Trigonal-prismatic and octahedral hexaruthenium boride clusters: molecular structures of [N(PPh3)2][Ru6H2(CO)18B], [Ru6(CO)17B{AuP(C6H4Me-2)3}], [Ru6H(CO)16B{Au(PPh3)}2] and [Ru6(CO)16B{Au(PPh3)}3]

The reaction of the [N(PPh3)2]+ salt of [Ru3(CO)9(B2H5)]– with [Ru3(CO)10(NCMe)2] yielded both the octahedral [Ru6(CO)17B]–1 and trigonal-prismatic [Ru6H2(CO)18B]–2 boride cluster anions. This result indicates that the choice of the trigonal-prismatic versus octahedral cage is not determined by the size of the interstitial atom. The salt [N(PPh3)2][Ru6H2(CO)18B] has been structurally characterised. The reactions of anions 1 and 2 with [AuCl(PPh3)], [AuCl{P(C6H4Me-2)3}], [{(Ph3P)Au}3O][BF4] and [{(2-MeC6H4)3PAu}3O][BF4] have been studied and the distribution of the products [Ru6(CO)17B{Au(PR3)}], [Ru6H(CO)16B{Au(PR3)}2] and [Ru6(CO)16B{Au(PR3)}3] as a function of R (Ph or 2-MeC6H4) and of the starting cluster has been examined. The trigold derivatives are best prepared by treating the octahedral anion 1 with [{(Ph3P)Au}3O]+. Single-crystal X-ray crystallography has confirmed that each of the gold(I) phosphine derivatives has an octahedral Ru6B core.