Synthesis of dicarbonyl and halogeno complexes of (η-pentamethyl-cyclopentadienyl)(nitrosyl)-molybdenum and -tungsten. Crystal structure of [{Mo(η5-C5Me5)(NO)Br(µ-Br)}2]
Abstract
Under appropriate conditions the reaction of [M(η5-C5Me5)(NO)(CO)2][M = Mo, (1) or W, (2)] with X2(X = Cl, Br, or l) gives [{M(η5-C5Me5)(NO)X2}n][M = Mo, (3a)–(3c); or W, (4a)–(4c); n= 1 or 2]. When M = W and X = Cl the new carbonylnitrosyl compound [W(η5-C5Me5)(NO)-Cl2(CO)](5) has been isolated and characterized; (5) is proposed to be an intermediate in the preparation of (4a) from (2). The compound (3b) or (4b) reacts with mono- or bi-dentate phosphines giving [M(η5-C5Me5)(NO)Br2L][L = PPh3, M = Mo, (6b); or W, (7); L = OPPh3, M = Mo, (8); or W, (9)] or [Mo(η5-C5Me5)(NO)Br(L–L)][Mo(η5-C5Me5)(NO)Br3][L–L = Ph2PCH2PPh2(dppm), (10); or Ph2PCH2CH2PPh2(dppe), (11)]. Complex (11) is in equilibrium with an isomer [Mo2(η5-C5Me5)2(NO)2Br4(dppe)](12). X-Ray structure analysis of [{Mo(η5-C5Me5)(NO)-Br(µ-Br)}2](3b) shows space group C2/c with a= 15.102(4), b= 8.403(6), c= 21.498(10)Å, β= 98.69(2)°, and Z= 4; R= 0.063 and R′= 0.055, based on 2 688 observed reflections. The molecule is dimeric with two bridging bromo atoms, in contrast with the monomeric nature of the recently reported structure of the parent (4c).