SPANphos: trans-spanning diphosphines as cis chelating ligands!

Abstract

Several SPANphos ligands based on a spirobichroman backbone, introduced as a putative trans ligand, form compounds of the type [Rh(nbd)(SPANphos)]BF(4) () in which both norbornadiene and SPANphos act as cis chelating ligands. The cyclooctadiene rhodium chloride derivatives form bimetallic complexes. Crystal structures for several of these compounds and free ligands are reported. Semiemperical AM1 and DFT calculations show that spirobichroman can assume several conformations, some of which are suitable for the formation of cis chelating SPANphos. All calculations on SPANphos complexes of PdCl(2), PtCl(2) and Rh(CO)Cl show that the trans complex is more stable by 4-10 kcal mol(-1). The cis conformation is enforced by the cis chelating norbornadiene ligand.

N‐Tetradentate SPANamine Derivatives and Their MnII‐Complexes as Catalysts for Epoxidation of Alkenes

“…The N py -Mn-N py bond angles are significantly less than 180°due to the structural constraints imposed by the tetradentate ligand. However, this deviation is more significant for chloride (C1) and nitrate (C6) compounds than for triflate (C2, C8 and C14) complexes [N(1)-Mn-N(4) angle: 160.25 (9) [22] and also considerably below the 90°expected for an Table 3. Catalytic epoxidation of styrene with complexes C1-C6 and C10-C15 using CH 3 CO 3 H as oxidant, in the absence and presence of additives.…”

“…[17][18][19] In recent years, van Leeuwen's group has developed a new series of preferentially trans-coordinating spirobi(chroman) diphosphanes (SPANphos), and their catalytic applications have been also studied. [20][21][22] This spirobi(chroman) skeleton is sufficiently flexible to allow the formation of cis complexes when trans sites are not available. The catalytic application of spirobi(chroman) phosphorus ligands has been intensively investigated, but nitrogen-containing analogues remain largely unexplored.…”

Unusually Large Bite Angle of a Distally Diphosphanylated Calix[4]arene Chelator

“…[15] This study shows, for the first time, that despite the rigidity of CALDIPs, the calixarene skeleton remains compatible with bite angles near 140°. Overall, within the family of chelators with wide bite angles, CALDIPs constitute rare examples [6,40] of diphosphanes giving access to bite angles not only lying at both ends of the range 100-180°, but also in the middle. Furthermore, it should be emphasised that our findings confirm that in CALDIP chelate complexes characterised by a P-M-P angle significantly larger than 110°, the steric pressure exerted by the PPh substituents on the first coordination sphere is drastically enhanced with respect to that seen in the resting state.…”

Ferrocenyl‐Aryl Based trans‐Chelating Diphosphine Ligands: Synthesis, Molecular Structure and Application in Enantioselective Hydrogenation

“…Indeed, in a very recent review such trans-chelating ligands were fittingly referred to as elusive ligands. [5] Nevertheless, a small number of potentially trans-chelating chiral diphosphines such as the TRAP [6] and SPANphos [7] ligand families, Trosts phosphinoamides [8][9][10] (Figure 1) or phosphino-substituted cyclodextrins [5,11] have been investigated and have to some extent been successfully used as ligands for asymmetric catalysts. Of all trans-spanning chiral ligands known to date, the TRAP ligand family shows by far the broadest range of applicability.…”