4. "Synthesis and Ligand Substitution Reactions of a Mesitylphosphido-Bridged Platinum(II) Dimer," Igor V. Kourkine, Michael B. Chapman, David S. Glueck, Klaus Eichele, Roderick E. Wasylishen, Glenn P. A. Yap, Louise M. Liable-Sands, and Arnold L. Rheingold, Inorganic Chemistry 1996, 35, 1478-1485.
The stable primary phosphine complexes trans-M(PH2Mes*)2Cl 2 [1, M = Pd; 2, M = Pt; Mes* = 2,4,6-(t-Bu)3C6H2] were prepared from Pd(PhCN)2Cl 2 and K2PtCl4, respectively. Reaction of Pt(COD)Cl 2 (COD = 1,5-cyclooctadiene) with less bulky arylphosphines gives the unstable cis-Pt(PH2Ar)2Cl 2 [3, Ar = Is = 2,4,6-(i-Pr)3C6H2; 4, Ar = Mes = 2,4,6-Me3C6H2]. Spontaneous dehydrochlorination of 4 or direct reaction of K2PtCl4 with two equiv of PH2Mes gives the insoluble primary phosphido-bridged dimer [Pt(PH2Mes)(µ-PHMes)Cl]2 (5), which was characterized spectroscopically, including solid-state 31P NMR studies.
The reversible reaction of 5 with PH2Mes gives [Pt(PH2Mes)2(µ-PHMes)]2[Cl] 2 (6), while PEt3 yields [Pt(PEt3)2(µ-PHMes)]2[Cl] 2 (7), which on recrystallization forms [Pt(PEt3)(µ-PHMes)Cl]2 (8). Complex 5 and PPh3 afford [Pt(PPh3)(µ-PHMes)Cl] 2 (9). Addition of 1,2-bis(diphenylphosphino)ethane (dppe) to 5 gives dicationic [Pt(dppe)(µ-PHMes)]2[Cl] 2 (10-Cl), which was also obtained as the tetrafluoroborate salt 10-BF4 by deprotonation of [Pt(dppe)(PH2Mes)Cl][BF4] (11) with Et3N, or by reaction of [Pt(dppe)(µ-OH)]2[BF4] 2 with two equiv of PH2Mes. Complexes 8, 9, and 10-Cl2CH2Cl 2.2H2O were characterized crystallographically.