The chlorine functions of CH 3 C(CH 2 Cl) 3 , 1, may be replaced involved in intramolecular hydrogen bonding to the CH 2 OH function (N•••H-O distance 280 pm). Blocking of the OH by pyrazolyl (pz) as well as imidazolyl (im) residues under the conditions of nucleophilic substitution leading to tripodal function of 10a by etherification, i.e. to form EtOCH 2 C(CH 2 PPh 2 )(CH 2 pz) 2 , 11, does not dramatically ligands CH 3 C(CH 2 X) 3 , X = pz, 2; X = im, 3. As a means of introducing two nitrogen donors and one phosphorus donor affect the coordination capabilities with 11 • Mo(CO) 3 (MeCN), 12d, being formed upon treatment with into a tripod ligand, substitution of the Br and OMs functions in O(CH 2 ) 2 C(CH 2 Br)(CH 2 OMs), 8, by nitrogen nucleophiles (MeCN) 3 Mo(CO) 3 . Again only one pz function is coordinated to the metal. Bidentate coordination by two phosphorus and subsequent cleavage of the oxetane ring by a phosphide nucleophile to give HOCH 2 C(CH 2 PPh 2 )(CH 2 X) 2 has been donors of 10c is observed in 10c • Mo(CO) 3 (MeCN), . The dangling arm pz donor function and the CH 2 OH group are developed, furnishing 10a (X = pz) and 10d (X = NEt 2 ), respectively. For the synthesis of 10a, K-pz was used as the intermolecularly hydrogen-bonded in this case. When the bulky P[3,5-Me 2 (C 6 H 3 )] 2 substituent of 10c is replaced by the nucleophile, while 10d was prepared using azide in the initial step, which then had to be transformed into NEt 2 in less sterically demanding PPh 2 donor in 10b, η 3 -coordination is finally observed with the formation of 10b • Mo(CO) 3 , 13. two subsequent steps. The nucleophugic functions of the oxetane 8 undergo selective substitution by K-pz and KPPh 2
The coordination capabilities of the new ligands are rationalized in terms of the size (six-, seven-, and eight-in THF to produce O(CH 2 ) 2 C(CH 2 PPh 2 )(CH 2 pz), 9b. Phosphide cleavage of the oxetane function leads to membered rings) and interference of the chelate cycles. All compounds have been characterized by the usual analytical HOCH 2 C(CH 2 PPh 2 )(CH 2 PR 2 )(CH 2 pz), R = Ph, 10b; R = 3,5-Me 2 (C 6 H 3 ), 10c. -The tris(pyrazolyl) tripod ligand 2 reacts and spectroscopic methods, with a complete assignment of the NMR data achieved by a combination of 2D-NMR with (MeCN) 3 Mo(CO) 3 to give 2 • Mo(CO) 3 (MeCN), 12a, in which only two of the three donor functions are coordinated.
techniques in some cases. The structures of the coordination compounds have additionally been deduced by X-ray Upon reaction with 10a, the same reagent gives 10a • Mo(CO) 4 , 12b, with one pyrazolyl coordinated and the other methods.