PREPARATION OF TRIMETHYLSILYL ALKYNE COMPLEXES OF BIS(PENTAMETHYLCYCLOPENTADIENYL)ZIRCONIUM, (ETA(5)-C5ME5)(2)ZR(RCCSIME3), AND THEIR REGIOSELECTIVE REACTIONS WITH NITROUS-OXIDE

Benzene solutions of Cp2ZrCl2 (1) (Cp* = eta(5)-C5Me5) react with the alkynes Me3SiC drop CPh, Me3SiC drop C(c-C5H9) and Me3SiC drop CCMe3 in the presence of Na/Hg amalgam to afford high yields of the respecti ve alkyne complexes CpZr-2(Me3SiC drop CPh) (2), Cp*Zr-2{Me3SiC drop C(c-C5H9) } (3) and CpZr-2( Me3SiC drop CCMe3) (4) as crystalline com pounds. Complex 2 crystallizes in the triclinic space group P (1) over bar with a = 9.791(6), b = 10.466(6), c = 15.756(12) Angstrom, alpha = 86.09(5), beta = 72.09(5), gamma = 72.06(4)degrees and Z = 2. The le ast-squares refinement converged to R(F) = 0.0604 and R(wF) = 0.0628 f or the 3655 unique data with F-0> 4 sigma(F-0). Salient metrical param eters of the bound alkyne include the following: C(30)-C(31) = 1.340(9 ) Angstrom; Zr-C(30) = 2.178(6) Angstrom; Zr-C(31) = 2.219(5) Angstrom ; C(30)-C(31)-Si = 141.0(5)degrees; C(31)-C(30)-C(26) = 135.5(5)degree s. Nitrous oxide reacts with 2 or 3 to afford CpZr-2(OCR=CSiMe3) ((5) R=Ph; (6) R = c-C5H9) and 1 equiv, of N-2 via an intermediate, CpZr- 2{N(O)NCR=CSiMe3}, which is unstable with respect to loss of dinitroge n to give the oxametallacyclobutene derivatives 5 and 6. The oxygen-at om insertion is regiospecific for the Zr-C bond that is attached to th e carbyl (Ph or c-C5H9) substituent. Under similar conditions, complex 4, in which the alkyne is particularly labile, gives a myriad of prod ucts in its reaction with N2O. (C) 1998 Elsevier Science S.A.