Nonosized (μ12-Pt)Pd164-xPtx(CO)72(PPh3)20 (x≈7) containing Pt-centered four-shell 165-atom Pd-Pt core with unprecedented intershell bridging carbonyl ligands:: Comparative analysis of icosahedral shell-growth patterns with geometrically related Pd145(CO)x(PEt3)30 (x≈60) containing capped three-shell Pd145 core
Nonosized (μ12-Pt)Pd164-xPtx(CO)72(PPh3)20 (x≈7) containing Pt-centered four-shell 165-atom Pd-Pt core with unprecedented intershell bridging carbonyl ligands:: Comparative analysis of icosahedral shell-growth patterns with geometrically related Pd145(CO)x(PEt3)30 (x≈60) containing capped three-shell Pd145 core
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DOI：
10.1021/ja073945q
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发表时间：
2007-09-19
影响因子：
15
通讯作者：
Dahl, Lawrence F.
中科院分区：
文献类型：
--
作者：
Mednikov, Evgueni G.;Jewell, Matthew C.;Dahl, Lawrence F.
本文介绍了以pt为中心的四壳层165个原子的Pd-Pt团簇（(mu 12)- pt）Pd164-xPt(CO)(72)(PPh3)（20) (x近似于7),1）的制备和晶体学/微分析/磁/光谱表征，取代了几何相关的三壳层二十面体Pd-145团簇，Pd-145(CO)(chi-)(PEt3)(30) (x近似于60),2，成为最大的晶体学确定的具有直接金属-金属键的离散过渡金属团簇。它们的壳生长模式的详细比较产生了关于完全意想不到的结构差异和相似性的重要立体化学意义，并为产生多壳金属团簇的可能合成方法提供了新的见解。由Pd-10(CO)(12)(PPh3)(6)与Pt(CO)(2)(PPh3)(2)反应，以小收率（< 10%）可重复性地制备1。通过低温（100 K） CCD x射线衍射研究，确定了其165个原子的金属核几何结构和20个PPh3和72个CO配体。确定的晶体结构主要归因于1具有立方T-h （2/m3）位对称，这是非晶体伪二十面体/(n) （2/m35）对称的最高晶体亚群。1的“完整”四壳层Pd-Pt解剖结构包括：(a)壳层1的中心（(mu 12)-Pt）原子被12原子二十面体PtxPd12-x笼包裹，x = 1.2(3)；(b)壳层2具有42个原子的二十面体Pt-chi Pd42-x笼，x = 3.5(5)；(c)壳层3为反mackay 60原子半正方十二面体PtxPd60-x笼，x = 2.2(6)；(d)壳层4具有50个原子(2)的五面十二面体Pd-50笼。由x射线数据的最小二乘（Pt-x/Pd1-x）占位分析得到的结晶学估计的Pt原子总数为83个（占位因子x = 1.00(3)），碰巧与x射线Pt/Pd微分析（WDS光谱仪）在3个1的晶体上发现的7.6个(7)一致。我们利用这种位点占用（PtxPd1-x）分析壳1-3源于微量分析结果；否则，假定的金属核组成将是（mu(12)-Pt）Pd-164。[或者，1的（mu(12)- pt）M-164核心几何可以被看作是一个伪-/(eta) pt中心的连续六壳体v，多面体体系，每个都具有径向等效的顶点原子：Pt@M-12（二十面体）@M30-（二十面体）@M-12（二十面体）@M-60（菱形十二面体）@M-30（二十面体）@M20-（五边形十二面体）]。I和2之间完全令人惊讶的结构差异是：(1)到目前为止，1只是可重复地分离为中心Pt原子而不是Pd原子的异质金属Pd-Pt簇；(2)与所有其他已知壳基结构的壳层生长过程相反，1中构成外层第4(2)五边形十二面体壳层的50个原子小于1中构成内第3壳层的60个原子；(3) 1中的PR3配体少了10个，需要更大的PPh3配体来保护pd - pt核的几何形状；(4) 72个CO配体由4壳层12个五边形内的6个桥接COS组成，并与壳层间金属原子配位。SQUID磁强计测量显示，单晶样品1在10-300 K的整个温度范围内具有抗磁性。
Presented herein are the preparation and crystallographic/microanalytical/magnetic/spectroscopic characterization of the Pt-centered four-shell 165-atom Pd-Pt cluster, ((mu 12)-Pt)Pd164-xPt(CO)(72)(PPh3)(20) (x approximate to 7), 1, that replaces the geometrically related capped three-shell icosahedral Pd-145 cluster, Pd-145(CO)(chi-)(PEt3)(30) (x approximate to 60), 2, as the largest crystallographically determined discrete transition metal cluster with direct metal-metal bonding. A detailed comparison of their shell-growth patterns gives rise to important stereochernical implications concerning completely unexpected structural dissimilarities as well as similarities and provides new insight concerning possible synthetic approaches for generation of multi-shell metal clusters. 1 was reproducibly prepared in small yields (< 10%) from the reaction of Pd-10(CO)(12)(PPh3)(6) with Pt(CO)(2)(PPh3)(2). Its 165-atom metal-core geometry and 20 PPh3 and 72 CO ligands were established from a low-temperature (100 K) CCD X-ray diffraction study. The well-determined crystal structure is attributed largely to 1 possessing cubic T-h (2/m3) site symmetry, which is the highest crystallographic subgroup of the noncrystallographic pseudo-icosahedral /(n) (2/m35) symmetry. The "full" four-shell Pd-Pt anatomy of 1 consists of: (a) shell 1 with the centered ((mu 12)-Pt) atom encapsulated by the 12-atom icosahedral PtxPd12-x cage, x = 1.2(3); (b) shell 2 with the 42-atom nu(2) icosahedral Pt-chi Pd42-x cage, x = 3.5(5); (c) shell 3 with the anti-Mackay 60-atom semi-regular rhombicosidodecahedral PtxPd60-x cage, x = 2.2(6); (d) shell 4 with the 50-atom nu(2) pentagonal dodecahedral Pd-50 cage. The total number of crystallographically estimated Pt atoms, 8 3, which was obtained from least-squares (Pt-x/Pd1-x)-occupancy analysis of the X-ray data that conclusively revealed the central atom to be pure Pt (occupancy factor, x = 1.00(3)), is fortuitously in agreement with that of 7.6(7) found from an X-ray Pt/Pd microanalysis (WDS spectrometer) on three crystals of 1. Our utilization of this site-occupancy (PtxPd1-x)-analysis for shells 1-3 originated from the microanalytical results; otherwise, the presumed metal-core composition would have been (mu(12)-Pt)Pd-164. [Alternatively, the (mu(12)-Pt)M-164 core-geometry of 1 may be viewed as a pseudo-/(eta) Pt-centered six-shell successive v, polyhedral system, each with radially equivalent vertex atoms: Pt@M-12(icosahedron)@M30-(icosidodecahedron)@M-12(icosahedron)@M-60(rhombicosidodecahedron)@M-30(icosidodecahedron)@M20- (pentagonal dodecahedron)].Completely surprising structural dissimilarities between I and 2 are: (1) to date 1 is only reproducibly isolated as a heterometallic Pd-Pt cluster with a central Pt instead of Pd atom; (2) the 50 atoms comprising the outer fourth nu(2) Pentagonal dodecahedral shell in 1 are less than the 60 atoms of the inner third shell in 1, in contradistinction to shell-by-shell growth processes in all other known shell-based structures; (3) the 10 fewer PR3 ligands in 1 necessitate larger bulky PPh3 ligands to protect thePd-Pt core-geometry; (4) the 72 CO ligands consist of six bridging COS within each of the 12 pentagons in shell 4 that are coordinated to intershell metal atoms. SQUID magnetometry measurements showed a single-crystal sample of 1 to be diamagnetic over the entire temperature range of 10-300 K.