Insertion of [Pt(PEt3)2] into a Strained Si−C Bond of Diphenylsila[1]molybdarenophane

Diphenylsila[1]molybdarenophane (1) reacted with [Pt(PEt3)3] to give the platinasila[2]molybdarenophane [{(Et3P)2Pt}(Ph2Si)(η6-C6H5)2Mo] (2) in an isolated yield of 52%. Species 2 was characterized by 1H and 13C NMR spectroscopy, mass spectrometry, elemental analysis, and single-crystal X-ray determination (monoclinic P21/c; a = 11.8115(3) Å; b = 17.6336(3) Å; c = 19.7795(4) Å; α = 90°; β = 122.1420(10)°; γ = 90°). The insertion of the [Pt(PEt3)2] moiety into the strained C−Si bond resulted in a reduction of the tilt angle α from 20.23(29)° (1) to 13.62(20)° (2). Species 1 reacted with Karstedt’s catalyst (6.9 mol %; toluene, ambient temperature) to be completely consumed within 3 h. As revealed by 1H NMR spectroscopy, new products were formed. These products could not be isolated or identified; however, small half-bandwidths of their peaks indicated that polymers had not been formed. Salt metathesis between bis(dilithiobenzene)molybdenum and R2SiCl2 (R = iPr, Me) resulted in new sila[1]molybdarenophanes with iPr2Si (3) and Me2Si bridging units (4), respectively. Neither species could be isolated in chemically pure form. However, 3 and 4 were unequivocally identified by 1H NMR spectroscopy, especially by a very distinctive pattern of the Mo-coordinated phenyl groups (δ (in C6D6): 5.52 (p-H), 5.05 (m-H), and 3.68 (o-H) for 3; 5.52 (p-H), 5.05 (m-H), and 3.69 (o-H) for 4).