Büschel Susanne, Jungton Ann-Katrin, Bannenberg Thomas, Randoll Sören, Hrib Cristian G, Jones Peter G, Tamm Matthias
Institut für Anorganische und Analytische Chemie, Technische Universität Carolo-Wilhelmina zu Braunschweig, Hagenring 30, 38106 Braunschweig, Germany.
Chemistry. 2009;15(9):2176-84. doi: 10.1002/chem.200802518.
Twice as reactive: The coordination chemistry of phosphane-functionalized Zr and Hf cycloheptatrienyl-cyclopentadienyl complexes gives rise to unusual secondary interactions associated with the presence of Lewis acidic 16-electron sandwich moieties. These structures can develop weak dative bonds as exemplified by the noncovalent Pd-->Zr interaction in the heterobimetallic {Zr(2)Pd} complex (see picture). Phosphane-functionalized cycloheptatrienyl-cyclopentadienyl Group 4 metal complexes of the type [(eta(7)-C(7)H(7))M(eta(5)-C(5)H(4)PR(2))] (M=Ti (9); M=Zr (10); M=Hf (11); R=Ph (a); R=iPr (b)) have been prepared by the reduction of [(eta(5)-C(5)H(4)PR(2))TiCl(3)] or [(eta(5)-C(5)H(4)PR(2))(2)MCl(2)] (M=Zr, Hf) with magnesium in the presence of cycloheptatriene (C(7)H(8)). In the solid state, the Ti complex 9 a and the complex 11 b are monomeric, whereas 10 a, 10 b, and 11 a form dimers, in which the sandwich units are linked by long Zr-P or Hf-P bonds. Density-functional theory (DFT) calculations indicate that the metal-phosphane interaction is weak, and accordingly, both the Ti complex 9 b and the Zr complex 10 b act as monodentate phosphane ligands upon reaction with [{(cod)RhCl}(2)] (cod=eta(4)-1,5-cyclooctadiene). The X-ray crystal structures of [(cod)Rh(9 b)Cl] (12) and [(cod)Rh(10 b)Cl] (13) reveal that only the latter exhibits a secondary intramolecular Cl-metal interaction. The complex [(10 b)(2)Pd] (14) was obtained by reaction of [(eta(5)-C(5)H(5))Pd(eta(3)-C(3)H(5))] with two equivalents of 10 b. The solid-state structure of 14 reveals a T-shaped Pd(0) center with a long Pd-Zr bond of 2.9709(3) A, which can be interpreted as a weak noncovalent Pd(0)-->Zr(+IV) bond, as indicated by the calculated relaxed force constant of 5.68 N m(-1).
膦官能化的锆和铪环庚三烯基 - 环戊二烯基配合物的配位化学产生了与路易斯酸性16电子夹心部分的存在相关的异常二级相互作用。这些结构可以形成弱配位键，如异双金属{Zr(2)Pd}配合物中的非共价Pd→Zr相互作用所示（见图）。通过在环庚三烯（C₇H₈）存在下用镁还原[(η⁵ - C₅H₄PR₂)TiCl₃]或[(η⁵ - C₅H₄PR₂)₂MCl₂]（M = Zr，Hf）制备了[(η⁷ - C₇H₇)M(η⁵ - C₅H₄PR₂)]类型的膦官能化环庚三烯基 - 环戊二烯基第4族金属配合物（M = Ti (9); M = Zr (10); M = Hf (11); R = Ph (a); R = iPr (b)）。在固态中，Ti配合物9 a和配合物11 b是单体，而10 a、10 b和11 a形成二聚体，其中夹心单元通过长的Zr - P或Hf - P键连接。密度泛函理论（DFT）计算表明金属 - 膦相互作用较弱，因此，Ti配合物9 b和Zr配合物10 b在与[{(cod)RhCl}₂]（cod = η⁴ - 1,5 - 环辛二烯）反应时均作为单齿膦配体。[(cod)Rh(9 b)Cl]（12）和[(cod)Rh(10 b)Cl]（13）的X射线晶体结构表明只有后者表现出分子内二级Cl - 金属相互作用。配合物[(10 b)₂Pd]（14）是通过[(η⁵ - C₅H₅)Pd(η³ - C₃H₅)]与两当量的10 b反应得到的。14的固态结构揭示了一个T形Pd(0)中心，其Pd - Zr键长为2.9709(3) Å，如计算得到的5.68 N m⁻¹的松弛力常数所示，这可以解释为弱非共价Pd(0)→Zr(+IV)键。
