N,N',N'-TRIMETHYLETHYLENEDIAMINE AS A SUBSTITUENT GROUP AT MAIN-GROUP CENTERS - INTRAMOLECULAR DONOR-ACCEPTOR INTERACTIONS AND UNUSUAL MODES OF COORDINATION IN COMPOUNDS OF SILICON AND PHOSPHORUS AND THEIR TRANSITION-METAL COMPLEXES

This review is concerned with the role of the N,N',N'-trimethylethylenediamine group as a substituent at phosphorus atoms in different coordination and/or oxidation numbers. A few examples for silicon are also presented. Intramolecular donor-acceptor interactions between the nitrogen atom of the dimethylamino group and Si or P as the central atom were first noted in some N,N',N'-trimethylethylenediamine-substit fluorosilanes (LSiF(3), PhSiF(2)L) and P(III)Cl systems, e.g. LPCl(2) and PhP(Cl)L (L=N,N',N'-trimethylethylenediamine group). These observations gave rise to a more detailed study of the coordinating behavior, especially of further phosphorus compounds of different substitution pattern. Spontaneous intramolecular coordination with formation of salt-like products was observed, especially, for compounds in which a phosphorus-bonded halogen atom is available to dissociate as an anion A dependence both on the nature of the halogen atom and on the nature of other ligands at P(III) [or P(V)] was noted and will be discussed. Through the action of Lewis acids, e.g. AlCl3 of PF5, or in the reaction with tetraphenylborate as a non-coordinating anion, halide abstraction and consequent formation of the Me(2)N --> P coordinative bond from acyclic N,N',N'-trimethylethyienediamine-substit halophosphines or trimethylethylenediamine-substituted fluorophosphoranes could be induced. No such Me(2)N --> P coordination took place during oxidation of N,N',N'-trimethylethylenediamine-substited phosphorus(III) compounds with oxidizing agents, e.g. sulfur, selenium, o-quinones or hexafluoroacetone. Numerous oxidation reactions were conducted on intramolecularly stabilized phospholidin-1-ium salts. They furnished the expected oxidation/addition products. This was accompanied in some cases (depending on the nature of the substituents at P(III)) by a scission of the coordinative Me(2)N --> P bond The reaction of phospholidin-1-ium salts with phenyl azide, dimethyl sulfoxide and sulfur furnished phosphonic acid diamides and substituted lambda(4)-phospholidin-1-ium salts, as well as substituted diazadiphosphetidines, as a result of the dimerization of P=N species. Intramolecular donor-acceptor interaction in N,N',N'-trimethyiethybnediamine-substituted fluorophosphoranes was only observed in the presence of the Lewis acid, phosphorus pentafluoride leading to the formation of hexafluorophosphate salts. The reaction of dialkylamino-substituted tetrafluorophosphoranes with N-trimethylsilyl-N,N',N'-trimethylethylenediamine took an unusual course. Instead of the expected P-F cleavage and formation of an N,N',N'-trimethylethylenediamine-substited dialkylaminotrifluorophosphorane, cyclic tetraduorophosphates with a lambda(6)P atom, and dialkylaminotrimethysilane were formed. The reaction of phosphorus(III)-N,N',N'-trimethylethylenedia compounds with transition metal compounds CFe(O), Cr(O), Mo(O), Pt(IIII furnished mono-, di- or trisubstituted coordination compounds, depending on the nature of the metal. The P(III) ligand was bonded in some cases via P(III) only (as a monodentate ligand) and in other cases as a chelating ligand coordinated via P(III) and N. A variety of variable-temperature NMR experiments have examined the dynamic processes occurring at room temperature in solution, and X-ray single-crystal structure determinations have been conducted in many cases to characterize these new and unusual compounds.