Capped square antiprisms

Bi-0 2.54(l)-2.68(2) A], In contrast, the nine-coordinate capped square antiprism geometry for bismuth in [Bi(N03)3(H20)3] (18-crown-6) does not involve the expected multidentate ether coordination to bismuth, but rather a hydrogen-bonded interaction of the crown ether with the hydrated bismuth center chelated by bidentate nitrate groups [Bi-0 2.38(2)—2.56(2) A] 32, implying that the hexado-... 

Capped Square Antiprism. Ge94, Sn94-, and Pb94- have the (9)(2) + 4 = 22 =... 

Figure 98 (a) Projection of the potential energy surface for (Mfunidentate) on to the B— f plane (in degrees). The five faint contour lines are for successive 0.02 increments in X above the minima, and the five heavy contour lines are for 0.2 increments above the minima, at T. The location of the tricapped trigonal prisms (T) and the capped square antiprism (C) are indicated, (b) As in (a), but with truncation at X = 0.1... 

The central metal ion has nine coordination sites. It is attached to the three nitrogen atoms and to five carboxylate moieties (oxygen atoms). A single water molecule is able to coordinate at the vacant ninth site resulting in a strong enhancement of the water proton relaxation rate. The chelate can be described as a distorted capped square antiprism according to X-ray analysis [6]. 

Nine-coordination is most commonly achieved by the tricapped trigonal prism, and is found in ReH and M(H20) + (M = lanthanide). Rarer is the capped square antiprism. 

Tricapped trigonal prism Capped square antiprism [NH4]3[ThF7], LiUFj, Th(tta)4 topo Li3ThF7, Th(tfa)4 -2H20, [C(NH2)3]5[Th(C03)3F3]... 

Rh9P(CO)2il 2- 130 16 (c) Capped square antiprism iso-bond valence with B9H13... 

A second form of Nd2(malonate)3 6H2O complex has been reported [169]. In this complex neodymium is nine-coordinate surrounded by six carboxylate, and three water oxygen atoms and the geometry is intermediate between the distorted capped square antiprism and the distorted tricapped trigonal prism. 

The C4V type stereoisomer exists for coordination polyhedra [158] of M(C204)(HC204) 3H2O, where M = Dy, Yb, Y or Er and there seems to be no example of Ci stereoisomer of a capped square antiprism at present. 

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