Reaction of Sulfur with Ga−C Bonds: Synthesis and Characterization of [PyRGaS]3 Formed from Ga(S2R)3 (R = Et, Me)

Abstract

The reactions of Ga(CH(2)CH(3))(3) with variable amounts of elemental sulfur, S(8), in toluene or benzene at different temperatures result in the insertion of sulfur into the Ga-C bonds to form the compounds Ga[(S-S)CH(2)CH(3)](3) (I) and Ga[(S-S-S)CH(2)CH(3)](3) (II). Compound I was isolated from the reaction at low temperature while at room temperature; compound II was the major product. Compound II exhibited the maximum extent of sulfur insertion even when the reactions were carried out with more than 9.0 equiv of sulfur. The reactions of Ga(CH(3))(3) with various amounts of sulfur in toluene or benzene only result in the formation of compound III, Ga[(S-S)CH(3)](3). In pyridine at -30 degrees C, deinsertion of the sulfur atoms from Ga-S-S-C bonds was observed for the first time from compounds I and III resulting in formation of the six-membered Ga-S ring compounds IV, [PyEtGaS](3), and V, [PyMeGaS](3), respectively. Compounds IV and V were characterized by (1)H NMR, (13)C NMR, elemental analyses, thermogravimetric analysis, and single-crystal X-ray diffraction. Compound IV crystallized in the monoclinic space group P2(1)/n, with a = 9.288(2) Å, b = 14.966(2) Å, c = 19.588(3) Å, beta = 90.690(10) degrees, and Z = 4. Compound V crystallized in the monoclinic space group P2(1)/c, with a = 10.385(1) Å, b = 15.300(2) Å, c = 15.949(2) Å, beta = 107.01(1) degrees, Z = 4, unit cell volume = 2423.5(5) Å(3), R = 0.030, and R(w) = 0.026. The sulfur insertion reaction pathway was investigated by time-dependent and variable-temperature (1)H NMR spectroscopy.