Under PTC/OH- (PTC = phase-transfer
catalysis) conditions, the reaction of
Au2(dppm)Cl2
(dppm = 1,1-bis(diphenylphosphino)methane) with
[Me2S(O)NMe2]BF4
produces a greenish
luminescent compound
[Au2(dppm)[(CH2)2S(O)NMe2]]BF4,
1, and a colorless tetranuclear
compound
[Au4(dppm)(Ph2PCHPPh2)[(μ-CH)(CH2)S(O)NMe2]]BF4,
2. Both compounds 1 and
2 also can be synthesized from
[Au4(dppm)(Ph2PCHPPh2)Cl3],
3, which can be produced
simply by the reaction of
Au2(dppm)Cl2 with OH-
in the presence of a PTC. For
Au2(dppe)Cl2
(dppe = 1,2-bis(diphenylphosphino)ethane) and
Au2(dmpm)Cl2 (dmpm =
1,1-bis(dimethylphosphino)methane), only
[Au2(dppe)[(CH2)2S(O)NMe2]]PF6,
4, and
[Au2(dmpm)[(CH2)2S(O)NMe2]]BF4, 5, are
obtained as the major product, respectively. Compounds
1−4 are
characterized by single-crystal X-ray analyses. Two
C
2-related cations of 1 are packed in
a
row with the intermolecular Au−Au distance (2.959 Å) shorter than
the intramolecular Au−Au distance (2.984 Å). Compound 2 has one of the ylide
carbon atoms bridging two gold(I)
atoms. The tetragold cluster of 3 is formed by an
Au−C linkage between
[ClAu(μ-Ph2PCH2PPh2)Au]+ and
[ClAu(μ-Ph2PCHPPh2)AuCl]-.
The digold cation of 4 is a nine-membered
dimetallocycle. In acetonitrile solution, dimerization of
1 and 5 through intermolecular Au−Au interaction occurs as evidenced by concentration-dependent absorption
spectroscopic
studies. Concentration-dependent absorption spectra of
1 and 5 suggest that equilibriums
between the monomer and dimer exist with equilibrium constants of 33
± 9 and 52 ± 7 M-1
in acetonitrile, respectively. Digold(I) compounds
1, 4, and 5 luminesce in the solid
state.