Reaction of o-(diphenylphosphino)(N-benzylidene)aniline (P∼N) with [Ir(COD)Cl]2 affords the substitution product [(P∼N)Ir(COD)Cl] (1). Treatment of 1 with AgBF4 yields the cyclometalated iridium hydride complex [P,N,C-(P∼N)Ir(COD)H]BF4 (2). On the other hand, under atmospheric pressure of CO, carrying out the substitution of [Ir(COD)Cl]2 with P∼N results in the formation of [P,N,C-(P∼N)Ir(CO)HCl] (5). Conversion of 4 into 5 can be achieved by the reaction of 4 with CO in the presence of tetraethylammonium chloride. Both 4 and 5 are characterized by spectroscopic and X-ray structural analyses. All iridium complexes are not good catalysts for hydroamination. However, the combination of 5 with NaB[3,5-C6H3(CF3)2]4 (denoted as NaBArF 4) provides a potent catalytic system for both intra- and intermolecular hydroamination of alkynes. Intramolecular reaction of o-(2-phenylethynyl)anilines produces the corresponding indoles in good yields. Furthermore, intermolecular hydroamination takes place smoothly to generate the imine intermediates, which could be subsequently reduced by triethylsilane using the same catalyst, giving N-silylated amines. However, the N-silylated amines readily hydrolyze to produce secondary amines.

2,6-Bis(2-phosphaethenyl)pyridine (PNP) complexes of Rh(I), Cu(I), and Ag(I) have been prepared and examined by NMR and X-ray diffraction analyses. The PNP ligand adopts κ3(P,N,P) coordination for Rh(I) and Cu(I) and κ2(P,P) coordination for Ag(I). The rhodium complex [RhCl(PNP)] in combination with AgOTf catalyzes conjugate addition of benzyl carbamate to enones.

The complex [RuCl(µ-Cl)(CO)(DPCB-OMe)] 2 (1a), bearing a low-coordinated phosphorus ligand (DPCB-OMe ) 1,2-bis(4-methoxyphenyl)-3,4-bis [(2,4,6-tri-tert-butylphenyl)phosphinidene]cyclobutene), is readily reduced to [RuH(µ-Cl)(CO)(DPCB-OMe)] 2 (2a) by the reaction with water and HSiMe 2 Ph. The reaction proceeds via a [RuCl 2 (CO)(H 2 O)(DPCB-OMe)] intermediate, which is characterized by X-ray diffraction analysis. Complexes 1a and 2a serve as highly efficient catalysts for Z-selective hydrosilylation of phenylacetylene. The reason for the high catalyst efficiency of DPCB-OMe complexes has been investigated by reaction and structure analysis of the presumed intermediate [Ru(CHdCHPh)Cl(CO)(DPCB-OMe)] (3a). It has been found that 3a has ample space to associate with hydrosilane and, therefore, readily undergoes metathesis between Ru-C and H-Si bonds. This structural feature in conjunction with the strong π-accepting ability of the DPCB-OMe ligand leads to highly efficient catalysis for Z-selective hydrosilylation of terminal alkynes.

1,2-Bis[(2,4,6-tri-tert-butylphenyl)phosphinidene]cyclobuta[l]phenanthrene (DPCB-phen) as a low-coordinated phosphorus ligand forms the platinum(0) alkyne complexes [Pt(alkyne)(DPCB-phen)] with extended π-conjugated systems. The colors of the complexes are highly dependent on alkyne ligands, showing a marked variation from reddish orange to teal.