SOME TRIS[(TRIORGANOPHOSPHINE)GOLD(I)]-OXONIUM AND TRIS[(TRIORGANOPHOSPHINE)GOLD(I)]-ORGANOIMONIUM TETRAFLUOROBORATES WITH BULKY SUBSTITUENTS

Tris{[tri(2-methylphenyl)phosphine]gold(I)}-, ris{[tri(2,4,6-trimethyl phenyl)phosphine]gold(I)}- and tris{[tri(cyclohexyl)phosphine]gold(I)} -oxonium tetrafluoroborate (1-3) have been prepared from the correspon ding (phosphine)gold(I) chlorides, silver oxide, and sodium tetrafluor oborate in acetone. These oxonium salts are excellent aurating agents for primary amines. Thus in the reaction with 1, t-butylamine tBuNH2 a nd aniline PhNH2 are readily converted into the trinuclear imino compl exes {[(2-MeC6H4)3P]Au}3NtBu+BF4- (4) and {[(2-MeC6H4)3P]Au}3NPh+BF4- (5) in high yields. With 3, both aniline and 8-amino-quinoline also gi ve the trinuclear complexes, i.e. {[(C-C6H11)3P]Au}3NPh+BF4 (6) and {[ (C-C6H11)3P]Au}3N(C9HN)+BF4- (7). Auration of aniline with the most st erically hindered reagent 2 yields only the binuclear complex {[(2,4,6 -Me3C6H2)3P] . Au}2N(Ph)H+BF4- (8). The reagents 1-3 and the products 4-8 have been characterized by analytical and NMR spectroscopic data, and the crystal structures of compounds 4 and 6 have been determined b y single crystal x-ray diffraction. In the cations of 4, a triangle of gold atoms with short Au ... Au contacts [3.036(1), 3.107(1), and 3.2 14(1) angstrom] forms a steep pyramid with the nitrogen atom, in which the angles Au-N-Au are all much smaller than the tetrahedral standard of 109.7-degrees: 94.8(4), 98.t(4), and 103.0(4)-degrees. This triang ular Au3 unit is staggered relative to the three methyl groups of the (t)Bu substituent at nitrogen. The results for 6 are similar [Au ... A u: 3.037(1), 3.071(1), and 3.222(1) angstrom; Au-N-Au: 95.3(3), 96.5(3 ), and 103.6(3)-degrees]. Variable temperature NMR studies of compound s 3 and 8 show hindered rotation of the mesityl groups about the P-C b onds of the ligands originating from the steric congestion within each tertiary phosphine.