On the Synthesis and Coordination Properties of N‐Aryl‐substituted 1, 3, 2‐Diazaphospholidine‐4, 5‐diimines

Abstract

New 1, 3, 2‐diazaphospholidine‐4, 5‐diimines were synthesized by condensation of lithiated oxalamidines with PCl3 or PhPCl2, and characterized by spectral and analytic data. The products react selectively with [(nbd)W(CO)4], [Mo(CO)6], or [(PhCN)2PdCl2] to give stable complexes, in which the heterocycle binds as chelating, bidentate ligand through the nitrogen atoms of the diimine unit. Formation of P‐bound or dinuclear complexes was not observed. Reaction with PCl3 or AsCl3 in the presence of SnCl2 as reducing agent was unspecific. Evidence for the formation of bicyclic products arising from formal [4+1] cycloaddition between the diimine unit and a transient pnictogen(I) species was not obtained, and only a diimine complex of SnCl4 was isolated in moderate yield. Single‐crystal X‐ray diffraction studies reveal that coordination of the diimine unit induces a substantial structural distortion of the ligand framework, which allows to explain the occurrence of substantial 31P coordination shifts despite the absence of a direct metal‐phosphorus bond.

A Metal‐Containing N‐Heterocyclic Germylene Based on an Oxalamidine Framework

“…comparable to 2 . Somewhat more pronounced values of 8.75 pm were found for the closely related κ 2 N ‐coordinated 1,3,2‐diazaphospholidine‐4,5‐diimine reported by Gudat . These features suggest strong contribution of π conjugation in the amidine unit in 3 (only one of the possible resonance structures is depicted in Scheme ).…”

“…Reports in Main Group chemistry are fewer in number. For instance, Gudat et al have recently described a metal‐containing 1,3,2‐diazaphospholidine‐4,5‐diimine (Scheme ) …”

Conformationally Constrained N-Heterocyclic Phosphine–Diimine with Dual Functionality

“…This assignment is backed by the finding that the νCN vibrational mode of the free ligand 4a experiences a slight blue shift upon formation of the tungsten complex, which is in marked contrast to the pronounced red shift induced by metal coordination at the diimine unit of the N-aryl diazaphospholidine−diimines 2a,b. 9 The IR spectrum of the reaction product reveals further the distinctive three-band pattern of νCO vibrational modes that is commonly associated with a W(CO) 5 moiety and is also in accord with the presence of appropriate 13 C NMR signals attributable to CO ligands in cis-and trans-position to a metal bound phosphorus atom. Considering that the number and multiplicity of 1 H and remaining 13 C NMR signals confirms that the ligand has retained its structural integrity, we assigned the product the molecular structure of a phosphine complex 7 (Scheme 1).…”

“…17 First studies on the coordination properties of the P−Cl and P−Ph substituted derivatives 2a,b revealed, however, that these compounds show no dual functionality but bind to metals exclusively via the nitrogen donor atoms. 9 The diazaphospholidine−diimines differ in this respect from the cyclic guadinates 3 18 which were recently reported by the group of Ragogna. These ring contracted monoimino analogs of 2 may bind Lewis acids via the exocyclic imine function, but the reported reaction with a Pt(0) substrate, which proceeded under ring fragmentation to give an iminophosphonium complex, indicates that also some P-activity may be retained.…”

“…A small amount of a crystalline precipitate formed which was collected by filtration (no yield determined) and characterized by 31 P NMR and IR spectroscopy, analytical data, and a single-crystal X-ray diffraction study. 31 9-Dimethylamino-4,4′,8a,8a′-tetraaza-9-phospha-2,3,6,7,8,8a,9,9a-octahydro-1H-fluorene-trichlorostibine complex (9). A solution of SbCl 3 (959 mg, 4.2 mmol) in THF (10 mL) was added dropwise to a solution of 4a (1.00 g, 4.2 mmol) in THF (10 mL).…”