to consist of more than 99% of the syn form (with the C==O bond syn with respect to the S--Br bond) in equilibrium with less than 1% of the anti conformer. Irradiation caused various changes to occur. First, conformational randomization took place, leading to a roughly equimolar mixture of the two rotamers, and so affording the first spectroscopic characterization of an anti-ClC(O)S-containing compound. Simultaneously, the novel constitutional isomer syn-BrC(O)SCl was also formed. Continued photolysis resulted in the decay of all these species while revealing a third reaction channel, leading to the elimination of CO and the formation of the new triatomic sulfur halide BrSCl. The assignment of the IR bands to the different products was made on the basis of the usual criteria, taking account (i) of the effects of the naturally occurring isotopic pairs (35)Cl/(37)Cl and (79)Br/(81)Br, (ii) of the vibrational properties of related molecules, and (iii) of the properties predicted for the relevant molecules by quantum chemical calculations.

Reactions of aluminum, gallium, and indium (M) atoms with phosphine: generation and characterization of the species M.PH3, HMPH2, and H2MPH.

Upon deposition of Al, Ga, or In atoms (M) together with phosphine in a solid argon matrix, metal atom complexes M.PH3 are formed. Photolysis of the matrices at lambda = 436 nm results in the tautomerization of the adduct species to the insertion products HMPH2 and H2MPH. In addition, PH is formed from the reactions with Ga and In, with HMPH2 being its most likely precursor. Further photolysis into the absorption maximum of HMPH2 near 550 nm results in decomposition of HMPH2 with partial re-formation of the adduct M.PH3 and further buildup of PH. H2MPH is photostable under these conditions but suffers decomposition under the action of UV light (200 < or = lambda < or = 400 nm). All the molecules have been identified by their IR spectra, the assignments being attested by the effects of deuteration and also by comparison either with the vibrational properties anticipated by density functional theory (DFT) calculations or with those of known, related molecules. The resulting analysis is elaborated for the light it sheds on the structures and properties of the new molecules and on the mechanisms of the reactions affording, or disposing of, them.

Monochlorogallane: physical properties and structure of the gaseous molecule H2Ga(mu-Cl)2GaH2 as determined by vibrational, electron diffraction, and ab initio studies.

Monochlorogallane, synthesized by the metathesis of gallium(III) chloride with an excess of trimethylsilane at ca. 250 K, has been characterized by chemical analysis, by its IR, Raman, and 1H NMR spectra, and by the products of its reaction with trimethylamine. The vibrational spectra of the vapor species isolated in solid Ar, N2, or CH4 matrixes at ca. 12 K imply the presence of only one species, viz. the dimer with an equilibrium structure conforming to D2h symmetry. The structure of this molecule has been determined by gas-phase electron diffraction (GED) measurements augmented by the results of ab initio molecular orbital calculations. An equilibrium structure with D2h symmetry has been assumed in the analysis of the electron diffraction pattern. However, as the molecule has a very low frequency Ga(mu-Cl)2Ga ring-puckering mode, a dynamic model was used to describe it with the aid of a set of pseudoconformers spaced at even intervals (deltadelta = 5 degrees, deltamax, = 20 delta) around the ring-puckering angle delta and Boltzmann-weighted according to a quartic potential V(delta) = V4delta4 + V2delta2. The differences in bond distances and angles between the different pseudoconformers were constrained to the values derived from the ab initio calculations employing second-order Moller-Plesset (MP2) methods (with all the electrons included in the correlation calculations) and a 6-311G(d) basis set. The results for the weighted average of the principal distances (ralpha) and angles (