The synthesis of the isomeric compounds 1,8-bis(diphenylphosphino)biphenylene (1) and 1,5-bis(diphenylphosphino)biphenylene (2) is reported. Compound 1 was used as bidentate ligand towards late transition metal chlorides giving rise to six complexes 1·MCl2 (M=Ni, Pd, Pt) and 1·MCl (M=Cu, Ag, Au), which have been fully characterized. The electronic bond characteristics of the polar-covalent M–P and M–Cl bonds of 1·MCl2 (M=Ni, Pd, Pt) and 1·MCl (M=Cu, Ag, Au) were determined by a computational real-space bonding indicator (RSBI) analyses including the atoms-in-molecules, electron localizability indicator, and non-covalent interactions (NCI) index methods based on the molecular structures established by single crystal X-ray diffraction. Consistent with the electronegativity differences, the polarity of the M–Cl bonds is found to be systematically higher compared to the M–P bonds. In addition, there is a tendency for decreasing bond polarities downwards the column (Ag–P is an exception). Consequently, the highest bond polarities are observed for the Ni–Cl and Cu–Cl bonds, whereas the lowest polarities are observed for the Pt–P and Au–P bonds.
The synthesis of 4-bromo-5-diphenylphosphino-9,9-dimethylxanthene (1a), 4-bromo-6-diphenylphosphinodibenzofuran (1b), 4-diphenylphosphino-5-dimethylsilyl-9,9-dimethylxanthene (2a), 4-diphenylphosphino-6-dimethylsilyldibenzofuran (2b), 5-dimethylsilyl-9,9-dimethylxanthen-4-yl-diphenylphosphonium tetrakis(pentafluorophenyl)borate [3a][B(C6F5)4], and 6-dimethylsilyldibenzofuran-4-yl-diphenylphosphonium tetrakis(pentafluorophenyl)borate [3b][B(C6F5)4] was reported. Unlike the benzofuran derivate [3b]+, the xanthene derivative [3a]+ shows an intramolecular dihydrogen bond of the type P–H···H–Si, which was studied by DFT calculation using a set of real-space bond indicators (RSBIs) derived from the Atoms-In-Molecules (AIM), Non-Covalent Interactions (NCI) indicator, and Electron Localizability Indicator (ELI-D) methods. Neither [3a]+ nor [3b]+ shows any propensity to release dihydrogen to give the 4-diphenylphosphino-9,9-dimethylxanthen-5-yl-dimethylsilyl cation [4a]+ or the 4-diphenylphosphino-dibenzofuran-5-yl-dimethylsilyl cation [4b]+, respectively.
Starting from 1,8‐dibromo‐biphenylene, [1‐(bromo)biphenylen‐8‐yl]diphenylphosphine (1) and [1‐(diphenylphosphanyl)biphenylen‐8‐yl]dimesitylborane (2) were prepared by sequential metal / halide exchange and salt metathesis reactions. The phosphinoborane 2 comprises a frustrated Lewis pair (FLP) mounted on a peri‐substituted biphenylene scaffold with a P···B distance of 4.100(3) Å. Attempts to capture dihydrogen and carbon dioxide failed, presumably due to the insufficient Lewis acidity of the dimesityl borane group. Compounds 1 and 2 were characterized by heteronuclear NMR spectroscopy and X‐ray crystallography.
,,Sehr storend ist die regelmassig stattfindende Anliydrdhildung, die umso starker ist. je konzentrirrtw die Sdure und je langer die Lagerung ist. In starker Verdunnung L . B. heim Gebraiich in den Lederfabrilen, zerfallt das Anhydrid wieder, sodass demnacli der SBuregehdt nur sckieinbar verringert war. 1;iine 50-proe. SBure sol1 hochstens 1,5% bis 1,8%, eine 80-proz. Saure 37+49/0 Anhgdrid enthalten, nicht aber l5"/, w k es bisw d e n bpi lang dauerndem Einkochen oder h i sehr langer Lngerung der hochprozentigen Saure vorlrommt ."Dass der Gehalt an anhydrisierter Saure in frisch hcrgestellter Handelsmilchsaure relativ gering ist, beweisen uns folgende Angaben aus der Technik6).
Aus dem Dipenten wurde mit Bromwasserstoff-Eisessig wieder Es wurde weiter Plantagenkautschuk bei 300° im Vakuum destil-fast quantitativ das Dihydrobromid ausgeschieden. liert mit folgendem Resultat : 50 gr Plantagenkautschuk gaben 28 gr Destillat + 21 gr Ruckstand, 100 gr Plantagenkautschuk gaben 47 gr Destillat + 49 gr Ruckstand. 100 gr Plantagenkautschuk im Kohlendioxydstrom bei 300° lieferte 29 gr Destillat und durch nachtragliches Erhitzen im Vakuum wurden noch 15 gr hohersiedende Zersetzungsprodukte erhalten, also gesamt 44 gr Destillat und 53 gr Ruckstand, der fast vollsthdig aus Poly-cyclokautschuk besteht.Schliesslich wurde Kautschuk stufenweise zersetzt, erst bei 300° i m Vakuum, dann der riickstandige Poly-cyclokautschuk durch hoheres Erhitzen auf 350-400°, und je 50 gr des Destillates wurden fraktioniert. Dabei zeigte sich, dass in der ersten Stufe wieder relativ vie1 Dipenten enthalten war (24% des Gesamtdestillates) und 20% hochsiedende Kohlenwasserstoffe, wahrend in der zweiten Stufe bei Zerfall des Polycyclokautschuks weniger tiefsiedende und mehr hochsiedende (uber 60 %) entstehen ; Dipenten konnte nicht nachgewiesen werden, Isopren nur unsicher. Entsprechend der Angaben in der vorigen Arbeit zerfallt also Poly-cyclokautschuk vor allem in hohersiedende Kohlenwasserstoffe und liefert kein Dipenten, wahrend Kautschuk in relativ guter Ausbeute Dipenten gibt.
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