Triphenylphosphineoxide and triphenylphosphinesulfide seven-coordinate complexes of molybdenum(II) and tungsten(II)

Abstract

The complexes [MI 2(CO) 3(NCMe) 2] (MMo or W) react with one equivalent of OPPh 3 in CH 2Cl 2 at room temperature to rapidly afford the iodo-bridged dimers [M(μ-I)I(CO) 3(OPPh 3)] 2 in good yield. By contrast reaction of equimolar quantities of SPPh 3 and [MI 2(CO) 3(NCMe) 2] react in CH 2Cl 2 at room temperature to give the monoacetonitrile monomers [MI 2(CO) 3(NCMe)(SPPh 3)]. The monomers [MI 2(CO) 3(NCMe)(SPPh 3)] dimerise very slowly on stirring at room temperature in CH 2Cl 2 for 24 h to eventually give the iodo-bridged dimers [M(μ-I)I(CO) 3(SPPh 3)] 2. The molybdenum iodo-bridged compound [Mo(μ-I)I(CO) 3(OPPh 3)] 2 reacts with two equivalents of L (LPPh 3, AsPh 3 or P(OPh) 3) to rapidly give the bridged cleaved products [MoI 2(CO) 3L(OPPh 3)]. The monoacetonitrile complexes [MI 2(CO) 3(NCMe)(SPPh 3)] react in situ with an equimolar quantity of [NBu n 4]I in CH 2Cl 2 at room temperature to give the expected anionic compounds [NBu n 4][MI 3(CO) 3(SPPh 3)] in good yield. The bis- acetonitrile compounds [MI 2(CO) 3(NCMe) 2] react with two equivalents of L (LOPPh 3 or SPPh 3) in CH 2Cl 2 to afford the bis-ligand compounds [MI 2- (CO) 3L 2] in high yield. However, one equivalent of L (LOPPh 3 or SPPh 3) reacts with [MI 2(CO) 3L 2] to give the monocationic complexes [MI(CO) 3L 3]I. The ionic nature of these complexes was confirmed by the formulation of the complex [MoI(CO) 3- (SPPh 3) 3][BPh 4] by iodide exchange with Na[BPh 4]. The reaction of [MI 2(CO) 3L 2] with two equivalents of L (LOPPh 3 (for MW only) or SPPh 3) give the dicationic compounds [M(CO) 3L 4]2I. The bis- tetraphenylborate complex [Mo(CO) 3(SPPh 3) 4]- [BPh 4] 2 was also prepared in the normal manner. Three equivalents of OPPh 3 react with [MI 2(CO) 3- (OPPh 3) 2] to give the dicarbonyl compounds [M(CO) 2(OPPh 3) 5]2I in high yield. The mixed ligand complexes [MI 2(CO) 3L′L] (MMo or W; LOPPh 3 or SPPh 3; L′PPh 3, AsPh 3 or SbPh 3) were synthesized by reaction of [MI 2(CO) 3(NCMe) 2] with an equimolar quantity of L′ in CH 2Cl 2, followed by an in situ reaction with one equivalent of L. The triphenylphosphine complex [MoI 2(CO) 3(PPh 3)- (OPPh 3)] on stirring in CH 2Cl 2 for 18 h gave the anionic complex [PPh 3H][MoI 3(CO) 3(OPPh 3)]. Low temperature 13C NMR spectra (carbonyl region) for several seven-coordinate complexes are interpreted to suggest structures for these compounds.