Platinum complexes chelating phosphorus ligands

Chiral bis-(binaphthophosphole) (bis(BNP)) ligands have been used in the asymmetric hydroformylation of styrene. In solution, the free diphospholes display fluxional behavior. Consistent with their structure, the reaction of the bis(BNP) compounds with platinum(II) derivatives gives either cis chelate mononuclear complexes or trans phosphorus-bridged polynuclear derivatives. Coordination to platinum enhances the conformational stability of bis(BNP)s and diastereomeric complexes can be detected in solution. In the presence of SnCl2, the platinum complexes give rise to catalysts that exhibit remarkable activity in the hydroformylation of styrene. Under optimum conditions, reaction takes place with high branched selectivity (80-85%) and moderate enantio-selectivity (up to 45% ee). 

Platinum(II)15 and palladium(II)16 complexes of phosphorus trichloride undergo solvolysis in water and alcohols to form complexes with orthophosphorous acid or orthophosphite ligands (equation 6). Similar reactions occur between the palladium(II) phenyldichlorophosphine complex (8) and the diols ethyleneglycol and catechol, but new chelate rings are not formed (Scheme 2). Solvolysis also occurs with attack of diphenylphosphinic acid or a similar diphenylchlorophosphine complex (9) (equation 7). The palladium complexes (8) and (9) are unstable to excess methanol, water or base and undergo reduction. Similarly, the phosphorus trichloride gold(I) complex (10) is reduced by water, but forms stable products on reaction with alcohols (equation 8).15 During the above reactions, the phosphorus—metal bond remains intact and the overall process is one of substitution at phosphorus. 

According to reaction (a) mixed substituted platinum(0)complexes of the hitherto unknown type Ptl L1 and PtLL 2 (where L and L are phosphorus ligands) can be isolated and characterized by nmr spectroscopy. Instead of Ph3P other R3P derivatives and Ph3As can be used. Complex D is very labile. IR data give evidence for a a-coordination of the CS2ligands. With the double ylide RR N-P(S)=NR (reaction (c) ) the four-membered chelate complex E with pentavalent phosphorus of coordination number four is formed. Compound F is an example of the well characterized alkyne complexes (here with the phospha(III)azene ligand L). 

---