Polycyclic Bis(tert-butylamido)cyclodiphosph(III)azane Complexes of Lithium and Magnesium:  Their Syntheses, Molecular Structures, and Relationships to Isoelectronic Cyclodisilazane Derivatives

Abstract

Syntheses and single-crystal X-ray diffraction studies of the bis(tert-butylamino)cylodiphosphazane cis-[(tBuNP)2(tBuNH)2], 1a, and its lithium and magnesium salts are described. The pristine molecule has crystallographic C 2 symmetry, both N−H groups being disposed in an endo fashion, and crystallizes in the monoclinic space group P2/c with unit cell dimensions (193 K) a = 9.600(4) Å, b = 5.904(4) Å, c = 18.97(1) Å, β = 101.09(3)°, and Z = 2. Treatment of 1a with nBuLi or (nBu)2Mg in refluxing THF yielded the heterocubic cis-[(tBuNP)2(tBuNLi·THF)2], 2a, and the seco-heterocubic {[(tBuNP)2(tBuN)2]Mg·(THF)2}, 3a, respectively. The crystal data (223 K) for the dilithio compound are monoclinic, space group P21 /c, a = 10.691(1) Å, b = 15.827(2) Å, c = 19.424(4) Å, β = 105.617(7)°, and Z = 4, and those for the magnesium derivative (213 K) are monoclinic, space group P21 /n, a = 10.6272(4) Å, b = 17.6643(7) Å, c = 16.3625(6) Å, β = 90.46(3)°, and Z = 4. The lithium and magnesium complexes are shown to be isostructural with isoelectronic cyclodisilazane species, and the development of a parallel coordination chemistry for both ligands is proposed.

Bis(amido)cyclodiphosph(III)azane Complexes of Yttrium and the Lanthanides

“…[18] The Li metal center of the cations in compounds 1 a-c are tetrahedrally coordinated by four THF molecules; a common structural motif. [25] …”

“…[18] Neutral chloride complexes: To avoid the formation of "ate" complexes we were interested in finding another synthetic protocol. One way to achieve this is by the use of potassium instead of lithium reagents.…”

“…Elemental analyses were carried out with an Elementar vario EL instrument. LnCl 3 , [37] [18] and cis-[(tBuNP…”

“…[15,16] Their preparation is usually based on the reaction of PCl 3 with an excess of a free amine. [17,18] Today cyclodiphos-A C H T U N G T R E N N U N G phA C H T U N G T R E N N U N G (III)azanes are well established as anionic N-donor ligands in main-group [18,19,20] and early-transition-metal chemistry. [21,22] Group 4 complexes of these ligands have been shown to have high activities in ethylene polymerization in the presence of methylaluminoxane (MAO).…”

“…Similar structures of cyclodiphosphA C H T U N G T R E N N U N G (III)azane complexes in main-group chemistry have previously been observed. [18,19] The coordination polyhedron of the pentacoordinated yttrium atom is best described as a distorted trigonal bipyramid with the NPh 2 substituents in the apex and in the plane. As expected the bond length between the neutral nitrogen atom and the yttrium ion (YÀN1 = 254.4(4) pm) is longer than the bond lengths of the corresponding anionic nitrogen atoms (Y À N3 = 227.1(5), Y À N4 = 225.3(4), Y À N5 = 229.4(5), Y À N6 234.8(5) pm)).…”