| 词条 | Trans-spanning ligand |
| 释义 |
Trans-spanning ligands are bidentate ligands that can span opposite sites of a complex with square-planar geometry. A wide variety of ligands that chelate in the cis fashion already exist, but very few can link opposite vertices on a coordination polyhedron. Early attempts to generate trans-spanning bidentate ligands relied on polymethylene chains to link the donor functionalities, but such ligands often lead to coordination polymers. HistoryA diphosphane linked with pentamethylene was claimed to span across a square planar complex. This early attempt was followed by ligands with more rigid backbones. "TRANSPHOS" was the first trans-spanning diphosphane ligand that usually coordinates to palladium(II) and platinum(II) in a trans manner. TRANSPHOS features benzo[c]phenanthrene substituted by diphenylphosphinomethyl (Ph2PCH2) groups at the 1 and 11 positions.[1][2] The polycyclic framework suffers sterically clashing hydrogen centers. Xantphos, SPANphos, TRANSDIP and related ligandsXantphos is a trans-spanning ligand, without the steric problems associated with TRANSPHOS. SPANphos is comparable to XANTPHOS but more reliably trans-spanning. TRANSDIP, based on a α-cyclodextrin, is the first ligand to give exclusively trans-spanned complexes, even with d8 metal ion halides.[3]References1. ^{{cite journal | last1 = Destefano | first1 = N. J. | last2 = Johnson | first2 = D. K. | last3 = Lane | first3 = R. M. | last4 = Venanzi | first4 = L. M. | year = 1976 | title = Transition-Metal Complexes with Bidentate Ligands Spanning Trans-Positions. I. The Synthesis of 2,11-Bis(Diphenylphosphinomethyl)Benzo[C]-Phenanthrene, A Ligand Promoting the Formation of Square Planar Complexes | journal = Helvetica Chimica Acta | volume = 59 | pages = 2674–2682 | doi = 10.1002/hlca.19760590806 | issue = 8}} 2. ^{{cite journal |author1=Mochida, J. A. |author2=Mattern, J. C. |author3=Bailar, Jr., J. | year = 1975 | title = Stereochemistry of Complex Inorganic Compounds. XXXV. A Complex Containing a Ligand That Spans Trans Positions | journal = J. Am. Chem. Soc. | volume = 97 | pages = 3021–3026 | doi = 10.1021/ja00844a017 | issue = 11}} 3. ^{{cite journal | last1 = Poorters | first1 = L. | last2 = Armspach | first2 = D. | last3 = Matt | first3 = D. | last4 = Toupet | first4 = L. | last5 = Choua | first5 = S. | last6 = Turek | first6 = P. | title = Synthesis and Properties of Transdip, A Rigid Chelator Built Upon a Cyclodextrin Cavity: is Transdip an Authentic Trans - Spanning Ligand? | journal = A European Journal | volume = 13 | pages = 9448–9461 | doi = 10.1002/chem.200700831 | year = 2007 | pmid = 17943701 | issue = 34}} 1 : Coordination chemistry |
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