Heterodi- and Heterotrinuclear Complexes Containing Highly Polar Metal−Metal Bonds

Reaction of the dichlorozirconium complex [CH 2 (CH 2 NSiMe 3 ) 2 ZrCl 2 (thf) 2 ] ( 1 ), containing a chelating amido ligand and having a trans disposition of the chloro ligands established by an X-ray diffraction study, with the carbonylmetalate derivatives K[MCp(CO) 2 ] (Cp = C 5 H 5 ) and Na[Co(CO) 3 (PPh 3 )] gave the heterotrinuclear complexes [CH 2 (CH 2 NSiMe 3 ) 2 Zr{MCp(CO) 2 } 2 ] (M = Fe ( 2 ), Ru ( 3 )) and [CH 2 (CH 2 NSiMe 3 ) 2 Zr{Co(CO) 3 (PPh 3 )} 2 ] ( 4 ), respectively. Of these, 2 and 3 were structurally characterized by X-ray crystallography, establishing two unsupported metal−metal bonds in each of the compounds [ 2, d (Zr−Fe) = 2.665(2), 2.664(2) Å; 3, d (Zr−Ru) = 2.7372(7), 2.7452(7) Å]. Reaction of 2 and 3 with 1 in a 1:1 molar ratio led to a quantitative redistribution of complex fragments, yielding the dinuclear complexes [CH 2 (CH 2 NSiMe 3 ) 2 (Cl)Zr−MCp(CO) 2 ] (M = Fe ( 5 ), Ru ( 6 ). Both products as well as the Zr−Co complex [CH 2 (CH 2 NSiMe 3 ) 2 (Cl)Zr−Co(CO) 3 (PPh 3 )] ( 7 ) were also obtained in moderate yields by reacting 1 with 1 molar equiv of the carbonylmetalate. Reacting 5 − 7 with NaCp gave the corresponding CpZr complexes [CH 2 (CH 2 NSiMe 3 ) 2 (Cp)Zr−MCp(CO) 2 ] (M = Fe ( 8 ), Ru ( 9 )) and [CH 2 (CH 2 NSiMe 3 ) 2 (Cp)Zr−Co(CO) 3 (PPh 3 )] ( 10 ), of which 9 was characterized by a single-crystal X-ray structure analysis [ d (Zr−Ru) = 2.8297(14) Å]. Compounds 5, 6, 8, and 9 insert methyl isonitrile to give the heterobimetallic metallaiminoacylzirconium complexes [CH 2 (CH 2 NSiMe 3 ) 2 (Cl)Zr{η 2 -C( NCH 3 )MCp(CO) 2 }] (M = Fe ( 11 ), Ru ( 12 )) and [CH 2 (CH 2 NSiMe 3 ) 2 (Cp)Zr{η 2 -C( NCH 3 )MCp(CO) 2 }] (M = Fe ( 13 ), Ru ( 14 )), respectively. Reaction of the heterotrinuclear compounds 2 and 3 with isonitriles exclusively gave the products of the insertion into one of the unsupported metal−metal bonds, [CH 2 (CH 2 NSiMe 3 ) 2 Zr{η 2 -C( NCH 3 )MCp(CO) 2 }{MCp(CO) 2 }] (M = Fe, R = Me, n Bu, Cy, Tol ( 15a − d ); M = Ru, R = Me, n Bu, Cy, Tol ( 16a − d )). A crystal structure analysis of 16a established the insertion into one of the metal−metal bonds while the intact Zr−Ru bond was elongated in comparison to that of 3 [ d (Zr−Ru) = 2.8639(6) Å]. Cleavage of both metal−metal bonds in 2 and 3 was observed in reactions with sulfoxides. Transfer of the S-bound oxygen atom to a carbonyl ligand led to CO 2 -linked trinuclear complexes in which the thioether thus generated was coordinated to the late transition metal center. The reaction at the two metal−metal bonds occurred cooperatively, precluding the isolation of intermediates.