Reactions of Cyclopentadienyl-Amidinate Titanium Imido Compounds with CS2, COS, Isocyanates, and Other Unsaturated Organic Compounds

• Published in: Organometallics 2006-02, Vol.25 (5), p.1167-1187
• Main Authors: Guiducci, Aldo E, Boyd, Catherine L, Mountford, Philip
• Format: Article
• Language: English
• ISSN: 0276-7333; 1520-6041
• DOI: 10.1021/om050784v

New single-, double-, and cross-coupling and imido group transfer reactions of cyclopentadienyl-amidinate titanium imido complexes are described. Reaction of Ti(η-C5R4Me)(N t Bu)Cl(py) (R = Me or H) with the lithiated benzamidinate Li[PhC(NSiMe3)2] or acetamidinate Li[MeC(N i Pr)2] afforded the tert-butyl imido complexes Ti(η-C5R4Me)(N t Bu){PhC(NSiMe3)2} (R = Me (5) or H (7)) and Ti(η-C5R4Me)(N t Bu){MeC(N i Pr2)2} (R = Me (6) or H (8)), respectively. Reaction of 6 with ArNH2 or TolNH2 (Ar = 2,6-C6H3Me2, Tol = 4-C6H4Me) afforded the corresponding aryl imido complexes Ti(η-C5Me5)(NR){MeC(N i Pr2)2} (R = Ar (9) or Tol (10)). Complexes 5, 7, and 8 underwent cycloaddition/extrusion reactions with CS2 and COS to form μ-sulfido dimers and t BuNCS and t BuNCO, respectively. Compound 6 reacted with COS to form t BuNCO and [Ti(η-C5Me5)(μ-S){MeC(N i Pr)2}]2, but with CS2 additional insertion into an amidinate ligand Ti−N i Pr bond occurred to form [Ti(η-C5Me5)(μ-S){N( i Pr)C(Me)N( i Pr)C(S)S}]2. For the aryl imido compounds 9 and 10 the intermediate cycloaddition products Ti(η-C5Me5){N(R)C(E)S}{MeC(N i Pr)2} (E = S or O) were observed. No further insertion of CS2 or COS into the Ti−NR bonds occurred. All tert-butyl imido compounds reacted slowly with t BuNCO or ArNCO to form μ-oxo-bridged dimers and t BuNCN t Bu or t BuNCNAr, respectively. Reaction of 9 with t BuNCO gave the N,O-bound ureate Ti(η-C5Me5){N(Ar)C(N t Bu)O}{MeC(N i Pr)2}, which extruded t BuNCNAr to form [Ti(η-C5Me5)(μ-O){MeC(N i Pr)2}]2. Reaction of 9 or 10 with aryl isocyanates gave the N,O-bound ureates Ti(η-C5Me5){N(R1)C(NR2)O}{MeC(N i Pr)2} (R1 = Ar, R2 = Ar or Tol; R1 = Tol, R2 = Ar or Tol (25)), which did not undergo extrusion. Reaction of 25 with TolNCO gave the net cycloaddition−insertion product Ti(η-C5Me5){OC(NTol)NTolC(NTol)O}{MeC(N i Pr)2}. Several heterocumulene cross-coupling cycloaddition−insertion reactions were studied:  for example, the sequential reaction of 10 with TolNCO and CO2 gave Ti(η-C5Me5){OC(O)NTolC(NTol)O}{MeC(N i Pr)2}. Aryl imides 9 and 10 reacted with TolNCNTol to form the guanidinate complexes Ti(η-C5Me5){N(Tol)C(NTol)N(R)}{MeC(N i Pr)2} (R = Ar or Tol). Reaction of 5 and 6 with PhNO gave t BuNNPh and μ-oxo-bridged dimers; the aryl imides 9 and 10 reacted similarly. Ketone and aldehyde CO/TiNR bond metathesis reactions occurred for certain tert-butyl and aryl imido compounds with MeCOMe, PhCOPh, PhCOH, and PhCOMe, and in some instances intermediates were observed. S