The molecular and electronic structure of 1-pyrazolylphosphazenes

Abstract

KEITH D. GALLICANO, NORMAN L. PADDOCK, STEVEN J. R E~G , and JAMES TROTIFR. Can. J. Chem. 70, 1855 (1992). The nature of the interactions between pyrazolyl and phosphazene rings has been investigated through the study of the structures of bis(1 -pyrazolyl)methane, CH2(H2pz),, 1, bis[l-(3,5-dimethylpyrazolyl)]methane, CH,(Me,pz),, 2, the pyrazolylphosphazenes N,p,(Me,p~)~, 3, N4P4(H2pz),, 4, and N,P,(Me2pz),, 5, and the partially substituted gem-N,P,ph,(Me,p~)~, 6. Crystal data are as follows: 1, orthorhombic, P2'2'2,, a = 7.997(2), b = 9.287(2), c = reflections. Interpretation of the structures through iterative extended Hiickel calculations shows that conjugative interactions lead to a quinonoid deformation of the pyrazole ring, similar to that in bis(1-pyrazoly1)carbonyl. a-Electron transfer to the phosphazene ring, facilitated by the use of acceptor d orbitals on phosphorus, is accompanied by a synergic a transfer to the pyrazole ring. The pyrazolyl group acts both as a strongly electronegative group and as a good potential donor. The calculations account satisfactorily for the bond lengths in the pyrazolyl group, the large bond angles at nitrogen in 4 and 5, the bond length inequalities in the phosphazene ring of 6, and the reactivity of the pyrazolylphosphazenes. [Traduit par la redaction]

Crystal structure of chlorido-(η 5-pentamethylcyclopentadienyl)-((bis-pyrazol-1-yl)methane-κ2 N,N′) rhodium(III) hexafluorophosphate. (C17H23ClN4RhF6P)

“…1,3-Bis(pyrazol-1-yl) propane forms eight-membered metallocycles or acts as a bidentate bridging ligand, whereas bis(pyrazol-1-yl)alkanes with four and more methylene groups in the spacer coordinate in a bridging mode to give coordination compounds of intriguing architectures and topologies [8][9][10]. We have prepared the title compound as part of our ongoing studies of Rh complexes with bidentate ligands [11,12]. The asymmetric unit of the title compound consists of an cationic Rh(III) complex with a PF 6 − anion.…”

Diatomic PN – trapped in a cyclo-tetraphosphazene

“…22 This synthetic protocol was further explored and several rings of the type [P(R 1 )N(R 2 )] 4 (R 1 ¼ Me, 22 Et, 22 Ph, 23 Mes; 24 R 2 ¼ Me, tBu) were prepared and their potential as ligands in transition metal chemistry was explored successfully. 23,25,26 However, to the best of our knowledge there are no reports, in which cyclo-tetraphosphazanes can be directly prepared from molecules, that already incorporate a PN moiety. Herein we present attempts to release molecular PN directly from 1 by thermal treatment in the presence of a trapping reagent (dmb) resulting in the formation of an unprecedented cyclo-tetraphosphazane.…”

First lanthanide complexes and unusual coordination behavior of hexakis(3,5-dimethylpyrazolyl)cyclotriphosphazene

“…7 Successful applications of exocyclic donors such as pyrazolyl [1][2][3][4] and cyclopentadienyl 5 groups are cases in point. However, the scope of the coordination chemistry of hexakis(3,5-dimethylpyrazolyl)cyclotriphosphazene (L), a potential multidentate ligand due to its multiple chelate sites, 8 has only been examined with d 10 metal halides 1 and d 9 Cu II ion, 2 revealing the limited coordination behavior with the binding cores of (k 3 N) for mononuclear species and (k 3 N-k 2 N) and (k 3 N-k 3 N) for dinuclear complexes. Here, we present the first examples of lanthanophosphazenes [L•LnCl 3 ] (Ln = La, Ce, Nd, Sm) where the ligand L acts as an unprecedented k 5 N binding core donor for a metal center to form a hendecahedral coordination sphere.…”