Chain Length and Coordinating Properties
The short-chain diphosphine dppm tends to promote metal-metal interactions as illustrated by A-frame complexes. When the two phosphine substituents are linked by two to four carbon centres, the resulting ligands often chelate rings with a single metal. The most common diphosphine ligand is 1,2-Bis(diphenylphosphino)ethane, which forms a five-membered chelate ring with most metals.
Some diphosphines, such as the extraordinary case of tBu2P(CH2)10PtBu2, give macrocyclic complexes with as many as 72 atoms in a ring.
To position phosphine donor groups trans on a coordination sphere, several atoms are required to link the donor centres and long-chain diphosphines are typically floppy and do not chelate well. This challenge has been resolved by the long but rigid diphosphine SPANphos.
Read more about this topic: Diphosphines
Famous quotes containing the words chain, length and/or properties:
“Nae living man Ill love again,
Since that my lovely knight is slain.
Wi ae lock of his yellow hair
Ill chain my heart for evermair.”
—Unknown. The Lament of the Border Widow (l. 2528)
“those far-fet helps be such
As do bewray a want of inward touch,
and sure at length stolen goods do come to light.
But if, both for your love and skill, your name
You seek to nurse at fullest breasts of Fame,
Stella behold, and then begin to indite.”
—Sir Philip Sidney (15541586)
“The reason why men enter into society, is the preservation of their property; and the end why they choose and authorize a legislative, is, that there may be laws made, and rules set, as guards and fences to the properties of all the members of the society: to limit the power, and moderate the dominion, of every part and member of the society.”
—John Locke (16321704)