The preparations of Rh/Zr “A-frame” and metal-metal bonded complexes are detailed. Treatment of Cp*MeZr(OCH2Ph2P)2 (2, Cp* = η5-C5Me5), prepared from Cp*ZrMe3 (1) and 2.0HOCH2Ph2P, with 0.5[(OC)2RhCl]2(3) afforded Cp*Zr(μ-OCH2Ph2P)2(μ2-η2-O=C(CH3))(μ-Cl)RhCO (4). The μ2-η2-acetyl bridge was cleaved from 4 by HC1 to yield acetaldehyde (61%) and Cp*Zr(μ-OCH2Ph2P)2(μ-Cl)2RhCO (5, 68%), more conveniently isolable from refluxing 4 in CHC13. 1H NMR and IR evidence for an acetyl-hydride intermediate, [Cp*Zr(μ-OCH2Ph2P)2(μ2-η2-O=C(CH3))(μ-Cl)Rh(CO)H]Cl ([4H]Cl), was obtained. Acetone (93%) and Cp*Zr(μ-OCH2Ph2P)2(μ-Cl)(μ-I)RhCO (7, 85%) are formed from exposure of 4 to Mel. The reaction of (Ph3P)3RhMe (8a) with 2 provided Cp*Zr(μ-OCH2Ph2P)2RhMe2(9), which contains a short 2.444 (1) A Rh-Zr bond generated via the oxidative addition of a ZrMe group to Rh. Crystal data: triclinic, PI, a = 11.734 (1) Å, b = 10.524 (1) Å, c = 15.266 (1) Å, a = 104.15 (1)°, β = 93.92 (2)°, and 7 = 112.90 (2)°, Z = 2, T = 25 °C, R = 0.063, Rw = 0.051 (2717 (60.2%) reflections where| Fo|≥ 3σ(Fo)). Byproduct Cp*Zr(μ-OCH2Ph2P)3RhMe (11) was best synthesized through the addition of Cp*Zr(OCH2Ph2P)3 (10) to 8a. Through a similar pathway, (Ph3P)3RhH (8b) and 2 yielded Cp*Zr(μ-OCH2Ph2P)2RhPPh3(12) concomitant with 0.96CH4. Hydrogenation of 12 or 9 (-1.9CH4) produced Cp*Zr(μ-OCH2Ph2P)2RhH2(PPh3) (13). The latter hydrogenated C2H4 to give ethane and 12 or Cp*Zr(μ-OCH2Ph2P)2Rh(η2-C2H4) (14), if excess was used. The reversible binding of PPh3 to 13 and 14 was evidenced. Extended Hückel calculations performed on a model of 9 revealed that the Rh-Zr interaction is 47% σ and 53% π in character, providing a strong indication of multiple bonding. Alternatively, 9 may be considered a donor/acceptor complex with Zr acting as a σ-and π-acceptor Lewis acid. The results were compared with calculations addressing similar M-M' bonded systems. The relationship of the compounds above to heterogeneous oxygenate-selective F-T catalysts and strong metal-support interactions (SMSI) is also discussed.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Organic Chemistry
- Inorganic Chemistry