Platinum−Rhodium Carbonyl Clusters: New Structures and New Types of Dynamical Activity

The reaction of Rh4(CO)12 with Pt(PBut3)2 in CH2Cl2 at room temperature yielded three new complexes:  Rh4(CO)4(μ-CO)4(μ4-CO)(PBut3)2[Pt(PBut3)], 10, Rh2(CO)8[Pt(PBut3)]2[Pt(CO)], 11, and Rh2(CO)8[Pt(PBut3)]3, 12. The reaction
of Rh4(CO)12 with an excess of Pt(PBut3)2 in hexane at 68 °C yielded the new hexarhodium−tetraplatinum compound,
Rh6(CO)16[Pt(PBut3)]4, 13, in a low yield. All four compounds were characterized by 31P NMR and single-crystal
X-ray diffraction analyses. Compound 10 contains an unsymmetrical quadruply bridging carbonyl ligand in the fold
of a butterfly tetrahedral cluster of four rhodium atoms with a Pt(PBut3) group bridging the hinge of the butterfly
tetrahedron. Compound 11 contains an unsaturated trigonal bipyramidal Rh2Pt3 cluster. Compound 12 is similar to
11 except the trigonal bipyramidal Rh2Pt3 cluster opened by cleavage of one Pt−Rh bond due to steric interactions
produced by the replacement of one of the carbonyl ligands in 11 with a tri-tert-butylphosphine ligand. Compound
12 undergoes facile dynamical rearrangements of the metal atoms in the cluster which average the three inequivalent
phosphine ligands on the platinum atoms. Compound 13 contains an octahedral cluster of six rhodium atoms with
four Pt(PBut3) groups bridging edges of that octahedron.

室温下，十二羰基四铑（Rh4(CO)12）与双(三叔丁基膦)合铂（Pt(PBut3)2）在二氯甲烷（CH2Cl2）中发生反应，生成三种新型配合物：10号配合物Rh4(CO)4(μ-CO)4(μ4-CO)(PBut3)2[Pt(PBut3)]、11号配合物Rh2(CO)8[Pt(PBut3)]2[Pt(CO)]以及12号配合物Rh2(CO)8[Pt(PBut3)]3。
当在68℃下，十二羰基四铑与过量的双(三叔丁基膦)合铂在正己烷中反应时，以较低产率得到新型六铑-四铂化合物13号配合物Rh6(CO)16[Pt(PBut3)]4。
上述四种配合物均通过磷-31核磁共振（31P NMR）与单晶X射线衍射分析完成了结构表征。
10号配合物的结构中，四个铑原子构成蝶形四面体金属原子簇，其褶皱处存在一个非对称的四桥联羰基配体，且Pt(PBut3)基团桥连该蝶形四面体的铰链位点。
11号配合物含有一个不饱和三角双锥型Rh2Pt3金属原子簇。
12号配合物与11号结构相似，但由于11号配合物中一个羰基配体被三叔丁基膦配体取代所产生的空间位阻效应，导致其Rh2Pt3三角双锥原子簇发生了一根Pt-Rh键的断裂，进而发生开环。
12号配合物的金属原子可发生快速动态重排，使铂原子上的三种不等价膦配体实现平均化。
13号配合物含有六个铑原子构成的八面体金属原子簇，四个Pt(PBut3)基团分别桥连该八面体的四条棱边。