Reaction of electron-deficient Group 4 metal s-cis-butadiene complexes with carbon monoxide

Abstract

Electronically unsaturated diene complexes Cp*M(diene)Cl (Cp* = q5-CsMes; M = Zr, Hf; diene = 2,3-dimethyl-l,&butadiene, 2-methyl-l,3-butadiene) react with CO through an intermediate adduct to form (di)methylcyclopentadiene and [Cp*M(O)Cl],. Incorporation of the CO carbon atom in the cyclopentadiene was confirmed by 13CO-labeling experiments. The less oxophilic Ti is unable to perform this CO bond cleavage. Cp*Ti(2,3-dimethy1-1,3-butadiene)Cl reacts with CO to form the dimeric titanaoxirane (Cp*Ti[p-OCCH2C(Me)=C(Me)CH2]C1),, which was characterized by X-ray analysis (space group Pi, a = 10.293 (3) A, b = 10.445 (2) A, c = 8.409 ( 3 ) A, a = 103.12 (2)O, p = 101.58 (3)O, y = 68.29 (2)' at 170K, 2 = 1). The molecule contains a highly symmetrical central Tiz02 unit, and the C-0 distance of 1.408 (4) A suggests CO reduction to a single C-0 bond.

Diene complexes of early transition metals: ideas and progresses at Osaka University

“…In 1983, ErkerÕs group [51,52] and TeubenÕs group [53][54][55][56][57] had started to prepare group 4 metal complexes. A series of diene complexes of Ti [58,59], Nb [60] and Ta [61,62] is shown in Fig.…”

Verbindungen mit planar tetrakoordiniertem Kohlenstoff

“…19(2) 1.606 (7) 1. 38(1) 1.40 (1) 1.384 (7) (6) 2.142 (3) 2.020(3) 1. 29(1) 1.312 (5) 1.286(11) 1.325 (5) 1.402 (3) 1.33(1) 1.324 (8) 1.353(17) 1.494(6) 1.418 (5) 2.55(1) 2.607(4) 2.483(7) 2.093 (4) …”

Properties of electron deficient 1,3-diene complexes of the group 4A metals

“…Since organic isonitriles are isoelectronic with CO, and are frequently used as models for CO reactions, we also examined the reactions of 2,6-xylylisonitrile with the unsaturated diene complexes. Cp Hf(2,3-dimethyl-1,3-butadiene)Me reacts with 2,6-xylylisonitrile by selective insertion into the Hf-Me bond to give the iminoacyl Cp Hf(2,3-dimethyl-1,3-butadiene)(η 2 -N(xy)=CMe) [32,37], but no further reaction of the iminoacyl ligand with the diene could be induced. Increase in the steric bulk of the metal-bound alkyl group can change the insertion preference of the incoming isonitrile: in Cp Hf(2,3-dimethyl-1,3-butadiene)R (R = Np, Ph, Cl) the isonitrile attacks specifically the Hf-diene M-C bonds to form the unusual hetero-spiro compounds Cp Hf(R)N(xy) CH 2 C-(Me)=C(Me)CH 2 (xy) (7) [32,37].…”

“…Cp Hf(2,3-dimethyl-1,3-butadiene)Me reacts with 2,6-xylylisonitrile by selective insertion into the Hf-Me bond to give the iminoacyl Cp Hf(2,3-dimethyl-1,3-butadiene)(η 2 -N(xy)=CMe) [32,37], but no further reaction of the iminoacyl ligand with the diene could be induced. Increase in the steric bulk of the metal-bound alkyl group can change the insertion preference of the incoming isonitrile: in Cp Hf(2,3-dimethyl-1,3-butadiene)R (R = Np, Ph, Cl) the isonitrile attacks specifically the Hf-diene M-C bonds to form the unusual hetero-spiro compounds Cp Hf(R)N(xy) CH 2 C-(Me)=C(Me)CH 2 (xy) (7) [32,37]. The formation of these compounds involves a 1,2-hydrogen shift after initial insertion of isonitrile into the Hf-diene bond, followed by a second isonitrile insertion and a ring closure.…”

“…5), formed by diene elimination and CC-coupling of two isonitrile molecules between two electron deficient Ti-centers [37]. Minor products are enediamide complexes (8), formed through insertion of two or three isonitriles into the Ti-diene bonds, followed by CC-coupling of two iminoacyl carbon atoms.…”