Catalano Jaclyn, Murphy Anna, Yao Yao, Yap Glenn P A, Zumbulyadis Nicholas, Centeno Silvia A, Dybowski Cecil
Department of Scientific Research, The Metropolitan Museum of Art, New York, NY 10028, USA.
Dalton Trans. 2015 Feb 7;44(5):2340-7. doi: 10.1039/c4dt03075c.
Despite their versatility, only a few single-crystal X-ray structures of lead carboxylates exist, due to difficulties with solubility. In particular, the structures of long-chain metal carboxylates have not been reported. The lone electron pair in Pb(ii) can be stereochemically active or inactive, leading to two types of coordination geometries commonly referred to as hemidirected and holodirected structures, respectively. We report (13)C and (207)Pb solid-state NMR and infrared spectra for a series of lead carboxylates, ranging from lead hexanoate (C6) to lead hexadecanoate (C18). The lead carboxylates based on consistent NMR parameters can be divided in two groups, shorter-chain (C6, C7, and C8) and longer-chain (C9, C10, C11, C12, C14, C16, and C18) carboxylates. This dichotomy suggests two modes of packing in these solids, one for the short-chain lead carboxylates and one for long-chain lead carboxylates. The consistency of the (13)C and (207)Pb NMR parameters, as well as the IR data, in each group suggests that each motif represents a structure characteristic of each subgroup. We also report the single-crystal X-ray diffraction structure of lead nonanoate (C9), the first single-crystal structure to have been reported for the longer-chain subgroup. Taken together the evidence suggests that the coordination geometry of C6-C8 lead carboxylates is hemidirected, and that of C9-C14, C16 and C18 lead carboxylates is holodirected.
尽管羧酸盐铅具有多种用途，但由于溶解度问题，只有少数羧酸盐铅的单晶X射线结构存在。特别是，长链金属羧酸盐的结构尚未见报道。Pb(ii)中的孤电子对可以是立体化学活性的或非活性的，分别导致两种通常称为半定向和全定向结构的配位几何构型。我们报道了一系列羧酸盐铅的(13)C和(207)Pb固态核磁共振和红外光谱，范围从己酸铅(C6)到十六酸铅(C18)。基于一致的核磁共振参数，羧酸盐铅可分为两组，短链(C6、C7和C8)羧酸盐和长链(C9、C10、C11、C12、C14、C16和C18)羧酸盐。这种二分法表明这些固体中有两种堆积模式，一种是短链羧酸盐铅的，一种是长链羧酸盐铅的。每组中(13)C和(207)Pb核磁共振参数以及红外数据的一致性表明，每个基序代表每个亚组的结构特征。我们还报道了壬酸铅(C9)的单晶X射线衍射结构，这是长链亚组中首次报道的单晶结构。综合这些证据表明，C6-C8羧酸盐铅的配位几何构型是半定向的，而C9-C14、C16和C18羧酸盐铅的配位几何构型是全定向的。
