SYNTHESES, CHARACTERIZATION, CRYSTAL AND MOLECULAR-STRUCTURES, AND SOLUTION PROPERTIES OF ET2GA(C5H5) AND ETGA(C5H5)(2)

The compounds Et(2)Ga(C5H5) and EtGa(C5H5)(2) have been prepared by li gand redistribution reactions in pentane solution between appropriate quantities of GaEt(3) and Ga(C5H5)(3). Both compounds have been fully characterized by elemental analyses, X-ray structural studies, cryosco pic molecular weight studies in benzene solution, mass spectroscopic s tudies, H-1 NMR studies of solutions, and 1H NMR studies of melts. Bot h compounds exist as pure single compounds in the solid state, The com pound [Et(2)Ga(C5H5)]infinity crystallizes in the centrosymmetric tric linic space group P $($) over bar$$ 1 (No. 2) with a = 7.803(2) Angstr om, b = 15.839(4) Angstrom, c = 16.318(4) Angstrom, alpha = 101.98(2)d egrees, beta = 95.23(2)degrees, gamma = 102.72(2)degrees, V = 1904.5(8 ) Angstrom(3), and Z = 8 (monomeric units). The structure consists of polymeric chains of [Ga-C5H5]infinity, in which each gallium(III) cent er is linked to two ethyl ligands and is in contact with one carbon at om from each of two bridging C5H5 ligands. The other compound [EtGa(C5 H5)(2)]infinity crystallizes in the noncentrosymmetric orthorhombic sp ace group P2(1)2(1)2(1) (NO. 19) With a = 8.213(5) Angstrom, b = 9.131 (4) Angstrom c = 14.277(10) Angstrom, V = 1070.7(11), and Z = 4 (monom eric units). The structure was refined to R = 7.01% for those 846 refl ections above 6 sigma, This structure is also polymeric with [Ga-C5H5] infinity chains. Each gallium(III) center is also bonded to an ethyl l igand and a terminal eta(1)-C5H5 ligand. When the compounds are dissol ved in benzene, toluene, cyclohexane, CHCl3, or THF, ligand redistribu tion reactions occur to form equilibrium mixtures of species, However, when [Et(2)Ga(C5H5)]infinity is melted, 1H NMR spectral studies sugge st the existence of only Et(2)Ga(C5H5), whereas when [EtGa(C5H5)(2)]in finity is melted, a single compound does not exist and a mixture of Et Ga(C5H5)(2), Et(2)Ga(C5H5), and Ga(C5H5)(3) is formed instead. Mass sp ectral studies of Et(2)Ga(C5H5) are consistent with the presence of Et (2)Ga(C5H5) in the gas phase, but when [Et(2)Ga(C5H5)]infinity is heat ed and vaporized, uncertainty regarding the identities of the species in the gas phase arises due to the occurrence of the ligand redistribu tion reactions in the melt.