The heteronuclear cluster chemistry of the Group IB metals XIV. The influence of the P(CH 2Ph) 3 ligand on the metal framework structures adopted by mixed-metal clusters containing M{P(CH 2Ph) 3} (M  Cu or Ag) fragments. Crystal structures of [Cu 2Ru 4(μ 3-H) 2(CO) 12{μ-P(CH 2Ph) 2-(η 2-CH 2Ph)}] and [Cu 2Ru 4(μ 3-H) 2(CO) 12{P(CH 2Ph) 3} 2

Abstract

Treatment of a dichloromethane solution of the salt [N(PPh 3) 2] 2[Ru 4(μ-H) 2(CO) 12] with two equivalents of the complex [M(NCMe) 4]PF 6 (M  Cu or Ag) at −30°C, followed by the addition of two equivalents of P(CH 2Ph) 3, affords the novel mixed-metal cluster compound [Cu 2Ru 4(μ 3-H) 2(CO) 12{μ-P(CH 2Ph) 2(η 2-CH 2Ph)}] (77% yield) when M  Cu, whereas the expected product, [Ag 2Ru 4(μ 3-H) 2(CO) 12{P(CH 2Ph) 3} 2] (37% yield), is obtained for M  Ag. When an acetone solution of [N(PPh 3) 2] 2[Ru 4(μ-H) 2(CO) 12] is treated with a dichloromethane solution containing two equivalents of the compound [CuCl{P(CH 2Ph) 3}], in the presence of TlPF 6, a mixture of [Cu 2Ru 4(μ 3-H) 2(CO) 12{μ-P(CH 2Ph) 2(η 2-CH 2Ph)}] (44% yield) and [Cu 2Ru 4(μ 3-H) 2(CO) 12{P(CH 2Ph) 3} 2] (12% yield) is produced. Single-crystal X-ray diffraction studies were performed on [Cu 2Ru 4(μ 3-H) 2(CO) 12 {μ-P(CH 2Ph) 2(η 2-CH 2Ph)}] and [Cu 2Ru 4(μ 3-H) 2(CO) 12{P(CH 2Ph) 3} 2]. The former cluster exhibits a capped trigonal bipyramidal metal framework structure (CuCu 2.532(2), CuRu 2.585(2)–2.813(1), RuRu 2.790(1)–2.981(1) Å) and the single P(CH 2Ph) 3 group adopts a novel bidentate bonding mode by bridging the two adjacent copper atoms via bonds from its phosphorus atom (CuP 2.199(2) Å) and an η 2-CH 2Ph ring (CuC 2.146(10) and 2.339(12) Å). In marked contrast, [Cu 2Ru 4(μ 3-H) 2(CO) 12{P(CH 2Ph) 3} 2] adopts an unusual metal core structure, which consists of a Ru 4 tetrahedron with one edge bridged by a Cu{P(CH 2Ph) 3} unit and a non-adjacent face capped by the second Cu{P(CH 2Ph) 3} group (CuRu 2.589(4)–2.724(4), RuRu 2.760(3)–2.984(4) Å). Infrared and NMR spectroscopic data show that [Ag 2Ru 4(μ 3-H) 2(CO) 12{P(CH 2Ph) 3} 2] exhibits a capped trigonal bipyramidal skeletal geometry, with the silver atoms in close contact. Thus, although the P(CH 2Ph) 3 ligand is evidently too bulky to allow two adjacent Cu{P(CH 2Ph) 3} units to be accommodated in the metal skeleton of [Cu 2Ru 4(μ 3-H) 2(CO) 12{P(CH 2Ph) 3} 2], the greater size of the silver atom relative to copper means that the analogous silver-containing species can adopt the metal framework structure which previous work suggests is preferred by clusters of this type. Variable-temperature 31P-{ 1H} and 1H NMR spectroscopic studies demonstrate that all three of the new heteronuclear cluster compounds undergo a number of interesting dynamic processes in solution.