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HgCl(CF=CF 2 )[Mn(CO) 5 Br] 0.5 equiv. cis-[Pt(PPh 3 ) 2 Cl 2 ] Me 3 SnCl HgCl 2

The crystal and molecular structures of [Au 2 {S 2 CN(C 2 H 4 OMe) 2 } 2 ], [Au(PPh 3 )(SCH 2 CO 2 H)], [Au(PPh 3 )(SCMe 2 -CO 2 H)] and [Au(PPh 3 )(SCH 2 CO 2 Me)] have been determined. All compounds contain an approximately linear primary co-ordination sphere of ligands about the gold atom, but they differ markedly in their type of intermolecular interaction. In [Au 2 {S 2 CN(C 2 H 4 OMe) 2 } 2 ] the supramolecular array is dominated by an almost linear, polymeric backbone of gold atoms with alternate gold-gold contacts of 2.7902(6) (intramolecular) and 3.1572( 7) Å (intermolecular), whereas in [Au(PPh 3 )(SCH 2 CO 2 H)] dimers associated through long gold-sulfur contacts of 3.131(2) Å are held together in a polymeric chain by hydrogen bonding between neighbouring carboxylic acid residues. The increased steric bulk of the thiolate ligand in [Au(PPh 3 )(SCMe 2 CO 2 H)] caused by the methyl groups on the α-carbon atom precludes association of the gold centres, but hydrogen bonding between carboxylates as in the SCH 2 CO 2 H compound causes dimerisation. Compound [Au(PPh 3 )(SCH 2 CO 2 Me)] exists as a monomer with no evidence of weak intermolecular interactions. Analysis of ambient-temperature EXAFS (extended X-ray absorption fine structure) measurements on solid samples of the first two compounds yield gold-gold separations of 2.775(2) and 3.271(6) Å and 4.188(15) Å, respectively. Gold-sulfur separations of 2.290(1) and 3.532(8) and of 2.329(4) and 3.124(19) Å, respectively, are also in good agreement with X-ray data.

The group 14 trifluorovinyl compounds Ph(3)ECF=CF(2) (E = Ge, Sn, Pb) have been prepared in high yield by the low-temperature reaction of the triphenylelement halide with trifluorovinyllithium, generated from tetrafluoroethane (CF(3)CH(2)F, HFC-134a) and 2 equiv of n-butyllithium. The X-ray crystal structures of these materials have been obtained, so affording the first structural series for such species. Subsequent reaction of Ph(3)GeCF=CF(2) with LiAlH(4) and a range of organolithium reagents has led to preparation of the 1,2-difluorovinylgermanes Ph(3)GeCF=CFR (R = H, Me, n-Bu, t-Bu, Ph). Multinuclear NMR spectroscopic and X-ray crystallographic studies of these compounds have been undertaken and have shown unequivocally the exclusive trans-geometry of the 1,2-difluorovinyl moiety.

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