Double metalation and iron-osmium bonding involving ferrocenyl moieties on clusters. Crystal and molecular structures of H2Os3(CO)8[(.eta.-C5H4)Fe(.eta.-C5H3PPr2-iso)] and H2Os3(CO)8[(.eta.-C5H4)Fe(.eta.-C5H3PFcEt)]

Abstract

As the calculated energy of distortion to an axial Cas-C angle of 180' is only 1.4 kcal/mol, it is not surprising that sterically encumbered ligands L can overcome this electronic effect and cause axial carbonyls to bend away from L.Other workers have also investigated the reasons why axial carbonyls bend toward ligands that are not ?r ac-ceptors. The seminal work of Elian and Hoffmann on metal carbonyl fragments& addressed distortion of M(C0)4 fragments but did not specifically discuss axial bending. Ziegler and co-workers have published LCAO-HFS calcu-lations@ for HCo(CO), that describe a mixing of the metal dyz orbital with an empty metal 4p, orbital to give a metal dp hybrid which enhances back-bonding to the equatorial carbonyls ( Figure 6). Eisenstein, Crabtree, and co-workers have more recently noted this d-p mixing using EHT.57 ConclusionsWe have confirmed the dominance of metallacyclopropane character in 1 and provided an explanation for the observed distortion of its axial carbonyl ligands. In addition we have documented, by comparison with its X-ray structure, the geometric accuracy of ab initio calculational methods for third row transition metal complexes and have demonstrated the utility of the Krauss-Stevens22 carbon and oxygen effective core potentials. Acknowledgment. (53) Axe, F. U.; Marynick, D. S. J. Am. Chem. SOC. 1984,106,6230. Much earlier theoretical work on 8 is referenced therein. (54) Ref 31 in ref 3 4 (a) +acenaphthalene: Cotton, F. A.; Lahuerta, P. Znorg. Chem. 1975,14,116. (b) $-furanone: Chisnall, B. M.; Green, M.; Hughes, R. P.; Wells, A. J. J. Chem. SOC., Dalton Trans. 1976,1899. (55) Elian, M.; Hoffmann, R. Inorg. Chem. 1975,14,1058. (56) Versluis, L.; Ziegler, T.; Baerends, E. J.; Ravenek, W. J. Am. (57) Jackson, S . A.; Eisenstein, 0.; Martin, J. D.; Albeniz, A. C.; Chem. SOC. 1989,111,2018.

Preparation and characterization of the osmium cluster complexes H2Os3(CO)8L(EtFcPCMe) (L = CO or PEt2Fc) and H2Os3(CO)8[(η-C5H3PEt2)Fe(η-C5H4)]

“…The Fe+Os bond length, 2.826(2) A, is similar to that found for the other compounds 9 (20,25). The C(l):Os(3) and C(6)-Os(1) distances at 2.168(8) and 2.08(1) A, respectively, are typical of carbon-osmium u-bonds, but there is probably also some interaction between C(1) and Os (1) The mass spectrum of 10 suggests the loss of two carbonyls from the parent complex and the analytical data are consistent with this formulation.…”

“…The structure of 9e is very similar to those of 9a-d previously described (20,25). It consists of a triangular array of three osmium atoms with one face capped by an axial phosphine and a doubly metalated ferrocenyl moiety.…”

“…25 (8) 0.2188 (7) 0.1415(9) 0.0416 (7) 0.3212(8) 0.203 l(7) 0.1287 (8) "B,, = (8/3) T ' C C U,,a,*a,*(a;a,).…”

Profound Steric Control of Reactivity in Aryl Halide Addition to Bisphosphane Palladium(0) Complexes

“…Easy access to the former structure can sometimes provide significant disadvantages for coupling chemistry. For example, the electron‐rich but less bulky ligand 14 is effective in the reaction outlined in Scheme 3, but only for about 40 turnovers with about 15 % of both biaryl and C−Br reduction product formed in side‐reactions 13. The loss of activity correlates well with the observed formation of the X‐ray characterized complex 15 ,10 which quite rapidly becomes the sole Pd‐containing species in the reaction when followed by NMR spectroscopy.…”

Profound Steric Control of Reactivity in Aryl Halide Addition to Bisphosphane Palladium(0) Complexes

“…Easy access to the former structure can sometimes provide significant disadvantages for coupling chemistry. For example, the electron‐rich but less bulky ligand 14 is effective in the reaction outlined in Scheme , but only for about 40 turnovers with about 15 % of both biaryl and C−Br reduction product formed in side‐reactions 13. The loss of activity correlates well with the observed formation of the X‐ray characterized complex 15 ,10 which quite rapidly becomes the sole Pd‐containing species in the reaction when followed by NMR spectroscopy.…”