SYNTHESIS OF (MU-BIS(AMINOCARBENE)) DIMETAL COMPLEXES OF CHROMIUM ANDIRON BY THE REACTION OF TERTIARY DIAMIDES WITH CR(CO)(5)(2-) OR FE(CO)(4)(2-) IN THE PRESENCE OF CHLOROTRIMETHYLSILANE

Reaction of an excess of Cr(CO)(5)(2-) with N,N,N',N'-tetramethylisoph thalamide (1a) or the N,N,N',N'-tetramethylamide of pyridine-2,6-dicar boxylic acid (1c) in the presence of chlorotrimethylsilane readily giv es (mu-bis(aminocarbene))dichromium complexes O)(5)Cr[mu-1,3(C(NMe(2)) )C6H4(C(NMe(2)))]Cr(CO)(5) (2a) or )Cr[mu-2,6-(C(NMe(2)))(C5H3N)(C(NMe (2)))]Cr(CO)(5) (2c), respectively. Under the same conditions, N,N,N', N'-tetramethylphthalamide (1b), binaphthyl bis(amide) 1d, and N,N,N',N '-tetramethylsuccinamide (1e) afford monocarbene complexes (CO)(5)Cr[C (NMe(2))(2-(Me(2)NCO)C6H4)] (3b), binaphthyl derivative 3c, and (CO)(5 )Cr[C(NMe(2))((CH2)(2)CONMe(2))] (3d) as the sole products. N,N,N',N'- Tetramethylglutaramide (1f) and N,N,N',N'-tetramethyladipamide (1g) fo rm mixtures of both bis- and mono(carbene) complexes with the bis(carb ene) complex strongly predominating. The reaction of Fe(CO)(4)(2-) wit h diamide 1a or 1c under similar conditions produces the (mu-bis(amino carbene))diiron complexes )(4)Fe[mu-1,3-(C(NMe(2)))C6H4(C(NMe(2)))]Fe( CO)(4) (2b) or )Fe[mu-2,6-(C(NMe(2)))(C5H3N)(C(NMe(2)))]Fe(CO)(4) (2d) , respectively. When a 1:1 molar ratio of 1a and Cr(CO)(5)(2-) is used , the monocarbene complex (CO)(5)Cr[C(NMe(2))(3-(Me(2)NCO)C6H4)] (3a) is formed in moderate yield along with 2a. The monocarbene complex 3a can be converted to the mixed chromium-iron mu-bis(aminocarbene) compl ex )(5)Cr[mu-1,3-(C(NMe(2)))C6H4(C(NMe(2)))]Fe(CO)(4) (4) on reaction with Fe(CO)(4)(2-) and chlorotrimethylsilane. This complex was fully c haracterized by X-ray diffraction study.