Preparation of Complexes η4-4-(1,3-Diphenyl-2-propen-1-one)-η3-3-(1,3,5-triorganyl-1,3,5-triazacyclohexane)carbonyltungsten(0) and Their Reactions with Diethyl Phosphite

Abstract

New tungsten complexes were prepared of a composition h 3 -[(1,3,5-triorganyl)-1,3,5-triazacyclohexane]-tricarbonyltungsten(0) where a tridentate coordination of the triazinane fragment to the metal center was found. The reaction of tricarbonyltriazinane tungsten complexes with 1,3-diphenyl-2-propen-1-one (chalcone) under thermochemical activation resulted in replacement of two carbon monoxide molecules in the coordination sphere of tungsten by a chalcone molecule linked to the transition metal atom through a system of p-bonds C=C and C=O. The phosphorylation of h 4 -(1,3-diphenyl-2-propen-1-one)-h 3 -[(1,3,5-triphenyl)-1,3,5-triazacyclohexane]-monocarbonyltungsten(0) with diethyl phosphite occurred at the carbonyl group of the coordinated heterodiene; the phosphonate thus formed underwent intracomplex phosphonate-phosphate rearrangement affording an organometallic phosphate.Although a long time has elapsed since the 1,3,5-triorganyl-1,3,5-triazacyclohexanes (triazinanes) have been described for the first time the chemistry of these heterocyclic tridentate ligands just now starts to develop [15]. Triazacyclohexane system should apparently be regarded as the smallest representative of the triazamacrocyclic ligands. Therefore its tridentate coordination with the metal center is characterized by a certain strain that might result in unpredictable changes in reactivity of the complexes including these systems. Relatively simple procedures for preparation of complexes (1,3,5-trialkyl-1,3,5-triazacyclohexane)metal(CO) 3 were reported in [2 5], and it was shown that notwithstanding the character of substituents at the nitrogen atom, for instance, alkyne [4] or hydroxyalkyl groups [5], in the chromium and in some cases in molybdenum complexes a tridentate n-coordination of the triazinane with metal was observed occurring at the expense of the unshared electron pairs of nitrogen.We formerly developed preparation procedures for organometallic compounds starting from a-enones and homoligand hexacarbonyl complexes of metals from the chromium subgroup and investigated hydrophosphorylation of unsaturated ligand within the coordination sphere of metal [6,7]. This study permit us establishing a fundamental possibility to govern hydrophosphorylation regioselectivity of a-enones included into the coordination sphere of a transition metal. Aiming at evaluation of the influence of ligands surrounding the transition metal atom, in particular, at replacement of carbonyl ligands by a triazinane, on the readiness to form heterodiene h 4 -complexes and on the features of the unsaturated ligand reactivity toward intracomplex hydrophosphorylation we performed reactions of 1-oxo-1-heterodienes with coordination compounds (triazinane)W(CO) 3 . The choice of tungsten as the complexing metal was due first of all to the presence in the natural isotope mixture of tungsten a magneticallyactive isotope 183 W that facilitated the study of phosphorylation by appearance in the NMR spectra of the spin-spin coupling phosphorustungsten. Besides ...