Hancock Robert D, Reibenspies Joseph H, Maumela Hulisani
Department of Chemistry, University of North Carolina at Wilmington, Wilmington, North Carolina 28403, USA.
Inorg Chem. 2004 May 3;43(9):2981-7. doi: 10.1021/ic030277a.
The synthesis and structures of Pb(DOTAM)2.4.5H2O (1) and Hg(DOTAM)2.0.5CH3OH.1.5H2O (2) are reported, where DOTAM is 1,4,7,10-tetrakis(carbamoylmethyl)-1,4,7,10-tetraazacyclododecane. Compound 1 is triclinic, space group P, a = 12.767(3) A, b = 13.528(2) A, c = 18.385(3) A, alpha = 101.45(2) degrees, beta = 93.32(2) degrees, gamma = 90.53(2) degrees, Z = 4, R = 0.0500. Compound 2 is monoclinic, space group Cc, a = 12.767(3) A, b = 13.528(2) A, c = 18.385(3) A, beta = 101.91(2) degrees, Z = 4, R = 0.0381. The Pb(II) ion in 1 has an average Pb-N = 2.63 A to four N-donors from the macrocyclic ring, and four O-donors (average Pb-O = 2.77 A) from the amide pendant donors of the macrocycle, with a water molecule placed with Pb-O = 3.52 A above the proposed site of the lone pair (Lp) on Pb. The Hg(II) in 2 appears to be only six-coordinate, with four Hg-N bond lengths averaging 2.44 A, and two Hg-O from pendant amide donors at 2.41 A. The other two amide donors appear to be noncoordinating, with Hg-O distances of 2.74 and 2.82 A. A water situated 3.52 A above the proposed site of the lone pair on Pb(II) in 1 is oriented in such a way that it might be thought to be forming a Pb-Lp.H-O-H hydrogen bond. It is concluded that that this is not an H-bond, but that the presence of the lone pair allows a closer approach of the hydrogens to Pb than would be true otherwise. The structural analogy in the VSEPR sense between Pb(II), which has the 5d(10)6s(2) outer electron structure, and the Hg(II) ion, which has the 5d10 structure, is examined. The tendency of Hg(II) toward linear coordination, with two short Hg-L bonds (L = ligand) at 180 degrees to each other, and other donor groups at roughly 90 degrees to this and at much longer bond distances, is paralleled by Pb(II). One of the short Hg-L bonds is replaced in the Pb(II) structures by the lone pair (Lp), which is opposite the short Pb-L bond, or in some cases 2-4 shorter Pb-L bonds.
报道了Pb(DOTAM)₂·4.5H₂O (1)和Hg(DOTAM)₂·0.5CH₃OH·1.5H₂O (2)的合成及结构，其中DOTAM为1,4,7,10 - 四(氨甲酰甲基)-1,4,7,10 - 四氮杂环十二烷。化合物1为三斜晶系，空间群P，a = 12.767(3) Å，b = 13.528(2) Å，c = 18.385(3) Å，α = 101.45(2)°，β = 93.32(2)°，γ = 90.53(2)°，Z = 4，R = 0.0500。化合物2为单斜晶系，空间群Cc，a = 12.767(3) Å，b = 13.528(2) Å，c = 18.385(3) Å，β = 101.91(2)°，Z = 4，R = 0.0381。1中的Pb(II)离子与大环环上的四个氮供体的平均Pb - N = 2.63 Å，以及来自大环酰胺侧链供体的四个氧供体(平均Pb - O = 2.77 Å)配位，一个水分子位于Pb上孤对电子(Lp)提议位置上方，Pb - O = 3.52 Å。2中的Hg(II)似乎仅为六配位，四个Hg - N键长平均为2.44 Å，来自侧链酰胺供体的两个Hg - O键长为2.41 Å。另外两个酰胺供体似乎不配位，Hg - O距离为2.74和2.82 Å。1中位于Pb(II)上孤对电子提议位置上方3.52 Å处的一个水分子的取向方式，可能会被认为形成了一个Pb - Lp·H - O - H氢键。得出的结论是，这不是一个氢键，而是孤对电子的存在使得氢原子比其他情况更接近Pb。研究了具有5d(10)6s(2)外层电子结构的Pb(II)与具有5d10结构的Hg(II)离子在VSEPR意义上的结构相似性。Hg(II)倾向于线性配位，两个短的Hg - L键(L =配体)相互呈180°，其他供体基团与此大致呈90°且键长长得多，Pb(II)也有类似情况。在Pb(II)结构中，其中一个短的Hg - L键被孤对电子(Lp)取代，孤对电子与短的Pb - L键相对，或者在某些情况下被2 - 4个较短的Pb - L键取代。
