Expect the unexpected. Isolation and characterisation of some unusual organometallic gold(I) complexes

The reaction of equimolar amounts of 2-Li-3-MeC6H3PPh2 and [AuBr(AsPh3)] gives a mixture of the cyclometallated digold(I) complex [Au2(μ-6-MeC6H3-2-PPh2)2] and the ‘half-cyclometallated’ complex [(Ph3As)Au(μ-6-MeC6H3-2-PPh2)AuBr] (1). This complex represents the first example of an intermediate of a cycloauration reaction that has been structurally characterised by X-ray diffraction. The reaction of [Au2(μ-6-MeC6H3-2-PPh2)2] with mercuric chloride gives the unusual heteronuclear Hg(II)/Au(I) complex [ClHg(μ-6-MeC6H3-2-PPh2)AuCl] (2), arising from electrophilic cleavage of a gold-carbon σ-bond, and not the oxidative addition product.