Synthesis of hydrido-bis(acetylide) complexes of rhodium and the molecular structures of mer-trans-[Rh(PMe3)3(H)(CCPh)2] and mer-trans-[{Rh(dmpe)(H)(CCSiMe3)2}2(µ-dmpe)](dmpe = Me2PCH2CH2PMe2)
“…In agreement with the different trans influences of the SnPh 3 and PMe 3 groups, the bonds Rh−P1 and Rh−P2 in compound 2 are somewhat shorter than the bond between Rh and P3. A completely similar situation has been found by Marder et al for [RhH(C⋮CPh) 2 (PMe 3 ) 3 ] 2 Molecular structure (ORTEP drawing) of 4 .…”
The reaction of
[Rh(η2-O2CMe)(PiPr3)2]
(1)
with Ph3SnC⋮CPh afforded, by elimination of
Ph3SnOAc, the five-coordinate complex
[Rh(C⋮CPh)2(SnPh3)(PiPr3)2] (2) in 75%
yield. Treatment of 2 with excess
PMe3 gave the octahedral compound
mer,trans-[Rh(C⋮CPh)2(SnPh3)(PMe3)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(η2-PhC⋮CC⋮CPh)(PiPr3)2] (4), which
could also be obtained from [RhCl(PiPr3)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, η2-coordinated diyne ligand.
“…In agreement with the different trans influences of the SnPh 3 and PMe 3 groups, the bonds Rh−P1 and Rh−P2 in compound 2 are somewhat shorter than the bond between Rh and P3. A completely similar situation has been found by Marder et al for [RhH(C⋮CPh) 2 (PMe 3 ) 3 ] 2 Molecular structure (ORTEP drawing) of 4 .…”
The reaction of
[Rh(η2-O2CMe)(PiPr3)2]
(1)
with Ph3SnC⋮CPh afforded, by elimination of
Ph3SnOAc, the five-coordinate complex
[Rh(C⋮CPh)2(SnPh3)(PiPr3)2] (2) in 75%
yield. Treatment of 2 with excess
PMe3 gave the octahedral compound
mer,trans-[Rh(C⋮CPh)2(SnPh3)(PMe3)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(η2-PhC⋮CC⋮CPh)(PiPr3)2] (4), which
could also be obtained from [RhCl(PiPr3)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, η2-coordinated diyne ligand.
“…X-ray diffraction provided conclusive proof of the trans configuration at the Pt center . The trans disposition of the acetylide units has also been established for Ni and Pd analogues, as well as for group 8 and 9 complexes 206 such as octahedral trans -[Ru(dppe) 2 (C⋮CC 6 H 5 ) 2 ] 207 and mer , trans -[Rh(PMe 3 ) 3 (H)(C⋮CC 6 H 5 ) 2 ], respectively. The binuclear Rh(I) complex [Rh(PMe 3 ) 4 (C⋮C−C 6 H 4 −C⋮C)Rh(PMe 3 ) 4 ] has also been characterized crystallographically (Figure ) .…”
Section: Iii12 Structural Studies and Bonding In The M−c⋮c
Fragmentmentioning
“…A five-coordinated (alkynyl)(hydrido)rhodium(III) compound corresponding to C has not been structurally characterized, but the structures of the six-coordinated complexes Rh(PMe 3 ) 3 (H)(C⋮CPh) 2 ( c ) and RhCl(P i Pr 3 ) 2 (Py)(C⋮CCMeCH 2 ) 2 ( d ) have been determined. ,10e The Rh III H distances found in a dinuclear complex, Rh 2 H 2 (O 2 CO)(PhC⋮CPh)(P i Pr 3 ) 3 , are 1.48(3) and 1.42(3) Å and thus in good agreement with the calculated value of C (1.499 Å). While the Rh III H bond length in d is only slightly longer, 1.56(4) Å, the bond length of 1.90 Å in c is unusually long which is probably due to the strongly electron donating PMe 3 group present in the trans position.…”
The transformation of a rhodium(I) η 2 -alkyne model complex RhCl(PH 3 ) 2 (HCtCH) (A) into the vinylidene form RhCl(PH 3 ) 2 (CdCH 2 ) (E) has been examined by ab initio theoretical calculations using MP2 level geometry optimizations and localized molecular orbital (LMO) analysis. The vinylidene form E has been found to be 7.8 kcal/mol more stable than A. The previously found intraligand 1,2-hydrogen shift mechanism in the Ru(II)-coordinated alkyne-vinylidene isomerization is not relevant for the present Rh system. The reaction proceeds via the oxidative addition product RhCl(PH 3 ) 2 (H)(CtCH) (C), followed by a bimolecular hydrogen shift from the metal to the terminal carbon of a second molecule rather than by intramolecular 1,3-hydrogen transfer. The LMO analysis of the transition state of the unimolecular 1,3-hydrogen shift indicates that the hydrogen moves as a proton while it interacts with the three centers simultaneously, i.e., Rh, CR, and C in the transition state. The hydrogen was analyzed to migrate also as a proton in the bimolecular mechanism. The barrier of the bimolecular pathway has been further calculated for a more realistic system with substituted phosphines, RhCl(P i Pr 3 ) 2 (H)(CtCH), using the integrated MO + MM (MP2:MM3) method. It was concluded that in the real system with substituents on both the phosphines and the alkyne, RhCl(P i Pr 3 ) 2 (HCtCR), the bimolecular hydrogen shift is still favored by ca. 15 kcal/mol in free energy of activation; unimolecular 1,3-H migration should become important in special cases like solid state isomerizations.
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