Preparation and Chemical Reactions of Ruthenium Cp Phosphine Complexes with 1,6-Endiyne.
Date Issued
2010
Date
2010
Author(s)
Lui, Ming-Chung
Abstract
Reactions of five 1,6-diynes 1, 1N, 2, 3 and 7, each with one terminal propargylic alcohol and one internal triple bond containing Me3Si groups, with [Ru]-Cl ([Ru] = Cp(PPh3)2Ru) led to two types of products. In the first type, only the propargylic group involves in the reaction leading to vinylidene, allenylidene or acetylide complexes. A C-C bond formation of two triple bonds in 1,6-diynes gave allylcarbene products of the second type. The reaction of 1 with [Ru]-Cl yielded only the first type, giving a mixture of two cationic complexes; the allenylidene complex 8 and the phosphonium acetylide complex 9, the latter resulting from further addition of a phosphine molecule to Cγ of 8. The same reaction in the presence of excess phosphine gave 9 only. However, with an additional methyl group, the 1,6-diyne 2 reacted with [Ru]-Cl to give the allylcarbene complex 11 also with a phosphonium group on the ligand. The reaction proceeds by a cyclization reaction involving two triple bonds on the metal accompanied with a migration of a phosphine ligand to Cα. In both reactions strong affinity between alkyne and phosphine was observed resulting in formations of P-C bonds in different regioselectivity. Addition of HCl to 11 transforms the five-electron donor allylcarbene ligand to the four-electron donor diene ligand along with formation of a Ru-Cl bond giving complex 12 in high yield. From the reaction of [Ru]-Cl with diyne 3 containing a t-butyl group at the propargylic carbon, both the allenylidene complex 13 and the allylcarbene complex 14 were obtained. The reaction of diyne 7 with [Ru]-Cl also gave both types of complexes, namely the vinylidene complex 16 and the allylcarbene complex 17. Crystal structures of complexes 9, 11, 12, 13, and 16 are determined by single crystal X-ray diffraction analysis.
We also studied the cyclic reaction of a series of the acetylide complexes. These acetylide complexes were prepared from the allenylidene or phosphonium acetylide complexes which using the Cp(PPh3)2RuCl and 1,6-diyne-4-ene-3-ol connected with an aromatic group in presence of KPF6 in CH2Cl2. Deprotection of the terminal alkyne were carried out in different alcohol solution under basic condition or TBAF in THF solution gave a series of acetylide complexes with terminal alkyne group. For 19, protonation of acetylide complex can lead two vinylidene complexes 20 and 20’ which possibly via a π-coordinated alkynyl complex followed by hydrogen and metal migration. For 21a - d, a C-C bond-forming cyclization reaction is occurred at Cβ and the terminal alkyne to generate a six-member ring in the vinylidene complex. The reaction may undergo a 6-endo-dig reaction pathway. These cyclic vinylidene complexes 22a - d under acidic-medium condition could form the alkoxy carbene 25a - b or acyl complexe 26 which with a naphathyl ring in the structure. This 1,3-alkoxy migration might via metal carbene complex as an intermediate. For 4N, that the difference to the acetylide complex 19 is containing an electrophilic pyridinyl ring, it could form the cyclic vinylidene complex 5N in presence of KPF6 in CHCl3. All structures determinations of the cyclic vinylidene complexes are using NMR spectra analysis and the acyl complex is using the single crystal X-ray diffraction analysis.
Subjects
Ruthenium
vinylidene complex
allylcarbene
Cyclic vinylidene complex
allenylidene complex
phosphonium acetylide complex
carbon-carbon bond formation.
Type
thesis
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