Exploring the Versatility of the Amidation of Aryl Acid Fluorides using the Germylamines R3 GeNMe2.

The formation of amide bonds is an important process since this linkage is an essential component in proteins, pharmaceuticals, and other medicinally and biologically significant molecules. Recently, it was demonstrated that germylamines R3 GeNR'2 were useful reagents for the conversion of acid fluorides to amides. This transformation occurs readily at room temperature and has a low activation energy. In the present study, the versatility of this amidation reaction with aryl acid fluorides is investigated. A series of thirteen acid fluorides with various substituents on the aromatic ring were reacted with the germylamine Ph3 GeNMe2 and twelve of these were converted to the corresponding amides in high yields, the exception being 1,4-benzenedicarbonyl difluoride. The germylamines Bun 3 GeNMe2 and Pri 3 GeNMe2 also could be used for this interconversion, and both of these species successfully converted 1,4-benzenedicarbonyl difluoride to the corresponding amide. In addition, the crystal structure of Ph3 GeNMe2 is reported. This represents one of only three crystallographically characterized germylamines. The synthesis and 19 F NMR characterization of three fluorogermanes R3 GeF (R=Bun , Pri , and Mes) are also reported herein.

Direct amidation of acid fluorides using germanium amides.

Amide functional groups are an essential linkage that are found in peptides, proteins, and pharmaceuticals and new methods are constantly being sought for their formation. Here, a new method for their preparation is presented where germanium amides Ph3GeNR2 convert acid fluorides directly to amides. These germanium amides serve to abstract the fluorine atom of the acid fluoride and transfer their amide group -NR2 to the carbonyl carbon, and so function as amidation reagents.

Transition metal-free hydrodefluorination of acid fluorides and organofluorines by Ph3GeH promoted by catalytic [Ph3C][B(C6F5)4].

It has been shown that the germane Ph3GeH converts aryl and aliphatic acid fluorides directly to their corresponding aldehydes without over-reduction via the conversion of Ph3GeH to the germylium cation [Ph3Ge]+ by a catalytic amount of the tritylium salt [Ph3C][B(C6F5)4]. Here, no transition metal catalyst is required and there is no decarbonylation of the acid fluoride, which are advantages over existing methods. The fluorine atoms can also be abstracted from organofluorine compounds using this method.

A luminescent and dichroic hexagermane.

The hexagermane Pr(i)3Ge(GePh2)4GePr(i)3 has been synthesized and is not only the first such linear oligogermane to be structurally characterized but also is the first such compound to exhibit fluorescence and dichroic properties when observed under different orientations of plane polarized visible light.

A divalent germanium complex of calix[5]arene.

The reaction of the germylene Ge[N(SiMe(3))(2)](2) with calix[5]arene yields the first example of a group 14 calix[5]arene complex. The crystal structure of this material has been obtained and contains two calix[5]arene macrocycles held together by a Ge(2)O(2) rhombus.

Formation and structures of germanium(II) Aryloxo/oxo clusters.

The reaction of Ge[N(SiMe(3))(2)](2) with a phenol lacking a substituent in one ortho position results in the formation of polynuclear clusters having terminal aryloxide ligands and bridging O atoms. Structures of this type have not been observed for germanium(II) aryloxides before, and the source of the bridging O atoms in these clusters was determined to be the phenol reactant.

Syntheses, structures and properties of linear and branched oligogermanes.

This Perspective surveys recent developments in the synthesis and characterization of discrete oligogermanes. The use of the hydrogermolysis reaction, combined with a protection/deprotection strategy for a Ge-H moiety, has resulted in the synthesis of a variety of oligogermanes where the number of catenated atoms and the identity of the organic substituents can be readily controlled. Relationships between the composition of these oligomers and their optical and electronic properties have also been established.

2,2,3,3,5,5,6,6-Octa-p-tolyl-1,4-dioxa-2,3,5,6-tetra-germacyclo-hexane dichloro-methane disolvate.

The title compound, C(56)H(56)Ge(4)O(2)·2CH(2)Cl(2) or Tol(8)Ge(4)O(2)·2CH(2)Cl(2) (Tol = p-CH(3)C(6)H(4)), was obtained serendipitously during the attempted synthesis of a branched oligogermane from Tol(3)GeNMe(2) and PhGeH(3). The mol-ecule contains an inversion center in the middle of the Ge(4)O(2) ring which is in a chair conformation. The Ge-Ge bond distance is 2.4418 (5) Šand the Ge-O bond distances are 1.790 (2) and 1.785 (2) Å. The torsion angles within the Ge(4)O(2) ring are -56.7 (1) and 56.1 (1)° for the Ge-Ge-O-Ge angles and -43.9 (1)° for the O-Ge-Ge-O angle.

Metal-dependent reactions of bulky metal(II) amides M[N(SiMe3)2]2 with 3,3'-disubstituted binaphthols (HO)2C20H10(SiR3)2-3,3': selective conversion of one equivalent -OH group to a silyl ether -OSiMe3.

The outcome of the reaction of the bulky metal(II) amides M[N(SiMe3)2]2. nTHF (M = Be, Zn, Ge, Sn, n = 0; M = Mg, Ca, n = 2) with (R)-3,3'-bis(trimethylsilyl)-1,1'-bi-2,2'-naphthol ((R)-1) or (S)-3,3'-bis(dimethylphenylsilyl)-1,1'-bi-2,2'-naphthol ((S)-9) depends on the identity of the metal and the nature of the 3,3'-substituents. When M = Be, Zn, or Ge, these amides serve as useful silylation agents that convert only one of the equivalent hydroxyl groups of the binaphthol (R)-1 to a trimethylsilyl ether, whereas the reactions of (R)-1 with the Mg, Ca, or Sn amides generate a polynuclear complex. The reaction pathway for these interconversions was qualitatively monitored using NMR ((1)H and (9)Be) spectroscopy. Treatment of Ge[N(SiMe3)2] 2 with (S)-9 yields both a silyl ether and the chelated germanium(II) binaphthoxide (S)-[Ge{O2C20H10(SiMe2Ph)2-3,3'}{NH3}], which was structurally characterized.

Synthesis and structures of an unusual germanium(II) calix[4]arene complex and the first germanium(II) calix[8]arene complex and their reactivity with diiron nonacarbonyl.

The protonolysis reaction of the germanium(II) amide Ge[N(SiMe3)2]2 with calix[4]arene and calix[8]arene furnishes the two germanium(II) calixarene complexes {calix[4]}Ge2 and {calix[8]}Ge4, respectively, which have been crystallographically characterized. The calix[4]arene complex contains a Ge2O2 rhombus at the center of the molecule and is one of the only four germanium(II) calix[4]arenes that have been structurally characterized. The calix[8]arene species is the first reported germanium calix[8]arene complex, and it exhibits an overall bowl-shaped structure which contains two Ge2O2 fragments. The latter complex reacts with Fe2(CO)9 to yield an octairon compound, which has also been structurally characterized and contains four GeFe2 triangles arranged around the macrocyclic ring. The germanium(II) centers are oxidized to germanium(IV) in this process, with concomitant reduction of the neutral diiron species to Fe2(CO)(8)2- anions.

Synthesis of group 1 metal 2,6-diphenylphenoxide complexes [M(OC6H3Ph2-2,6)] (M = Li, Na, K, Rb, Cs) and structures of the solvent-free complexes [Rb(OC6H3Ph2-2,6)]x and [Cs(OC6H3Ph2-2,6)x: one-dimensional extended arrays of metal aryloxides.

Reaction of 2,6-diphenylphenol (HOC(6)H(3)Ph(2)-2,6) with (n)BuLi, NaH, KH, or Rb or Cs metal in benzene gives the solvent-free complexes [M(OAr)]x in excellent yield. The complex [Rb(OC(6)H(3)Ph(2)-2,6)](x)() exhibits a ladderlike structure in the solid state with triply bridging oxygen atoms and Rb-O distances of 2.743(3), 2.930(2), and 2.973(2) A. The Rb cations interact with the pi-electron cloud of the arene moieties, giving rise to a high Rb coordination number. The cesium-containing congener forms a layered, columnlike structure consisting of [Cs(2)(mu(2)-OAr)(2)] units, with nearly identical Cs-O distances of 2.945(2) and 2.947(2) A. The individual layers are held together solely by Cs-arene pi-interactions.