Formation and Reactivity of the Early Metal Phosphides and Phosphinidenes Cp*2ZrPR, Cp*2Zr(PR)2, and Cp*2Zr(PR)3

The reactions of Cp*2ZrCl2 with 2 equiv of LiPHPh led to the formation of the unstable species Cp*2Zr(PHPh)2 (1), which yields Cp*2Zr(PPh2) (2) on standing for 1 h and a third product Cp*2Zr(PPh)3 (3) which appears after 1 week. The compound 3 is derived cleanly from mixtures of 1 and 2 by addition of excess PH2Ph. In the related reactions, Cp*2ZrCl2 reacts with 2 equiv of LiPH(C6H2Me3) to give the wine-red diphosphido-species Cp*2Zr(PH(C6H2Me3))2 (4). This compound converts slowly to ortho-metalation product Cp*2Zr(CH2C6H2Me2PH) (5) and the species Cp*2Zr(PC6H2Me3)2 (6). These reactions infer terminal phosphinidene intermediates. Such an intermediate can be intercepted via reaction of 4 with MeCN affording Cp*2Zr(NCMe)2P(C6H2Me3) (7). Further evidence for the intermediacy of a phosphinidene complex is derived from the reaction of Cp*2ZrCl2 and LiPH(C6H2Me3) in DME where the species Cp*2Zr(P(C6H2Me3))(Cl)Li(DME) (8) is observed. A bent terminal phosphinidene derivative Cp2Zr(P(C6H2t-Bu3))(PMe3) (9) (ZrPR, 2.505(4) Å) is isolated from the reaction of Cp2ZrCl2 with Li(PH(C6H2t-Bu3)) in the presence of PMe3. While the phosphinidene intermediate affords the novel phosphametallocycle 7, the species 5, 6, and 3 also act as synthons for unprecedented phospha-, diphospha-, and triphosphametallocycles. Compound 5 reacts with MeCN and benzaldehyde to effect insertion of the organic reagents into the ZrP bonds yielding the phosphametallocycles Cp*2Zr(CH2C6H2Me2PH(C(Me)N)) (10) and Cp*2Zr(CH2C6H2Me2PH(C(Ph)O)) (11), respectively, while similar reactions of compound 6 afford the 1,2-diphosphametallocycles Cp*2Zr(NC(Me)PC6H2Me3)2 (12) and Cp*2Zr(OCH(Ph)PC6H2Me3)2 (13). Compound 12 reacts with NH4C1 affording Cp*2ZrCl(NC(Me)P(C6H2Me3)PH(C6H2Me3)) (14). Cleavage of the ZrP bonds in compound 6 is effected by sequential acidolysis with HCCPh affording Cp*2Zr(CCPh)(P(C6H2Me3)PH(C6H2Me3)) (15) and Cp*2Zr(CCPh)2 (16), while reaction of 6 with acetone gives the dienolate complex Cp*2Zr(OC(Me)CH2)2 (17) and reaction of 6 with CH2I2 affords Cp*2ZrI2 (18). Compound 3 acts as synthon for new 1,2,3-triphosphametallocycles as reactions of 3 with MeCN and benzaldehyde afford Cp*2Zr(NC(Me))(PPh)3 (19) and Cp*2Zr(OCH(Ph))(PPh)3 (20), respectively. The chemistry of these ZrP species offers synthetic routes to a variety of unprecedented phosphameta Uocycles which augurs well for metal-mediated synthesis of organophosphorus compounds. The formulations of a number of these compounds have been confirmed crystallographically. These data are summarized as follows: 6, P21/n, a = 11.464(3) Å, b = 19.140(5) Å, c = 16.165(5) Å, β = 90.93(3)°, V = 3546(3) Å3, Z = 4; 9, P21/c, a = 15.011(5) Å, b = 9.824(5) Å, c = 21.745(5) Å, β = 103.21(3)°, V = 3122(2) Å3, Z = 4; 11, P21/c, a = 19.352(6) Å, b = 10.444(8) Å, c = 19.647(12) Å, β = 109.20(3)°, V = 3750(4) Å3, Z = 4; 13, P21/c, a = 21.301(7) Å, b = 10.478(4) Å, c = 25.102(7) Å, β = 111.75(2)°, V = 5204(3) Å3, Z = 4; 14, P21/n, a = 14.731(11) Å, b = 17.401(5) Å, c = 17.143(9) Å, β = 113.83(5)°, V = 4020(4) Å3, Z = 4; 15, P212121, a = 14.572(10) Å, b = 28.618(12) Å, c = 11.084(6) Å, V = 4622(4) Å3, Z = 4; 19, P1̄, a = 12.634(4) Å, b = 17.690(4) Å, c = 10.169(4) Å, a = 103.43(2)°, β = 113.66(2)°, γ = 82.00(2)°, V = 2022(1) Å3, Z = 2. © 1993, American Chemical Society. All rights reserved