The first example of a germanium(II) cyanide complex [GeCN(L)] (2) (L=aminotroponiminate (ATI)) has been synthesized through a novel and relatively benign route that involves the reaction of a digermylene oxide [(L)Ge-O-Ge(L)] (1) with trimethylsilylcyanide (TMSCN). Interestingly, compound 2 activates several aldehydes (RCHO) at room temperature and results in the corresponding cyanogermylated products [RC{OGe(L)}(CN)H] (R=H 3, iPr 4, tBu 5, CH(Ph)Me 6). Reaction of one of the cyanogermylated products (4) with TMSCN affords the cyanosilylated product [(iPr)C(OSiMe3 )(CN)H] (7) along with [GeCN(L)] quantitatively, and insinuates the possible utility of [GeCN(L)] as a catalyst for the cyanosilylation reactions of aldehydes with TMSCN. Accordingly, the quantitative formation of several cyanosilylated products [RC(OSiMe3 )(CN)H] (7-9) in the reaction between RCHO and TMSCN by using 1 mol % of [GeCN(L)] as a catalyst is also reported for the first time.

Fluorination of aminotroponiminate (ATI) ligand-stabilized germylene monochloride [(t-Bu)(2)ATI]GeCl (1) with CsF gave the aminotroponiminatogermylene monofluoride [(t-Bu)(2)ATI]GeF (2). Oxidative addition reaction of compound 2 with elemental sulfur and selenium led to isolation of the corresponding germathioacid fluoride [(t-Bu)(2)ATI]Ge(S)F (3) and germaselenoacid fluoride [(t-Bu)(2)ATI]Ge(Se)F (4), respectively. Similarly, reaction of aminotroponiminatogermylene monochloride [(i-Bu)(2)ATI]GeCl (9) with elemental sulfur and selenium gave the aminotroponiminatogermathioacid chloride [(i-Bu)(2)ATI]Ge(S)Cl (11) and aminotroponiminatogermaselenoacid chloride [(i-Bu)(2)ATI]Ge(Se)Cl (12), respectively. Compound 9 has been prepared through a multistep synthetic route starting from 2-(tosyloxy)tropone 5. All compounds (2-4 and 6-12) were characterized through the multinuclear NMR spectroscopy, and single-crystal X-ray diffraction studies were performed on compounds 2, 4, and 8-12. The germaselenoacid halide complexes 4 and 12 showed doublet (-142.37 ppm) and singlet (-213.13 ppm) resonances in their (77)Se NMR spectra, respectively. Germylene monohalide complexes 2 and 9 have a germanium center in distorted trigonal pyramidal geometry, whereas a distorted tetrahedral geometry is seen around the germanium center in germaacid halide complexes 4, 11, and 12. The length of the Ge═E bond in germathioacid chloride (11) and germaselenoacid halide (4 and 12) complexes is 2.065(1) and 2.194(av) Å, respectively. Theoretical studies (based on the DFT methods) on complexes 4, 11, and 12 reveal the nature of the Ge═E multiple bond in these germaacid halide complexes with computed Wiberg bond indices (WBI) being 1.480, 1.508, and 1.541, respectively.

The catalytic utility of a germylene cation 4 is reported. In the presence of compound 4, a variety of aldehydes and ketones can be hydroborylated using HBpin.

Use of a substituted digermylene oxide as a ligand has been demonstrated through the isolation of a series of group 11 metal(I) iodide complexes. Accordingly, the reactions of digermylene oxide [{(i-Bu)2ATIGe}2O] (ATI = aminotroponiminate) (1) with CuI under different conditions afforded [({(i-Bu)2ATIGe}2O)2(Cu4I4)] (2) with a Cu4I4 octahedral core, [({(i-Bu)2ATIGe}2O)2(Cu3I3)] (3) with a Cu3I3 core, and [{(i-Bu)2ATIGe}2O(Cu2I2)(C5H5N)2] (4) with a butterfly-type Cu2I2 core. The reactions of compound 1 with AgI and AuI produced [({(i-Bu)2ATIGe}2O)2(Ag4I4)] (5) with a Ag4I4 octahedral core and [{(i-Bu)2ATIGe}2O(Au2I2)] (6) with a Au2I2 core, respectively. The presence of metallophilic interactions in these compounds is shown through the single-crystal X-ray diffraction and atom-in-molecule (AIM) studies. Preliminary photophysical studies on compound 6 are also carried out.

A simple heating of aminotroponiminate (ATI) ligand stabilized germylene monochlorides [(R)2ATIGeCl] (R = t-Bu 1, i-Bu 2) with an excess of potassium hydroxide in toluene resulted in the first ATI ligand stabilized digermylene oxides [{(R)2ATIGe}2O] (R = t-Bu 3, i-Bu 4), respectively. Reaction of compound 3 with elemental sulfur and selenium gave the first germaacid anhydride complexes [{(t-Bu)2ATIGe(E)}2O] (E = S 5, Se 6) with (S)Ge-O-Ge(S) and (Se)Ge-O-Ge(Se) moieties, respectively. The digermylene oxide complexes 3 and 4 and germaacid anhydride complexes 5 and 6 were characterized by multinuclear NMR spectroscopy and single-crystal X-ray diffraction analysis. In its (77)Se NMR spectrum, compound 6 showed a resonance at -78.9 ppm. The Ge-O-Ge bond angles in compounds 5 and 6 are 178.66(2)° and 179.81(2)°, respectively. To understand further the bonding features, DFT calculations followed by MO, AIM, and NBO analysis were carried out on compounds 3, 5, and 6. The computed Wiberg bond indices of Ge-O bonds are slightly less than 0.5 in all the aforementioned compounds, and the same for the Ge═E bonds in compounds 5 and 6 are close to 1.4.

By means of a two-step synthetic route, aminotroponimine [(t-Bu)2ATI]H (3) with a tert-butyl substituent on the nitrogen atoms has been synthesized from 2-(tosyloxy)tropone. Lithiation of 3 with n-BuLi in THF afforded the lithium salt [(t-Bu)2ATI]Li·(THF)2 (4). Reaction of 4 with GeCl2·(1,4-dioxane) resulted in the germylene monochloride complex [(t-Bu)2ATI]GeCl (5). Treatment of 5 with the lithium derivative of ethynyl ferrocene [(C5H5)Fe(C5H4)CCH] (6) and phenyl acetylene (C6H5CCH) (7) gave the corresponding alkynyl germylene complexes [(t-Bu)2ATI]GeCC(C5H4)Fe(C5H5) (8) and [(t-Bu)2ATI]GeCCC6H5 (9), respectively. Compounds 3, 4, 5, 8, and 9 have been characterized by elemental analysis and various spectroscopic (multinuclear NMR, mass, and IR) techniques. Further confirmation came from the single-crystal X-ray structural studies on all these compounds. The structure of the alkynyl germylenes reveals the presence of a slightly bent Ge(II)−CC moiety [bond angle in 8 168.4(3)° and 9 170.8(2)°].

Although germanium analogues of ketones, carboxylic acids, acid halides, and amides are known, an example of a germaester complex is still missing. Therefore, the first examples of germathioesters [(R) 2 ATI]Ge(S)Ot-Bu (R = t-Bu 5 and R = i-Bu 6) and germaselenoesters [(R) 2 ATI]Ge(Se)Ot-Bu (R = t-Bu 7 and R = i-Bu 8) stabilized through aminotroponiminate (ATI) ligands are reported here. Aminotroponiminatogermylene alkoxides [(t-Bu) 2 ATI]GeOt-Bu (3) and [(i-Bu) 2 ATI]GeOt-Bu (4) serve as starting materials for the synthesis of the aforementioned ester complexes. Compounds 5−8 were characterized by multinuclear NMR spectroscopic and single-crystal X-ray diffraction studies in the liquid and solid state, respectively. 77 Se NMR spectra of compounds 7 and 8 showed a singlet resonance at −77.76 and −285.10 ppm, respectively. The germanium center in compounds 5−8 adopts a distorted tetrahedral geometry. The average GeS and GeSe bond lengths in germathioester (5 and 6) and germaselenoester (7 and 8) complexes are 2.078 and 2.219 Å, respectively.

The reaction of the pentaphenylborole [(PhC)BPh] (1) with sodium phosphaethynolate·1,4-dioxane (NaOCP(1,4-dioxane)) afforded the novel sodium salt of phosphaboraheterocycle 2. It comprises anionic fused tetracyclic P/B-heterocycles that arise from multiple bond activation between the borole backbone and [OCP]anion. Density functional theory calculations indicate that the [OCP] anion prefers the form of phosphaethynolate O-C≡P over phosphaketenide O═C═P to interact with two molecules of 1, along with various B-C, C-P, and C-C bond activations to form 2. The calculations were verified by experimental studies: (i) the reaction of 1 with NaOCP(1,4-dioxane) and a Lewis base such as the N-heterocyclic carbene I [:C{N(Ar)CH}] (Ar = 2,6-iPrCH) and amidinato amidosilylene [{PhC(NtBu)}(MeN)Si:] afforded the Lewis base-pentaphenylborole adducts [(PhC)B(Ph)(LB)] (LB = I (3), :Si(NMe){(NtBu)CPh} (4)), respectively; (ii) the reaction of 1 with the carbodiimide ArN═C═NAr afforded the seven-membered B/N heterocycle [B(Ph) (CPh)C(═NAr)N(Ar)] (5). Compounds 2-5 were fully characterized by NMR spectroscopy and X-ray crystallography.