Synthesis and characterization of tetranuclear hydroxcarbonyl complexes of molybdenum and tungsten, [Et 4N] 4[Mo(CO) 3(η 3-OH)] 4 and [Et 4N] 4[W(CO) 3(η 3-OH)] 4

Abstract

Reaction of M(CO) 3(PMTA) (M  W, Mo; PMTA = 1,1,4,7,7-pentamethyldiethylenetriamine) with a stoichiometric amount of hydroxide ion in aqueous THF solution yields [M(CO) 3(η 3-OH)] 4− 4 ( 1, M  W; 2, M  Mo). These tetranuclear metal carbonyl complexes were isolated as their Et 4N + salts. The crystal structures of both complexes have been determined. Compounds 1 and 2 are isostructural; the crystals are monoclinic, space group C2/ c, Z = 4, with unit cell dimensions a 23.86(3), b 12.317(7), c 23.21(1) Å, β 123.8(2)° for 1; and a 23.888(7), b 12.300(2), c 23.254(3) Å, β 123.85(2)° for 2. The anions consist of a distorted cubic A 4B 4 (A = metal, B = oxygen) core with triply bridging hydroxide groups and M(CO) 3 units. The MM distances (average 3.59(6) Å for 1 and 3.58(6) Å for 2) within the M 4O 4 core clearly show non-bonding between metal atoms which is consistent with a closed-shell metal configuration.