The syntheses and properties of novel, extremely strong uncharged polyaminophosphazene bases up to a high level of steric hindrance are described. Most of the systems were readily prepared in up to molar quantities and conveniently recovered from their salts. They are of appreciable to high chemical and thermal stability. Crystal structures of their salts were determined in order to parametrize a force field, which is utilized in molecular modeling studies. The latter offer a rationalization of the high conformational mobility of these systems. These bases cover a range of ca. 15 pK units in basicity and extend the range of uncharged auxiliary bases by ca. 19 pK units up to DMsopKsH+ values of 34-35. They are proposed as a novel class of auxiliary bases for deprotonation of very low acidic compounds where chemists have been so far left to classical metalorganic bases. Depending on the basicity range and the degree of steric protection of the basic center, these systems are particularly applicable to E2 elimination or to in situ generation of highly reactive "naked" anions.Uncharged nitrogen bases have a long tradition as widely used and often irreplaceable standard reagents in organic synthesis; many attempts to improve basicity and to reduce nucleophilicity have been reported"] since the classical work of Hunig et a1.L21. Until recently, amidines and guanidines as described by Eiter et al.f31, Eschenmoser et al.f4I, and Barton et al. ['] were generally considered the strongest synthetically useful auxiliary bases. In the early sixties there was a single report by Flynn et a1.L8] concerning applications of a somewhat stronger isobiguanide base. This base was even commercially available, but surprisingly has not been accepted by synthetic chemists.In connection with our own activities in this field we exploited among other s t r u~t u r e s [~~'~] the structural type of peralkylated triaminoiminophosphoranes. The simplest representative 1 was already known" l] and in our hands turned out to be of unprecedented base strength among kinetically active uncharged bases. The derivatives of this leading structure we synthesized s~bsequently['~,'~] proved to be chemically very stable, highly versatile and easy to recover auxiliary bases with a very broad range of steric shielding of the basic enter[',^*'^]. The Concept of Phosphazene BasesAt the outset there was the question, whether it would be possible to further enhance basicity by the same formal "homologization" which converts weakly basic tertiary amines to strongly basic triaminoiminophosphoranes.

Durch Kristallisation von CaI2 aus wäßrigen Lösungen sind die Hydrate CaI2 · 6,5H2O und CaI2 · 4H2O zu erhalten. Die Kristallstruktur von CaI2 · 6,5H2O (monoklin; Raumgruppe C2/c; a = 1675,5(5) pm; b = 816,2(8) pm; c = 1787,8(5) pm; β = 107,76(3)°; Z = 8) wird aus zweikernigen Ca2(OH2)134+‐Kationen und I−‐Anionen aufgebaut. In den Kationen sind zwei Ca(OH2)8‐Antiprismen über eine gemeinsame Dreieckfläche verbunden. Das Tetrahydrat CaI2 · 4 H2O ist isotyp mit FeCl2 · 4 H2O. In der Kristallstruktur (monoklin; Raumgruppe P21/c; a = 682,5(9) pm; b = 784,6(2) pm; c = 963,71(15) pm; β = 110,47(12)°; Z = 2) sind oktaedrische, transkonfigurierte Ca(OH2)4I2‐Baugruppen enthalten.

Das quecksilberreiche Chloromercurat 2CaCl2 · 11HgCl2 · 16H2O ist durch Kristallisation aus konzentrierten wäßrigen Lösungen von CaCl2 und HgCl2 bei Raumtemperatur zu erhalten. In der kubischen Kristallstruktur (a = 18,170(3) Å, Raumgr. F23, Z = 4) bilden Hg6Cl13−‐ und Hg5Cl133−‐Anionen ein Gerüst mit großen Hohlräumen, in denen sich Ca(H2O)82+‐Kationen mit dodekaedrischer Konformation befinden. Von den 104 Cl‐Atomen in der Zelle bilden 96 einen Bauverband cP2[12i] mit acht Cl12‐Ikosaedern, die jeweils durch ein Cl‐Atom zentriert sind. Bei vier der Ikosaeder befinden sich 6 Hg–Atome auf Kanten, so daß Cl(HgCl2)6−‐Anionen resultieren. Bei den Hg5Cl133−‐Anionen besetzen jeweils 3 Hg‐Atome Kanten und 2 Hg‐Atome Flächen der Ikosaeder, so daß die zentralen Cl−‐Anionen von 3 HgCl2‐ und 2 HgCl3‐Gruppen koordiniert sind. Die Hg5Cl13‐ und Ca(H2O)8‐Baugruppen sind kristallographisch fehlgeordnet.

Abstract The tetrahalogenometallates CaHgBr4·8H2O, CaCdI4·8H2O and SrCdI4·8H2O which have been obtained by crystallization from aqueous solutions form different structures. The orthorhombic compounds CaHgBr4·8H2O (Cmca, a = 1720.1(6) pm, b = 1329.2(4) pm. c = 1369.5(7) pm, Z = 8, R =0.041) and SrCdI4·8H2O (Pnma, a = 1404.6(2) pm, b = 1841.1(5) pm. c = 1420.6(3) pm, Z = 8, R = 0.037) are built up from dodecahedral [A(H2O)8 ] cations (A = Ca, Sr) and tetrahedral MX4 anions (M = Hg, Cd) which are cubic closed packed in a CuAu type structure. The tetragonal structure of CaCdI4·8H2O (P4/nbm, a = 1268.14(13) pm, c = 536.96(35) pm. Z = 2, R = 0.034) contains antiprismatic [Ca(H2O)8]2+ cations and tetrahedral Cdl4 anions, which form together a tetragonal primitive rod package.

The tetrahalo‐metallates (I)‐(III) are obtainable by crystallization from aqueous solutions.