Five- and Six-Coordinate Bis(alkynyl)rhodium(III) Complexes Containing a Rh−SnPh₃ Bond

The reaction of [Rh(η 2 -O 2 CMe)(P i Pr 3 ) 2 ] ( 1 ) with Ph 3 SnC⋮CPh afforded, by elimination of Ph 3 SnOAc, the five-coordinate complex [Rh(C⋮CPh) 2 (SnPh 3 )(P i Pr 3 ) 2 ] ( 2 ) in 75% yield. Treatment of 2 with excess PMe 3 gave the octahedral compound mer, trans- [Rh(C⋮CPh) 2 (SnPh 3 )(PMe 3 ) 3 ] ( 3 ), the molecular structure of which has been determined. Compound 2 reacted with an equimolar amount of iodine to yield the rhodium(I) diyne complex trans -[RhI(η 2 -Ph C ⋮ C C⋮CPh)(P i Pr 3 ) 2 ] ( 4 ), which could also be obtained from [RhCl(P i Pr 3 ) 2 ] 2, 1,4-diphenylbutadiyne, and NaI. The X-ray crystal structure analysis of 4 confirmed the square-planar geometry around the rhodium center and the coordination of a bent, η 2 -coordinated diyne ligand.