We report on the first unambiguous detection of the elusive [HSi ] anion in solutions of liquid ammonia by various Si and H NMR experiments including chemical exchange saturation transfer (CEST). The characteristic multiplicity patterns of both the Si and H resonances together with CEST and a partially reduced H, Si coupling constant indicate the presence of a highly dynamic Si entity and a Si-H moiety with slow proton hopping. Theoretical calculations corroborate both reorganization of Si on the picosecond timescale via low vibrational modes and proton hopping. In addition, in a single-crystal X-ray study of (K(DB[18]crown-6))(K([2.2.2]crypt)) [HSi ]⋅8.5 NH , the H atom was unequivocally localized at one vertex of the basal square of the monocapped square-antiprismatic cluster. Thus experimental studies and theoretical considerations provide unprecedented insight into both the structure and the dynamic behavior of these cluster anions, which hitherto had been considered to be rigid.

We report the first solvate structure of the silicide anion Si 4 4-, which provides circumstantial evidence of the stability of the highly charged anion in liquid ammonia solutions. The solvate Rb 1.2 K 2.8 Si 4 ·7NH 3 crystallized from a mixture of the ternary compound K 6 Rb 6 Si 17 with the transition metal complex [(C 6 H 5 ) 3 P] 2 -Ni(CO) 2 [bis(triphenylphosphine)dicarbonylnickel] in the presence of the chelating agents 18-crown-6 (1,4,7,10,13,16-hexaoxacycloocta-

The existence of [μ‐HSi4]3− in liquid ammonia solutions is confirmed by 1H and 29Si NMR experiments. Both NMR and quantum chemical calculations reveal that the H atom bridges two Si atoms of the [Si4]4− cluster, contrary to the expectation that it is located at one vertex Si of the tetrahedron. The calculations also indicate that in the formation of [μ‐HSi4]3−, protonation is driven by a high charge density and an increase of electron delocalization compared to [Si4]4−. Additionally, [Si5]2− was detected for the first time and characterized by NMR. Calculations show that it is resistant to protonation, owing to a strong charge delocalization, which is significantly reduced upon protonation. Thus, our methods reveal three silicides in liquid ammonia: unprotonated [Si5]2−, terminally protonated [HSi9]3−, and bridge‐protonated [μ‐HSi4]3−. The protonation trend can be roughly predicted by the difference in charge delocalization between the parent compound and the product, which can be finely tuned by the presence of counter ions in solution.

The new carbonyl nickelate salt [A([18]crown‐6)]2[Ni(CO)3]·8NH3 (A = K, Rb) serendipitously crystallized from a solution of (PPh3)2Ni(CO)2, [18]crown‐6, [2.2.2]cryptand, and K6Rb6Ge17 in liquid ammonia. The [Ni(CO)3]2– anion represents the first tricarbonyl compound of nickel characterized by X‐ray diffraction studies and completes the row of known carbonyl metalates. The planar anion displays approximately D3h symmetry. The calculated electron localization function (ELF) of the complex shows plane basins above and below the molecular plane and the twofold negative charge is spread over the Ni(CO)3 entity.

Background:Intramembranous bone formation is essential in uncemented joint replacement to provide a mechanical anchorage of the implant. Since the discovery of bone morphogenic proteins (BMPs) by Urist in 1965, many studies have been conducted to show the influence of growth factors on implant ingrowth. In this study, the influence of bone morphogenetic protein-2 (rhBMP-2) and transforming growth factor β2 (TGF-β2) on implant osseointegration was investigated.Materials and Methods:Thirty-two titanium cylinders were implanted into the femoral condyles of both hind legs of New Zealand White Rabbits. Four experimental groups were investigated: controls without coating, a macromolecular copolymer + covalently bound BMP-2, adsorbed BMP-2, and absorbed BMP-2+TGF-β2. All samples were analyzed by ex vivo high-resolution micro-computed-tomography after 28 days of healing. Bone volume per total volume (BV/TV) was recorded around each implant. Afterward, all samples were biomechanically tested in a pull-out setup.Results:The highest BV/TV ratio was seen in the BMP-2 group, followed by the BMP-2+TGF-β2 group in high-resolution micro-computed-tomography. These groups were significantly different compared to the control group (P < 0.05). Copolymer+BMP-2 showed no significant difference in comparison to controls. In the pull-out setup, all groups showed higher fixation strength compared to the control group; these differences were not significant.Conclusions:No differences between BMP-2 alone and a combination of BMP-2+TGF-β2 could be seen in the present study. However, the results of this study confirm the results of other studies that a coating with growth factors is able to enhance bone implant ingrowth. This may be of importance in defect situations during revision surgery to support the implant ingrowth and implant anchorage.