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Two phosphonite ligands bearing the highly sterically demanding 2,6-bis (2,6-dimethylphenyl)phenyl group (ArXyl2), PArXyl2(OPhNO2)2 and PArXyl2(OPhNO2,Me)2, were prepared from the parent dihalophosphines PArXyl2X2 (X = Cl, Br) and the corresponding phenols, 4-nitrophenol and 4-nitro-2,6-dimethylphenol, respectively. DFT methods were used to examine their structural features and to determine three steric descriptors, namely the Tolman cone angle, the percentage of buried volume, and the percentage of the coordination sphere protected by the ligand. A comparison with the related terphenyl phosphines is also provided. Reactions of PArXyl2(OPhNO2)2 and PArXyl2(OPhNO2,Me)2 with several Pt(II) precursors were investigated, revealing a high tendency of both phosphonites to undergo C-H activation processes and generate five- or six-membered cyclometalated structures. The coordination chemistry of the new ligands was explored with isolation, among others, of three carbonyl complexes, 1-3∙CO, and the triphenylphosphine adduct 3∙PPh3. X-ray diffraction methods permitted the determination of the solid-state structures of the mononuclear methyl carbonyl complex 1∙CO, the dinuclear chloride-bridged complex 2 and the doubly cyclometalated complex 3∙SMe2, including the conformations adopted by the ligands upon coordination. All of the new compounds were characterized by multinuclear NMR spectroscopy in solution. [ABSTRACT FROM AUTHOR]

Metal‐only Lewis pairs (MOLPs) in which the two metal fragments are solely connected by a dative M→M bond represent privileged architectures to acquire fundamental understanding of bimetallic bonding. This has important implications in many catalytic processes or supramolecular systems that rely on synergistic effects between two metals. However, a systematic experimental/computational approach on a well‐defined class of compounds is lacking. Here we report a family of MOLPs constructed around the RhI precursor [(η5‐C5Me5)Rh(PMe3)2] (1) with a series of s, p and d‐block metals, mostly from the main group elements, and investigate their bonding by computational means. Among the new MOLPs, we have structurally characterized those formed by dative bonding between 1 and MgMeBr, AlMe3, GeCl2, SnCl2, ZnMe2 and Zn(C6F5)2, as well as spectroscopically identified the ones resulting from coordination to MBArF (M=Na, Li; BArF−=[B(C6H2‐3,5‐(CF3)2)4]−) and CuCl. Some of these compounds represent unique examples of bimetallic structures, such as the first unambiguous cases of Rh→Mg dative bonding or base‐free rhodium bound germylene and stannylene species. Multinuclear NMR spectroscopy, including 103Rh NMR, is used to probe the formation of Rh→M bonds. A comprehensive theoretical analysis of those provides clear trends. As anticipated, greater bond covalency is found for the more electronegative acids, whereas ionic character dominates for the least electronegative nuclei, though some degree of electron sharing is identified in all cases. [ABSTRACT FROM AUTHOR]

To broaden the limited knowledge concerning the zinc(II) coordination chemistry with amino alcohols, reactions of [Zn(quin)2(H2O)] (quin− = quinaldinate, C10H6NO2) with 3-amino-1-propanol (3-apOH, C3H9NO) and N-methylaminoethanol (N-maeOH, C3H9NO) were investigated. The starting material, zinc(II) with two quinaldinates coordinated in a bidentate chelating mode, provides a structurally rigid core with two sites available for interaction with amino alcohol ligands. When the reactions were carried out in acetonitrile in autoclaves at 105 °C, an unforeseen decomposition of amino alcohols to ammonia took place. This was accompanied by crystallization of an ammine complex [Zn(quin)2(NH3)] (1). Mass spectrometry of the gaseous phases confirmed unambiguously the presence of ammonia in such reaction mixtures. The desired complexes with coordinated amino alcohols could be obtained in good yield by carrying out the reactions at room temperature and/or in various solvents. Two novel amino alcohol complexes were prepared, [Zn(quin)2(3-apOH)] and [Zn(quin)2(N-maeOH)]. The 3-apOH ligand was coordinated to zinc(II) in a monodentate manner via the amino nitrogen. The 3-apOH complex crystallizes as an acetonitrile (2a), ethanol (2b), 2-propanol (2c) or water (2d) solvate. The conversion of 2a to 2d was monitored by IR spectroscopy. In [Zn(quin)2(N-maeOH)] (3), the N-maeOH ligand was coordinated in a bidentate chelating manner through both functional groups. DFT calculations were performed on the isomers of [Zn(quin)2(3-apOH)] and [Zn(quin)2(N-maeOH)], which differ in the binding modes of their amino alcohol ligands. Complete characterization of all compounds by means of X-ray structure analysis, infrared spectroscopy and NMR spectroscopy is presented. [ABSTRACT FROM AUTHOR]