Synthesis of Dinuclear Rhodium Complexes with 1,3-Butadiyndiyl Bridges. Coupling of the C₄ and the Two C₂ Units of a C₂RhC₄RhC₂ Chain^,¹

Abstract

Compounds trans -[RhF( C CHR)(P i Pr 3 ) 2 ] ( 2 − 4 ), of which 2 (R = H) was prepared for the first time from [Rh{η 2 -O 2 S(O)CF 3 }(P i Pr 3 ) 2 ], C 2 H 2, and KF, reacted with Ph 3 SnC⋮C−C⋮CSnPh 3 to give the dinuclear C 4 -bridged rhodium(I) complexes trans, trans -[{Rh( C CHR)(P i Pr 3 ) 2 } 2 (μ-C⋮C−C⋮C)] ( 5 − 7 ) in 78−88% isolated yield. On a similar route, by using trans -[RhF(CX)(P i Pr 3 ) 2 ] ( 8, CX = CNC 6 H 3 Me 2 -2,6; 9, CX = CO) and Ph 3 SnC⋮C−C⋮CSnPh 3 in the molar ratio of 2:1 as the starting materials, the diisocyanidedirhodium and dicarbonyldirhodium derivatives trans, trans -[{Rh(CX)(P i Pr 3 ) 2 } 2 (μ-C⋮C−C⋮C)] ( 12, 13 ) were obtained. The reactions of 8 and 9 with equimolar amounts of Ph 3 SnC⋮C−C⋮CSnPh 3 gave the mononuclear complexes trans -[Rh(C⋮C−C⋮CSnPh 3 )(CX)(P i Pr 3 ) 2 ] ( 10, 11 ), which on further treatment with 8 or 9 afforded the dinuclear compounds 12 and 13, respectively. The C−SnPh 3 bond of 10 could be cleaved both by Al 2 O 3 /H 2 O and trans -[RhF( C CHPh)(P i Pr 3 ) 2 ] ( 3 ) to give the butadiynyl compound trans -[Rh(C⋮C−C⋮CH)(CNC 6 H 3 Me 2 -2,6)(P i Pr 3 ) 2 ] ( 14 ) and the unsymmetrical dirhodium complex trans, trans -[{Rh( C CHPh)(P i Pr 3 ) 2 }{Rh(CNC 6 H 3 Me 2 -2,6)(P i Pr 3 ) 2 }(μ-C⋮C−C⋮C)] ( 15 ). Moreover, treatment of 5 and 6 with CNC 6 H 3 Me 2 -2,6 or CO led to a 2-fold migratory insertion reaction to yield the novel dinuclear compounds trans, trans -[{Rh(CX)(P i Pr 3 ) 2 } 2 {μ- C ( CHR)C⋮C−C⋮C− C ( CHR)}] ( 16 − 18 ), which contain a highly unsaturated eight-membered C 8 chain as a bridge. The molecular structure of 17 (CX = CO; R = Ph) was determined by X-ray crystallography.