Oligonuclear Tricarbonylchromium- and Tricarbonyltungsten Derivatives of Tris(1-cyclohepta-2,4,6-trienyl)phosphane, P(C7H7)3, and Related Ligands

Abstract

A series of trinuclear carbonylmetal complexes of tri(1-cyclohepta-2,4,6-trienyl)phosphane, P(C7H7)3 (1), has been prepared by the reaction of P(SiMe3)3 with η7-tropylium halfsandwich salts, [(η7-C7H7)M(CO)3]BF4, (M = Cr, Mo, W). While phosphorus remains uncoordinated in the chromium complex P[(η6-C7H7)Cr(CO)3]3 (2a), the molybdenum and tungsten analogues, (M = Mo (2b), W (2c)), contain a coordinated phosphorus atom together with a η4-norcaradienyl substituent. Reaction of 2a with pentacarbonylmetal fragments, [M(CO)5], leads to trinuclear products, - (CO)4][(η-C7H7)M(CO)3]2 (M = Cr (5a), W (5c)), in which phosphorus is coordinated next to an η2-cycloheptatrienyl substituent. Several alkyl- and arylphosphanes containing [(η6-C7H7)Cr(CO)3] substituents (X), e. g. Ph2P(X) (6a), RP(X)2 (R = Me (7a), CH2Ph (8a), Ph (9a)) and (X)2P(R')P(X)2 (R' = methylene (10a) or ο-phenylene (11a)), have also been synthesized. The chromium complexes 6a - 11a contain an uncoordinated phosphorus center, but in contrast to 9a, the corresponding tungsten compound PhP (9c) has again a structure similar to 2c. The arsenic complexes, As[(η6-C7H7)M(CO)3]3 (M = Cr (12a), W (12c)) both contain an uncoordinated arsenic center, analogous to 2a. The molecular structures of all new complexes in solution at room temperature were deduced from a consistent set of 1H, 13C and 31P NMR data, and X-ray structure determinations were carried out for 2a and 5c.