Transition metal–carbon bonds. Part 54. Complexes of palladium, platinum, rhodium, and iridium with But2PCH2CHMe(CH2)3PBut2. Crystal structures of [PdCl(But2PCH2CHMeCHCH2CH2PBut2)] and [IrH(Cl)(But2PCH2CHMeCHCH2CH2PBut2)]

Abstract

The new diphosphine Bu^t ₂PCH₂CHMeCH₂CH₂CH₂PBu^t ₂(L) is shown to have ¹³C n.m.r. shifts which can be calculated empirically from the ¹³C n.m.r. shifts of related diphosphines. It reacts with [PdCI₂(NCPh)₂] to give the cyclometallated complex [[graphic omitted]Bu^t ₂)](1c), with the 2-methyl group in a pseudo-equatorial position, as shown by the crystal structure. With [PtCl₂(NCBu^t)₂] it gives [Pt₂Cl₄L₂] as a complex mixture of isomeric 16-atom ring chelates, which, on treatment with CF₃COOH followed by LiCl, gives [[graphic omitted]Bu^t ₂)]; this was not isolated pure but probably has a structure similar to (1c). Compound L also reacts with [Ir₂Cl₂(C₈H₁₄)₄](C₈H₁₄= cyclo-octene) to give the cyclometallated hydride complex [[graphic omitted]Bu^t ₂)](2c) with an equatorial methyl group. Some of the isomer with a pseudo-axial methyl group was also formed but it slowly, but completely, isomerises to (2c) in solution. Compound (2c) does not lose dihydrogen to give a carbene on heating, in contrast to [[graphic omitted]Bu^t ₂)]. Compound L reacts with [Rh₂Cl₂(C₈H₁₄)₄] to give [[graphic omitted]Bu^t ₂)](2e), but with RhCl₃·3H₂O it also gives two other species, probably rhodium(I)–olefinic diphosphine complexes. Compound (2e) with sodium propan-2-oxide and CO gives [[graphic omitted]Bu^t ₂)]. Proton, ¹³C, and ³¹P n.m.r. and i.r. data are given. Cell dimensions: (1c)a= 1.1907(3), b= 1.6466(4), c= 1.3537(4) nm, and β= 103.99(2)°; (2c)a= 1.1954(4), b= 1.6509(5), c= 1.3665(5) nm, and β= 104.18(3)°.