SYNTHESES, STRUCTURES, AND REACTIVITIES OF UNUSUAL 4-MEMBERED METALLACYCLES FORMED IN INSERTION REACTIONS OF N=N=O, N=N=NR, AND N=N=CR2 WITH (ETA-5-C5ME5)2ZR(C2PH2)

Nitrous oxide reacts with Cp⋆2Zr(C2Ph2) (1, Cp⋆ = η5-C5Me5) to afford an organometallic product in which N2O has been incorporated without loss of dinitrogen. This adduct, Cp⋆2Zr{N(O)NCPh=CPh}(2), is isolable yet thermally unstable with respect to loss of dinitrogen at ambient temperature to give the monomeric diphenyloxametallacyclobutene derivative Cp⋆2Zr(OCPh=CPh) (3). 3 crystallizes from toluene solution in the monoclinic space group P21/n with a = 9.194 (2) Å, b = 19.422 (4) Å, c = 16.642 (4) Å, β = 104.60 (2)°, and Z = 4. The least-squares refinement coverged to R(F) 0.051 and R(wF) = 0.058 for the 1849 unique data with Fo > 4σ(Fo). Salient metrical parameters of the four-membered oxametallacycle include the following: Zr…C(l), 2.543 (6) Å; Zr-C(2), 2.219 (7) Å, Zr-O, 2.065 (5) Å; C(l)-C(2), 1.348 (12) Å; O-C(l), 1.440 (10) Å. 3 reacts with H2 to give the enolate hydride Cp⋆2Zr(H)(OCPh=CHPh) (8) and with HCl to give Cp⋆2ZrCl2 and deoxybenzoin. Substrates with acidic hydrogens (H2O, PhOH, O=CMe2, HC≡CH, HC≡CPh, and HC≡CtBu) react with 3 to give enolate derivatives Cp⋆2Zr(X)(OCPh=CHPh) (9, X = OH; 10, X = OPh; 11, X = OC(CH2)Me; 12, X = C≡CH; 13, X = C≡CPh; 14, X = C≡CtBu), respectively. In contrast, insertion reactions into the Zr-C bond of 3 are observed for (O=CH2)x, O=CHTol, O=CH(n-Hex), TolN3, Ph2CN2, CO, and tBuN≡C, affording the 5- and 6-membered metallacycles Cp⋆2Zr(OCPh=CPhCH2O) (15), Cp⋆2Zr(OCPh=CPhCHTolO) (16), Cp⋆2Zr{OCPh=CPhCH(n-Hex)O} (17), Cp⋆2Zr- {OCPh=CPhN(N=NTol)} (18), Cp⋆2Zr{OCPh=CPhN(N=CPh2)} (19), Cp⋆2Zr{OCPh=CPhC(=0)} (20), and Cp⋆2Zr{OCPh=CPhC(=NtBu)} (21), respectively. p-Totyl azide and diphenyldiazomethane react with 1 to afford Cp⋆2Zr{N-(N2-p-C6H4CH3)CPh=CPh} (4) and Cp⋆2Zr{N(N=CPh2)CPh=CPh} (5), respectively; these complexes do not cleanly lose N2 on thermolysis. 4 crystallizes from benzene solution in the monoclinic space group P21/c with a = 9.912 (4) Å, b = 30.919 (9) Å, c = 13.583 (5) Å, β = 98.97 (2)°, and Z = 4. The least-squares refinement converged to R(F) = 0.067 and R(wF) = 0.064 for the 2439 unique data with Fo > 3σ(Fo). Important metrical parameters of the planar four-membered azametallacycle include the following: Zr-C(21), 2.285 (8) Å; Zr-N(l), 2.173 (8) Å; C(21)-C(22), 1.373 (16) Å; C(22)-N(l), 1.423 (12) Å; N(l)-N(2), 1.341 (12) Å; N(2)-N(3), 1.305 (12) Å. Water adds accross a Zr-C bond of 1 to give the hydroxy vinyl species Cp⋆2Zr(OH)(CPh=CHPh) (6), but H2O adds across the Zr-N bond of 5 to yield Cp⋆2Zr(OH){CPh=CPhNH-(N=CPh2)} (7). © 1990, American Chemical Society. All rights reserved.