title: Group VI metal complexes of tris(diphenylphosphinomethyl)phenylborate: modulation of ligand donation via coordination of M(CO)3 units at the borate phenyl substituent.
abstract: A series of d(6) metal complexes of tris(diphenylphosphinomethyl)phenylborate ([PhB(CH2PPh2)3](-), PhBP3), including [Et4N][M(CO)3(PhBP3)] (M = Cr, Mo, W), inaugural group VI metal tris(phosphino)borate complexes, and zwitterionic Mn(CO)3(PhBP3) have been synthesized and fully characterized. An analysis of IR ν(CO) data for [Et4N][M(CO)3(PhBP3)] indicates that PhBP3 is significantly less strongly donating than Tp towards zerovalent M(CO)3 fragments; PhBP3 does not function as a strongly donating scorpionate in this system as its does towards cationic metal fragments suggesting that PhBP3 may not function as an effective surrogate of hydrotris(1-pyrazolyl)borate towards zerovalent metals. While the metal centers of [Et4N][M(CO)3(PhBP3)] are very likely still more electron-rich than those of M(CO)3(triphos), the anions of [Et4N][M(CO)3(PhBP3)] do not provide robust oxidative addition products analogous to those of M(CO)3(triphos). A new bi-functional role for PhBP3 was investigated via the synthesis of seven structurally characterized bimetallics in which zerovalent M(CO)3 and monovalent [Mn(CO)3](+) fragments bind the three phosphine atoms and the borate phenyl substituent. IR ν(CO) data support modest attenuation of PhBP3 donor ability at phosphorus upon η(6)-phenyl substituent binding, representing a new inductive strategy for tuning tris(phosphino)phenylborate donation at the κ(3)-phosphine-bound metal fragment.
authors.affiliation: Department of Chemistry, Macalester College, 1600 Grand Avenue, Saint Paul, Minnesota 55105, USA. fischer@macalester.edu.
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Fischer
authors.forename: Alexander B
authors.initials: AB
authors.lastname: Weberg
authors.forename: Trent D
authors.initials: TD
authors.lastname: Bohrmann
authors.forename: Hanyue
authors.initials: H
authors.lastname: Xu
authors.forename: Victor G
authors.initials: VG
authors.lastname: Young