Germanium complexes coordination geometry

As in the spirocyclic five-coordinated germanium complexes discussed above, the geometry about the tin atom in some of the mono- and bi-cyclic stannates, listed in... 

The coordination polyhedron geometry of tin-, antimony- and germanium-capped iron(II) dioximates was analyzed in the previous section. As mentioned above, the boron-capped clathrochelates have a distorted TP structure and positive QS values, whereas tin-, antimony- and germanium-capped clathrochelates have distorted TAP geometry, preferably for complexes with electronic configuration d , and a negative QS sign. 

The ligand (49) reacts with two equivalents of GeCl2 diox to give the linear (50), with two-coordinate germanium centers (Ge-N 1.856 A, N-Ge-N 80.93°) (Scheme 17). Tin, in the corresponding reaction, forms the complex (51), which has a geometry more closely related to a cubane structure (Sn-N 2.247 A, N-Sn-N 110.8°V ... 

Triphenyl phosphine coordinates germanium(II) chloride or iodide " to form 1 1 complexes with tbp geometry at the metal and bond lengths Ge—P 2.511 A and 2.507 A, respectively. These complexes are in some ways analogous to ylides (R 3P = CR ) and have some properties in common with these lighter homologues. 

X = Ln, Tl, M = Sn, Pb show that the complexes comprise octahedral [FgM] ions and isolated fluoride ions rather than any seven-coordinate metals. Other tin fluorides have more complex structures, such as the dimeric [Su2F4] ion present in [NH4]4[Sn2F4](N03)2" and in mixed halide complexes, such as Cs2SngBr3Fii which has in the crystal three distinct tin sites, each of which has close contacts with the fluoride ions only." The electronic effects of adduct formation of halides of germanium(IV) and tin(IV) have been reviewed with particular reference to the geometry of the complexes formed. 

Baines and coworkers later illustrated that an NHC-stabilized GeCl2 complex could be converted to its iodide analog by treatment with trimethylsilyl iodide. Upon addition of excess carbene to this Gel2 adduct, the first NHC-stabilized germanium dication was isolated. The iodine atoms are displaced as anions, while the coordination sphere around the germanium dication is occupied by three NHC ligands in a pyramidal geometry [209]. 

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