Synthesis and structures of gallium alkylthiolate compounds

Gallium alkylthiolate complexes have been prepared from gallium amide compl exes and thiols. The amide complex [Ga(NMe2)(3)](2) reacts with excess t-Bu SH to give the amine adduct Ga(S-t-Bu)(3)(HNMe2), In contrast, the bulky am ide complex Ga(N-i-Pr-2)(3) reacts with t-BuSH to give the homoleptic thiol ate dimer [Ga(S-t-Bu)(3)](2). The analogous reaction between Ga(N-i-Pr-2)(3 ) and i-PrSH produces the salt [i-Pr2NH2][Ga(S-i-Pr)(4)], which on heating under vacuum loses amine and thiol to give the dimer [Ga(S-i-Pr)(3)](2). Re actions of [i-Pr2NH2][Ga(S-i-Pr)(4)] and [Ga(S-t-Bu)(3)](2) With excess pyr idine give the adducts Ga(SR)(3)(py) (R = i-Pr or t-Bu). X-ray crystallogra phic studies show that the dimers have two bridging thiolate ligands. The G a(mu-SR)(2)Ga four-membered ring in [Ga(S-i-Pr)(3)](2) has a planar anti ge ometry while the ring in [Ga(S-t-Bu)(3)](2) has a butterfly syn configurati on. In the solid state, Ga(S-t-Bu)(3)(HNMe2) and [i-Pr2NH2] [Ga(S-i-Pr)(4)] have trigonal-pyramidal and distorted tetrahedral geometries, respectively . The [Ga(SR)(3)](2) compounds exhibit solution fluxional behavior consiste nt with two separate processes, bridge-terminal thiolate exchange and effec tive inversion at the bridging sulfur atoms. Ab initio molecular orbital ca lculations on [Ga(SH)(2)(mu-SH)](2) at the MP4(SDQ) level predict activatio n energies for the two processes of 17.6 and 11.9 kcal/mol, respectively. C rystal data are as follows. Ga(S-t-Bu)(3)(HNMe2), C14H34GaNS3 at 223 K:. P2 (1)/n (monoclinic), a = 9.6373(5) Angstrom, b = 12.7183(7) Angstrom, c = 16 .9708(9) Angstrom, beta = 91.9810(10)degrees, and Z = 4. [i-Pr2NH2] [Ga(S-i -Pr)(4)], C18H44GaNS4 at 223 K: P2(1)/n (monoclinic), a = 12.0179(6) Angstr om, b = 15.4813(8) Angstrom, c = 14.3875(8) Angstrom, beta = 93.801(1)degre es, and Z = 4. [Ga(S-i-Pr)(3)](2), C18H42Ga2S6 at 223 K: P-1 (triclinic), a = 8.6813(8) Angstrom, b = 9.2969(8) Angstrom, c = 11.1804(10) Angstrom, al pha = 107.385(2)degrees, beta = 95.987(1)degrees, gamma = 117.285(1)degrees , and Z = 1. [Ga-(S-t-Bu)(3)](2), C24H54Ga2S6 at 223 K: C2/c (monoclinic), a = 10.0630(10) Angstrom, b = 17.698(2) Angstrom, c = 19.836(2) Angstrom, b eta = 98.500(10)degrees, and Z = 4.