Less common modes of coordination in α,ω-bis(di-tert-butylphosphino)alkane and α,ω-bis(di-tert-butylphosphino) (poly)ether complexes of rhodium(I)†

α,ω-Bis(di-tert-butylphosphino)alkane and α,ω-bis(di-tert-butylphosphino) (poly)ether ligands are prepared in appreciable yields via reaction of the appropriate dihalide with two equivalents of Lip-t-Bu2. Reaction of [Rh(COD)(acetone)2][OTf] with the former ligands yields bridged complexes of the type [Rh(COD)(OTf)]2[μ-t-Bu2P(CH2)n,P-t-Bu2] (n = 5 and 8), containing coordinated triflate. With the ligand t-Bu2PCH2CH2OCH2CH2P-t-Bu2 the monomeric complex [Rh(COD)(P∩P)][OTf] is isolated, in which the diphosphine ligand is coordinated through oxygen and one phosphorus atom. In the case of the ligand t-Bu2P(CH2CH2O)2CH2CH2P-t-Bu2, the bridged complex [[Rh2(COD)2(OTf)](μ-P∩P)][OTf] is formed, containing both coordinating and non-coordinating triflate. In solution this complex rearranges to [[Rh(COD)]2(μ-P∩P)][OTf]2, in which the ligand is coordinated to both rhodium nuclei via one phosphorus and one oxygen atom. With Cl−, CO and SO2, [Rh(COD)(t-Bu2PCH2CH2OCH2CH2P-t-Bu2)][OTf] reacts to [Rh(COD)(Cl)]2-(μ-P∩P), [Rh(CO)(P∩P)][OTf] and [Rh(SO2)(P∩P)][OTf], respectively. In the reaction of [Rh(COD)(OTf)]2[μ-t-Bu2P(CH2),P-t-Bu2] with CO2 one of the reaction products is most probably [Rh(CO)3(P∩P)][OTf] with cis-coordinated diphosphine. [Rh(COD)(Cl)]2(μ-t–Bu2PCH2CH2OCH2CH2P-t-Bu2) reacts with CO to [Rh(CO)(P∩P)][Rh(CO)2(Cl)2].