Synthesis and Structure of New Osmium−PCP Complexes. Osmium-Mediated C−C Bond Activation

The new complex Os{1,3-( i Pr 2 PCH 2 ) 2 C 6 H 3 }(Cl)(PPh 3 ) ( 2 ) was obtained from the reaction between the diphosphine {1,3-( i Pr 2 PCH 2 ) 2 C 6 H 4 } ( 1 ) and OsCl 2 (PPh 3 ) 3 . 2 reacts with H 2 to yield the dihydrido species Os{1,3-( i Pr 2 PCH 2 ) 2 C 6 H 3 }(H) 2 (Cl)(PPh 3 ) ( 3 ). Addition of 1 equiv of carbon monoxide to 2 led to the formation of Os{1,3-( i Pr 2 PCH 2 ) 2 C 6 H 3 }(CO)(Cl)(PPh 3 ) ( 4 ), while in the presence of excess CO, the bis-carbonyl complex Os{1,3-( i Pr 2 PCH 2 ) 2 C 6 H 3 }(CO) 2 (Cl) ( 5 ) was formed. Both 2 and 5 were structurally characterized by X-ray diffraction studies. The reaction of OsCl 2 (PPh 3 ) 3 (under hydrogen pressure) and OsHCl(PPh 3 ) 3 with the diphosphine {1,3,5-(CH 3 ) 3 -2,6-( i Pr 2 PCH 2 ) 2 C 6 H} ( 6 ) led to the formation of the C−C activation products Os{3,5-(CH 3 )-2,6-( i Pr 2 PCH 2 ) 2 C 6 H}(H 2 )(Cl)(PPh 3 ) ( 7 ) and Os{3,5-(CH 3 )-2,6-( i Pr 2 PCH 2 ) 2 C 6 H}(Cl)(PPh 3 ) ( 8 ), respectively.