[Rh(μ-OH)(PiPr3)2]2: Versatile Tool for the Binding of Alkynyl, Diynyl, and Diyndiyl Ligands to an Electron-Rich Rhodium(I) Center

The reaction of [RhCl(P i Pr 3 ) 2 ] 2 ( 1 ) with NaOH under phase-tranfer conditions afforded the labile and extremely air-sensitive hydroxorhodium(I) complex [Rh(μ-OH)(P i Pr 3 ) 2 ] 2 ( 2 ) in 80% yield. The X-ray crystal structure analysis of 2 confirmed the dimeric nature of the molecule containing a nearly planar Rh 2 O 2 unit. Compound 2 reacted with CO to yield trans -[Rh(OH)(CO)(P i Pr 3 ) 2 ] ( 4 ) and with PhC⋮CSiMe 3, in the presence of pyridine or CO, to give trans -[Rh(C⋮CPh)(py)(P i Pr 3 ) 2 ] ( 5 ) and trans -[Rh(C⋮CPh)(CO)(P i Pr 3 ) 2 ] ( 6 ), respectively. Treatment of 4 with Me 3 SiC⋮CC⋮CSiMe 3 yielded the binuclear diyndiyl complex [(P i Pr 3 ) 2 (CO)Rh(C⋮CC⋮C)Rh(CO)(P i Pr 3 ) 2 ] ( 7 ), while the corresponding reaction of 4 with Me 3 SiC⋮CC⋮CSnPh 3 gave the mononuclear product trans -[Rh(C⋮CC⋮CSiMe 3 )(CO)(P i Pr 3 ) 2 ] ( 8 ). The X-ray crystal structure analysis of 7 revealed the presence of an almost linear Rh−C 4 −Rh linkage with the midpoint of the central C−C bond as a crystallographic center of symmetry.