“…Similar to H 2 CLi 2 , these higly ionic compounds are likely polymeric in the solid state. Recently, some stabilized molecular dilithiomethandiides have been structurally characterized. − The use of the bis(iminophosphorano)methane ligand in the syntheses of a well-defined dilithiomethandiide complex 10 [ 4 − Li 2 ] 2 , as well as in a rather polar lanthanide carbene complex 4 − Sm(NCy 2 )·THF, urged us to probe this ligand in the synthesis of a calcium carbene. …”
Attempted 2-fold deprotonation of the bis(iminophosphorano)methane ligand, H(2)C(Ph(2)P=NSiMe(3))(2) (4-H(2)), with a calcium amide led only to mono-deprotonation. The crystal structure of (4-H)(2)Ca shows two tridentate ligands with short Ca-N and a rather long Ca-C bond. Reaction of 4-H(2) with a dibenzylcalcium complex gave the desired 2-fold deprotonation and formation of 4-Ca, which crystallized as a dimeric complex. Analysis of the calculated atomic and group charges in 4-H(2), (4-H)(2)Ca, and [4-Ca](2) showed that the negative charge at the imine nitrogens only slightly increases upon successive deprotonation of 4-H(2). The electron density at the central carbon, however, increases considerably: the charge on the carbene carbon in [4-Ca](2) is ca. -1.8. The negative charge in 4(2)(-) is therefore mainly located on the carbon. Reaction of [4-Ca](2) with benzophenone in benzene gave the remarkably stable adduct [4-Ca](2) x O=CPh(2), which was characterized by X-ray diffraction. Reaction of [4-Ca](2) with adamantylcyanide gave exclusive formation of the adduct [4-Ca](2) x (N identical withCR)(2), which did not react further, even at higher temperatures. Addition of cyclohexyl isocyanate to a benzene solution of [4-Ca](2) gave immediate [2 + 2]-cycloaddition and formation of a dianionic tetradentate ligand that binds to Ca(2+) through two nitrogens, the central carbon, and an oxygen. This product crystallized as a dimer with bridging oxygen atoms.
“…Similar to H 2 CLi 2 , these higly ionic compounds are likely polymeric in the solid state. Recently, some stabilized molecular dilithiomethandiides have been structurally characterized. − The use of the bis(iminophosphorano)methane ligand in the syntheses of a well-defined dilithiomethandiide complex 10 [ 4 − Li 2 ] 2 , as well as in a rather polar lanthanide carbene complex 4 − Sm(NCy 2 )·THF, urged us to probe this ligand in the synthesis of a calcium carbene. …”
Attempted 2-fold deprotonation of the bis(iminophosphorano)methane ligand, H(2)C(Ph(2)P=NSiMe(3))(2) (4-H(2)), with a calcium amide led only to mono-deprotonation. The crystal structure of (4-H)(2)Ca shows two tridentate ligands with short Ca-N and a rather long Ca-C bond. Reaction of 4-H(2) with a dibenzylcalcium complex gave the desired 2-fold deprotonation and formation of 4-Ca, which crystallized as a dimeric complex. Analysis of the calculated atomic and group charges in 4-H(2), (4-H)(2)Ca, and [4-Ca](2) showed that the negative charge at the imine nitrogens only slightly increases upon successive deprotonation of 4-H(2). The electron density at the central carbon, however, increases considerably: the charge on the carbene carbon in [4-Ca](2) is ca. -1.8. The negative charge in 4(2)(-) is therefore mainly located on the carbon. Reaction of [4-Ca](2) with benzophenone in benzene gave the remarkably stable adduct [4-Ca](2) x O=CPh(2), which was characterized by X-ray diffraction. Reaction of [4-Ca](2) with adamantylcyanide gave exclusive formation of the adduct [4-Ca](2) x (N identical withCR)(2), which did not react further, even at higher temperatures. Addition of cyclohexyl isocyanate to a benzene solution of [4-Ca](2) gave immediate [2 + 2]-cycloaddition and formation of a dianionic tetradentate ligand that binds to Ca(2+) through two nitrogens, the central carbon, and an oxygen. This product crystallized as a dimer with bridging oxygen atoms.
Größe ist wichtig: Geminale Bis(amidophosphorano)methandiid‐Dimetallkomplexe der schweren Alkalimetalle K und Rb sind relativ stabil, doch der von Cs, dem größten und elektropositivsten Alkalimetall, zersetzt sich zu einem cyclischen Produkt, das mit Benzylcaesium kokristallisiert.
Planierter Kohlenstoff: Ein monomeres Dilithiomethandiid weist ein Kohlenstoffatom mit verzerrter, trans‐planarer Vierfachkoordination auf. Die Struktur dieser Verbindung wurde durch Röntgenbeugungsanalyse bestimmt (siehe Bild: C schwarz, N blau, P rosa, Li rot) und durch DFT‐Rechnungen bestätigt.
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