Electron-deficient (pentamethylcyclopentadienyl)titanium trialkyls: evidence of [cyclic] Ti.cntdot..cntdot..cntdot.H-C and [cyclic] Ti.cntdot..cntdot..cntdot.C-C interactions. Crystal and molecular structure of .mu.-[o-(CH2)2C6H4]{(.eta.5-C5Me5)Ti[o-(CH2)2C6H4]}2