Reactions of bis(ditertiaryphosphine) complexes of rhodium(I) with carbon monoxide, dioxygen, dihydrogen, and hydrogen chloride

The products, resulting from addition under mild conditions of the gaseous molecules CO, O2, H2, and HCl, to some rhodium(I)–bis(ditertiaryphosphine) complexes, are described; the [Formula: see text] phosphines used were Ph2P(CH2)nPPh2, n = 1–4, and (+)-diop (diop = 2,3-O-isopropylidene 2,3-dihydroxy-1,4-bis(diphenylphosphino)butane). Monocarbonyls were isolated from addition of CO to [Formula: see text] complexes (n = 1 and 3), the reactions being reversible; there was no reaction with the n = 2 system, while the n = 4 and diop systems absorbed > 1 mol of CO per Rh to give mixtures of products. The same cation precursors add O2 to yield cis-[Formula: see text] adducts (n = 1–3), the binding being reversible for the n = 2 system; pure products were not isolated with the n = 4 cation which absorbs 3 molO2/Rh; the diop system was unreactive toward O2. Reversible additions of 1 mol H2 yield isolable cis-[Formula: see text] complexes with the n = 3 and diop systems; the n = 1 and 2 [Formula: see text] cations are unreactive toward H2, while a mixture of hydrides is formed from the n = 4species. The chlorohydrido cations [Formula: see text] (A = Cl, BF4, PF6, SbF6), n = 1–3, were prepared via routes involving addition of gaseous HCl to precursor [Formula: see text] complexes; however, the reactions with the n = 4 and diop systems did not yield pure products.The solution structures of all the isolated five- and six-coordinate addition products have been determined using 1H and variable temperature 31P nmr. The five-coordinate carbonyl with n = 1 shows equivalent phosphines from −50 to 25 °C, while the n = 3 system shows inequivalent phosphines resulting from a trigonal bipyramidal structure with an equatorial carbonyl. The [Formula: see text] cation, n = 3, has cis geometry, while trans-structures are preferred for the n = 1 and 2 species.