Pyridine-phosphite ligands

In 2010, Cazin introduced a new family of ruthenium-indenylidene metathesis precatalysts that bore phosphite ligands in place of phosphine ligands" " this was followed in 2011 by the disclosure of the corresponding benzylidene variants (from the reaction of G2-derived bis(pyridine) complex G2py)" and subsequent fuU papers in 2012 and 2013 where a range of indenylidene species were reported." ... 

The pyridine ligand in some alkenyl cobalt(III) DMG complexes may be replaced by methyl or ethyl phosphite by addition of the phosphite to a solution of the (DMG)2 complex in ethanol. In a similar manner aniline may be displaced by (CH30)3P from [CH2=CHCo(DMG)2C6HjNH2] (129). 

Phosphite-pyridine ligands (191) derived from racemic biphenyl units and homochi-ral BINOL have been developed for enantioselective (<96% ee) Cu(I)-catalysed conjugate additions of Et2Zn to a variety of acyclic enones, such as ArCH=CHCOR.229 Ligand (192) was equally successful (90-99% ee).230... 

Reaction with P-Donors. In accord with the expectations dis-cussed above, Cp2Mo2(C0K reacts readily with two equivalents of soft nucleophiles, e.g., phosphines, phosphites, CO, etc., to give exclusively the trans-products indicated in eq. 7. With one equivalent of ligand, only disubstituted product (1/2 equiv.) and unreacted 1 (1/2 equiv.) are isolated. Hence, the addition of the first ligand is the slow step (eq. 18). Complex 1 does not react with hard bases, e.g., aliphatic amines, pyridine, ethers, alcohols, or ketones. Bulky phosphines, e.g., (cyclohexyl)3P, and Ph3As or Ph3Sb also fail to react at room temperature. Rather... 

The reaction of Os3(CO)i2 with H2 at 110°C. produces a reactive, unsaturated hydrido cluster Os3(/u.-H)2(CO)io. This dark purple complex is analogous to diborane and has the two hydrides bridging a very short Os s bond. It can add phosphines, phosphites, arsines, pyridine, and isocyanides to form Os3H2(CO)ioL (Scheme 25). The hydrido cluster adds alkenes and alkynes. Initially, an addition complex with a r-bonded alkene or alkyne is formed. Hydride addition to the unsaturated ligand follows. 

Where halogen or acetate is the counterion, the cyclomet-alated products are halide- or acetate-bridged dimers. Particularly in the case of halides, these dimers are easily cleaved by various ligands, such as pyridine, phosphines, phosphites, and acetylacetone, to give more soluble, monomeric species. Cyclometalation, especially with nitrogen atom donors, inserts into C-H bonds to form five-membered rings. However, formation of six-membered rings can occur (equation 67). 

Ligand abbreviations are as follows pop, dianion of pyrophosphite (p20sH2 " ) pep, dianion of /x-methylenebis(phosphite) im, anion of imidazole 4-mpyt, anion of 4-methylpyridine-2-thiol pyt, anion of pyridine-2-thiol pymS, anion of pyrimidine-2-thione bttz, anion of l,3-benzothiazole 2-thiol form, anion of di-p-tolylformaraidine dpb, /V,A -diphenylbenzamidine mhp, anion of 6-methyl-2-hydrox3T)yridine chp, 6-chloro-2-hydrox3T)yridine dpt, 1,3-diphenyltriazen. 

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