Details

Autor(en) / Beteiligte

• Tomsu, Gerald
• Mastalir, Matthias
• Pittenauer, Ernst
• Stöger, Berthold
• Allmaier, Günter
• Kirchner, Karl

Titel

Ligand-Enforced Switch of the Coordination Mode in Low-Valent Group 6 Carbonyl Complexes Containing Pyrimidine-Based Bisphosphines

Ist Teil von

• Organometallics, 2018-06, Vol.37 (12), p.1919-1926

Ort / Verlag

American Chemical Society

Erscheinungsjahr

2018

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• The reaction of M­(CO)6 (M = Cr, Mo, W) with N,N′-bis­(diisopropylphosphine)-N,N′-dimethylpyrimidine-4,6-diamines (PymR-iPr) bearing R = Me, Ph, tBu substituents in the 2-position was investigated. The pyrimidine-based bisphosphine ligands with R = Me, Ph reacted with M­(CO)6 to yield mononuclear and homobimetallic complexes of the types [M­(κ2 P,N-PymMe-iPr)­(CO)4] and [M­(CO)4-μ2-(κ2 P,N-PymPh-iPr)­M­(CO)4], respectively. Heterobimetallic complexes of the type [M1(CO)4-μ2-(κ2 P,N-PymMe-iPr)­M2(CO)4] were obtained by reacting mononuclear complexes [M1(κ2 P,N-PymMe-iPr)­(CO)4] with 1 equiv of the respective M2(CO)6. Replacing these substituents by a bulky tBu group led to a switch in the coordination mode of the pyrimidine ligand. In the case of chromium, the complex [Cr­(κ3 P,CH,P-PymtBu-iPr)­(CO)3] containing an η2-Caryl–H agostic bond was selectively formed and no C–H bond cleavage took place. However, in the case of molybdenum, the reaction led to the formation of an inseparable mixture of the agostic complex [Mo­(κ3 P,CH,P-PymtBu-iPr)­(CO)3] and the hydrido carbonyl complex [Mo­(κ3 P,C,P-PymtBu-iPr)­(CO)3(H)], and with tungsten the hydrido carbonyl complex [W­(κ3 P,C,P-PymtBu-iPr)­(CO)3(H)] was exclusively formed. In the presence of strong bases both complexes could not be deprotonated. In addition, hydride abstraction with Ph3C+PF6 – failed. However, treatment of [W­(κ3 P,C,P-PymtBu-iPr)­(CO)3(H)] with Ph3C+PF6 – in a benzene/THF mixture resulted in protonation of one of the pyrimidine nitrogen atoms to form two isomeric cationic hydride species. X-ray structures of representative complexes are presented.