3.2.2. Cd(DETA)]2[Cd(DETA)2]0.5[Cd2(phen)2V12O41Ge8(OH)7(0.5H2O)]·7.5H2O (**2**)

The building block [H7Cd2(phen)2Ge8V12O48(0.5H2O)]<sup>5</sup><sup>−</sup> (Cd2Ge8V12) of **2** is almost identical to that of **1**, which is also a cadmium di-substituted Ge-V-O cluster; each substituted cadmium is also coordinated by a phen ligand. The main difference between the building blocks of compounds **2** and **1** is the number of the attached hydrogen atoms. There are only slight differences between the bond lengths and angles in compounds **2** and **1**. Bond valence sum calculations for Ge and V also indicate that Ge and V are in the +4 oxidation-state (Table S1).

Except for [Cd(phen)]2+ TMCs, there are two different TMCs which are [Cd(DETA)2] 2+ and [Cd(DETA)]2+ (Figure 2). The two TMCs are thoroughly different from those in **1**. Cadmium of [Cd(DETA)2] 2+ is bound to six nitrogens from two DETA ligands and a terminal oxygen from Cd2Ge8V12 with Cd-O and Cd-N distances of 2.46(1) and 2.38(3)–2.52(3) Å. [Cd(DETA)2] 2+, performing a similar role as Cd(4) TMC in compound **1**, serves as a TMC supported by Cd2Ge8V12. Cd of [Cd(DETA)]2+ is bonded to three nitrogens from a DETA with Cd-N distances of 2.26(1)–2.40(1) Å and two terminal oxygens from two {Ge2O7} from two adjoining Cd2Ge8V12 with Cd-O distances of 2.234(8)–2.240(8) Å, exhibiting a five-coordinated trigonal bipyramidal geometry. Cadmium of [Cd(DETA)]2+ serves as a bridge connecting the two Cd2Ge8V12. It should be noted that the two terminal oxygens was shared by the two [Cd(DETA)]2+, meaning that two terminal oxygens simultaneously connect two [Cd(DETA)]2+ to form a novel dimer [Cd2(DETA)2O2]. The role of [Cd2(DETA)2O2] in compound **2** is only partly similar to that of Cd(3) TMC in compound **1**. Two Cd(3) TMCs serving as a double bridge links two Cd2Ge8V12 to form a dimer in compound **1**, but [Cd2(DETA)2O2] in compound **2** acting as a single bridge connects two Cd2Ge8V12, and for its two components [Cd(DETA)]2+, is also joined by the two terminal oxygens to form a single building unit. Most importantly, [Cd2(DETA)2O2] in compound **2** connects Cd2Ge8V12 to form a novel 1-D extended chain structure. It should be noted that the neighboring Cd2Ge8V12 in the extended chain are oriented up and down, as shown in Figure 2. To our knowledge, compound **2** is the first extended structure based on a metal-substituted Ge-V-O cluster of aromatic organic ligands. Yang et. al. also reported a 1-D chain structure formed by similar substituted Ge-V-O clusters and coordination fragments [54]. However, Yang's cluster is based on aliphatic organic ligands but not aromatic organic ones. Secondly, Yang's coordination fragment is formed by en ligands rather than DETA ligands. Finally, the 1-D chain of Yang's compound is sinusoidal, but the one here is linear.

**Figure 2.** Ball-and-stick and wire representation of the building unit in the 1-D chain structure (**upper**) and the 1-D chain structure formed by Ge-V-O clusters and [Cd2(DETA)2O2] (**lower**).

3.2.3. [Cd(en)3]{[Cd(η2-en)2]3[Cd(η2-en)(η2-μ2-en)(η2-en)Cd][Ge6V15O48(H2O)]}·5.5H2O (**3**)

The asymmetric unit of compound **3** is composed of [Ge6V15O48(H2O)]12<sup>−</sup> (Ge6V15), [Cd(η2-en)2] 2+, [Cd(η2-en)(η1-en)]2+, [Cd(η2-en)3] 2+ and 5.5 water molecules. The framework of the cluster in compound **3** is similar to those of {As6V15O42} [16–18] and {Sb6V15O42} [19–24], with {Ge2O7} displacing {As2O5} and {Sb2O5} in {As6V15O42} and {Sb6V15O42}. Although the oxo-cluster in compound **3** is thoroughly different from those in compounds **1** and **2**, the bond lengths and angles in compound **3** are comparable to those in compounds **1** and **2**. Bond valence sum calculations for Ge and V reveal that oxidation states of both Ge and V are +4 (Table S1).

It should be noted that [Cd(η2-en)2] 2+ of the five has two different configurations (Figure 3a). Cd(3) of [Cd(η2-en)2] 2+, which exhibits a trans-octahedral geometry, is bonded to four nitrogens from two en and two oxygens from two Ge6V15 with Cd-N and Cd-O distances in the range of 2.26(1)–2.31(2) Å and 2.229(9)–2.242(9) Å. Therefore, the transoctahedral Cd(3) TMC joins two Ge6V15. Cd(5) of [Cd(η2-en)2] 2+ has a cis-octahedral geometry, which is coordinated by four nitrogens from two en with Cd-N distances of 2.33(2)–2.44(2) Å and two terminal oxygens in two cis-positions from two Ge6V15 with Cd-O distances of 2.228(7)–2.337(7) Å. Thus, the cis-octahedral Cd(5) TMC also connects two Ge6V15. Although Cd(3) and Cd(5) TMCs show different configurations, both their terminal oxygen atoms come from {Ge2O7} units of Ge6V15.

There are also two different [Cd(η2-en)(η2-μ2-en)]2+ TMCs in compound **3**. [Cd(6)(η2 en)(η2-μ2-en)]2+ presents a six-coordinated octahedral geometry with two nitrogens from a η2-en, one nitrogen from a η2-μ2-en and three oxygens from two Ge6V15 with Cd-N and Cd-O distances of 2.30(1)–2.37(1) Å and 2.235(8)–2.610(8) Å (the first one oxygen is from one Ge6V15 and the remaining two oxygens are from the other Ge6V15). Cd(6) also serves as a bridge linking two Ge6V15. It should be noted that two oxygens of Cd(6) octahedron from two Ge6V15 are shared by Cd(5) octahedron. [Cd(4)(η2-en)(η2-μ2-en)]2+ is only five-coordinated by two nitrogens from a η2-en, one nitrogen from a η2-μ2-en, and two oxygen atoms from two Ge6V15 with Cd-N and Cd-O distances of 2.29(1)–2.38(1) Å and 2.228(8)–2.238(8) Å, exhibiting a square pyramidal geometry. Cd(4) and Cd(6) are linked by η2-μ2-en to form a dumbbelllike dimer [Cd(η2-en)(η2-μ2-en)(η2-en)Cd]4+. All five TMCs serve as bridges linking their

neighboring clusters to form a novel 3-D framework structure. It should be noted that two terminal oxygens of Cd(1) octahedron are also shared by Cd(4) pyramid.

**Figure 3.** (**a**) Ball-and-stick and wire representation of the [Ge6V15O48] <sup>12</sup><sup>−</sup> cluster and five different types of TMCs in compound 3; (**b**) the framework structure viewed along [101]; (**c**) the framework structure viewed along [011]; (**d**) the framework structure viewed along [110].

With the exception of the four different TMCs, there is a dissociated TMC [Cd(η2 en)3] 2+. Cd(2) of [Cd(η2-en)3] 2+ is chelated by three en with Cd-N distances in the range of 2.36(1)–2.40(1)Å. [Cd(μ2-en)3] 2+ did not interact with any Ge6V15, which only serves as the space-filling agent and counterion.

In conclusion, there are five types of TMCs in compound **3**. To the best of our knowledge, compound **3** contains the largest number of TMC types.

The TMCs and the Ge6V15 clusters are fused to form a novel 3-D framework structure via Cd-O covalent interactions, and the framework exhibits channels running along the [101], [110] and [011] directions. As shown in Figure 3, the framework exhibits gold ingotshaped pores along the [101] direction. It should be noted that there are two kinds of such pores with different orientations. The framework exhibits dumbbell-shaped pores along the [110] direction; there are also two kinds of such pores with different orientations. The framework exhibits cross-shaped pores along the [011] direction; the pores here exhibit two orientations as well. The three kinds of channels intersect one another. Yang et al. also reported a 3-D structure formed by similar Ge-V-O clusters and coordination fragments [6]. However, there are several significant differences between our compound and Yang's compound. Firstly, and most importantly, the Ge-V-O cluster of Yang's compound is Ge4V16, but the corresponding cluster of our compound is Ge6V15. Secondly, Yang's compound is based on diethylenetriamine ligands but not en in our compound. Finally, Yang's compound did not exhibit various channels that were found in our compound.

#### *3.3. BVS Calculations to Determine the Locations of Hydrogen Atoms of Compounds 1–3*

Single crystal X-ray diffraction cannot exactly determine the positions of the hydrogen atoms from the Fourier maps. For further verifying the correctness of the formula of the three compounds, BVS calculations [75] were carried out to determine the positions of the hydrogen atoms for all the three compounds. As for compound **1**, the oxygens can be classified into eight groups: (1) seven Ge-Ot terminal oxygens; (2) one Ge-Ot-Cd μ2-oxygen; (3) eleven V-Ot terminal oxygens; (4) one V-Ot-Cd μ2-oxygen; (5) eight μ3-oxygens located between two vanadiums and one germanium; (6) eight μ3-oxygens located between three vanadiums; (7) eight μ3-oxygens between a vanadium, cadmium and germanium; and (8) four μ2-oxygens between two germaniums. All the atoms of the eight groups except groups (1) and (2) can be assigned to the −2 valence state, with BVS calculation results in the range of 1.56–2.16. With respect to the group (1) oxygens, all seven oxygens exist in the -1 valence state, with BVS results ranging from 1.01–1.04, indicating that all seven terminal Ge-Ot oxygens are mono-protonated. The BVS value of the group (2) oxygen is 1.38, meaning that although this oxygen is coordinated by both one cadmium and one germanium, it exists in the −1 valence state. Therefore, the cluster in compound **1** is attached by eight hydrogens, and all eight hydrogens are attached on the eight Ge-O terminal oxygens.

As for compound **2**, the oxygens can also be divided into eight groups. Seven of the eight groups are similar to the corresponding groups in compound 1. Only the eighth one is not found in compound **1**: it is a μ3-oxygen between two cadmiums and a germanium. This μ3-oxygen is a terminal oxygen from a {Ge2O7} simultaneously interacting with two cadmiums and one germanium. Therefore, its valence state is not −1 but −2, with the BVS result of 1.85. In conclusion, only six of the eight terminal Ge-Ot oxygens are monoprotonated. Thus, there is still one hydrogen atom whose position cannot be determined. We think this hydrogen should be disorderedly distributed on the surface of the cluster.

There are also seven groups of oxygens in compound **3**. However, only five of the seven have corresponding groups in compound **1**. The five groups are: (1) V-O**<sup>t</sup>** terminal oxygens; (2) μ**3**-oxygens between two vanadiums and one germanium; (3) μ**3**-oxygens between three vanadiums; (4) μ**2**-oxygens between two germaniums; and (5) μ**2**-oxygen between one terminal vanadium and one cadmium. The remaining two groups are: (6) μ**3** oxygen between two cadmiums and one germanium, which has the corresponding group in compound **2**; and (7) μ**2**-oxygen between one cadmium and one germanium, which is only observed in compound **3**. Compound **3** did not contain Ge-O**<sup>t</sup>** terminal oxygens, and all the Ge-O**<sup>t</sup>** terminal oxygens simultaneously interact with one or two cadmiums and finally form the group (6) and (7) oxygens. For the contributions of the cadmiums of group (6) and (7) oxygens, the BVS values of these oxygens are in the range of 1.56–2.01, indicating that there are no hydrogens attached on the cluster in compound **3**.
