Structural Features and Dynamical Behavior of Heteroleptic trans-C,C-Bisaryl-Platinum(II) and -Palladium(II) Complexes

Abstract

Several heteroleptic trans-bisaryl-Pt II complexes, trans-C,C-[Pt(NCN)R] (6-9), have been prepared starting from the readily available precursor [PtCl(NCN)] (1, NCN ) [C 6 H 3 (CH 2 -NMe 2 ) 2 -2,6] -) and ortho-substituted phenyl-or naphthyllithium reagents, respectively. Variable-temperature 1 H NMR spectroscopy shows that in solution the NCN ligand is η 3 -coordinated and that rotation of the trans-aryl ligand about the Pt-C ipso bond is slow or even nonexistent on the NMR time scale. Moreover, in the temperature range -80 to +90°C no dissociation of the Pt-N (NCN) coordination occurs. In contrast, the analogous Pd II complex 13 shows fluxional behavior of the nitrogen-to-metal coordination (above 0°C). The dynamic properties of this type of complexes can thus be tuned by the choice of metal. The crystal structure determinations of two trans-C,C-[M(NCN)(C 10 H 6 (CH 2 NMe 2 )-2)] complexes (8 (M ) Pt), 13 (M ) Pd)) are reported. The most significant feature in these structures is that the η 3 -N,C,N-coordinating NCN ligand present in 1 has been retained in 8 and 13; that is, the ortho-(dimethylamino)methyl group of the naphthyl ligand remains noncoordinating and cannot compete with the ortho-(dimethylamino)methyl groups of the NCN ligand.

Noble metals

“…230 Heteroleptic trans-C,C-bisaryl-Pt(II) complexes [Pt(NCN)R] [NCN = 2,6-{C 6 H 3 (CH 2 NMe 2 ) 2 )} À ; R = o-substituted Ph or naph] have been studied using VT 1 H NMR spectroscopy showing that in solution the NCN ligand remains Z 3coordinated, but the analogous Pd(II) complex shows fluxional behaviour of the nitrogen-to-metal coordination. 231 It has been shown that the complex [(cod)PtI 2 ] reacts with Ph 3 PQCQPPh 3 giving the novel complex [Z 3 -C 8 H 11 Pt (C 6 H 4 PPh 2 CPPh 3 )] where in addition to the coordination of the ylidic carbon atom, two further Pt-C s-bonds with one ortho phenyl group and the cod ligand result; the Pt(0) complex [Pt(PPh 3 ) 2 (CH 2Q CH 2 )] does not react but decomposes at elevated temperatures to give the known dinuclear complex [Pt 2 (PPh 3 ) 2 (m-PPh 2 ) 2 ]. 232 In addition, an unusual organometallic s-edge bond to the corannulene derivatives has been prepared by oxidative addition of bromocorannulenes to Pt(PEt 3 ) 4 .…”