Exploring the coordination chemistry and reactivity of dialkylamino- and bis(dialkylamino)-phosphines in the coordination sphere of metals

Abstract

The coordination chemistry of a range of dialkylamino- and bis(dialkylamino)-phosphines, RxP(NR′2)3 − x (x = 1 or 2; R = Cl, Me, Ph, C6F5; R′ = Et, Pri), 1–7, has been studied and the resulting Group 6 tetracarbonyl and platinum dichloride bis(phosphine) complexes fully characterised. Subsequently, the reactivity of the P–N bonds of the metal-bound phosphines was probed. Treatment of R″OH (R″ = Me, Et, allyl) solutions of the bis(dialkylaminodiphenylphosphine) complexes with anhydrous HCl gas led to substitution of NR′2 by OR″; the resulting P-alkoxy complexes were isolated in excellent yields. Acidification of ethylene glycol solutions of the aminophosphine complexes afforded the corresponding bis(chlorodiphenylphosphine) derivatives. Following reaction of trans-[W(CO)4(P{NEt2}Ph2)2] with either aqueous HCl or H2SO4, trans-[W(CO)4(P{OH}Ph2)2] could be isolated as its dichloromethane solvate in excellent yield (81%). Reactions of the bis(bis{dialkylamino}phenylphosphine) complexes under identical conditions yielded a range of unidentified products. Reactions of ligands 1–7 with [{RhCl(CO)2}2] and elemental selenium have been undertaken and the products used to assess the phosphines' donor capabilities. Depending on the substituents at phosphorus, either trans-diphosphine or cis-dicarbonyl complexes result from reaction with [{RhCl(CO)2}2]. The sterically demanding phosphine P(NPri2)2Ph (5) proved unreactive towards complexation with metals, although its selenide could be prepared and isolated. In order to probe the observed lack of oxidation or complexation the molecular structure P(NPri2)2(C6F5) has been determined by X-ray crystallography.