Organometallic Complexes Containing 17-Ethynyl-17β-hydroxyandrost-4-en-3-one and Related Ethynyl Steroids

Gold complexes of 17-ethynyl-17β-hydroxyandrost-4-en-3-one,
17-ethynyl-3-methoxyestra-1,3,5(10)-trien-17β-ol, and 17α-ethynylestra-1,3,5(10)-triene-3,17β-diol
have been prepared and characterized. The
title compounds were prepared by treatment of the parent ethynyl steroid
with sodium bis(trimethylsilyl)amide followed by the addition of R3PAuCl. Using a variety of phosphorus donors, a total of 36
gold
steroid compounds were readily prepared using this approach. Compounds
containing basic low cone
angle phosphines such as PMe3 and PEt3 exhibited
broad signals in the 13C{1H} NMR spectrum for
the
alkyne moiety, while compounds containing triarylphosphines or moderately
bulky trialkylphosphines
exhibited sharp signals. Correlations between common measures of phosphine
donor ability with 2
J
CP
and 3
J
CP as well as changes in the 31P chemical
shift were made. While the use of low cone angle phosphines was successful,
analogous reactions with trimesitylphosphine or tris(2,4,6-trimethoxyphenyl)phosphine
resulted in intractable mixtures containing significant amounts of
free phosphine. The incorporation
of electron-withdrawing groups into the organic fragment of the phosphine
donors was tolerated except
for P(C6F5)3, where displacement
of the phosphine was observed. The molecular structures of five
representative examples are presented and discussed. These determinations
represent the first structurally
characterized examples where the transition metal is σ-bound
to the ethynyl fragment of the steroid.