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(η 5-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).